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how to extract broken drill bit?

bmellis11

Well Known Member
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Just my luck. Tonight I was match drilling #30 the forward fuselage skins to the lower longeron and had a brand new cobalt drill bit break off while drilling one of the holes common to the gear tower weldment on my RV-8. I have attached a snippet of the plans with the area I'm talking about highlighted. The bit broke inside the hole, so I can't grab it with vise grips. There is a hole where the bit would have exited the inboard side of the gear tower weldment, but the bit isn't sticking out yet to grab onto, and I can't use a punch to push it out because the weldment has a steel bar running forward to aft that blocks access to the hole.

Does anyone have advice on how to get this bit out? This hole is going to be enlarged to #19 for a screw, so I can get away with enlarging this hole a bit while removing the bit. Is there such thing as a bit extractor?
 

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You might be able to use two sewing needles, get one in each groove and then use pliers to twist it out. Using some penetrating oil might help a little.
 
Try some fine tweezers in the drill bit flutes. Otherwise, can you "easily" remove the weldment to get to the exit hole? (I'm not familiar with that detail on the -8).
 
I am guessing the bit got hung up on the steel portion of the stack up. If so, it will likely be quite difficult to remove, depending upon the length of the bit remaining. what is the on ctr spacing of those holes? Enough room to leave that be and put new holes/screws on either side of it with adequate edge distance? You could fill the bad hole before paint with no one the wiser. Clearly a structural area, but am sure Van's would have ideas on addressing it without having to remove the broken bit.

In the future, you need caution when match drilling steel. The near correct size hole encourages the bit to dig in aggressively and then one side of the bit digs too deep and tries to tip the bit sideways but the stem doesn't allow it, then "snap." WHile no issue with the soft alum, it is real problem with steel (especially those like 4130 that are stronger than mild steel) when using small drill bits. Slow and steady is the name of the game. The operator must keep the bit from going in too rapidly. Easy to get sucked into this trap after matching drilling a 1000 holes into aluminum, where there is no risk.
 
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Drill a small hole on the back side and punch it out. Or enlarge the hole on the back side and punch the bit thru from the front side.
 
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Re: how to extract a broken drill bit?

Maybe a tap extractor???
 

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LR172; said:
What is the on ctr spacing of those holes? Enough room to leave that be and put new holes/screws on either side of it with adequate edge distance? You could fill the bad hole before paint with no one the wiser. Clearly a structural area, but am sure Van's would have ideas on addressing it without having to remove the broken bit.

Wow! Hide a problem in a structural area because??? I get that you have a problem, but call Vans and follow their recommendations. I would discourage trying to cover up a mistake. Fix it the right way and then build on.

-Marc
 
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Wow! Hide a problem in a structural area because???

-Marc

I didn't say to hide a structural problem. It is a common repair to shoulder two new fasteners around a problem fastener (broken bit, misdrilled hole, elongated or egg shaped holes, etc.), assuming there is enough edge distance available to squeeze them in. My suggestion was NOT to hide a flaw, as the hole with the broken bit is no longer a structural flaw once it is shouldered with new fasteners on each side of it. If enough ED does not exist, then on to plan B. I also suggested that the OP contact Vans for a recommendation. There is nothing wrong with covering up a mistake as long as an engineering approved fix has been put in place to address any compromise to the structure made by that mistake. I stand by my recommendation to get Van's opinion on a recommended method to address this.

Larry
 
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Stuck drill

Ben

You said there was a hole on the inside but you cannot get a punch on it.

I would suggest a piece of piano wire with a bent stub that you could force into the hole on the inside to push the drill far enough out to grip it.

Good luck
Rob
 
I was able to drill out broken tap using a diamond drill bit. They do sell 1/8" diamond bits so you could try that if you are unable to get something on the end of the drill bit to tap it loose from the inside. Make sure and use a good quality bit at slow speeds with Boelube or cutting oil when drilling those weldment holes. Easy to harden the 4130 if you drill at too high a speed and get it hot. M35 or 42 Cobalt bits are the best but a quality HSS will work as well if used properly. It will be lots of fun drilling the 3/8" and 7/16" gear attach bolt holes in the weldment and 1/4" wear plate if you don't have quality bits.
 
Or

Along the above post line, if you use a diamond hole saw, you don’t need to drill the broken bit; the hole saw will go around the broken bit and cut the aluminum.
 
Thanks everyone for the responses! I ordered a Rescue Bit, which I read can be used to drill out broken drill bits. But after taking a step back, I came to the much simpler solution, which was to remove the skin and longeron, which are just clecoed and bolted in at this time, and when I did that the bit got pulled out with the longeron and was easy to remove without damage. :cool:
 
Rescue bit

Thanks everyone for the responses! I ordered a Rescue Bit, which I read can be used to drill out broken drill bits. But after taking a step back, I came to the much simpler solution, which was to remove the skin and longeron, which are just clecoed and bolted in at this time, and when I did that the bit got pulled out with the longeron and was easy to remove without damage. :cool:

The rescue bit will indeed cut the drill bit but it is more of a grinder and can be difficult to control, especially in a small space…
 
Like most issues we come across building, we spend more time worrying about the fix than it takes to fix it! Good job.
 
Thanks everyone for the responses! I ordered a Rescue Bit, which I read can be used to drill out broken drill bits. But after taking a step back, I came to the much simpler solution, which was to remove the skin and longeron, which are just clecoed and bolted in at this time, and when I did that the bit got pulled out with the longeron and was easy to remove without damage. :cool:

I too tried a Rescue bit prior to the diamond bit. The Rescue bit is carbide. Not as hard as the diamond bit. It didn't work at all for me. Glad you figured out a solution!
 
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