How strong is a drill bit?

As posted in my oft neglected build thread (shameless postwhoreing...its HERE http://grassrootsmotorsports.com/forum/build-projects-and-project-cars/sand-rail-autocrossskid-pad-build-or-why-my-wife-hates-me/96288/page1/)

I was drilling out the new shift linkage for a tension pin (roll pin if you are like me but the hardware store dude corrected me on it) and just as the drill bit was breaking through the other side, it snapped...$%&@#

Its in there good and solid. I started thinking about how I was going to get it out and then I wondered. Is a drill bit really any less strong than a tension pin?

If it matters it was a really good quality drill bit :)

No way you drill out a drill bit, but they are fairly brittle, as you may have noticed. Can you get at the back side with a punch and hammer? Can you weld a nut on the remains of the bit and turn it out backwards? Can you heat the tip with a torch and then beat it out?

Streetwiseguy wrote: No way you drill out a drill bit, but they are fairly brittle, as you may have noticed. Can you get at the back side with a punch and hammer? Can you weld a nut on the remains of the bit and turn it out backwards? Can you heat the tip with a torch and then beat it out?

Sadly the answer to all of the above is nope. Not simply anyway. I can disassemble half the vehicle and remove it all and then get to it if needed. FWIW, the drill bit is not taking all of the effort in the scenario, the fit of the shaft into the fitting is very tight, and offset so there is additional "binding" not crated by the pin/bit. Im tempted to leave it and if it fails I'll tear it all down :) I'll bring the tension pin with me to the skidpad challenge.

Or I'll tear it down next weekend when Im not in so much pain (back is out again) On that note we're having a skidpad challenge car prep weekend at Casa De Misfits. We'll be working on the rail and TB Cahill's E30 as well as any other projects that show up, anyone in the Philly/South Jersey area is welcome to stop by! https://www.facebook.com/events/886801524715064/

I deal with roll pins, broken bent and otherwise, on a daily basis at my job. drilling them out is pretty much always the wrong answer. Sometimes they need to be driven out in the opposite direction of the easily accessible end. Sometimes you need heat. Sometimes you need to let it soak in a really good penetrating oil. Sometimes you need a bigger hammer. You always need a properly sized roll pin punch, preferably from snap on. It's not unheard of to need all of the above.

And a pox be upon the house of everyone that does not re-assemble them with a liberal amount of Anti-seize.

HappyAndy wrote: I deal with roll pins, broken bent and otherwise, on a daily basis at my job. drilling them out is pretty much always the wrong answer. Sometimes they need to be driven out in the opposite direction of the easily accessible end. Sometimes you need heat. Sometimes you need to let it soak in a really good penetrating oil. Sometimes you need a bigger hammer. You always need a properly sized roll pin punch, preferably from snap on. It's not unheard of to need all of the above. And a pox be upon the house of everyone that does not re-assemble them with a liberal amount of Anti-seize.

There may be some confusion. I was drilling the part to insert a roll pin, not drilling out an old roll pin. There is no pin stuck in there, just a drill bit which is currently doing the job a roll pin was supposed to do.

In reply to JThw8: Sorry, reading comprehension fail.

HappyAndy wrote: In reply to JThw8: Sorry, reading comprehension fail.

LOL, no worries, probably a fail on my clarity of writing as well.

In reply to JThw8:

OK then, back on to the real issue. Can a drill bit work as a substitute for a roll pin? I would say probably, but it would depend on the diameter of the bit, and the type of stresses being applied to it. As someone already mentioned, drill bits are very hard, but also very brittle. The roll pins that I deal with are seldom used as load bearing parts, but rather to retain load bearing parts. It sounds like your pin is being used as an actual pivot shaft, not an ideal use of a roll pin, but in a shifter linkage it will probably survive, as long as no one starts slamming it like an old 4spd toploader.

HappyAndy wrote: In reply to JThw8: OK then, back on to the real issue. Can a drill bit work as a substitute for a roll pin? I would say probably, but it would depend on the diameter of the bit, and the type of stresses being applied to it. As someone already mentioned, drill bits are very hard, but also very brittle. The roll pins that I deal with are seldom used as load bearing parts, but rather to retain load bearing parts. It sounds like your pin is being used as an actual pivot shaft, not an ideal use of a roll pin, but in a shifter linkage it will probably survive, as long as no one starts slamming it like an old 4spd toploader.

Not actually a pivot shaft, but it will take some load when shifting. Its keeping the shift rod coupled to the coupler which attaches it to the shifter. There is enough space I suppose I could just drill a 2nd hole and put the roll pin in behind the drill bit. It's a 5/32nds pin

Carbide arbor bit in a Dremel tool. I went through a EZ-out in an engine block this way. Go slow.

A diamond bit in a Dremel will also chew through it very very well. But never use a diamond bit dry, or the diamond particles will fly off.

Drill bits are high speed steel, the only thing that beats HSS is carbide.

Sorry. Drill it our w/carbide, poke it with the pointy end of a tap and try to "unwind" it, or EDM it out if it's a one of a kind item

Dan

Meh, I drilled a 2nd hole and put the roll pin in that. The drill bit in hole 1 is backup.

That's the safest bet.

914Driver wrote: Drill bits are high speed steel, the only thing that beats HSS is carbide.

This, although you forgot one step. HSS<Cobalt<Tungsten Carbide.....even then, Tungsten Carbide has various grades and coatings for specific things if you want to get all technical.

In reply to JThw8:

That's what I was about to suggest.

There's a product sold under the "Omegadrill" name specifically for drilling out broken taps. They really work, and well, but only if used correctly, which requires the part containing the broken tap or drill to be in the vise of a milling machine.

If it broke breaking out the far side of the hole - which is when drills break - can't you drive it back out from behind?