Wednesday, December 28, 2016

Bearing Design Guide: Chapter Twenty-Three: CBBI Manual Bearing Procedure and Notes

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1. Identify the particular application from Fig. 6 through 10 in the CBBI Manual.

2. Pick up the recommended value for M from the type of machinery application.

3. A= M(squared)W I D(squared)Z N

 W = load in pounds
 D = diameter of shaft or bush ID
 Z = absolute viscosity ( centipoises)
 A = characteristic number

a. Assume an operating temperature

b. Z can be determined for the lube at assumed temperature T(2)

c. A fair approximate of lubricant temperature rise can be made.
Forced feed or pressure lubrication, temperature rise will average between 5 and 10 degrees F, if less oil is supplied bearing will run hotter, thus for other lubricating techniques, such as oil bath, splash feed and ring oiling, lubricant may rise from 1 0 to 1 00 degrees F.

d. After substitution, if "A" falls in the range of .0005 and .50, practical full-film lubrication is possible.

A large value for "N' indicates a heavily-loaded or slow-speed bearing.

Conversely, light loads and high speeds, a very low "A" number will be obtained.

With a light load or no load, eccentricity ratio "e" will be zero and centered.

As the load increases, the journal moves eccentrically.

While eccentricity "e" is increasing, the minimum film thickness (Ho) is decreasing.
Ho = c-e = c (i-e)

If the load becomes great enough, the journal may eventually touch the bearing for this condition:
"e" = c, (Ho) = 0.

Once the bearing characteristic number is determined, a suitable length for the bearing can be determined.


Hydrodynamic Mode:
1. Surface velocity in excess of 25 FPM
2. Coefficient of friction is .001-.005
3. Proper viscosity of lube
4. Proper lube flows
5. Proper design methods

Mixed film/Lubrication Mode:
1. Surface velocity in excess of 10 FPM
2. Coefficient of friction .02-.08
3. Journal BRG goes through all three modes

Boundry Lubrication Mode:
1. Generally slow rotary motion, less than 10 FPM
2. Oscillating motion
3. Coefficient of friction .08-.14
4. Generally grease lubricated

Press Fits or Shrinkage Fits:
1. Generally . 00 1" minimum press fit should be sufficient for ODS up to 3" OD
2. Adjust press fit for bearings through 6" OD to about .002 minimum
3. Following a press fit or shrinkage fit, the bearing ID will close in on the ID by 100% of the press fit allow. Heavier wall bearings will average 60 to 80% close in based on the interference fit allowance.

Bearing Retention Methods:
1. Press fit or shrinkage fit
2. Set screws
3. Woodruff keys
4. Bolted through flange
5. Threaded/screwed bearing

Clearance Allowances:

1. Machined bearings with ground journals for use in steam turbines, generators, etc., usually have a running clearance of. 001 per inch of shaft diameter.
2. Clearances of .0015 through .0035/ inch of diameter are used for grease and solid lube conditions.

Thank you for joining me on this journey.  Although we are done with The Bearing Design Guide, don't be sad.  I have more exciting things coming in the New Year!

That's all for now.  Until 2017 my metal loving friends! 

Mechanical Bronzes (Brass World & Platers Guide, March 1924)
Development in Centrifugal Casting (Metal Industry, Aug. 1939)
Wear and Surface Finish (Gisholt Machine Co. 1947)
Plain Bearing Recommended Practice (AISI April1951)
·Bearing Materials and Properties (Machine Design March 1966)
Cast Bearings (Machine Design March 1966)
The Science ofTribology (CDA London Engineer 1969)
Plain Bearing (Machine Design Jtme 1970)
How to Install Plain Bearings (Power Transmission Nov. 1970)
Plain and Premounted Sleeve Bearings (Machine Design June 197 4)
Copper Alloy Casting Design (CDA United Kingdom)
Boundary Lubricated Sleeve Bearings (Battelle, Columbus, Ohio)
Wear of Cast Bronze Bearings (Incra Aug. 197 6)
Physical Properties of Copper Alloys (Casting Engineering 197 6-77)
Wear Properties of Heavily-loaded Copper-based Bearing Alloys
Power Transmission Design (1994)
When Designing Journal Bearings (Bruce Dunham, Sun Oil Co.)
Bearing Design & Applications (Wilcox, Booser, McGraw-Hill, 1957

Thursday, December 22, 2016

A Christmas Story Moment "Stuck" In History


Stuck? Stuck?! STUCK! STUCK!  Come back! Don't leave me, come back!
           Who doesn't remember the iconic scene from the movie A Christmas Story where Flick, while surrounded by his instigating school pals in the school yard at Warren G. Harding Elementary School, got his tongue stuck to a pole. In my opinion, its one of the best scenes in the movie.

          Apparently I'm not the only one that thinks its a classic. The small town of Hammond, Indiana where the movie was filmed and where the incident took place felt it needed a permanent reminder of the classic.

          In 2013, on the films 30th anniversary a bronze statue was erected capturing the moment perfectly.  The statue was brought to its new home in a shipping crate appropriately marked with "Fragile" just like Ralphie's fathers "major award", the famous Leg Lamp. A grand Celebration was had and who better to debut the statue was none other than A Christmas Story's own Flick, also know as actor Scott Schwartz.

Scott Schwartz having fun with the statue
          The statue sits in front of the Welcome Center in Hammond, Indiana just off Interstate 80-94.  Travelers are encouraged to visit, but might not want to try and re-enact the famous scene because this flag pole is made of metal and you could very well get your tongue stuck if you try.

          So...take a night this holiday season and watch A Christmas Story, or if you're feeling adventurous, take a trip to visit the now famous landmark.

         I triple dog dare you...


