stoning MIM parts?

[jeffrey]

When doing an action job on a newer S&W revolver, should I stone the MIM parts or just leave them alone? For example, there is an area on the trigger that is divided into three small areas (all a bit rough), that is one long area on a forged trigger. I could either grind it down a bit, or leave it alone.

 

[dfariswheel]

Leave it alone.
These parts are case hardened with a very thin "crust" that makes the parts wear well.
Do almost any polishing and you'll break through the hardening and ruin the parts.

This also holds for the older forged and milled revolver parts.

 

[AzShooter]

Stone them just don't get carried away. Usse a hard Arkansas stone with oil. Listen when stoning and when you no longer hear the scraping sound you should be done.

Stone 10 strokes then put everything back together and test. Repeat as needed.

 

[bountyhunter]

Originally posted by jeffrey:
When doing an action job on a newer S&W revolver, should I stone the MIM parts or just leave them alone? For example, there is an area on the trigger that is divided into three small areas (all a bit rough), that is one long area on a forged trigger. I could either grind it down a bit, or leave it alone.

The only surfaces I polish on a trigger are the sides near the boss pins.

The first MIM rebound slide I polished was soft enough to scare me. I polished it on 600 paper and metal was coming off quickly. On the older forged slides, they are hard as a rock. I would be careful on the new parts, not because they are mIM but because some of them seem to be made of a softer steel formula or not properly hardened.

YMMV

 

[David LaPell]

The first trigger job I ever did was on my 25-13 MG which has the MIM parts. I just followed Jerry Miculek's video, and it was no problem, just go easy, like you would on non MIM parts.

 

[jeffrey]

Thanks for the advice. I followed Jerry Miculek's video and worked on an older gun (and managed not to screw it up!) but the newer guns look a little bit different than the gun he used in the video.

 

[Bullseye Smith]

Going to give away a trade secret here now

, Take 1500 wet sand paper and two sided tape and a 6 inch stainless ruler and cover with the tape and put on the paper and trim. Use this to polish with and leave the stone at home

. I don't think the MIM is case harden it is just hard. But you can do forged with this and don't go thur the case harding. All you do is polish. This is what they do to the clear coat on your car is to sand it with 1500 or 2000. Now the world knows

.

 

[herbie1]

1500 & 2000 grit sandpaper should be readily available at most auto parts stores.

Some knife sharpening websites sell 3000 grit strips of sandpaper that they use for knife sharpening.

I have used combination of these to polish my GP100 and it worked out really well. With these grits you can almost get a mirror finish.

H.

 

[bountyhunter]

Originally posted by Bullseye Smith:
Going to give away a trade secret here now

, Take 1500 wet sand paper and two sided tape and a 6 inch stainless ruler and cover with the tape and put on the paper and trim.

Been doing it for years, but I use 600 and 800 paper and oil.

Originally posted by Bullseye Smith:
I don't think the MIM is case harden it is just hard.

The hammers and triggers definitely are surface hardened. The RB slides seem to be pretty soft.

Originally posted by Bullseye Smith:
All you do is polish. This is what they do to the clear coat on your car is to sand it with 1500 or 2000. Now the world knows

.

I have to admit, I spent quite a few years rubbing out car finishes and I never used paper finer than 800. Then I switch to medium polish compound and then fine compound. The new clearcoat polish compounds are so fine they have about as much "cut" as cottage cheese.