Advice getting out stripped Allen heads in flexplate (Solved!)

[Basilbomb]

Today I was trying to get out the flexplate allen bolts and whoever was in here before torqued the hell out of them. Ive got a huge milwaukee impact good for over 1000ft/lbs and couldn't budge them. The first try the engine jumped and the allen head bolt stripped. I used a big breaker bar to get the rest out but there's that buggered bolt still in there.

I first tried sacrificing my allen socket by welding it into the bolt, but of course the welding wrecked the temper and it sheared off.

I then tried welding a big nut onto the bolt, and that sheared off too when I leaned on the breaker bar

.

Now I'm stumped. Those bolts are hardened and I sure don't want to try drilling it out.

Any suggestions?

[Vanagon Nut]

I don't have any real advice other than forcing in a star shaped head on those Allen head sockets.

Maybe change your subject title to include "flex plate" or some such? That might get more attention and help? What I"m seeing is a pretty specialized situation.

Neil.
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[djkeev]

You need to show us what you have right now.

After the welding, after the breaking of welds, what is there?

Odds are quite good that you have already removed a lot if the temper by welding on it.
After all, yes some of temper is an alloy mix but also using various cooling techniques from a hot state.
Heating to red hot and slowly air cooling removes a lot of a steels strength.

The solution is probably to Buy a good drill bit from an industrial supply and go at it. WW Grainger, MSC, Fastenal, etc

Get several sizes, start small and work your way up.
You want to remove the head, not the threads.

Dave
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[Wildthings]

The problem at this point would be finding the center of the bolt and getting it punched accurately. You only have to get the head off so you don't have to drill all that deep, originally it would only have been 1/8" or so of metal to drill through.

[Abscate]

Lop of the head with a Dremel , grind flat

Center punch by eye , to within 1mm

Drill with good bit. Not from Harbor Fright or Lowes
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[vanagonjr]

[?Waldo?]

Pounding in a triple-square works 486 TIMES as well as pounding in a Torx. Just saying. That would have been my step 1 rather than welding.

[sanchius]

A trick I learned from 10ceentlife is to give stubborn bolts some hard whacks with a heavy mallet. That helped me loosen an unyielding high-torque main crank bolt once.

If pounding in a triple-square doesn't work and you do end up drilling it out, supporting your drill with a strap or jack stand (as shown below) helps you focus on keeping your drilling straight.

I had to do something similar with a non-recessed flexplate bolt on a different vehicle. Once I had ground off the exposed bolt head with an fiber disc and removed the flexplate, I could turn out the remaining unloaded bolt shaft with just my fingers. Hopefully the PO didn't use thread-lock on those.

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[Basilbomb]

Thanks for all the suggestions. FYI, I thought about the triple square as I do have those, but no way was it going to budge that bolt with that kinda torque on it. It would have just rounded it more.

Right now the hole is pretty much filled with hard weld material, but I'll see what I can do to dremel it out so I don't have to drill through that crap as well as the bolt.

I was hoping someone had a trick I hadn't heard of yet, but it sounds like buying some expensive cobalt drills is my only option right now.

I wonder if heating the bolt before drilling it would make it softer or just bugger the drill bit?

[9.5isCanadian]

My .02 Canadian would be to flatten your weld out with a Dremel as noted above and drill it.
The welding heat cool cycling will have reduced the hardness of the grade 8 cap screw. Only go far enough to pop the head off.
If you have access to a left hand drill bit, use that. “Sometimes” the drilling forces can jar it loose but I doubt that will help in this case as you’ve tried some pretty severe techniques so far without success.

Alternatively you could heat it again, if you weld another nuts let’s say, and hit it with some Lloyd’s spray (or equivalent - other sprays are available). The shock can loosen the bond with the counter bore and the head of the cap screw.

I don’t envy you. This is a grim situation if you end up needing to drill the fastener out of the back end of the crank.
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[9.5isCanadian]

[16CVs]

Sacrifice the flex plate and grind the head off the bolt off and then I’d bet the newly created stud will spin out with your finger. A replacement flex plate is cheaper and quicker than buying a bunch of drill bits and risking further damage to the crank.

I agree with others though, a Torx or triple square might have done it from the outset.

Stacy
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[Sodo]

Wow this is a knock-down, drag-out fight.
And you are fighting admirably, i have to say this does not liook like your first rodeo.

[Basilbomb]

[Vanagon Nut]

If an impact wrench isn't available this hammer type impact tool might work along with a triple square or other appropriate bit:

https://www.amazon.ca/Lisle-30200-Hand-Impact-Tool/dp/B000P0TZ9W

I wore out my Lisle which might speak to a lack of quality in that brand but it did work on at least a several projects.

I agree. Heating the bolt metal red then letting it air cool would likely make it softer than it was. In part I guess that would depend on bolt grade and metal type?

The other consideration is that a PO may've put blue lactate or similar on those bolts. Especially if bolts were re used (IIRC, they're "always replace" types). Heating the bolts might help loosen any thread locking compound.

Neil.

[jlrftype7]

[tjet]

Drill the head off as wildthings suggested. You need to use a bit just larger than the bolt shank. When drilling, you need to go as slow as possible, while applying firm pressure. The drill bit should not be singing ( high pitch squeal). If it does, its already toast. Light oil will help. This method works, it just takes patience. The harder the metal, the slower you go.

[Basilbomb]

I ground out the weld filling in the bolt with a dremel, and that took quite awhile. but after that, a single 1/4" cobalt bit had it done in 15 min!

There's always a way.

[jlrftype7]

[Wildthings]

If you are just starting from scratch, you could drill say a 3/16 or 7/32" hole down through the sockethead. This may be enough to lessen the tension on the bolt to where it will back out, or if not make it so the head will shear off.