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Q&As since 1989
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Surface Finishing/Profile/Roughness for Copper Washers
Q. DEAR SIR,
WE ARE A THRUST WASHER MANUFACTURING COMPANY AND ARE RECENTLY DEVELOPING SOME ENGINE BRG THRUST WASHERS IN COPPER ALLOY. FOR A PARTICULAR ENGINE, THIS WASHER HAS A PROFILE OF THICKNESS ON THE FACE (CRANK FACE) WHICH WE ARE ACHIEVING; HOWEVER THE SURFACE FINISH REQUIRED IS 16 MICRO INCHES ON THE FACE. WE TRIED VARIOUS BURNISHING METHODS ON CONVENTIONAL LATHE, ETC., BUT NO RESULTS. COULD SOMEONE SUGGEST SOME PARTICULAR BURNISHING TOOL DESIGN OR PROCESS TO ACHIEVE THIS FINISH ON A COPPER WASHER FACE?
REGARDS,
SHANTANU PARDESI- POONA, MH, INDIA
A. Nearly all bearing parts, races, are done in mass finishing systems here in the USA. Unless there are some other special requirements your specifications look standard.
AF Kenton
retired business owner - Hatboro, Pennsylvania
Specifying surface finish for copper washer interfaces
Q. I have read a lot of your postings regarding the Ra to Rz and reverse conversions. Need help in a similar situation. My interface is a copper washer interface in a banjo bolt joint. I need to define the surface finish of the surfaces in contact. Is it advised to mention Ra or in Rz or both?
Please advise urgently.
product designer - Chennai, India
May 20, 2014
A. Good question. To play it safe, I'd go with both. The reason is there are different people, countries, and industries involved, so the more info you can provide the more likely you are to get what you want.
AF Kenton
retired business owner - Hatboro, Pennsylvania
May 21, 2014
Q. What finish do you suggest for this interface. I have Ra 2 being specified, Rz25 and Ra 3.2. Any suggestions from experience?
Nirmal Mathew [returning]product designer - Chennai, India
May 22, 2014
A. Not sure how to answer you. You are talking about a fine finish. I don't know if the finish is possible because I do not know anything about the raw material. Meaning if your raw material is of poor quality or grade, you may not be able to get that fine of a finish of Ra2. Then again if someone else is making it that tells them something about the quality you are looking for.
AF Kenton
retired business owner - Hatboro, Pennsylvania
May 23, 2014
Q. Still have not completely come out of this issue ... the component is to be used on an engine and hence the finish is quite important. If I give a rough face, obviously the copper washer will not seal as leakage or seepage will be there through the asperities.
Currently decided to go with Ra 1.6.
If any other suggestions please help.
- Chennai,Tamil Nadu, India
January 2, 2016
A. Hi Nirmal. This is probably not so much a suggestion for you as a reminder to other readers who may be dealing with copper washers and be less familiar with them: It is my limited understanding that copper washers are supposed to be annealed to dead soft condition so they can do a better job of sealing. I have also seen such washers plated with matte tin, but I am not sure if that improves the surface roughness or not.
Regards,
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
January 2016
A. Got a little better understanding of your problem. I don't think your washers are good candidates for mass finishing. I still do not know what Ra you are starting with, on top of that a mechanical process will probably work harden your parts unless you go to a dry organic process. That will give you a better smoother finish, but it will take a lot longer and you have to be careful of volume and/or part on part contact.
AF Kenton
retired business owner - Hatboro, Pennsylvania
January 7, 2016
A. Thanks Tony. Maybe the full answer is that the washers need to be hard/hardened, polished to whatever Ra Nirmal needs via mass finishing, then annealed to dead soft before use?
Regards,
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
January 2016
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