Author Topic: Drilling out broken bolts  (Read 2005 times)

PonoBill

  • Cortez Bank Status
  • *****
  • Posts: 25461
    • View Profile
Drilling out broken bolts
« on: June 10, 2022, 08:54:27 PM »
Lots of people have asked how to extract broken bolts on foil fuselages. Here's the bottom line--if you broke a bolt while tightening it, any advice about screw extractors and the like comes from people who have never done this shit. If you break a bolt loosening it at least the threads are not jammed tight against the thread faces. But most bolts get broken during tightening, and you can't loosen them with some device that applies less torque than the original bolt head. Period. No, not going to happen. So you need to drill out the bolt leaving a thin shell with the threads intact so you can make the threads and the remaining thin shell of the bolt collapse (generally with a chisel and hammer), and take it out. Or you can weld a nut onto the threads and turn it out. The problem with welding a nut onto stainless bolts is that you need to spill argon everywhere to get a decent weld. No way to back purge the stainless so you just gotta blow argon everywhere.

If you choose to drill out the bolt, then that takes precision drilling, and that means you need the right toys--I mean, tools.

Specifically, you either need 30 years of experience or an optical center punch. Optical center punches take less time to acquire and are fairly inexpensive. Once you have one your drilling precision increases hugely and you'll find yourself to be a drilling precision snob. 

Here's how this works:

Grind the bolt flat--I used my belt grinder.

Locate dead center of the bolt optically. If you look at the picture of the optical element you'll see where I fucked up. I didn't grind the bolt completely flat, just enough to get a good flat area for the centerpunch. But then I centered the optics on the flat area and skewed it a little towards the flat segment instead of taking the full bolt size center.

Swap the centerpunch for the optical element and whack the centerpunch with a hammer.

Presto, dead center--sort of. It's not the tools fault--it's the nut behind the wheel. I drilled this out but the threads were kind of rough and skewed a bit after I picked out the old threads. So I drilled it to 21/64ths and ran a Helicoil tap through to see how it looked. The threads were clean and full depth, so I ran in an 8mm Helicoil coated with red locktite, the remaining options would have been a 3/8ths Timesert or tig welding the hole up and re-tapping to 8mm, but the 8mm Helicoil worked fine. I fucking hate Helicoils, but they work and I have lots of them.

It helps to have a hard rock playlist running while you do this. Heavy Metal or 90's thrash goes well with metal work. I put on Skating Polly when I'm welding aluminum. Tradition.





« Last Edit: June 10, 2022, 09:27:12 PM by PonoBill »
Foote 10'4X34", SIC 17.5 V1 hollow and an EPS one in Hood River. Foote 9'0" x 31", L41 8'8", 18' Speedboard, etc. etc.

sflinux

  • Rincon Status
  • ***
  • Posts: 237
    • View Profile
    • Email
Re: Drilling out broken bolts
« Reply #1 on: June 13, 2022, 09:40:40 PM »
I feel your pain.
i've had to do this on quite a few surfboards.  Now I remove the fins after each session.  If a screw starts feeling stripped, I replace it.  The Finpuller tool has been convenient for fins that are stubborn to pop out.
With hydrofoils, I apply grease inside the holes for the bolts, which helps to prevent the screws from seizing. 
Quiver Shaped by: Joe Blair, Blane Chambers, Kirk McGinty, and Bob Pearson.
Me: 195#, 6'2"

jondrums

  • Peahi Status
  • *****
  • Posts: 813
    • View Profile
Re: Drilling out broken bolts
« Reply #2 on: June 13, 2022, 10:20:46 PM »
I've had good luck with penetrating oil first for 24hrs or so, then drill with a LEFT HAND drill bit a bit smaller than the fastener root diameter.  Follow that with extractor if necessary.