Monday, December 19, 2016

Bearing Design Guide: Chapter Twenty-Two: Soldering, Brazing and Welding of Bronze Alloys

          Copper-based alloys, like other metals, occasionally require joining by soldering, brazing and welding. The following is intended to assist in those procedures.
          In soft soldering, the low melting solders of tin and lead, in varying proportions, are used to join bronzes at relatively low temperatures well below the melting point of the bronze alloy or its lead content (if the lead content is 3% or less). The solders most generally used are the 60 tin and 40 lead solder which melts at 374 degrees F and the 50 tin and 50 lead solder which melts at 477 degrees F.  You can see a great detailed example of this here.

          Soldering is used to provide a convenient joint that does not require any great mechanical strength. It is used in combination with mechanical staking, crimping or folding and used to seal against leakage or to assure electrical contact.

          Fluxes for soldering: Soldering requires the metals being joined to be clean and fluxes clean the surface by removing the oxide coating present, keep the area clean by preventing formation of oxide films and lower the surface tension of the solder by increasing its wetting properties.

          Rosin, tallow and stearic acid are mild fluxes but are not too effective in removing oxides present. Zinc chloride and ammonium chloride used separately or in combination will remove oxide films readily, however, this flux residue must be removed or neutralized to prevent their corrosive effects. Washing with water or with commercial water soluble detergents will neutralize any further corrosive effects.

          Methods of application: Soldering can be done with a soldering iron, a torch, electric induction or resistance heating. There are no special techniques used to solder except the usual precautions of cleanliness and fit of mating surfaces. The advantage of soldering is a low-temperature process, good manual application, no fusion of parent metals, and, therefore, no warpage. It is applicable to most copper-based alloys (with less than 3% lead) with minimum finishing requirements being necessary.

          Brazing is a method of joining two metals through the use of heat and a filler metal below the melting point of the metals being joined. Brazing creates a metallurgical bond between the filler metal and the surfaces of the two metals being joined.

          Again, here in order to obtain a sound joint, the surfaces in the join and around it must be free from oil, dirt and oxides. Cleaning can be achieved by chemical means such as using trisodium phosphate, carbon tetrachloride and trichlorethlene for chemical method and the use of filing, grinding, machining or sand-blasting for mechanical means of cleaning.

          Fluxes are used mainly to prevent formation of oxides and to remove oxides from the base and filter metals and to promote free flow of the filler metal.

          We're in the home stretch.  Only ONE more chapter to go!  Be sure to check out the Blog on Thursday the 22nd for a special Christmas edition of Metalchic.

That is all for today...Until next time, my metal loving friends!

Next Up: Chapter 23: CBBI Manual Bearing Procedure and Notes

Monday, December 12, 2016

Bearing Design Guide: Chapter Twenty-One: Corrosion Resistance Of Some Bronzes

We are going to continue with our chapter, but first a little announcement...

And now onto...Bearing Design Guide: Chapter Twenty-One: Corrosion Resistance Of Some Bronzes

          Corrosion is defined as the eroding of a metal as a result of a reaction with its environment, or exposure to various liquids or gases.

          Some metals and alloys are naturally resistant to certain corrosive environments. The product of a corrosive film which forms when metals are subjected to corrosive attack protects them from speedy damage by virtue of this protective oxide film.

          Corrosion can occur in bronzes as a result of slow dissolution of copper and copper alloys either because no protective film is formed or because as fast as a film is formed, it enters into solution in the corroding medium.

          Outdoors, copper and copper alloys develop a relatively protective skin of sulfides, oxides or soot. The sulfides form as a result of a reaction with sulfuric acid in the atmosphere and oxides as a result of a reaction with oxygen in the air. These reactions speed up in humid and rainy climates. They would cease entirely in the absence of water.

          Galvanic corrosion is caused by compounds which are electrical conductors when in solution in water and are known as electrolytes. The ions in these electrolytes are ever ready to conduct electricity if an anode (the positive ion) and cathode (the negative ion) of any type are present.

           Solutions of carbon dioxide, sulfur dioxide, oxygen, chlorides and fluorides are condensed or precipitated from the atmosphere. When a metal is to be used where there is an electrolytes as in sea water, the coupling of metals must be close together in the EMF series; to reduce the tendency to corrode the least nobler (cathodic) material.

          Galvanic corrosion often can be prevented by separating the less noble material by insulating it with rubber or synthetic resins.

           Although aluminum alone as a base material possesses good corrosion resistance to dry atmospheres, it actually corrodes very rapidly until a surface film forms. The surface film arrests further action to sea water, many fresh waters, chemicals and foods.

          This oxide film is extremely thin and, when damaged or scratched, corrosion will reform another thin film. Aluminum, therefore, depends on the resistance of the formed oxide film to attack rather than to the base metal.

          If aluminum is coupled with a copper-based alloy as bronze in a wet atmosphere, such as in marine environments, corrosion of the aluminum will continue unabated and would be an unfavorable galvanic couple. However, in a dry atmosphere, there is no precipitable galvanic action encountered.

          The high-leaded tin bronzes, leaded tin bronzes and tin bronzes have poor resistance to most acids but good resistance to sea water, fresh water, gasolines, fuel oils, alcohols, Freons and many other mediums. But it is recommended that the copper alloys be tin-coated or plated.

          For the most corrosive resistant alloys, the aluminum bronze alloys offer the greatest protection. The aluminum bronze alloys are used for their strength primarily and extensively used in general outdoors, marine service and exposure to many acids.

Galvanic Corrosion On Propeller

          A brief list follows showing the acceptable and non-acceptable exposure to various corrosive medium by aluminum bronzes.

          In the case of manganese bronzes, which contain less than 80% copper, zinc is selectively removed from the alloy by most acids when diluted in water. Manganese bronzes can be used for marine applications, water pump rotors and in sea water.

That's it for today.  Until next time my metal loving friends...

Next Up: Chapter 22: Soldering, Brazing and Welding Of Bronze Alloys

Wednesday, December 7, 2016

Bearing Design Guide: Chapter Twenty: Thrust Bearings or Washers

We are going to continue with our chapter, but first a little announcement...

