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A Hard Reciver To Drill

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#1 GunnerHAF

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Posted 14 March 2006 - 07:18 PM

I'm trying to drill and tap a K98 reciver for my scope mount but I ran into a little problem. I was able to drill and tap 2 of the holes in the front ring of the reciver but I have already dulled one bit and broke a second on the rear bridge of the reciver. Is there a trick for drilling through real tough case harding beside dulling and breaking bits.

#2 Sailormilan2

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Posted 14 March 2006 - 07:40 PM

There is a special carbide bit for beaking through the case hardening.

http://www.brownells...D CARBIDE DRILL

#3 GunnerHAF

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Posted 14 March 2006 - 07:45 PM

Thanks I'm going to order one right now. But will this problem have any affect on trying to tap the holes.

#4 donmarkey

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Posted 14 March 2006 - 07:56 PM

QUOTE(GunnerHAF @ Mar 14 2006, 08:45 PM) View Post

Thanks I'm going to order one right now. But will this problem have any affect on trying to tap the holes.

Generally not, the case hardening isn't that thick. Enco sells carbide drills also, alot cheaper. So will any machine shop supply.

#5 Limpid Lizard

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Posted 14 March 2006 - 08:41 PM

Two things. As the bridge material is rather thick, it could be hardened almost clean through. This could lead to problems when tapping. You would be better served to spot anneal the bridge. LL

#6 GunnerHAF

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Posted 14 March 2006 - 08:52 PM

That is what I was thinking. With trying to drill through the bridges bolt guide I was thinking that it might be hardened all the way through. I might spot aneal after I get the holes drilled to try to keep the heat to as small of an area as possible the try to tap them.

#7 manureman

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Posted 14 March 2006 - 08:54 PM

Gunner, when tapping it's a good idea to use carbon steel taps so if you break one you can shatter whats left of it in the hole with a punch,the hard taps can be a real bear to get out when they break off.Use a guide or jig of some kind too,and some folks even recomend a fresh carbon steel tap for each hole.Not a bad idea,especially on a feller's first ones' it's cheap insurance.Just take it slow and easy and use lots of good cutting & tapping oil and you'll do fine, Jim.

#8 Limpid Lizard

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Posted 14 March 2006 - 09:22 PM

The bridge is not a real critical area for heat treat. Some of the harder receivers to drill are the double heat treat 03's. I polish a very small spot and heat it with a neutral flame until it just starts to blue. I then repolish and heat. I heat and polish 3 times. This leaves just a small spot annealed. LL

#9 fritz


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Posted 15 March 2006 - 09:36 PM

The only Mauser receiver I ever had a problem with drilling was a Columbian receiver that was made for the Nato cartridge (marked as such).

Since this was only hard on the surface, I ground off a bit of the surface and then drilled and tapped as usual.

Your mileage may differ.


#10 Horsefly

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Posted 16 March 2006 - 06:08 AM

What fritz said was kinda what I was thinking.I've drilled several Mausers,and never had any trouble at all,wishing a few times,they were a little harder,spooky how soft they seemed to be.Jerry

#11 Guest_Uncle Starret_*

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Posted 16 March 2006 - 02:45 PM

Usually on the better Mauser actions, the rear bridge is hardened from the bottom up......what this means is the drill does fine most of the way and near the bottom of the hole it encounters a crust of hardness that runs the gamut of tough to glass brittle, reason being, the area you are drilling into is the bolt guide race......that needs to be hard so the bolt doesn't gall going back and forth......you will find that all the commercial pre-war actions and a lot of the military built at Oberndorf and Berlin and some other armourys have the hardened rear bridge bottom,
Thru the years I have tried several different methods of tapping a clean hole without breaking the tap.....the one method that worked best day in day out was always use a new tap and lube it with a dab of Perma-tex 300 gasket seal.......if I break a drill or tap using this method it;s because I have allowed the tap wrench to tilt or I have gotten ham handed and rushed the job.

#12 GunnerHAF

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Posted 18 March 2006 - 06:33 PM

Well finaly got it done! That bit from Brownells did the trick. It made the job a whole lot easier. I only thought it was hard on top, the underside was even harder. I had to put a little bit more pressure and a lot more cutting oil to get through it. Tapping was a lot more fun. Took my time and I tried not to get in a rush with it but I managed to break a tap in each hole. Took all your advice and bought the hard taps so they just shattered out of the holes.I finally finished with the taps and chased the holes and ended up with 4 perfect holes that lined up perfect with my base. I would have never thaught that the 98K reciver was this tough. I have drilled a few VZ and Yugo recivers and none of them were this tough. Well live an learn. Thanks to all, gunnerHAF

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