Drilling and tapping into stainless

[ssdesigner]

I need to drill and tap an M4 hole in the barrel of this stainless Ruger Mark II. The photos below show a plastic site mount that needs to sit just right on the side of the barrel. The hole that I will need to make is circled in red.

The part that concerns me is the angle that I'll need to come at the barrel. It's off center and I'm concerned that anything I came at it with will just glance off. I'll be using my LMS 3990 mini mill for this operation.

Any tips or advice would be greatly appreciated.

 

[GeneT45]

Once you locate the hole , go in with a small (center-cutting) endmill and spot-face a flat no bigger than your drill size (although in this case, the mount would cover it if you wanted to go larger). Then center-drill in the flat and proceed as usual. I wouldn't worry too much about it being stainless. The SS used in firearms is normally very machinable.

GsT

 

[ssdesigner]

That sounds like a really great approach. Thanks GsT!

 

[tq60]

If you use the mount as a guide, move nothing in x or y until finished.

Use full screw size drill to locate hole.

Buy new good tap.

Lock table ad remove mount.

Spot mill

Put mount back and verify location.

Drill and tap.

Attach.

Do additional holes.

Sent from my SM-G781V using Tapatalk

 

[mmcmdl]

That looks like the printed part ! Did you ever make the aluminum parts yet ? Gene is correct here . Locate , flat bottom center cutting EM , center drill and drill .

 

[ssdesigner]

That looks like the printed part ! Did you ever make the aluminum parts yet ? Gene is correct here . Locate , flat bottom center cutting EM , center drill and drill .

Not yet. I ordered a pile of new tooling and raw material though. Should be able to jump right into it this weekend!

 

[Reloader1776]

People have the right approach as far as milling a flat spot before drilling.

As far as the drilling and tapping, I would recommend bleach when drilling and tap magic when cutting the threads.

Ditto to the comment about buying a good tap. A lot of cheap taps are some sort of heat treated carbon steel that are very brittle. If you buy from McMaster, they will specify the tap material, and I would highly recommend looking for HSS.

 

[ssdesigner]

The bleach idea is super interesting. Never heard that one before. Is it a stainless steel thing or…? Tap magic for sure. Always wondered if a 3 in 1 lube works as well as tap magic?

 

[Reloader1776]

Bleach is unique to drilling in stainless. The idea as I understand it is to cool without lubricating so the bit makes good chips. All I know is it works better than anything- anchor lube, hogwash, tap magic, etc.

For tapping, tap magic is the go-to for most people I know. Never tried 3 in 1, but I know tap magic has some sulfides in it that 3 in 1 wouldn't have, so I'd stick with the purpose made stuff.

 

[benmychree]

I have used TapMagic on all sorts of machining stainless and steel for that matter, never found anything better, including the original Rapid Tap.