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I have broken 6 drill bits.. help!!


jccampbe2001

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I have broken off 6 drill bits trying to drill out a bolt that broke off. I have managed to drill 1/8 of a inch in to the bolt. What type of drill bit is the best to drill a bolt out? I have also broken off 3 of those reverse thread drill bits trying to get it out. Help

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Where have you been buying your bits? Also, where is the bolt you're trying to drill out? Is it some place on the car you could use a propane touch to heat cycle it? That can help break it loose.

As for the best type of bit, I prefer the left-handed (reverse) bits myself. Remember to drill slowly and don't apply too much pressure. If you aren't using a variable speed drill buy/borrow one.

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For smallish bits. You want high speed and low feed. You also want coolant, and a steady, steady hand. Dive the bit back out a little, every 5 seconds or so, to help get out the chips. Keep the pressure on the bit perfectly centered. It's also essential that the bit be sharp. If it's not sharp, all you do is make heat.

Edited by cygnusx1
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Don't use WD-40 as cutting fluid/coolant. Bacon grease works GREAT if you don't want to buy actual cutting fluid. Sharp bits are a very good suggestion. I've had shockingly good luck with Harbor Freight's Cobalt bits. Their other bits are crap IMO, but the cobalt ones are pretty amazingly good, and the price is so low that you don't have to freak out about losing or breaking one.

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For smallish bits. You want high speed and low feed. You also want coolant, and a steady, steady hand. Dive the bit back out a little, every 5 seconds or so, to help get out the chips. Keep the pressure on the bit perfectly centered. It's also essential that the bit be sharp. If it's not sharp, all you do is make heat.

My experience is different. I drill 9/64 pilot holes- stepping up to 17/64 and/or 21-23/64 holes- all day long in stainless steel pipe and steel I-beams. We have great success with pressure and low RPM. We never use any lubricants and a single bit will drill dozens of holes.

Maybe we're just lucky. We teach our helpers- "if it's curling, it's cutting" and is proof that material is being cleared fron the hole. In my opinion, high speeds overheat the bit and it loses it's temper. The relatively low volume of cutting/cooling fluid that you can apply by hand doesn't provide sufficient cooling to be of any use. There are "feed and speed" charts for various drilling applications, I'm just relating my experience, which I have used on automotive bolts, etc. with the same success.

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