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topic 2501

Chrome repair of undersize parts

A discussion started in 1999 & continuing through 2017


Q. I am looking for a chroming process to buildup bearing journals on heat treat shafts that have been ground slightly undersize.

I once saw a process that utilized a paste, an applicator and a small power source to produce a very rough satin chrome finish to the part while it rotated slowly in an engine lathe. The process was effective at salvaging parts that would have been scrapped and for repairing worn machine parts.

Any help in identifying this process and/or a source for equipment would be appreciated.

Don Golien
- Clarksville, Arkansas


A. The process that you refer to is Brush Plating. There are numerous vendors of the solutions and equipment. Brush chrome historically is a "cap", very thin applied over nickel or cobalt or other choice of metal. Liquid Development Corp. has a trivalent chrome gel that requires flow thru technology that is capable of a thicker coating of chrome. It is not capable of thicknesses from a chrome tank, but is quite a bit thicker than "regular" brush chrome.

An engine lathe is an expensive device to use if you are using the lathe as the negative source. It does the bearings no good. Nearly every brush plate vendor sells a rotating device that can be mounted on a table top, making drip collection a lot simpler and the equipment significantly more portable.

Solutions other than the trivalent chrome are sold by many vendors, so shopping can save money if you are going to use it a lot; and buy from a well known company.

You may not need chrome. Hardened nickel or cobalt may be enough.

James Watts
- Navarre, Florida


A. I want to add (many years later) that we have successfully repaired industrial engine's crankshafts using chroming processes. OEM do not recommend this practice but, instead of buying a new crankshaft, which usually takes 8 to 10 weeks to be delivered from factory, we can in eight days rebuild the damaged bearing surfaces back to original specs. For any industrial process this means equipment availability and up-time for achieving production targets.

Juan M. Gonzalez
- Bogota, Colombia

April 12, 2013

Q. I want to perform hard chroming on shaft in order to compensate the reduction in thickness where bearing installed.The temperature around shaft is 200 °C. Does hard chroming maintain its strength at this temperature?

Asim Rehman
Engineer - Karachi

April 12, 2013

A. Hi Asim. Chrome plating should be okay, but electroless nickel plating or brush plating with nickel may be easier (and probably better). When you say "compensate the reduction in thickness", though, I hope you are referring solely to restoring the dimensions; you can't neck down a shaft and compensate for the loss in strength by chrome plating it. Good luck.


Ted Mooney,
Teds signature
Ted Mooney, P.E.
Pine Beach, New Jersey

April 14, 2013

Q. Thanks Ted Mooney, P.E. RET, Yes I was referring to restore the shaft dimension where bearings are installed. Further I also want to know what are the parameters to check the hard chroming quality?

Asim Rehman
Engineer - Karachi, Pakistan

May 5, 2013

Q. We are facing problem in balancing the rigid shaft, i.e., after performing balancing of the shaft, if we remove the shaft from machine and again install by rotating 180 degrees, the machine again shows that the shaft is unbalanced. Have also tried in different machines but same result comes. Please help on this.

Asim Rehman
Engineer - Karachi

May 7, 2013

A. Perhaps there is a confusion with the term "unbalanced".
Balance refers to mass distribution around a center or axe, not dimensions. Dimensional variations are usually referred to as "run-out".

G. Marrufo-Mexico

Guillermo Marrufo
Monterrey, NL, Mexico

May 7, 2013

A. Chrome for bearing shaft repair should be put on at 0.005" minimum and ground to no less than 0.003" per side.

Grinding requires lots of coolant and the proper wheel. The wrong choice of resin and grit will lead to failure! It requires very thin passes or it will peel from the heat.

QC is what your customer wants. Normally if it is sort of bright with no white areas, it probably is good IF it lives thru the grind operation.

Judging from your last post, the machinist is loading the part off center, both times, probably in the same direction with the part rotated 180. Off center is definitely a machinist problem.

James Watts
- Navarre, Florida

May 10, 2013

A. Sir: If your shaft was hard chrome plated, and was not ground properly, it is probably "off center". This means that your shaft is not completely round after plating and grinding; this will make your shaft vibrate after installation. I will recommend that you take a digital micrometer or caliper and measure the area that was plated all around, see if you find different readings. Thanks.

Nick Cordero
Plating Specialist - New York, New York

May 17, 2013

A. I don't mean to start a discussion about geometry or mechanics here but I have to disagree with Mr. Cordero's comment about roundness. A diameter could be perfectly round and still run out. In situations of very tight tolerances, this is generally a consequence of part distortion or different machining operations using different surfaces or items of the part (i.e., between centers or resting on journals). Regards,

Guillermo Marrufo
Monterrey, NL, Mexico

316SS Part Is Undersize

August 20, 2017 -- this entry appended to this thread by editor in lieu of spawning a duplicative thread

Q. Can we repair the Dia. of SS-316. Because first we have done machining, but after machining the dia. is 1 to 2 thou down. So Please tell us can we increase this dia with heating or compression or with any other thing? Otherwise our part will be scrap :-(

Ahmad Kareem
- Saudi Arabia

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