Broken drill bit

[ltdann]

Things were going well on my current build.  I even made the comment to the wife,  "wow, I'm getting the hang of this building thing".   Should have kept my mouth shut. 

So last night, I'm drilling a pilot (1/16) hole in the lock bolster for the rear bolt.   I've got it in the drill press vice, all lined up, oil applied and slowly drilling and backing out to clear chips, moderate pressure.   It's going well, no heat build up.  Just as the tip of the bit clears the other side, it grabs and snaps.

The bit is in the middle of the bolster broken below the surface.  I tried punching it out.  I tried drilling from the other side, and punching.   I tried Kroil and punching.  I tried heating and punching.  Even my titanium coated bits won't cut that HSS.

I can't move the hole, its where it needs to be.  Frankly, I'm out of ideas?

Anybody got any other suggestions?

[Stoner creek]

Yep. I feel your pain. Just wait until you break a tap off in there. When this happens just go on into you living room and set a spell.

[smallpatch]

Dan,
As you probably already know...... don't use a 1/16" for a pilot.  Even a 5/64" is much less prone to breakage.  Larger is better.  After all, for a 8/32 screw, you'll need a #18 or 16 for a clearance hole.
Tap hole is #29, so that's usually what I make my pilot hole with, then clearance for the tap.
As far  as getting the old one out,.... if it has poked through, drive it out with a suitable punch, and redrill.

[Pukka Bundook]

Dan,

I can't see why it wouldn't drive out from the opposite side.  If the tip's  just  breaking through, it should be an easy job providing your punch is fine enough.
I'd not drill a pilot hole under 1/8" as the smaller the drill the more they can wander. Usually drill to the size I need to tap like Dane above.

Good luck and let us know how you fare.

R.

[Tim Crosby]

 Heat it up and punch it out or stick it in the freezer and let it shrink a bit, it may fall out then.

  Tim C.

[ltdann]

Heat it up and punch it out or stick it in the freezer and let it shrink a bit, it may fall out then.

  Tim C.

hmm.  Hadn't thought of the freezer.  The heating didn't work, so that might help.

What about carbide tipped drills?  will that cut HSS?

[flinchrocket]

Dremel makes a diamond ball shaped cutter about 1/32 in diameter. If it will reach you might use one in your drill press to open the hole up a little to drive the broken piece on through.

[ltdann]

Dremel makes a diamond ball shaped cutter about 1/32 in diameter. If it will reach you might use one in your drill press to open the hole up a little to drive the broken piece on through.

I tried going up to 1/8 on both sides, hoping that would loosen it, no joy.  I've got to stop at the hardware store anyway, to replace my bent pin punches.  I'll look at the dremel section and see what they have.

Sometimes I think this gun building thing is just a journey from one mistake to the next

[ddoyle]

Is'nt that the way life goes. You think your doing everything right and proper and then whamo it all goes to heck.
If it makes the recovery more bearable here is a silver lining. No matter what mess is left in that bolster when you done it is an easy and rewarding task to fill the hole and start again. This is an aggravation but not an issue that will detract from your over all success.  Hack, beat and smash away it with out concern or stress it will fall out and you'll be back to making progress in no time.

[ltdann]

Is'nt that the way life goes. You think your doing everything right and proper and then whamo it all goes to heck.
If it makes the recovery more bearable here is a silver lining. No matter what mess is left in that bolster when you done it is an easy and rewarding task to fill the hole and start again. This is an aggravation but not an issue that will detract from your over all success.  Hack, beat and smash away it with out concern or stress it will fall out and you'll be back to making progress in no time.

LOL, Nothing the wire feed welder can't fix eventually.

[ddoyle]

If only peening or welding could fix all our troubles eh.

[D. Taylor Sapergia]

When using a 1/16" bit to drill in steel, or any other metal for that matter, use the highest speed your drill press can generate, at least, 2500 rpm.  Slow feed, clear chips often, and gently through the other side.    Pilot drill needs to be only a few 'thou' under tap drill.  Tap drill for #8 x 32 tpi is #29 drill.  Two sizes under of fractional of appropriate diameter is fine.  1/16" is way way too small.

A music wire pin punch a few 'thou' less than 1/16" (.0625") should drive that drill bit out without issue.   Drive it from the exit side.

[Justin Urbantas]

Throw away all of those 1/16 bits!!!  I have switched to all 3/32" pins. I got tired of broken and flexing those tiny bits.

[Scota4570]

Here is a "gutsie" move that can clear a tap or drill bit in seconds.

Use an oxy-acetylene torch to heat the bit red-orange hot.  Go fast so the plate is not glowing.  Cut off the gas and hit it with pure oxygen.  The tap or bit will boil and disappear. 

Do it as a last resort.

