File wear Hard steel

I purchased quite a few Grobet Swiss Pattern Files 8" tang not included.(not needle files) Expensive but work great! I make a small item (less than 1" long) One side has lathe cut radius of .900" in the center and .25 radius on each end. .25 radius is small on each end. I did use a corner rounding mill but still have to blend the two, material removal so little in most cases I file it. Material is bronze. Question is can I make an outline needed and harden the steel to use it as a template attached to my part to get consistent radius part to part. But not damage the file. File to slide over the surface with no attempt to remove any of the hard metal since the purpose of using hardened steel is to not have it altered by the file yet I don't want my expensive files damaged by the hard steel.

Hardened steel filing guides are OK and should not damage the file. The idea is that you are filing the work (softer material) down to the line of the hardened guide or template. The surfaces the file will contact on the hardened guide or template need to be smooth and should be polished after hardening to remove any oxide or scale. I'd also put a radius on the 'leading edges' of the template so the file does not catch a square corner on the hardened template.

The file will 'skate' on the polished surface of the hardened template and will cut the work. By the time you have filed the work down to where the file will contact the template, you should be taking light cuts with the file, using light pressure.

Model Engineers and other machinists have used hardened templates as file guides where a number or parts with a particular profile or dimension had to be made. I think there are two key parts to preserving the file: make sure the file is bearing flat on the hardened edge of the template;
use light pressure on the file when nearing the template

Yes, you probably can. Get some tool steel that hardens "glass hard" and give it no tempering (or just enough so it doesn't shatter when you use it).

An alternative might using a form tool on the lathe to minimize the need for blending.

What about filing buttons?

Like these filing buttons - Google Search

Ideally a hard file guide will have a surface that spans several file teeth at least. As such, wear to the file will be minimal to immeasurable depending on the span. I can't quite picture your part but if your guide is more than a few teeth across and you are filing and not "scrubbing" should be fine.

Thanks guys, I do intend to polish the surface of the template mirror finish, round the edge so as not to cut the file plus being glass hard not tempered so it will not chip or cut me!
I can't use form tool, I alter the radius on the ends of 1.800" diameter after cutting a machined ring into 4 pieces.