Question for the PROS in the house

[hoytheld]

Hello,

I have a question. At my work we have a specialized knife that fits into a housing. The marriage of these two are very close in tolerance. After a time in service, the knife (which is cylindrical) wears out. What can the knife be plated with to bring it back to the OEM diameter?


Material: 440c stainless steel

[engineerscott]

See message below.

[engineerscott]

We need more information. What does this knife cut? Is it perhaps an electrically heated knife used to cut through some sort of plastic? The only plating that I think might be considered long wearing would be industrial chrome and possibly nickel. The industrial chrome will be very tough but will require a large amps per square inch plating current. This will require a large power supply if the knife is very large, but if the knife is reasonably small it would be manageable. Nickel plating will not be as hard and long wearing as industrial chrome but it is a much easier process to manage. I don't think you would want to plate with the brighteners used in Caswell's Copy Krome process. I think they would add nothing in terms of coating performance and probably would unnecessarily complicate the plating process to achieve a aesthetic result you do not require.

The biggest problem you will have is maintaining tight dimensional tolerances over time. Depending on how the knife is used it is likely that some sections are going to be worn away quickly while other areas will see little wear. If you take this unevenly worn knife and plate up what will be a fairly constant plating thickness, metal on top of the areas that see little wear will now be plated well above their original dimensions. To fix this you could take your knife after plating and then machine back to the original dimensions. If it is a cylinder you could do this on a metal lath. This would remove most or all of the plating on the areas with little wear while leaving material in the high wear areas. This is of course another complication but if you already have access to a machine shop it would not necessarily be a big deal.