Good luck

[D. Taylor Sapergia]

Justin:  I don't agree.  3/32" would be the maximum pin diameter I'd like to see on a longrifle.  1/16" is way nicer, but sometimes I use a finishing nail that is .073" if I want a honking huge pin.

[davec2]

Ltdann,

Don't drive yourself mad and don't ruin the part.  Take it to a shop that does EDM (Electrical Discharge Machining) and have them remove the broken drill.  For me, the small expense in having that done is well worth all the trouble and time spent if the simple "drive it out with a punch" trick doesn't work. 

Oh, and by the way, I highly disagree with Scota's torch / oxygen burn out idea.  Using the equivalent of a cutting torch to remove a 1/16 inch broken drill from a lock plate bolster....well....just throw the lock plate away now and save yourself the trouble....

[flehto]

A lot of people have problems drilling small holes and as Taylor said, at too low an RPM. Some drill presses don't have a high enough RPM for smaller drills and some electric "hole shooters" don't either. For a 1/16 dia drill,  my drillpress speed is 1800 RPM. All the pins in my builds are 1/16 dia music wire because pins aren't things of beauty so  smaller is better.
 
Starting out when drilling is to have a large enough center punch dimple, choosing a pilot drill that has a "point" that fits in the dimple  and a final drill that has a "point" that fits in the pilot hole. If the drill "point" is too large in either case, the drill will wander and mis-locate the hole.  Anyways, that's what I was taught when serving my apprenticeship.

If you have access to a local machine shop,  most have an EDM which will neatly "burn" it out......Fred

[ddoyle]

What taylor said about the speed. I have a 1/16 collet on a sewing machine motor, at that speed the little bits cut with zero trouble. In my bench drill press at the highest speed it wanders and mostly just gets hot. 


Remember lock plates are cheap as borsch and you have a template to redrill all the holes in a new one so do not take any of it too serious.  It aint like you got the head off your work truck and are looking at a bolt broken off in the block!

[jerrywh]

  Get a carbide 1/8" bit and drill from the other side until you hit the 1/16" drill bit. then just drive the 1/16"  bit out. you need a hardened punch. Those cheap ones don't work well. Forget the torch ideas. You might ruin the whole plate.

[FDR]

Ltdann,

Don't drive yourself mad and don't ruin the part.  Take it to a shop that does EDM (Electrical Discharge Machining) and have them remove the broken drill.  For me, the small expense in having that done is well worth all the trouble and time spent if the simple "drive it out with a punch" trick doesn't work. 

Oh, and by the way, I highly disagree with Scota's torch / oxygen burn out idea.  Using the equivalent of a cutting torch to remove a 1/16 inch broken drill from a lock plate bolster....well....just throw the lock plate away now and save yourself the trouble....

Dave got it right! Ask me how I know!! Saved the gun and no damage!

[ltdann]

A quick call to several shops in town tell me nobody does EDM.  They all ship to either San Diego or Santa Ana to have the work done, so that's not an easy or quick option. 

I'll try a combination of carbide bits, freezing and a stiffer punch.  I had no idea that HSS was that tough....

[Justin Urbantas]

Justin:  I don't agree.  3/32" would be the maximum pin diameter I'd like to see on a longrifle.  1/16" is way nicer, but sometimes I use a finishing nail that is .073" if I want a honking huge pin.

I drill all my holes with a hand drill, and have broken two 1/16" bits while drilling the barrel lugs. They were a big pain to get out.  3/32" just seemed simpler. Do you think bigger pins look bad?

[Nate McKenzie]

For lock bolsters I start with a punch, then go to a center drill, and then the tap size drill.

[ddoyle]

Yes the pin size matters in a huge way- if you want to be satsified in the future. 3/32  make the entire rifle much larger. It is not the visible end of the pin that is the problem it is the wood it takes to encompmass them and the lowering of the RR.   

I ignored the wisdom for a couple years. big expensive frustrating mistake. Oh well when I am old and have no money for new barrels and locks I can restock em.

Edi: were they a pain to get out because you were trying to drill all the way thru with the barrel in the stock? Most books say not to do that.

[ltdann]

And the winner is.....

Dremel makes a diamond ball shaped cutter about 1/32 in diameter. If it will reach you might use one in your drill press to open the hole up a little to drive the broken piece on through.

Sort of.  I tried the carbide tipped spade bit/multi-use first.  That didn't last but a few seconds.

I used small tapered diamond dremel bits in the drill press.  They cut but burned up pretty fast (even with oil), but I could tell they were making progess.  The third one went through and then I used a high tensile punch and that did the trick.

The hole looks a little enlongated on the lock face.  Not sure it will be noticeable until I tap it and put a bolt in.  I may try and peen it a bit (a nod to ddoyle  ).  If it drives me crazy, I'll just weld it and redrill.

Thanks gang, another minor disaster averted.  Note to self: HSS is TOUGH.