I'm finally getting around to installing a fork brace that I bought from Srinath a few months ago.  While I was drilling the mounting holes, I've had 2 drill bits break off (I was using too much pressure and cheap drill bits).  One was fairly easy to grab with a pliers, the other one left just enough to grab... but I'm pretty sure a bit of it is still in there.  I can't see it, but using another bit I can hear it and the next drill bit is going nowhere or just walking.  Any advice on getting it out or getting around it somehow?  I currently don't have a drill press to work with, so this is a bit of a PITA.

My one thought so far is to drill from the other direction, but it may be tough to line up the holes.

What we use around the shop we call a dental bur or rotary file.  It is a little carbide tipped ball on a spindle. They aren't that expensive and will eat through a High   speed steel drill bit pretty quick.  Just  be careful when using it because it will eat through the parent metal even quicker.  Lowes or Home depot has them by the drememl and router section.  Good luck.

Alex

Eeeww. That's ugly. I don't think you would ever get an opposite hole lined up using hand tools, and probably not even with machine tools.

Is the bit broken off in the brace or the GS?  (me thinks the brace).

Afzzzr12 is right, the carbide tool will move through the tool steel bit very well. Oil it up and take your time.

How did you bust the bit to start with? 

Yeah, in the fork brace, a 1/2" thick piece of 7475 aluminum, IIRC.

As I said, I was probably pushing a little too hard, and I think the drill bits are pretty cheap.  This would be much easier with a drill press... but I don't have one.

I had to go to the hardware store for some longer bolts anyway, so it won't be too much trouble to pick up a carbide tool

lol, breaking it in alli as well, must not have been holding right. did you drill a pilot hole first??

That was supposed to be my pilot hole

AL is quite sticky to drilling. You said you didn't have a press and that just makes it worse. Any misalignment or wobble tends to grab too much metal.

Before the next attempt, at the very least, use WD40 as a lubricant. I have a bottle of drilling/tapping fluid, but then I poke a lot of holes in metal.

Like all things, you try and learn. A broken tap is actually a little easier to retrieve than a bit. Special gadgets exist for fishing them out.

1/2" thick!?!  Ok...

How much is broken off?   If it's the whole nose of the drill, here is a suggestion:

Buy a good-quality drill much smaller than the hole diameter, say 3/32".  Transfer the center to the opposite side with a paper template and a centerpunch.  Now use the smaller drill to drill through to the drill bit.  When you get to it insert a 1/16" welding rod and beat out the piece of HSS.

Go back to the first face and drill through.


Option 2:  (I know you don't have a drill press, but I'll throw this out there anyway.)

Find a carbide drill of the necessary size.

Lube hole with tap matic or some kind of EP gear lube.

Clamp to drill press table.

Drill through at about 750-1200 RPM.

When drilling aluminum you can use very high speeds and relatively heavy feeds.  At the size drill you'll be using go as fast as you can.  A 1/4" HSS drill can be run at about 10,000RPM with coolant less than 4 diameters deep.

Spark errosion is the recognised way of dealing with this problem, anything else is just a compromise. The hardest part will be finding someone local who does it. The link will give you some info.
http://www.helicoilservices.co.uk/spark_eroding.htm

Quote from: manofthefield on December 17, 2006, 02:44:18 PM
As I said, I was probably pushing a little too hard, and I think the drill bits are pretty cheap.  This would be much easier with a drill press... but I don't have one.

Everyone should have a drill press.  Harbor Freight has an inexpensive one:

http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=44506

For $40, it won't last more then a month or so of continuous use.  But if you only use it occasionally, that may be enough for the rest of your life. 

Oh, I fully intend to own a drill press, and this would present the perfect excuse to buy one, but I will be moving in a month or so and don't really have a place to put it/ don't need more to move.  I think it's time to put a drill press on my list of tools to buy though; the list has been shrinking and needs some more substance