Tumble finishing stainless steel plate and screws

My UK based company is developing a range of very high end leather on carbon fiber cases for guitars, violins and laptops.

The structural element of the handle is a 316 stainless steel strip approx. 3mm thick x 30 mm wide x 300 mm long. This strip has a 20mm wide x 270mm long x 1mm deep recess into which we lay a strip of leather which matches the exterior of the case. The plate has 4 countersunk holes to take 4mm machine screws which attach the whole handle to the case.

Currently the strip is brush finished and I am using stock machine head screws with allen key sockets. I am not satisfied with this look
- it does not match the quality of the rest of the case. We have tried hand polishing the strip but this gives too shiny a look and it is v difficult to polish the heads of the screws to match the finish on the strip.

I want to give the stainless steel quality finished which is discreet
- not flashy - and which will look good after many years use.

My current thinking is to give the steel a very high quality matte finish - probably by tumbling. I hope I can tumble the machine screws as well so the heads match the finish of the plate.

I am looking for advice on 1) how to achieve the finish on the steel
- is tumbling the best route? 2) Should any such processing be done before or after the recess is cut ? 3) Can I apply the same process to the machine screws so the heads have a finish which exactly matches the strip?


Thanks

Even though you furnished visuals, it is difficult to see the exact texture you are trying to match. If you are considering mass finishing and are looking for a satin/semi-brushed surface finish, I would suggest a dry process and a product that we call 6A. It is about 60% organic product (mostly wood sawdust) and 40% inorganic (pumice). Because of its light weight (about 30-35#'s/cu.ft.) it is a slower process than a wet system. There are other alternatives, but it does give an excellent brush like finish. We stock it.