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topic 1576



Q. I am looking for a plating or finishing process that will provide an extended life to centering cams. They are being used on an assembly fixture which must position magnets which are approximately 3 inches in diameter by .375 thick. The centering cams are made of non-magnetic stainless steel. These cams are positioned with an internal ring gear which causes them to wipe the magnet as they center it.

The wiping action against the magnet as it is centered is causing excessive wear on the cams. I am looking for a finish that will minimize the amount of wear and provide a significantly longer life for these cams.

This method of positioning/centering was chosen due to the need to fit the fixture into an extremely limited space. At this time, I only have three of these cams in this one fixture and I do not believe that I will be using more than one or two more similar fixtures with this wear problem. This will make the cost of doing this finishing of the cams quite expensive but probably not nearly as expensive as having to make and replace them very frequently.

So far, I have been unable to find anyone who can give me any preferred finish, plating, metal spraying, plasma coating, or such with any significant amount of information as to how much of an improved wearing effect that such a finish might provide. Can anyone provide some help in making such a determination?

Vern Castle

Hard Chromium Plating
by Guffie
from Abe Books



A. The traditional wear coating for such applications has always been hard chromium plating. Very low friction, very hard, very low wear, non-galling, readily lubricable if necessary. There are individual cases where a different coating may be superior, but the other coatings are usually more expensive, and have one limitation or another. I can't picture your application in its entirety, but it sounds like hard chromium plating is the first thing to consider.

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


A. I agree with Ted Mooney. I am familiar with several alternatives, especially PVD hard coatings. But for a small number of parts each batch, it will cost you more to coat that make a new part. I have been through many similar discussions with customers and had come up with the same answer. One of the problem you may have is too much friction between materials. Hard chrome will be my first choice.

Mandar Sunthankar
- Fort Collins, Colorado


A. You didn't mention how hard these cams are, or exactly what metal they were made of. If they have had any hardening at all, the next step would be to try cryogenic processing to improve the abrasion resistance. Then a coating containing a lubricant will reduce the friction, and provide longer life.

F. Diekman
Streamwood, Illinois, USA


A. Perhaps, and this is a good guess, these cams can be coated with nylon at the wear points. It will most likely give you the wear resistance and reduced coefficient of friction you require. I have performed such services in the past for many companies with expensive locating, positioning, driving devices.

Best of Luck,

Jim Cummings
- Buffalo, New York


A. Surface hardening by nitriding may provide the additional wear resistance that you require at a reasonable cost. 300-series stainless steels respond well to the proprietary nitriding processes commonly available at many heat treating shops.

larry hanke
Larry Hanke
Minneapolis, Minnesota


A. Hard finish on a stainless cam. Have you given any thought to Ceramichrome? It's a radiation impinging process that drives the ceramic and chrome gases into the target. Some aircraft engine cylinders are finished this way.

G. Loftiss
- Elk City, Oklahoma


Q. I have a very similar situation, except all of my parts have to be electropolished for very clean vacuum service. Parts in this condition fuse together on contact. What surface treatment will provide the necessary hardness differential, will not outgas, and survive a 500 °C bakeout? Lubricant are pretty much out of the question. Thank in advance for any assistance.

Richard Miller
-Dublin, California


A. Chrome plating of electropolished stainless steel is commonly done, and should prevent the fusing together, as long as the contacting surfaces are stainless against chromium. Chromium probably won't fuse to chromium, but may not offer as reliable a reliable coefficient of friction.

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

Effect of Surface Coatings and Treatments on Wear
from Abe Books



A. We offer a proprietary surface hardening for austenitic stainless steels. Contrary to nitriding, it does not reduce the corrosion resistance of austenitic stainless steel, neither does it change the size, shape, color or surface roughness of a component. No coating is added. The surface is hardened by pure diffusion, resulting in a surface hardness of 1100 to 1200 Vickers (comparable with > 70 Rockwell C) for 316 stainless steel.

Very closely toleranced machined austenitic stainless steel parts can be hardened without any need for re-machining.

deleted by editor
deleted by editor

Ed. note: Apologies everyone, but this forum just won't work for trying to publicize proprietary products. For one thing, people won't generally comment negatively about a proprietary product for fear of the company's lawyers -- leaving the readers seeing only the glowing, positive side and never the disadvantages (which is completely inappropriate for a technical Q&A forum). And who pays for the advertisement? Not the company who posted it, but the supporting advertisers of this site who offer competitive products. We thank our advertisers for making this site possible for camaraderie and technical discussion, and we can't ask them to also pay their competitors' advertising bills :-(

Those wishing to introduce the readers to a class of coatings, a technology for coatings, or an approach to coatings, should please pose the proposition generically rather than as if only a single vendor can offer the solution; or they should take an advertisement here or elsewhere rather than using forums for their ads. Thanks!

February 25, 2012



March 7, 2012

A. Hi Ben!

No, 304 and 316 are almost identical when it comes to mechanical properties. Those are going to be determined by the amount of cold working the material has seen, so you can get annealed, quarter-hard, half hard, full hard, etc with both rods and sheet. Thick things like plate are going to be annealed, and low hardness.

Stronger non-magnetic stainless steels would include the Nitronic series (Nitronic 40, Nitronic 50, Nitronic 60) and A286 precipitation hardenable stainless steel.

Good luck!

lee gearhart
Lee Gearhart

November 14, 2012

A hard austinetic stainless steel alloy would work nice for you. My company happens to make specialized hardfacing welding alloys for this purpose.

chris postle
- cleveland ohio usa

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