Broken center drill

[Dennis Glazener]

I was just center drilling a screw hole in the tang of a rifle I just started. Broke the tip off a very small HSS center drill. Tried to get it out but its too deep in the steel. I tried tapping on the other side of the tang, no good. Then I heated the tang dull red and tapped on the other side with a small hammer still no good. Right now I have it in the vise with a drop of Aqua Fortis in it, hoping there is still enough acid in it to eat enough of the metal to release the point. If that doesn't happen I guess I will soak it in some Muratic Acid in the morning. Anyone else have any better suggestion? Seems like I read somewhere that acid doesn't do much for HSS but it might eat enough of the tang steel to loosen the tip. The hole is not all the way through the tang.
Dennis

[Jim Kibler]

If you can carefully locate the hole from the underside, drill nearly to the broken center drill and then use a small punch to drive the broken bit out.

[Keb]

It's too late now but you have to spin those little c-drills really fast or they will break every time.

If Jim Kibler's suggestion fails, get a carbide tipped drill. That will go right thru that HSS.

[Birddog6]

The problem will be staying centered on the drill. 

I would drill to it with a carbide end mill  from the bottom, then when you get to it, take a small punch & punch it out. 

Keith Lisle

[angus]

I don't have a good example here at home to post a pic of, so I will do my best to explain.
Using what is left of you broken center drill, use a cutoff wheel in one of them high speed hand held grinders, ie (Dremel) and proceed to cut a slot vertically. What you will end up creating is a fish tail looking cutter. Be sure to relief grind enough that the broken piece will fit inside.
Start back into your hole, provided the center drill can pick up on the countersink of the hole. Small pecks and clean out the chips. Sometimes you will drill deep enough to cut a plug out the other side.
A rigid setup is key.
If you get carbide, rigidity is an absolute. Carbide loves speed and feed, but not chatter.

[dannybb55]

Dennis,                                                                                                       You have probably already solved the problem but here is a blacksmith's take on the dilemma. Scarf the end of the tang for a faggot weld, forge the tang back on itself and weld it shut. Draw the tang back to its original dimensions and continue on. The hole is gone and the pesky alloy is somewhere else. You could even draw the tang up over the comb for style points.
                                                         Danny

[billd]

I would definitely NOT use a carbide drill unless I had a Bridgeport type mill and some experience using carbide drills. They break so easily you'll think it was made of glass.  Carbide stuck in the hole and you're really screwed.  Drill thru from the other side and tap it out.  Worst thing that can happen is you're off a little bit and have to weld up the hole and start over.  

Another option is if you have a shop or tech school nearby that has one of those electronic tap extractors. The name escapes me now but they use electronic pulses to burn up the tap or drill.  

Bill

[davec2]

EDM - electrical discharge machining will take it out in a heartbeat.  A local shop should be able to do it for x$.  

The other way is to take a separating disk (very thin abrasive disc) in a dremel tool (or, in my case a dental hand piece) and cut two perpendicular slots (like a phillips screw head) on the back side of the tang deep enough to cut into the tip of the center drill.  (The abrasive wheel won't care if you hit the tip of the center drill - in fact you need to cut into it.)  If the tip doesn't fall out by itself (make sure you grind deep enough) it should tap out very easily with a center punch from the back side.  Once the center drill tip is out, you should be able to pick up the original center from the top side and carry on with the drilling like nothing bad ever happened.

[Nate McKenzie]

How about just installing a new breech plug.

[bob243]

What size is "very small" ?   What size hole are you intending to drill?     

I agree with drilling it from the other side.  Drill a #52 drill or a #2 center drill and tap it out with a 1/16" pin

[Keb]

How about just installing a new breech plug.

Then send me the old one

[dannybb55]

How about just installing a new breech plug.

Good answer!!

[KentSmith]

Dennis,  I've got some nitric acid if you want to bring it over and give that a try.

[Dennis Glazener]

Some good suggestions and I will try one of them later today when I have more time. Don't want to fit a new breech plug since I forged this one out (dang fantail plugs, always forget to order the barrel with a straight tang breech plug).

Will let you know what worked.
Dennis

[Steve-In]

In the feature try a spotting drill instead.  It does not have that point that breaks off all the time.  Spot drills are rigid and more durable than center drills especially in a manual application.  The only thing we use the center drills for in the shop is on turning stock for a place for the lathe centers to go in.  I agree with drilling from the backside and pushing the point out.
http://www1.mscdirect.com/CGI/NNSRIT?PMPXNO=4679584&PMT4NO=87690702

[oldiemkr]

Could you use a small cut off type wheel on the backside? A small thin slot on the back could let you punch it out.

If its really small you might get away with some 1/16" holes just around the OD of the broken part. then maybe it could be driven from one side to another to loosen it up. That will make the hole a little harder to start but I know it works.

Them little ones break easy. I avoid them unless necessary. They don't shed the chip very well and as soon as the chip is stronger, well you know.

[bs2]

If you can carefully locate the hole from the underside, drill nearly to the broken center drill and then use a small punch to drive the broken bit out.

I have done several this way.

Not my own, but for other people!

[Dennis Glazener]

If you can carefully locate the hole from the underside, drill nearly to the broken center drill and then use a small punch to drive the broken bit out.

Couldn't work on the rifle yesterday but I just tried Jim Kibler's suggestion and it worked great. I didn't hit the hole exactly from the underside but it thinned the metal under the broken piece so I could drive it through with a long tapered pin punch. I just drove the tapered punch in until it trued up with the original hole. Hole is now better centered in tang than what I usually do without a broken bit! Thanks Jim and others for good suggestions.
Dennis

[bs2]

Just want to share this bit of advice.

Center drills must spin true, no wobble. If they wobble, they will snap the tip [pilot] off a center drill.

Replace the chuck blades or get a new chuck.

My tip of the........................

No-BS

[Dphariss]

If you can carefully locate the hole from the underside, drill nearly to the broken center drill and then use a small punch to drive the broken bit out.

Couldn't work on the rifle yesterday but I just tried Jim Kibler's suggestion and it worked great. I didn't hit the hole exactly from the underside but it thinned the metal under the broken piece so I could drive it through with a long tapered pin punch. I just drove the tapered punch in until it trued up with the original hole. Hole is now better centered in tang than what I usually do without a broken bit! Thanks Jim and others for good suggestions.
Dennis

I love it when a disaster turns into a blessing.
Wish it happened more often

Dan