And now onto...Bearing Design Guide: Chapter Twenty: Thrust Bearings or Washers


          There are three basic types of thrust washers which are defined by their mode of operation. Thrust bearings designed correctly to operate under either one of the following modes have theoretical justification for their load capacities.

          1. Flat boundary lubricated 100 PSI.
          2. Flat thermal wedge, hydrodynamically lubricated 1200 PSI.
          3. Contoured wedge, hydrodynamically lubricated 5000 PSI.

          However, in actual practice, these values are not achieved other than in theoretical design. In practice, the load capacity of each reduce to about 60% of theoretical values of 60 PSI, 700 PSI and 3000 PSI.

         For the greater majority of flat thrust washers, it is impossible to prevent some degree of hydrodynamic lubrication so that even in the worst design, the allowable loading will be greater than 60 PSI.

         In conditions of a sparse oil supply mated with steel, the high leaded tin bronze alloys (20% or greater lead content) are much more capable of satisfactory service providing their is no large amount of dirt or debris.

         If there is a fair amount of dirt present which is fairly coarse in particle size and movement or motion is infrequent or slow, the lower content leaded tin bronze alloys (20% or less) are preferred.

          For un-lubricated applications against steel, the preferred thrust washer materials are the sintered powdered bronze oil impregnated or Teflon-coated and plastic materials.

         For applications in which the non-lubricating film such as water or silicone fluids are present, the preference should be for Teflon-coated or impregnated bronzes or plastics.

         Oil Distribution Grooves: These are grooves that separate each sector of the thrust washers. The grooves must not go completely across the thrust face of the washer unless the thrust washer is completely immersed in the lubricant.

          If the lubricant is supplied at the ID of the washer, then the grooves should extend from the ID going outward covering about 80% of the distance to the outer edge.

         If the direction of rotation can be in either direction, the grooves should be radial; but if the direction of the rotation is fixed, the grooves should be slanted so that the viscous drag of the rotation will pull the lubricant into the groove in the direction of movement. The slanted angle should be between 10 to 40 degrees to the diameter.

          If the lubricant is supplied from the outer circumference (which is an undesirable condition) then the grooves must be slanted 20 to 60 degrees; but if the grooves are in the stationery member, they should be pointed in the direction of the rotation; if the grooves are on the moving member, they should be pointed against the direction of the rotation.

          Oil Collection Grooves: These grooves, like spreading grooves, should only go part way across the surface from 50 to 80% of the distance is suitable. They also should be slanted in the same direction as the oil-spreading grooves. These grooves are positioned just before the oil distribution grooves if the washer is supplied with oil from the ID.

          Oil Groove Dimension: The length of the groove is controlled by the degree of slant and should go about 80 to 90 % of the way across the annular surface.

          The groove cross-section should be in the form of a wide "V" to promote the formation of an oil film or a tear-drop design which blends into the surface.

          The thrust washer with grooves such as through grooves, tear-drop (or stopped oft) and tapered land grooves are superior to a plain washer. By adding four through grooves to the plain washer, the oil flow increases across the thrust surface and the load-carrying capacity increases by 30%.

          While restricting total oil flow through the washer with tear-drop grooves, an 85% increase can be obtained.

          With the tapered land groove which promotes an oil wedge, the increase in load-carrying capacity increases to 3 00% of a plain washer.

          According to theory, if the plain washer is perfectly flat, it would have no load capacity so surface waviness is not undesirable if it is fitted into a rigid aligned housing.

          The speed of operation of a thrust washer is not generally a problem if the surface speed is at least 25 fpm. At very high speeds - above 2000 to 4000 fpm - it may become a problem to supply ample lubricant although there is a compensating advantage of realizing a higher unit load. There also is the possibility of the oil carbonizing at this high speed, depending upon the load.

          Lubricant is important since the higher viscosity lubes such as SAE 50 offer greater chances that hydrodynamic film formation will be realized.

         The normal hydrocarbon oil lubricants are suitable for washers but the non-polymer modified oils are preferred for their higher viscosity.

          We are coming down to the home stretch, only three more chapters to go.  I know its a lot of information and a lot to take in, but if I have helped one person with this, I will be happy.  

That's it for today.  Until next time my metal loving friends...

Next Up: Chapter 21: Corrosion Resistance of Some Bronzes

Wednesday, November 30, 2016

Bearing Design Guide: Chapter Nineteen: Heat Treatment of Aluminum Bronze Alloys

C95400 Cast Aluminum Bronze

          The cast aluminum bronzes consist of copper and aluminum with lesser additions of iron, nickel or manganese elements, primarily to enhance the tensile strength, yield strength, hardness, wear resistance, fatigue resistance and corrosion.
          The more popular aluminum bronzes contain from 8 to 13 % aluminum, up to 5% iron, nickel and manganese in various combinations.

          As the aluminum content increases, the tensile strength, yield strength and hardness also increase but ductility decreases.

          The aluminum bronze alloys with 10% or more aluminum content can be heat-treated successfully to further increase the physical and mechanical properties of the alloy.

         The normal heat treatment sequence of aluminum bronze alloys with 10% or more aluminum content is to solution heat soak the alloy at 1650 degrees F for at least two hours, then quenching rapidly in water. Slow cooling results in "self-annealing" and produces a coarse structure with greatly-reduced properties.

          Following the heat-treatment sequence, a tempering treatment is required by reheating the casting to 1000 to 1150 degrees F for one hour then quenching in water.

          The heat-treatment changes the "as cast" alloy's micro-structure to a finer grain, resulting in substantial increases in tensile strength, yield strength and hardness but with a fairly high reduction in ductility.

          The wear resistance also is greatly improved by heat treatment without correlation to hardness. It does not seem to cause increased damage to steel shafts.

Solution Heat Treating
That's it for today.  Until next time my metal loving friends...

