On Jun 11, 9:09*am, "Pete S" wrote:
A guy just emailed me *to comment on my "taptips" page,http://www.spaco..org/taptips.htm
I said that I don't allow any (plain)carbon steel taps in my shop.
He commented that gunsmiths DO use carbon steel taps because they tend to
break a lot, but are easy to remove by smashing them.
* I don't do any gunsmithing- *the idea of drilling into someone's gun
barrel scares the dickens out of me. *But here's my question:
* Isn't maybe, the REASON the little taps break often that they ARE carbon
steel?
And just for information, how DO you tap a 2-56 *or 4-40 or whatever hole in
a gun barrel? * If you can only go 2 or 3 threads deep, you can't start with
a taper or even a plug tap, can you?
Are gun barrels hardened/hardened and tempered or are they just an annealed,
tough steel like 4140?
Pete Stanaitis
--------------- *
The pros use a bushed fixture like this:
http://www.forsterproducts.com/store...33&catid=19938
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