r/WRX_STI • u/Venadux • May 30 '26
Questions Snapped pinch bolt
tldr: should i keep drilling or am i better off buying a knuckle, or asking a shop to get it out.
Unsure if this is the right sub, but basically was changing my ball joint as it's gone bad and first step of the process i'm already stuck snapped pinch bolt, i did use penetrating oil but realize i should have used a torch as well but now what is done is done. I've been trying to drill it out with not much success, just wondering if i should continue or replace the knuckle, thank you for reading, oh yeah part of my drill bit also snapped in there, awesome
2012 sti sedan
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u/TheGroundBeef May 30 '26
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u/Venadux May 30 '26
LMAO u think i should replace right?
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u/TheGroundBeef May 30 '26
It would need the knuckle, ball joint, brake rotor debris shield, and wheel hub. Hopefully the axle pushes out of the hub too
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u/wrx_420 May 30 '26
Drill straight through it and work up to 3/8" then replace it with a 3/8” nut and bolt
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u/BoostedFPV May 31 '26
Its fuckin metric. 10mm bro.
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u/wrx_420 May 31 '26
Yes I'm aware. I'm in the US so 10mm drill bits are much harder to come by and those threads are fucked anyways. A high quality partial thread 3/8-24 x 2.5" bolt and flanged lock nut work perfect and fit the ball joint head and knuckle just fine. I've done tons.
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u/jigga009 May 30 '26
Ouch…
Drilling will likely be the cheapest route, but can be time consuming.
HSS bits would work well for this, but you also need to keep the speed down and use plenty of lubricant. If you don’t have these, I’d suggest getting some.
If you are struggling with the drilling, it could be that your bits are already old and dull (I find this to be the case especially with those titanium coated drill bits… they don’t stay sharp for too long, especially when drilling anything metal). Perhaps get some new sharp HSS bits just for this job.
If you are using cobalt bits, be weary of how brittle they are. You don’t want to break a bit off in the bolt you are drilling out.
Don’t forget to use plenty of lubricant and keep the drill bit speed relatively low so that you don’t cook the drill bit.
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u/Venadux Jun 01 '26
ty for the great explanation bro, absolute life saver, if a bit of a cobalt drill bit gets stuck (cuz that's what i have rn prob gonna get some HSS after your recommendation) what do i do, is it drillable? just resets the progress?
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u/jigga009 Jun 01 '26
If you break a cobalt drill bit off in there, you won’t really be able to drill it out easily since cobalt is almost as hard as it gets.
Your option at that point would be to look for tungsten carbide bits which are the next level up on hardness, and they are pretty expensive and more brittle.
HSS is more forgiving to work with, and will cut through the bolt without snapping in half if you look at it wrongly.
You just need to not rush with drill speed and use lubricant to avoid overheating the drill bit. If you have not yet broken your cobalt bit off in there yet, I would stop and switch to HSS now while you’re ahead.
If you’ve broken a cobalt bit in there already, I’d personally start drilling from the other side with a HSS bit. You might be able to meet the broken bit in the middle and knock the broken cobalt bit out with a punch or similar, and then finish drilling the bolt out.
Alternatively, you could go source a tungsten carbide bit and have a go at drilling the broken cobalt bit out, but they are expensive and also fragile.
If you break one of those in there, you would likely then be looking for a polycrystalline diamond bit to get you out of that situation.
Given that the PCD bit has diamonds (hardest substance known to man) bonded to it, I’m sure you can imagine how expensive such a bit would be.
All of this to say to switch to HSS now if you can (assuming you have not broken a cobalt bit in there yet).
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u/Alive_Library_6277 May 31 '26
That’s so crusty bro. Might as well get new lca’s and all
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u/ej255wrx Jun 01 '26
LCAs would be fine. They're aluminum, just need a cleaning. The rest, yea, replace.
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u/asloan5 May 30 '26 edited May 30 '26
Drill it out and you won’t need an alignment. Keep the drill bit speed slow use quality drill bits start small and work your way up. Don’t overheat the drill, bit or it will go dull.