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Press fit considerations for Iridited parts

We have an operation in manufacturing that is pressing a shaft into a backplate, and the shaft is galling during the operation. We have successfully performed this press fit operation in the past on parts that were not coated. Now at the same dimensions and amount of interference, the coated parts are not going together cleanly. Engineering doesn't feel the Iridite should make a difference in the press fit, and point out that there are other factors which could be responsible for the issue (which there probably are). The question is, COULD Iridite affect the press fit? A change to surface friction or hardness that would initiate the galling? We have done some test press fits with and without Iridite, but don't think the tests are conclusive because all the variables weren't controlled.

Terry Bartick
designer - Portland, Maine, USA
August 25, 2010

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August 26, 2010

Hi,Terry

Iridite is a trade name for chromate conversion coating chemistry. People are usually referring to aluminum components, but that trade name can occasionally be used to refer to chromate conversion coating processes on zinc plated items. So, just to be sure, we're talking about aluminum parts here?

Regards,

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

Yes, the parts are aluminum. The backplate is 6063-T5, and the shaft is 6061-T6.

Terry Bartick
- Portland, Maine, USA
First of two simultaneous responses -- August 27, 2010

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It could be that the uncoated parts have some residual lubricant whereas the Iridited parts were clean and dry.

Jeffrey Holmes, CEF
Spartanburg, South Carolina
Second of two simultaneous responses -- August 27, 2010