Next Up: Chapter 20: Thrust Bearings or Washers

Monday, November 14, 2016

Bearing Design Guide: Chapter Eighteen: Important Features of Aluminum Bronzes

         Aluminum Bronzes are a family of copper-based alloys offering a combination of mechanical and chemical properties unmatched by any other alloy series.  This feature makes the Aluminum Bronze the first choice for demanding applications.  No...I'm not on an Aluminum Bronze Campaign kick, BUT I love to learn about an alloy family that outshines the rest.  Well, at least in some areas!
So what are the attributes that make Aluminum Bronzes so hot and in demand? Check these out:

          Non-sparking: The non-sparking characteristics make the aluminum bronzes suitable for manufacturing of tools, equipment for petroleum and chemical processing, in mine service, handling explosives and in gas equipment.

           Cold Working Capability: The aluminum bronzes with less than 8% aluminum content are most suitable for cold working into tube sheets, flats, wires and other modified configurations.

           Hot Working Capability: The aluminum bronzes with 8 to 10% aluminum content result in
progressively increased mechanical strength and hardness of the alloy, requiring them to be hot worked. The hot working temperatures range from 1300 degrees F and up.

           Corrosion Resistance: The aluminum bronzes have outstanding corrosion resistance for marine, chemical and in atmospheric service because of its.rapid formation of an aluminum oxide film. If the film is damaged, scratched or abraded, this oxide film is self-healing and reforms almost immediately. The aluminum bronze alloys are resistant to exposure, to chlorides and similar other chemicals and to many acids.

          Oxidation Resistance: The aluminum bronzes are suitable for all air and steam and in temperature service up to 750 degrees F. They do not lose their mechanical strength as rapidly as the manganese bronzes or other leaded and tin bronze alloys. They are generally considered for temperature service.

          Magnetic Permeability: The aluminum bronzes have magnetic permeability often less than 1.07 at 200 oersteds. They are used in highly-stressed, rotating, non-magnetic parts.

           Electrical Conductivity: The aluminum bronzes have a relatively low value of electrical conductivity compared to copper. The lACS percentage drops as much as 75% of the original value.

          Since aluminum bronzes contain elements of aluminum, manganese, iron and nickel, the aluminum bronzes have an average of 13% lACS at 20 degrees C value of copper.

          Thermal Conductivity: Metals with high electrical conductivity usually transfer heat well, too. The aluminum bronzes, as other copper-based alloys, have better heat dissipation properties required for bearing service than steel, cast iron and other ferrous metals. The average aluminum bronze thermal conductivity value is about 15% of that of copper taken as 226 BTU/square foot/hour/degree F 68 degrees F.

          Thermal Expansion: Copper-based alloys have higher thermal expansion and contraction values than many other metals. Their approximate average expansion and contraction values are twice that of steel or cast iron. This is why it is necessary to adjust mating sizes if higher or lower than normal ambient temperature service is involved.

          The aluminum bronzes have an average coefficient of linear thermal expansion inch per inch per degree F as shown in the comparison below:

          Aluminum bronze             .000009 or 9 x 1 0 to the minus sixth power
          Manganese bronze            .000012 or 12 x 10 to the minus sixth power
          Leaded bronze                  .0000108 or 10.8 x 10 to the minus sixth power
          Tin bronzes                       .00010 or 10.0 x 10 to the minus sixth power
          Steel                                  .0000633 or 6.33 x 10 to the minus sixth power
          Cast Iron                           .0000655 or 6.55 x 10 to the minus sixth power

          Heat Treatment of Aluminum Bronzes: The aluminum bronzes with more than 9.5% aluminum content with small additions of iron, nickel or manganese which are added for specific properties (such as higher strength ,hardness, wear resistance, fatigue strength, etc.) can be heat-treated to enhance these properties more. Heat treatment increases the tensile and yield strength and hardness of the alloy but the elongation is somewhat reduced. The heat treatment of aluminum bronzes involve bringing the casting up to 1650 degrees F (900 degrees C) for two hours per inch of section thickness with a water or oil quench followed by a tempering treatment, the temperature of which must be selected in correct combination of strength hardness and ductility. This second treatment generally is done at 1000 to 1150 degrees F for one hour of section thickness.

          Stress Relieving: Stress relieving may be required when the copper-based alloy is used for bearings that are split longitudinally or when the stresses in the alloy from casting or other operation must be removed so as not to cause dimensional changes after machining the split. Such stresses may be removed or minimized by heating the casting, or semi-finished part at 1000 degrees F for an hour per inch of section thickness, followed by cooling in air (without quenching). For stress relieving leaded and tin bronzes, this temperature should be reduced to 600 degrees F.

          Wear Resistance: Tests have proven that aluminum bronzes have better wear resistance than the leaded tin bronzes, tin bronzes and manganese bronzes. (See Chapter 17)

That's it for today.  Until next time my metal loving friends...

Next Up: Chapter 19: Heat Treatment of Aluminum Bronze Alloys

Monday, November 7, 2016

Bearing Design Guide: Chapter Seventeen: Wear Resistance of Bronze Bearing Materials

And now back to the Bearing Design Guide...

  Although most sleeve bearings are designed to operate in a film lubricant separating the mating parts, this does not always happen. Generally, the mated surfaces will deteriorate gradually by wear of hard particles infiltrating the surface area along with breakdown of lubricant. Lubricant starvation also may occur.

          Many wear tests have been performed to determine the comparisons that various alloys exhibit under the same conditions of lubrication, shaft and material hardnesses and surface finishes.

          In comparison tests, the results were reported to be as follows:

          Aluminum bronze CDA 954 exhibited the highest wear resistance.
          CDA 954 performed better than 3.9 times alloy CDA 938.
          CDA 863 performed better than 2.5 times CDA 938.
          CDA 905 showed a better wear resistance over CDA 938 by 1.9 times.

          CDA 932 alloy was found to be more wear resistant than CDA 938 by 1.2 times.

This chapter is short, sweet and right to the point.  If you don't want to "wear" yourself down with machine maintenance and part replacements, be sure to choose the correct material for your project.

That's all for now, until next time my metal loving friends...

