[Dounraey]

I removed the back plate from the steering knuckle on SRX18501 but unfortunately sheared off one of the four 2BA allen screws. I'm wondering the best way of extracting this sheared off setscrew. The thing is, since it is just a backplate (RR refers to it as a brake shield) maybe it would be better to just rely on the remaining three setscrews to hold it in place. My fear is that if I try to drill out the snapped off setscrew I might nick the side of the hole and introduce a stress point to the knuckle. It may be the knuckle is so strong this would not matter. Another possibility would be to drill out the broken off setscrew and re-thread it slightly oversize, if this would not undermine the integrity of the knuckle.

I'm looking for advice on how to proceed.

 

[Jeff R 1]

BA threads are pitch based like metric, 2BA is about 31.4 TPI.
You could tap it out to 10/32, or even go a little bigger to 12/32.
Going over sized to 10 or 12/32 isn't going to weaken such a large piece which is probably forged steel.

If it was my project, I would centre punch the twisted off screw as close as possible and drill out with some sort of oil to lubricate the bit.
I would make a jig out of wood on a drill press to keep the hand drill at 90 degrees to the work.
Always use a new bit.

 

[Wraithman]

Those screws are horrible and I always renew them and use anti-seize.
sand or file down the old fastener to get a flat surface, and like Jeff said, punch it so the drill does not walk. I like a very small bit first and then larger.
It's not critical, they just hold the shield in place.

 

[Dounraey]

Jeff and Rob. Thanks for your replies.

I managed to successfully drill the sheared off bolt. I used a hinge drill to get the hole central. Then disaster - I tried to remove the sheared off bolt with a stud extracter, which snapped off. The upshot is I finally managed to grind the stud extractor out using diamond rotary bit from (would you believe it) Harbor Freight, after all else failed. Took about 3 hours, not including trips to HF.

In future I doubt I will ever use a stud extractor again but instead drill and re-tap the hole. The rationale being that if a thread is so "welded" in, a stud extractor is unlikely to free it.

 

[Wraithman]

I rarely use a stud extractor. I find heat, Kroil, and precision drilling/ and re-tapping gets the job done.

 

[Jeff R 1]

Yes, I agree totally with that Wraithman.
It only takes one experience with a stud extractor not to use them again.
I've never found them useful for anything.

 

[Dounraey]

Well I'm now a definite convert

 

[jake66]

I sometimes use "left hand drills" for sheared off bolts or studs as usually the drill will go so far then the stud or sheared bolt will wind out on the end of the drill. I, like others, have never had any success with stud extractors and do not even think about using them.

Jake.

 

[Martin Pearson]

I have just done the same on mine. I just drilled out the broken bolt taking care not to go deeper than the bolt length.
The holes in mine go all the way through so I tapped the last remaining length of hole and fitted longer bolts.
You could always put a nut on the back. Not so authentic but safe.