Carbon steel taps vs HSS for gunsmithing?

Most holes for sights are 6-48. The barrels are usually just tough steel, but the receiver is where you do most of the drilling and tapping, and they can be all over the place. You start the tap with a guide so a lot of starting taper isn't needed.

Carbon steel taps are slightly harder than HiSpeed. They are also more brittle and shorter lived. That's ok, most gunsmiths I know only use them once. They also grind the shank on them down to weaken it. That way, if it breaks, it'll break at the shank and not down in the hole. The real old timers would reharden them to cut really hard materials. Also, if it does break off, You can soften a carbon steel tap with a torch. It is easier to drill that way.

Paul K. Dickman

.org/taptips.htm

The pros use a bushed fixture like this:

And barrels are EASY to drill. They have to be drilled the long ways, after all, at least once, plus reaming and rifling. So can't use really nasty machining steels for that. No, the problems are with drilling and tapping military bolt actions. Post-WWII commercial actions usually come with holes already in them, just turn out the plug screws and mount the appropriate base. Military bolt actions in the really old days were mild carbon steel that was machined and then pack-hardened. Those are a bear to do, fortunately, the guns are getting too valuable as collector's items to make into sporters now, they went for as little as $10-20 back in the '50s and '60s. You can sink more than the cost of a new commercial rifle into such a sporter and reduce the value to half what you spent, now. On those case- hardened actions, these days you can get carbide drills to make the holes, old-timers had to use mercury-hardened carbon steel drills and even then sometimes didn't manage to chew through the skin. Heavy black sulfur cutting oil is the best stuff for tapping. Bushing- guided fixtures are a must for drilling and tapping, just asking for trouble without them. That's the reason that Forster fixture has been in production for decades.

Fine-pitch screws are used, usually not in the standard series. 6-48 and 8-40 are common, taps are a little more robust, too. Carbon steel taps are more than adequate for barrel steels and cleaning out buggered threads on commercial guns. A small dogbone tap wrench gives a good feel, you can tell when a tap starts winding up and back off before it goes. Shallow holes where there's about 5-6 threads, use the fixture with a 2nd tap to start followed by a plug tap.

Stan

Stan

I read somewhere that melting a blob of solder on the receiver would anneal the case enough for drilling and tapping. I haven't tried it. Case-hardened scrap hydraulic cylinder rod cuts well enough with carbide.

jsw

Case-hardened '30 actions can also be spot-annealed with a cut-off nail in a drill press. You just use friction to get a small spot very hot.

As an earlier poster says, this is not something one would do today with a rifle that old.

That's '03 actions, plain carbon and case-hardened. You can tell by the serial numbers which ones were made this way.

.

Not just '03 actions, Mauser actions were made that way clear through at least WW1. Krag actions were done that way as well. Since all three types were used for making cheap sporters for at least 60 years, that's a lot of holes!

Stan

Thanks for all the good info. My son just got one of those old rifles and he asked me to drill for sights. Now I know enough to find a gunsmith, or wait until I can build a fixture.

I summarized all of your inputs and added it to my taptips page at the bottom, "tapping holes in gun barrels":

If you check it out and find that I have screwed up in any way, please let me know.

Pete Stanaitis

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