Next Up: Chapter 18:Important Features of Aluminum Bronzes

Monday, October 31, 2016

The "Other" Legend of Sleepy Hollow

Since it's Halloween, I thought I'd change things up a bit and tell a story that many people may not know.

We all know the famous telling of the tale of a Headless Horseman that terrorizes the Dutch settlement of Tarry Town, NY in a small hidden glen called Sleepy Hollow.

The Headless Horseman, is believed to be the ghost of a Hessian trooper that had his head shot off by a cannonball during a battle of the American Revolutionary War. Story has it that he "rides forth to the scene of battle in nightly quest of his head". 

Please enjoy the story below and read on to find out the "Other" Legend of Sleepy Hollow.

The Legend of Sleepy Hollow tells the tale of Ichabod Crane, a skinny, superstitious, scaredy-cat of a man who is a schoolmaster from Connecticut.  He is in love with Katrina Van Tassel, the daughter of a local wealthy farmer.  Unfortunately he is not the only one who wants Katrina's hand in marriage.  A local "hero" as some called him named Abraham "Brom Bones" Van Brunt also had his eyes on Katrina.  For whomever was to marry her, was also set to one day inherit the farmer's wealth.   

One night, Ichabod decided to attend a harvest party at the Van Tassels' home. He eats, he drinks, plays games and listens to ghost stories just like the rest of the guests, but really only has one thing on his mind and that is to propose to Katrina at the end of the night.  For one reason or another, his efforts failed and was left to go home from the feast alone and defeated.

As he traveled his sad and lonely route through the woods between Van Tassel's farm and the Sleepy Hollow settlement, he passed many of the so called haunted spots the town folk had spoken about in there stories. Spot after spot, he grows more and more frightened of the sights and sounds and just after riding under a devilishly shaped lightning charred tree supposedly haunted by the spirit of a British Spy,  Ichabod is met by a tall, dark cloaked figure on a horse.  Horribly shaken by the size and eeriness of this sight, he is more frightened to see that this ghostly figure did not have a head on his shoulders, but it sat just under his ghostly arm along side his saddle. 

In a frightful race to the bridge next to the Old Dutch Burying Ground, where the Headless Horseman is said to "vanish, according to rule, in a flash of fire and brimstone" after crossing it, Ichabod rides like the wind, pushing his sluggish plow horse down the Hollow and over the bridge. As Ichabod looks back, he is met with the horror of the ghostly figure crossing over the bridge.  The horseman stops, rears his horse, and throws his severed head into Ichabod's frightened face.

As the towns people awakened the next morning, Ichabod was no where to be found as if he just completely vanished from existence. The only evidence that he was ever there was his horse found wandering, a tattered hat, a broken saddle and the puzzling remains of a shattered pumpkin.

With never hearing from Ichabod again, Katrina took the hand of Brom and was married shortly thereafter.   Many say that Brom was behind the whole thing and that he himself was the Headless Horseman as he always has a look of uneasiness as the story of Ichabod is being told.

Many people have different opinions of the story and interpret it in their own way, but usually come to the same conclusion that the ghostly Headless Horseman was really Brom in disguise. Still no one knows where Ichabod Crane has gone and as the story goes on generation after generation the old Dutch story tellers continue to believe and preach that Ichabod was "spirited away by supernatural means," and this leaves us with the legend about his disappearance and sightings of his lost and lonely spirit.

You may think that this is the only ghostly story to come out of Sleepy Hollow, but in fact you are wrong.  There is but another one and I am here to tell you, The "Other" Legend of Sleepy Hollow.  It only seems fitting that is a story about a "bronze" statue.  Who knew bronze could be so scary?!

The Bronze Lady

Halloween night 1916, on the heels of a dare a little girl wanders into the Sleepy Hollow Cemetery. She walks slowly and cautiously around and in between the mausoleums and headstones and then out of no where, she is stopped in her tracks by a sorrowful sound.  As she listens more closely, it is the sound of a woman crying.   

Pushing her fears aside, she follows the sound and is led to a larger than life statue of a seated woman.  The crying has stopped, but she notices something strange about the woman's face.  She climbs up in to the lap of the statue, caresses its face and finds tears falling from the eyes. 

Over the years, some just hear the crying, others just see the tears as the statue sits across from the tomb of the Civil War general Samuel M. Thomas.  Some believe she cries because of a tragedy in her life.  Perhaps, the death of General Thomas. The statue was in fact ordered by his widow shortly after his death in 1903.  The artist was Andrew O'Conner Jr. and he named it Grief.  It is said that she didn't really like the statue at first because she didn't think the woman was gay enough. 

I cannot find any stories or articles about any strange occurrences documented about this statue prior to 1916.  Is it possible that Mrs. Thomas passed in 1916 and maybe it is her spirit in the lady crying over her deceased husband? 

Some say the "tears" can be explained with a scientific theory that its just the statue interacting with the weather and the environment, but the question that always remains is, where is the crying coming from? and that is one question that has yet to be answered.

Tell me...are you brave enough to go visit this statue?

I hope you enjoyed my story telling Halloween edition of our Metalchic Blog.  I hope you have safe, fun filled, Happy Halloween!

Monday, October 24, 2016

Bearing Design Guide: Chapter Sixteen: Effect of the Casting Method on Bronze Alloys

          The casting method should not be ignored but given consideration of the type of service the bronze alloy will be subjected to.

           In particular, the type of load - whether steady and continuous, intermittent or with shock impact or pounding loads - the surface speeds to be encountered and other important features required to be met.

          The casting method has a definite impact on the bronze alloy such as the resulting grain size, density, hardness, mechanical and physical properties, soundness and structure.

          In general, the slower chilled or cooled casting will give rise to coarser and larger grain size. These have a profound effect on the surface qualities, coefficient of friction, wear rate or wear resistance and loads.

          The faster cooled or chilled castings result in greater density, hardness, finer grain size, improved soundness and structure.

