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Thread: Broken Drill Bit Removal?
07-29-2005, 12:53 AM #1
I'm sure removing a broken drill bit is something they teach you in tradeschool quite early, and I'm sure it's a topic that's been beaten to death on this board, but I still thought I'd ask:
I was drilling 6061-T6 1/2" aluminum plate yesterday, in a stack, so the cut was 1" in depth. I was using a crappy 1/8" drillbit with a bad temper in the tip and a drill chuck with lots of runout. Well, as one can predict, the bit broke, and now I have a vital hole jammed with drill bit remnants.
Here's my problem: I don't have the money, patience, or material to make another replacement part for the one holding the broken bit (part of being a high school student and a HSM). I can't put the hole in another spot. I can't heat the piece up enough to kill the temper of the fragment of the bit, because the'll kill the vital temper of the aluminum. I tried punching out the fragments with a nail set. it worked on one, and on the other I now have a hardened fragment of nail set stuck in the aluminum aswell. I tried soaking the piece in boiling water so as to heat it so it'd expand and I could remove the parts witha center punch. No dice.
Any suggestions? And what other techniques are out there for bit removal? I've already tried my strongest neodymium magnets, by the way.
07-29-2005, 12:59 AM #2
Place a 1/8" dowel pin in your good drill chuck. Lower the pin and clamp it in the vise. Clamp the vise to the table. Release the chuck and raise it up. You now have a pin aligned with the chuck.
Now, hopefully you've got a wee bit of round hole available in your stack of parts. Turn the stack over, and slide the stack down onto the dowel pin held in the vise. Now, put a drill in the chuck and drill through from the back. Knock out the old pieces.
That is just a general procedure. You will need to take appropriate measures to keep the part level and square to the drill, and to protect yourself from possible amputation by positioning the stock against a stop.
07-29-2005, 01:00 AM #3
We were discussing a method to chemical corrode taps out a few days ago. No reason it wouldn’t work on a drill bit that’s stuck. Given that its aluminium, you might be lucky.
07-29-2005, 02:02 AM #4
You can drill right through HSS with a solid carbide spade drill, or even a centercutting endmill. Both of which, I might add, are available in 1/8". If you ruin the hole when drilling thru the HSS, simply oversize it and turn a plug with an interference fit of .0005" or so and drive it in, milling it flush later and then re-drill. HuFlung's method sounds like a winner for a quick alignment.
07-29-2005, 02:22 AM #5
If I could just add, drilling 1/8” dia thru 1” of aluminium. (8 Times diameter), might have been ambitious with a less than stellar set up. Or with out frequent pecking to clear the flutes. You could go, just past your ½” depth, so that it spots the second plate. – Regards Phil.
07-29-2005, 03:00 AM #6
A possibility is to C-clamp the stack together to keep the relative position. Small clamps, several of them.
Pickup the same location from the other side of the stack...may have to use some tall parallels to set it up the same.
Drill say a 1/16" hole on the same location from the other side.
Drive out the 1/8" bit remnant with a pin punch....you may have to modify the 1/16" to whatever pin size you have, a dowel pin would also be a good choice IMHO.
If you so choose, you can go back to the original side and continue drilling, however the hole may follow the 1/16" pilot hole. A 1/8" endmill may be more rigid to get the hole back thoroughly straight again.
07-29-2005, 01:07 PM #7
Oh, yeah, i forgot to mention this is the first of 3 alignment holes, so i seperated the stack already. i got the bit out of one hole, since i had the part indexed in the vise i just useed a new bit and tried to drill it out.
I was about 1/8" from completing the hole when the bit shattered. Yes, i say shattered because when the piece that I did get out came out, it was not 1 piece but 5 or 6. I was pecking quite a bit near the end.
I don't really wanna go for a chemical means of tap removal, being as I don't really have the capability to deal with strong acids in my shop right now.
I tried driving out the bit with a few dowel pins, they just broke.
Did I hear I need a solid carbide endmill or a hss one? I only have a cheap chinese 1/8" endmill someone gave me a while back. it is sharp, though. I already broke two 3/16" EM's from that same factory, so I'm not very satisfied by the quality of them.
07-29-2005, 01:12 PM #8I don't really wanna go for a chemical means of tap removal, being as I don't really have the capability to deal with strong acids in my shop right now.
07-29-2005, 01:18 PM #9
They make Dremel bits in the size needed to cut out your pieces of drill.
Grizzly sells a 50-piece set of these carbide cutters in various sizes. That would work. Yes, you do need carbide to cut HSS.
Also, I have found on eBay, sets of 1/8" and 3/32" carbide end mills, with the standard 1/8" Dremel style shank.
If you are in SF, you can stop by here and take a couple of them. Spin them at the highest speed of your drill press, so they won't rattle so much. Or you can use a Dremel tool with a Dremel drill press.
Also, to prevent future broken drill bits, you can use a lubricant in aluminum. Some people recommend a tiny bit of WD-40. At work here, they use ethyl alcohol, which evaporates and leaves no residue. In older times, they used kerosene. Also, there are commercial products made specifically for aluminum. You don't need much, just enough to make a thin film that will prevent the Al from welding onto the drill bit.
[ 07-29-2005, 03:54 PM: Message edited by: Jon_Spear ]
07-29-2005, 02:01 PM #10
A pencil eraser, mounted in a drill, can sometimes remove a broken drill bit if you go at it in reverse.
Or vibration can do it also. Try vibrating the piece with a sander or something...
08-01-2005, 12:18 AM #11
I broke a 6-32 3 flute tap off in a blind hole in a priceless, irreplaceable robot part that I absolutely had to be on a plane with in 2 days.
I could have paid crazy money to have it EDM'ed out, but happened to see something in a flyer from Travers tool before I resorted to that.
Solid micrograin carbide sort of spade shaped bits called "Omega bit" or "Omega drill"...something like that. A bit (ha) spendy, but they swear they work.
I bought the set (since my employers were paying) Set it up per the instructions, and 10 minutes later I was helicoiling the hole.
They work really well. A week later I used one to remove an 8mm tap an associate broke off in the shock stud of someone else's Very Expensive Yamaha V-Max. Saved his ass, I did.
08-01-2005, 02:45 AM #12
That was a lot more fun than fixing the robot part I bet!