Removing over-torqued torx screw...

[Wannashootit]

Customer fucked up and torqued a Sig red dot to his rail with 20 ft lbs, instead on inch pounds...
The T-10 tips aren't strong enough to break this free- they snap off clean leaving the screw head intact and undamaged.

I put some Kroil on it to see if it might soak in enough to lessen the force needed to break this free but no go.
I'm thinking some judicious heat around the end of the screw (it's a thru-bolt type mount) where it pokes out of the plate it's screwed into?

Any other suggestions? Trying to avoid treating it like a snapped-off scope mount screw and drilling it out on the mill.

 

[Old Man with Gun]

That sounds more like permanent thread locker than over tightened. How did they tighten to 20ft/lbs without snapping the screw bit or screw?

Heat and solvents?

If the metal fused under the heat/pressure it is basically welded, might as well drill it out.

 

[Makinchips208]

Drill the head off, a drill bit that is slightly larger diameter than the thread diameter.
Sometimes you use a left hand drill bit will help it spin on out after the head pops off.
If thread lock has been used then this isn’t much help.

 

[Makinchips208]

Or maybe a snap-on or high quality torx bit? Some of the cheaper bits are... well.. cheap.

 

[Im2bent]

Drill the head off, a drill bit that is slightly larger diameter than the thread diameter.
Sometimes you use a left hand drill bit will help it spin on out after the head pops off.
If thread lock has been used then this isn’t much help.

I just had to do this on my scope rail. I was bedding it and the next day when I went to remove the screws they were locked up. I had torqued to 18 inch/lbs. I thought I had accidentally got jb weld on the threads. I sheared a brownells tip it was so tight. I drilled off the head at which point the body of the screw spun right out. There will be a bit of the screw left protruding from the hole when the head pops off that you can grab. It was weird. No way he got 20ft/lbs without shearing the screws.
There should be no need to drill the entire screw out unless something happened like severely cross threaded.

 

[Old Man with Gun]

I have used a dremel to make a big flat head, but it can get squirrely and leave scars if not very careful.

 

[Wannashootit]

Brownell's torx bits... never been a fan of their taps, but I haven't had issues with their screw tips.
I've got a small e-z out, but if the screw could be broken free by that (or a left-handed drill bit) I think it would loosen without extraordinary measures. The head is undamaged, it's just that the tip cannot handle the torque needed to break it free without snapping off.

Sounds like it's going into the mill vise to get drilled out and pick out the threads...

 

[Statusquo]

Go to your local lumber yard and a get a T10 bit for an impact driver.

 

[Mike Casselton]

How the hell did the shank of that little screw survive that much torque?
I can snap most of those .08/.10 size with a screwdriver, and my name is not Gorilla Monsoon.

 

[Wannashootit]

Go to your local lumber yard and a get a T10 bit for an impact driver.

Great idea, thanks!

How the hell did the shank of that little screw survive that much torque?

That's what I was wondering. Maybe SIG doesn't use cheap/soft Chicom screws

 

[Vodak]

I second the idea of getting impact rated bits, and using an impact driver if you have one.
I worked on street lights right on the coast. Fighting with corroded and seized screws I’ve found that a lot of times the impact will free up screws in conditions where a hand driver strips or spins the head off.

 

[ma smith]

Great idea, thanks!

That's what I was wondering. Maybe SIG doesn't use cheap/soft Chicom screws

If I'm reading the below table BOLT SHEAR CAPACITY high grade scews will still shear off in these smaller sizes lik m3.5 well below 20 ft lbs (27nm)...you'd need something well above m4/m5 survive that. I'd suspect loctite (or corrosion) possible problems here.

https://www.boltsgalore.com.au/downloads/technical/Bolt%20Shear%20Strength%20-%20Metric.pdf

 

[hafejd30]

Can believe that screw held with 20 ft lbs. I feel like they barely handle 20 in lbs when I tighten them. If nothing else I gained confidence in the mount reading this

Just drill the head off. Screw should back out once the head it removed. Unless it’s red loctite or something of the sort

Your trying to save the mount. Keep in mind there’s a chance he jacked the mount threads up when tightened that much anyways

 

[Mike Casselton]

If there's no thread locker, I bet that thing stretched like a wet rope

 

[Mike Casselton]

Is it counter sunk or is the head on the surface? If you can grab it with vise grips, it'll come out or the head will shear.

 

[FuhQ]

Customer fucked up and torqued a Sig red dot to his rail with 20 ft lbs, instead on inch pounds...
The T-10 tips aren't strong enough to break this free- they snap off clean leaving the screw head intact and undamaged.

I put some Kroil on it to see if it might soak in enough to lessen the force needed to break this free but no go.
I'm thinking some judicious heat around the end of the screw (it's a thru-bolt type mount) where it pokes out of the plate it's screwed into?

Any other suggestions? Trying to avoid treating it like a snapped-off scope mount screw and drilling it out on the mill.

Bust out the milling jig vise and stick it in the drill press... And be extremely careful.

 

[elwarpo]

A hand impact with quality bit is the best choice. Only way I know of.

 

[Wannashootit]

A hand impact with quality bit is the best choice. Only way I know of.

Just picked up impact rated bits.
I have a hand impact screwdriver- and was thinking about using it- but have concerns over rattling the guts out of the red dot.
I'm going to see if I can clamp this upper in a padded vise to immobilize it enough so it can't move if I whack it with the impact screwdriver.

Will give it a try later when I get into the shop. Thanks for the feedback guys will let you know how it ends...

 

[Hobo Hilton]

Take some of those cheap torx drivers and do this:

Heat the torx driver red hot and insert it into the head of the bolt.... Just let it sit there and sizzle.... Watch what boils out around the threads / head.... Allow it to cool slowly and repeat again..... After it cools for the second time go ahead and try the high grade Torx driver you just bought....
Only heat the bolt, not the mount.

 

[E. Bryant]

If you want to heat the screw, just use a soldering iron.

If this were my mess, I'd drill off the heads to get the red dot out of the way, and hopefully have enough screw remaining to grab it with an appropriate tool (like Vampliers).

 

[Wannashootit]

Put a red-hot tip into the screw for 30 seconds.
A stack of adapters to get my 1/2" impact screwdriver down to the 1/4" torx driver.
Set the upper onto a plastic bench block with a shim of the proper thickness supporting the SIG mount, one swing for the fences with a 20 oz hammer and...success.

No visible damage to the screw but I'm sure the threads have been stretched so it'll be replaced.

 

[The D]

If you want to heat the screw, just use a soldering iron.

If this were my mess, I'd drill off the heads to get the red dot out of the way, and hopefully have enough screw remaining to grab it with an appropriate tool (like Vampliers).

This. I deal with broken/corroded screws every day and this is exactly how I handle most of them

 

[FuhQ]

If you want to heat the screw, just use a soldering iron.

If this were my mess, I'd drill off the heads to get the red dot out of the way, and hopefully have enough screw remaining to grab it with an appropriate tool (like Vampliers).

Yep, that's why my first post mentioned the milling jig and the drill press... I spent nearly 20 years doing welding and custom fab work... Had to do this routinely with equipment and tools, even to a couple of pic rail scope bases for friends, and 1 of my own, that had shitty screws that stripped-out.

 

[E. Bryant]

And for those who are newbies to drilling out fasteners - give it a shot with a left-hand-twist bit. If you do this, the odds are decent that the screw will zip right out as soon as the head is relieved far enough to release the preload. I've been occasionally fixing fuck-ups (both my own and others) for a quarter-century, and it's still amusing when this process works.

When it doesn't work, slow down and consider the next steps very carefully.