Gunsmithing Ion Bond / DLC coatings and tolerances.

[Petrov]

I am thinking of having my big horn action DLC coated.
The brochure says it is 2-6 microns thick. This will also coat the receiver threads, will this affect the barrel fit?

 

[Gene Poole]

A micron is 0.00003937 inches, so at a max of 6 microns, you're looking at about 2.4 tenths, so probably not unless your smith made it really really tight.

 

[LRI]

I can say with reasonable confidence that there isn't a gun shop in the Continental United States that can accurately measure and qualify the film thickness that DLC applies at. This process is done frequently to things like wrist pins on high output performance engines as it'll run with near zero lubrication. If it'll put up with 9, 10, 12+ thousand rpm engines, our lowly bolt guns will be in good shape.

That said: Not all DLC is the same. I would encourage you to insist on Richter Precision in Michigan. Jackie is who you want to speak with.

Good luck.

C.

 

[bill alexander]

DLC is a generic term and as with many things the devil is in the details. The coating is applied by PVD (physical vapor deposition) but the way the plasma is generated and how it is moved to the substrate will influence the performance of the applied film. Cathodic arc generally creates a dull grey sooty colored film which is exceptionally hard wearing, not particularly pretty and can be fussy about adhesion even on perfectly clean parts. To get the best from this the base material must be hard in its own right or you are adding a very thin brittle crust to a substrate that moves and flexes. Sputtering is the other common method of developing the film. This is softer, a little more flexible and a very dark uniform color. It generally seems to provide a more uniform film coating.

For mechanisms such as carrier pistons and sliding high speed parts the former type provides the best properties but must be carefully applied to steels that exceed 45 HRC. Impact surfaces are always a problem. Film thicknesses and adhesion levels are difficult to measure but we do have to do this in some applications. It is rarely necessary for most parts.