           Referring to the illustrations on the following page, please note the finer grain sizes developed by each method of casting.

          Sand Casting: Since molten bronze is poured into a sand mold, the sand or silica having thermal insulating characteristics, will cause slow cooling or chilling of the casting in air. This slow cooling permits the grain size to grow larger, the density, the soundness and structure to be less than by other casting methods.

          Permanent Molded or Chill Casting: The thermal insulating sand is replaced by nickel steel or cast-iron dies. The metal mold quickly chills the casting and this faster solidification results in finer grain size, no interconnected porosity, finer surface finish and improved physical and mechanical properties.

          Centrifugal Casting: Molten metal is poured into a rotating steel or cast-iron die. The centrifugal force impacts the molten metal against the inside of the die, eliminating any porosity. the rotating or spinning die is then sprayed with water coolant to obtain a faster chill than the first two methods discussed the finer grain size further improves the physical and mechanical properties still further.

         Continuous Casting: The molten metal flows by gravity through a graphite die which is chilled
immediately by the cooling jacket surrounding the die. This faster cooling further reduces the grain size and results in still higher physical and mechanical strength.

          The average increase progressively in the tensile and yield strengths is about 5000 to 10,000 PSI and hardness is increased by 10 to 20 points of Brinell hardness.

          Remarks: To further enhances the physical and mechanical properties of the bronzes, extrusion and forging operations can reduce the grain size additionally. These are special processes and the four methods of casting described earlier in this chapter cannot achieve comparable mechanical and physical strength.

Casting Effect On Grain Size and Density

 you can see above, things may look the same on the outside, but they can be very different on the inside.  It is always important to really understand the final application your part will be used in so you know which casting method would be best for you.

          Well...that's it for today. I say goodbye for now. Until next time my metal loving friends...

Tuesday, October 18, 2016

Bearing Design Guide: Chapter Fifteen: Comparative Casting Methods

      When I first starting working here and learning the industry, whenever I would think about molds and castings I would automatically picture Play-Doh in my head.  I mean its a little messy, but seriously, who doesn't like playing with it?  I'm a grown woman and still can't keep my hands off it when my kids have it out.  You can basically manipulate that stuff into whatever shape or form you want and how cool is that?!   Here at Atlas, it just puts that end result on a bigger scale and there are so many more methods of casting your material to get to the desired finished product.

         I love learning about new things and teaching others too whenever I can.  About four years ago I had the opportunity to go to a local elementary school and help the 2nd grade class learn about mass, matter, solids and liquids and just how material can go from solids, to liquids, and right back to solids again.  So instead of Play-Doh...I had a better idea.

          When I was explaining to them that a customer can come to us and ask us to make something for them in the exact shape and size that they want, I decided to show them what I meant.  In order to give the kids a visualization, I decided to bring in some candy melts and candy molds.  As the candy melted in the pot the kids were amazed just how quickly the candy melted.  Once it was ready I showed them the candy mold and started to fill them with the melted chocolate just as if we were pouring molten metal into a mold.  And, just like that with in seconds it began to harden and take a solid form again in the exact shape of the candy mold.

          Needless to say they were pretty amazed and of course a little more excited about the candy treat they were about to have.

          There are various casting methods available for casting ferrous and non-ferrous metals. A brief
description of each follows with a listing of advantages and disadvantages as well as other pertinent data.

Sand Casting: Moist bonded sand or resin coated sand is packed around a wood or metal pattern of the item or items to be cast. The pattern is removed and the cavity or cavities are filled with the molten bronze.

          Following the air cooling of the mold, the casting or castings are removed to be cut or sheared off from the gate and runner as individual castings. Watch the video below.


          Advantages: Any metal can be cast -ferrous or non-ferrous- without limitations to size, weight or shape. It is one of the most versatile and low-cost methods available including tooling costs. This method is economical and suitable for low to unlimited quantities.

          Disadvantages: Close tolerances are difficult to achieve and some machining may always be necessary. Interconnected porosity is generally inherent to this process and a fairly rough surface finish averaging 1000 RMS is obtained. The typical tolerances range from plus-or-minus 1/32 to as much as plus-or-minus .090 and greater across parting lines.

     Permanent Mold Casting: The mold cavities are machined out of a nickel steel or cast-iron die blocks since they are designed for repetitive use. Generally, steel cores are used although sand cores of intricate design can be used. Because of the casting heat, the sand cores are expended while the steel cores can be expected to give reasonable life before they are replaced. The mold halves are clamped together and the molten bronze poured into the cavity by gravity without turbulence or under a low-vacuum pressure.

          The mold is opened within a few seconds following approximately a 50-degree drop from casting, temperature with aluminum bronze or manganese bronze alloys. The casting with gate and riser is ejected immediately.

          Advantages: Good dimensional accuracy is obtained, good grain size and structure results from the rapid chill. Casting tolerances possible range from plus-or-minus .010 to plus-or-minus .015 per side or surface and parting lines can beheld to about plus-or-minus .030.

Casting variations from casting are rarely existent except after tooling begins to show signs of wear.

          Disadvantages: This method is normally limited to non-ferrous alloys. Size, shape and intricacies also are somewhat limited, although many sections can be cast thinner than sand castings. To justify this method, a moderate volume of 1,000 through 50,000 pieces yearly would be necessary to offset expensive tooling costs. Each individual casting must have a gate and riser which reduces the effectiveness of the yield.

          Centrifugal Casting: In this process of casting, steel or cast-iron dies are used and the molten metal is poured into the rotating or spinning die. After pouring, a water spray is directed onto the rotating die, cooling it more rapidly.


           Advantages: Since the molten metal is forced by centrifugal action of the rotating die, the metal thus centrifuged is free of porosity, more dense with a structure designed to carry heavy loads with impacts. The alloy cast in this method can withstand substantial hydraulic pressures without leaking. This method is suitable for ferrous and non-ferrous alloys.

