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Countersink bit tip broke of in longeron

T

Thunderpig

Member
With 7 holes left to countersink, the tip of the bit broke off and is now stuck in the hole. Tried to drill it out gently, but to no avail...anyone ever have this problem and what a solution might look like. I've already broken two 1/4" titanium bits trying to get an in with a # 40. Considered drilling up to a #30 and putting in a 4-5 rivet but the tip seems to be laughing at the bits.
 
Can you accurately drill in from the back of the longeron and use a drift or punch from that side to drive out the countersink?

That, or a drill bit remover...
 
Can you get to it with your rivet squeezer? If so, you might be able to push it free from the back side (same idea as the punch, but with a bit more control). With a little work at tool making, you can make your own punch to fit the squeezer and an oversize female die for the other side of the squeezer jaw.

Charlie
 
Punch

BrianDC said:
Can you drive it out with a 3/32 pin punch from the non counter sink side?
Click to expand...

Take a step back. Don't drill. Punch from he back side with a helper holding a bar with a hole in it over the pin hole. It will come out. I had the same problem.
Every hole gets a little buzz with a reamer now. All it takes is a tiny burr to snag a pilot and snap it.
 
The countersink cutter is made of highly hardened tool steel.
You will not be able to drill it.
Breakage is usually caused by the hole not actually being the proper diam., and being a tight fit for the cutter pilot).

I have pressed thing out of holes by making a small tool to put in a hand rivet squeezer.
Drill the center of a short AN3 bolt for a tight fit on a 3/32 drill bit. Cut the smooth portion off of a drill bit and press it into the hole in the bolt. Use the pin to press out the pilot, using a rivet squeezer.
 
Something to try....

Different expansion rates might turn out to be your friend here, try applying a bit of heat.

Also, when hot, rub a candle on the broken stub, let the wax melt into the interface area.

Use a heat gun, not a gas fired torch.

Try pushing/punching the broken stub out while still hot.

A bit of lube on the pilot when countersinking thick stock is helpful. Bees wax or Boelube are good.
 
Pin punch

rvbuilder2002 said:
The countersink cutter is made of highly hardened tool steel.
You will not be able to drill it.
Breakage is usually caused by the hole not actually being the proper diam., and being a tight fit for the cutter pilot).

I have pressed thing out of holes by making a small tool to put in a hand rivet squeezer.
Drill the center of a short AN3 bolt for a tight fit on a 3/32 drill bit. Cut the smooth portion off of a drill bit and press it into the hole in the bolt. Use the pin to press out the pilot, using a rivet squeezer.
Click to expand...

That is a cool idea. Logging that one for future use.
I have a rivet gun set drilled 3/16" for pin punch use. I have pin punches milled down to 3/16". I never shared the idea because it's kinda tricky to use. Have to dial down the pressure and feather the trigger. Works when there's no one around to help. One hand on the gun, one with bar. Also have a set of bars with 3/16" holes for shop heads or rivet sets.
https://drive.google.com/open?id=0B7hyZ-sKQmtremd0cEtqaW1NMWc
 
3 hardware stores, no punches...ended up cutting the end off a #40 12" bit...ironically, I had just ordered a replacement bit. Had tried an old bit, but the temp was an issue initially, thanks guys.
 
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