This kit is affordable, but there are lots of similar kits

https://www.amazon.com/COMOWARE-Screw-Extractor-Broken-Remover/dp/B07Q5GMQ4Z/ref=sr_1_4?crid=3NOJ0PPDWTPF9&keywords=extractor+left+hand&qid=1655183885&sprefix=extractor+left+hand%2Caps%2C151&sr=8-4#customerReviews

PonoBill

  • Cortez Bank Status
  • *****
  • Posts: 25461
    • View Profile
Re: Drilling out broken bolts
« Reply #3 on: June 14, 2022, 05:41:58 PM »
I have a set of left hand bits for just that purpose but they generally work best for lightly stuck stuff. If I'm convinced that the threads can be saved I tig weld a nut onto the broken bolt. the combination of heat and lots of torque works well. But I assume any stainless bolt broken off in aluminum is basically welded in place.
Foote 10'4X34", SIC 17.5 V1 hollow and an EPS one in Hood River. Foote 9'0" x 31", L41 8'8", 18' Speedboard, etc. etc.

JohnnyTsunami

  • Rincon Status
  • ***
  • Posts: 110
    • View Profile
Re: Drilling out broken bolts
« Reply #4 on: June 14, 2022, 11:31:11 PM »
I got some fancy 316 stainless torx footstrap screws special ordered from Germany. Put them in my board. Ripped the head off one. I needed a session, so I put the second one in a different hole really lightly. That head ripped off on the way out!

One came out with an easy out - just barely. I thought I would snap the easy-out, but it worked.

The other I tried to drill into, the drill broke. A milling center drill was used - that broke. A carbide bit was used - that broke.

I ended up getting a cheap set of 100% carbide bits for my dremel. I dug that screw out in about 30 tedious minutes. Just felt around, when it got easy, that means you are off the bolt. Ended up making the hole in the chinook 5 hole footstrap plug a bit wider than normal but not into the foam, so I just dropped some epoxy in - problem solved.

It doesn't get much worse than that.

 


* Recent Posts

post Re: Dave Daum Build Series - Foilboard Construction A to Z - Q & A
[The Shape Shack]
tarquin
Today at 12:18:13 AM
post 2020
[General Discussion]
AndrewTauSh
Today at 12:11:15 AM
post Re: Heading to Maui next week…….
[Wingsurfing, Windfoiling, Wingfoiling, Wing SUP]
PonoBill
December 03, 2022, 10:39:26 PM
post Re: Another revelation about the Barricuda style Kalama board!
[Foil SUP]
Beasho
December 03, 2022, 07:27:28 PM
post Re: Heading to Maui next week…….
[Wingsurfing, Windfoiling, Wingfoiling, Wing SUP]
JohnnyTsunami
December 03, 2022, 05:03:20 PM
post Re: New Winging specific boards from Naish.
[Wingsurfing, Windfoiling, Wingfoiling, Wing SUP]
Badger
December 03, 2022, 03:46:30 PM
post Re: Heading to Maui next week…….
[Wingsurfing, Windfoiling, Wingfoiling, Wing SUP]
John65
December 03, 2022, 02:29:42 PM
post Re: New Winging specific boards from Naish.
[Wingsurfing, Windfoiling, Wingfoiling, Wing SUP]
Solent Foiler
December 03, 2022, 02:28:42 PM
post Re: Dave Daum Build Series - Foilboard Construction A to Z - Q & A
[The Shape Shack]
JohnnyTsunami
December 03, 2022, 12:42:36 PM
post Re: Heading to Maui next week…….
[Wingsurfing, Windfoiling, Wingfoiling, Wing SUP]
PonoBill
December 03, 2022, 11:49:32 AM
post Heading to Maui next week…….
[Wingsurfing, Windfoiling, Wingfoiling, Wing SUP]
John65
December 03, 2022, 10:50:56 AM
post Re: Blue Planet Show- Wing Foil interviews
[Wingsurfing, Windfoiling, Wingfoiling, Wing SUP]
blueplanetsurf
December 03, 2022, 10:26:35 AM
post Re: One Fine Day
[Random]
daswusup
December 03, 2022, 06:28:05 AM
post Re: Plastic Buckles
[Wingsurfing, Windfoiling, Wingfoiling, Wing SUP]
tj_boof
December 03, 2022, 05:08:14 AM
post Re: Something new?
[Foil SUP]
tarquin
December 03, 2022, 04:21:38 AM
SimplePortal 2.3.7 © 2008-2022, SimplePortal