          Disadvantages: Although a controlled stock allowance is set by the die, a machining operation is generally required to remove the rough surface finish and excess stock.

         Continuous Cast Method: In this process, the die is made out of carbon graphite which is surrounded by a cooling jacket through which water flows to chill and solidify the cast tube, bar or shape. As it exits from the furnace proper by gravity, the casting solidifies. It is pulled out slowly by pull rolls or pinch rolls. This rapid cooling reduces the grain size and as the casting exits from the lower section of the holding furnace, a homogeneous micro-structure is obtained.

           Advantages: A minimum of stock allowance can be controlled to plus-or-minus . 015 reducing the amount of machining necessary as in other methods. Various shapes are cast reasonably to size without need for precision machining. The resulting structure is generally suitable for acceptance by radiographic tests and will withstand a substantial hydraulic pressure without leaking.

           Disadvantages: Initial high unit cost investment and space; graphite dies must be replaced after each run and each size requires a cooling jacket.

Die Casting: Molten metal is forced into closed steel dies at high velocities by application of pressure.


          Advantages: Excellent dimensional accuracy is obtained across parting lines plus-or-minus .005 and plus-or-minus .001 to plus-or-minus .003 across extremities and surface finishes 100 RMS or less.

          Disadvantages: This process requires high volumes of20,000 to a million pieces or more since the relative die cast is extensively high. It also is limited to non-ferrous metals and porosity may be encountered as a result of entrapped air in the die. Size is limited to 3 feet square and under 15.0 pounds.

           Investment Casting: Various ferrous and non-ferrous materials are used to make a wax or thermoplastic pattern which is expendable in the process. Hot wax or plastic is injected to make a pattern under pressure into the die and multiple patterns are mounted on a common sprull made of the same material. The assembly, called a tree, is dipped into a liquid surry followed by several immersions in dry fluidized bed of fine sand. Each dipping operation requires drying time. As many as five to eight clippings are required to build a shell around the tree. For wax removal, the tree is placed into a steam autoclave. Before pouring, the molds are kiln-dried and tongued from the furnace to the pouring box and poured while cherry red.

          Advantages: There is no parting line and no draft. The surface finishes are less than 125 RMS and shapes are cast which couldn't be produced by other methods. This process becomes most economical when two or three machining operations can be eliminated. The typical tolerances are usually plus-or-minus .005 and high volume is not a criterion. Tooling is less costly than pressure-die casting.

          Disadvantages: Although this method has the fewest design limitations of shapes, size or design, pound for pound the cost of this process is comparatively high.

          There are several other methods of casting which include shell molding as a modified sand casting which offers closer tolerances as plus-or-minus .007 to .015. The surface finish is much better than sand casting and there is better definition of details such as lettering, etc. The cost of pattern equipment is higher than for sand casting and the process necessitates higher quantities.

  Plaster molding and ceramic mold casting are similar to investment casting. But the molding material is more expensive and the processes have never been suitably automated to reduce the labor intensity of making the molds. The casting tolerances are reasonably close to investment casting.

          I have to tell you this was the best post I have done so far!  Watching all the videos was so much fun.  I hope you enjoyed learning about the different options of casting and watching how all of the processes are done.

Well...that's it for today.  I say goodbye for now.  Until next time my metal loving friends...

Next Up: Chapter 16:Effect of the Casting Method on Bronze Alloys

Monday, October 3, 2016

Bearing Design Guide: Chapters Thirteen and Fourteen

Bearing Design Guide: Chapters Thirteen and Fourteen

The next two chapters focus on lubrication and lubricants so I have paired them up for this weeks post.

Bearing Design Guide: Chapter Thirteen: Lubrication & Lubricants

          The importance of an oil depends mainly on its film forming ability which depends further on its viscosity.

         An oil of lowest viscosity is generally more suitable for an application since a higher viscosity oil will waste power to overcome the internal friction of the oil itself

          There are many ways to supply a lubricant to a bearing.  We will explore the different options below.


      Pressure lubrication is probably the most positive and efficient means to provide lubricant to a bearing.
In addition to offering a more copious supply of oil lubricant, up to an average pressure of 50 PSI, it coats the bearing, maintaining a more stable viscosity range and it assists in flushing out dirt and wear debris from the bearing surface.


  Oil bath lubrication is where the bearing is submerged in oil which makes it the next reliable method to the pressure-fed oil. The shaft speed should not be so great as to cause excessive churning of the oil.

          Splash-fed lubrication involves the oil being splattered onto the bearing surface by movement of other adjacent parts. The housing should be reasonably oil-tight to prevent excessive loss and leakage of the lubricant.



Oil ring lubrication involves a revolving or processing ring on a shaft in contact with the oil sump. When the shaft is at low speed, sufficient oil may not be brought to the bearing surface or if the shaft speed is too great, the oil will be centrifuged beyond where it is needed. It also may not keep pace with the oil required.

          For best results, it has been proposed that the peripheral speed should be in the range of 200 to 2000 feet per minute. The safe load based on full hydrodynamic lubrication mode should be reduced by one half of pressure lubricated bearings.

          Wick or waste-pack lubrication delivers oil to a bearing surface by capillary action of a wick or waste-pack as done in many old railroad axles using bobbitted bronze backed partial sleeve bearings.


          The safe load when compared with pressure-fed full hydrodynamic load should be reduced to 1/4 of the load.

         Grease-packed bearings: Grease is generally packed to surround the bearing and although is substantially less effective than oil, it is much more permanent but the bearing will generally operate in boundary conditions.

Bearing Design Guide: Chapter Fourteen: Lubricant Selection

           The selection of a lubricant is based on various factors such as the type of operation, whether full hydrodynamic, mixed film or boundary film conditions in addition to the surface speed and bearing load involved.
          Various lubricant articles suggest some recommended viscosities for specific services.
          As a rule of thumb, the following suggested viscosities should be considered on the basis of surface speed with a qualified load.

