Shaping hardened parts?

[FrankenMauser]

I've got a Marlin 336 carrier and carrier rocker here than I'm attempting to adapt for use in a Model 36 that I stuffed a 444 barrel into. D)

However, the rocker is hardened.
I don't want to anneal the part and then attempt re-hardening. (A: Because I don't want to. B: Because I have no idea what the material is.)
And, of course, neither my sander nor my grinder can get into the small space on this rocker to grind away the material that I need to remove - at least not with the sharp corners and moderate precision required.


What do you do when you have a hardened part that requires shaping, but you can't get in to the area with the normal tools?
Just turn to the Dremel with stones or cut-off wheels?
Or go old-school with sandpaper on a stick?

...I haven't tried sandpaper on a stick, yet. I did try some good stones, and the part ate them alive. I figured I'd poll the brain trust before moving on.

 

[Scorch]

Carbide.

 

[HiBC]

I'll agree with carbide burrs .
Another option for detailing (not stock removal) there are diamond burr sets ,dental stuff,from China on E-bay cheap.

 

[jaguarxk120]

Diamond burrs from HF.

 

[mete]

While carbide or diamond should do the job , the part may be just case hardened . That is the part is of soft steel with carbon added to the surface which is then hardened . Remove the case and you'll have to redo it !

 

[James K]

You might not have to do anything, depending on how much you plan to use the "new" gun. In that application, just plain unhardened steel should be good for hundreds, maybe thousands of rounds. If course, no maker would take that view, but modern factory firearms are way over-designed and built for obvious reasons. If an owner is willing to sacrifice some durability (when safety is not involved), many shortcuts are possible in repairs. (For example, I saw a single barrel shotgun a couple of months ago with the forearm held on with friction tape. It looked like heck, but worked OK.)

Jim

 

[FrankenMauser]

I considered mild steel.
But I don't really want to sacrifice durability.
I'm looking for a result more along the lines of: Build it. Test it. Call it good. Shoot it until I die.




Thanks for the replies, guys.

The part seems to be through-hardened. I've removed about 0.090" in one area, and there's been no apparent change in hardness. The whole thing is only about 0.190" thick.

I'll look into carbide.
...But the only tool I currently have available that might be suitable is the worn-out Dremel, which probably isn't up to the task. (Worn bearings. Too much run-out. I don't want the bit chattering/bouncing and killing itself.)


I need a mill...
(A new rotary tool was ordered a month ago ... still hasn't arrived.)

 

[guncrank]

Carbided end mill in milling machine

 

[dahermit]

It depends upon how hard the part is. When studying Machine Tool Technology in college the instructor would state that if it was close to or at 67 on the Rockwell C scale, then the part would have to be ground. However, I have observed a hardened part being "machined" in a factory on a lathe using a carbide cutter and using an extremely high RPM. The chips that were coming off the part were nearly molten. It was a one-time operation, not production, so what appeared to be abuse of the tool was likely a last resort. In short, if your part is very hard (67 Rockwell C), the carbide is not likely to cut very well...I would use your Dremel and grinding bits.

 

[HiBC]

Of course the obvious straight line answer is a mill. Might as well throw in a surface grinder and a Handsvedt sinker EDM.
If you have access. And,certainly a case can be made for turning the job over to a smith or a machinist who has the tools.
Great ideas!!True,also.

However,I took it that the OP had other ideas,about using resources he had access to.So,while we are impressed that someone knows the pro path to do it,
I'm not sure it helps.

Another thought,OP,when you get to final shaping and blending,there are cheap import diamond files and rifflers,too.
Good luck!

 

[FrankenMauser]

I ended up just using abrasives - mostly the old fashioned way.
Sand paper, emery cloth, stones, and 1/4" sanding drums on the crappy Dremel.

The part still needs a little finishing work, but I got it shaped well enough to function as intended during testing.