broken drill

[neonman]

I was making a rocker arm for my Marion 25 model, and while drilling an oil hole I broke a drill off in the hole.

The material is cast iron, about 1/4 thick
where it broke. The hole is a #70, and when
the drill was just breaking through it snapped.
THere is about 3/16 of drill in the hole, and it just protrudes into the bearing hole, .313.
It's about 1/2" from the end of the bearing hole.

I've tried to drive it through with the long part of the drill, and tried to puhs it out from inside the bearing hole. no luck.

Any ideas on how to get it out?

neonman

[wierdscience]

Is there enough sticking out that you could maybe silver solder a washer or nut on it and then twist it out with pliers?

Maybe try washing out the hole with solvent and then using Alumn to dissolve it?

[Ries]

No.70, Huh? How can you even see the damn thing?
With a bigger bit, I would suggest grabbing it with vise grips, or tig welding a small bolt to it, or pulverizing it with a center punch, or drilling the end and using an easy-out. Sometimes I heat em up with the finest tip I have on the oxy-acetylene torch, which anneals em, then you can drill em out.
But with something that small, its tough. Driving it out with a punch might be your best way to go.
Or find somebody with an old electro arc tap disintegrator- the very first EDM's, which were built to remove busted off taps. We had one in my machine shop classroom many years ago, and it would do what you need- disintegrate the drill bit, and leave the parent metal.

[neonman]

Wierdsience, there is not enough sticking out
to solder to. Inside the bearing there is only about .010, just enoudh to scratch the H--- out
of the shaft, the other end broke inside the hole.

I may just have to grind it off incide the bearing with a dremil, and leave it in as a last resort.

neonamn

[cntryboy1289]

If you have access to some liquid nitrogen, freeze it and then tap it, most of the time it will shatter. Nitric acid had been none to work as well.

[Tinkerer]

What if you took a piece of drill rod the same size as your shaft... put a chamfer the same angel and the bit and introduce it from the opposite end from the twist of the drills cuts. You maybe be able to unstick the broken drill. This has work for me in the past on a somewhat larger bit.

[John Garner]

neonman --

I think I'd try forcing the piece of drill out of its nest from the inside of the bearing bore. A hard plug (with a wee bit o' taper at its nose so as to slip underneath the drill tip) with a cylindrical body that barely slides into the unobstructed bearing would probably put enough axial force on the drill to back it out.

John

[neonman]

Thanks guys, I'll give some of these ideas a shot.

neonman

[J Tiers]

That small, I think grinding it off, with a bit of extra for relief sounds pretty good. You can drill another hole....

I'd work some epoxy down there after washing it as well as possible.... don't want it dropping in one day.

BTW, #70 hole is so small that oil is as likely to pull UP INTO it, as to go down it.... I have had really bad luck trying to scale physical things like surface tension and flow.........

[Your Old Dog]

As you said it just started to break thru the other side, I would:

square off the broken end with a dremel/or grind it off flush with the work Turn a thick punch with a nibben the size of the bit and use that nibben with brute force j(hammer) to get it started moving. Then a regular punch to move it the rest of the way out.

[chief]

Try to heat the cast iron and once it's hot
try to drive it backout the way it came.

[Jesse168]

I would try a carbide drill. A carbide drill will drill through a regular drill.

I would first try drilling from the bearing side. This would hopefully loosen the broken drill from your piece.