                                Speed(fpm)                 Viscosity(sus)                   SAE Oil
                                 30 or less                       1200-1800                           80
                                 70                                    800-1200                           70
                                 150                                  500-800                             60
                                 300                                  300-500                             50
                                 600                                  150-300                             40
                                 1200                                120-150                             30
                                 2400                                  90-120                             20
                                 5000                                  40-90                               10
                                 over 5000                            5-40                                 5

          As a general rule of thumb, heavier oils are recommended for high loads and lighter oils for high speeds.
          In order to obtain a quick conversion of viscosity (sus) to centistokes (cSt), multiply the (cSt) value by 5. The multiple will be the approximate (sus) value.

         To obtain the (cSt) value, divide the (sus) value by 5.

         These results are reported to be accurate within 7% in the range of75 to 7000 (sus) and 15 to 1500 (cSt).

          But also be cautioned that this assumption should not be used below 75 (sus) or 15 (cSt).

          For more explicit lubrication data, we suggest you refer to the CBBI manual or to the Machine Design article of March 10, 1966.

I hope this weeks post wasn't too DRY for you and this helped you learn about lubricating methods with ease.  Anyway, that's it for now.  Until next time my metal loving friends...

Next Up: Chapter 15: Comparative Casting Methods

Tuesday, September 27, 2016

Bearing Design Guide: Chapter Twelve: Recommended Shafting and Journal Material

           The shaft or journal is the mating part of any bearing application and, therefore, requires ample consideration when mated with one of the many bronze alloys which have varying mechanical properties compatibility and hardnesses.

          The designer must first choose a shaft or journal material that will satisfy the applications requirements of torque, shear stress, fatigue strength, fracture toughness, rigidity, wear resistance, corrosion resistance and have the ability to provide a good surface finish and sufficient hardness.

          Various type of shaft or journal materials such as cast gray iron, modular iron, forged steel, induction hardened steel, case hardened, chrome-plated and polished steels are used.
The cast iron, gray and modular iron shafts offer low cost but since they do not pose all of the desirable shaft properties of steel, they have somewhat limited usage. Further, they require specific grinding and polishing instructions.
          The more popular shafting steels are mild SAE 1020 and low-carbon steels of SAE 1040. The highercarbon steels- AISI 1045, 1060,4140,4340, 52100 and M 50 tool steels and stress-proof steels are used after hardening, grinding and polishing finish.

                      The general range of such shafts are classified by hardness as follows:

                                                      Soft 165 BHN to 290 BHN
                                                      Medium 300 BHN to 390 BHN
                                                      Hard 400 BHN to 1000 BHN

          There are commercially available standard shafts which have soft cores but a sub-surface which is case hardened to various depths, chrome-plated and polished.

          Tests have proven that various hard bronze alloys, when mated with a soft shaft, will tend to seize or weld to the shaft at substantially lesser loads than when mated with a hard shaft.

          The harder shaft will permit an appreciably higher unit load to be sustained with a lower wear rateresulting in extending the life of the assembly.

          With the high leaded bronze aUoys, which range in hardness of 50 to 70 BHN, a soft or mild steel, or cold-rolled steel shaft ranging in hardnesses of 165 BHN to 290 BHN are a suitable combination.

          Shafts mated with the high copper-tin alloys which contain little or no lead having a range of hardnesses of 70 BHN to 80 BHN, would be adequately served by the medium shaft hardness range of 300 minimum.

           The aluminum bronze alloys, not heat-treated, with average hardness of 140 BHN to 170 BHN are best combined with the hard shaft category of 400 BHN minimum.

          Heat-treated aluminum bronze alloys, including the manganese bronzes with hardness ranges from 180 BHN to 240 BHN, require the shaft hardness range to be above 500 BHN or recommended to be used with shafts RC60 minimum being preferred.

          In bearing tests conducted by various sources, the results indicated that the harder shafts with the highest polished finishes offer the best combination for improved load carrying ability over the speed ranges tested with the lowest wear rate.
          Initially, most bronze alloys will show a high wear rate while "bedding" or "running in" but will level off to a more constant lower value.

          The surfuce finishes of the shaft have a profound effect in any bearing application on the lubricating mode.

          In full hydrodynamic conditions, the bronze bearing alloy should have a RMS finish in the range of 25 to 32 RMS and the shaft or journal held to polished to 6 RMS to 12 RMS.

          In mixed film conditions, the bronze bearing alloy can range between 32 RMS to 43 RMS and the journal polished to 8 RMS to 16 RMS. Since the bearing goes in and out of full hydrodynamic mode, the better the finish the less the initial wear.

          For boundary conditions, where the surface speed is much lower, the relative roughness of the bearing .and journal are not as critical. However, it is best to maintain at least a 43 RMS to 63 RMS finish on the bronze bearing and the journal to 32 maximum.

          A hardened and super finished shaft has the ability to double the load before seizure when compared to a soft shaft finished to 10 RMS under the same conditions. In loads over 3000 PSI, a 10 RMS shaft finish is recommended.

          In the case of sintered powdered metal self-lubricating bearings, a cold-rolled steel or mild steel shaft would be acceptable. However, a hardened carbon steel shaft such as C1137 with chrome-plating will double the PV factor while reducing shaft and bearing wear.

          Whenever a stainless steel shaft must be considered because of corrosion conditions, it is not
recommended that the 303 austenitic stainless series be used in combination with sintered bronze bearings unless it is chrome-plated or the sintered bearing is re-impregnated with a special lubricant containing oxidation and corrosion inhibiting additives.

          If a stainless steel shaft is necessary, it is recommended the 400 SS Series with the 440 C being the preferred shaft since it does not require the special lubes.

           Remember, in all cases, that the harder the shaft, the greater the load-capability and the better the surface finishes, the less the wear rate with longer bearing life. Shaft roundness and shaft size control without nicks, gouges or sharp edges will offer the most satisfactory performance.

 Next Up: Chapter Thirteen: Lubrication & Lubricants
Chapter Fourteen: Lubricant Selection