Drill bit broke in receiver Help !

[hylander]

I was drilling and tapping my K98 Mauser for Lupy'y mount's
and the receiver is very hard.
I burned up 3 #31 drill bits on one hole. on the third bit I got it to hot and the tip of the bit broke off in the receiver, perfectly flush.
Only about a 16th inch deep.
The other hole's are a success, but what do I do about the hole with the broke bit, how do I get it out. It is a 2 peice mount so that mount only has one screw to hold it.
Is there a reverse drill bit or one that will cut through a standard high speed bit.

[Iowegan]

Use a tweezers to grip the bit and pull it out or use a punch and break up the drill bit.  Bits are very brittle and will break without damaging the receiver if you're careful. Next time use some cutting oil and keep your drill speed down to 300 rpm or so and go slow..

[gunnut69]

These are the ones you earn your money on.  I have even taken a sharp bit and heated the cutting surfaces a bright red, quenching in cold water.  The bit WON"T last but wil cut nearly anything until one of those cutting edgess chips. Also one can pick up some number 31 cobalt bits.  These bits are super tough and will drill nearly anything.  Oh and just to sort of lighten your day,, after it's drilled your still gonna have to tap that hard sucker...  I usually use a large nail with the end turned to fit the hole(before threading of course).  Insert it into the drilled hole and heat the nail glowing red hot, the whole nail.  Use a 20 penny spike and allow the nail to cool on it's own..  The hole will be nicely annealed but not the complete receiver ring..  IOWEGEAN's advise should always apply!!

[BoarHunter]

Old Mauser 98 actions were casehardened, leading to a very hard but not deep surfaces. In Brownells Kinks books they give plenty advices how to carry on this type of work.

An oxy-acetylene torch with a small tip for example. No need to bring it to cherry red, a dark blue is OK and no risk for the rest of the action.

You can also ask your dentist for worn carbide or ever better diamant coated cherry. You can cut through the hard surfaces and then use your drill.
Be carefull once you go through, slow down as both surfaces are hard.

Or as stated earlier use of a carbide drill but they are not cheap.

The real fun will start when you will tap it as you may also break or wear out your tap.  Again you can soften the steel around the hole with a small tipped torch.

[HKusp40]

Like BoarHunter said you should definitely spot anneal before drilling. I actually just use a hot soldering Iron and hold it in the area that I will be drilling and bring it locally to a dark blue.  I also wrap the areas around with wet shop rags.

I have never done the nail in the hole before tapping.  It is difficult however the case hardening does not go down very far and after doing the spot anneal do not find it necessary.

[Judson]

Neat tricks you guys!!!!   I will have to try some of them and see how they work out.     For me, if I berak off a drill bit I use the old oxy heat wrench with tho O2 cranksd high and the gas low and take the temper right out of the bit.    Then if you go slow the three fluted carbide drill bits from Brownells will eat the drill bit no problems.    If you do break the bit send it back and they will replace it you could not ask for a better tool guarentee from any company.