Broken Bolt Removal Advice?

OSS

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Stainless steel bolts are the worst choice to screw into that aluminum housing. Or any aluminum. Cadmium plated Toyota bolts are best. Just replace the housing bolts every time the thermostat is replaced (every 10 years) and the bolts won't ever seize in the threaded holes again (if antiseize grease is used)
 
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I was a tool and die maker for 10 yrs before I retired, the best thing I’ve found on bolts is to soak them overnight, then center punch, now drill with a left hand drill bit, small at first and work your way bigger. It will usually catch and back the bolt out. I usually have a 60%-80% success rate with that method. Once you get a small hole through the bolt, take your center punch and go around the bolt hitting it and the shock will relax the tight fit.

definitely buy a left hand drill bit set. Good for lots of jobs. And keep them safe and sharp.
 
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I was a tool and die maker for 10 yrs before I retired, the best thing I’ve found on bolts is to soak them overnight, then center punch, now drill with a left hand drill bit, small at first and work your way bigger. It will usually catch and back the bolt out. I usually have a 60%-80% success rate with that method. Once you get a small hole through the bolt, take your center punch and go around the bolt hitting it and the shock will relax the tight fit.

definitely buy a left hand drill bit set. Good for lots of jobs. And keep them safe and sharp.
How do you get the hole going in the center so you don't wreck the threads as you drill bigger? It usually wanders.
 
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Sometimes being off center helps break one free, cam action!

If you will start the hole small and work bigger you can correct being off center by angling the drill very slightly, shifting the hole to the center, then the next size up will be even closer to the center. pretty soon after a few screw ups you’ll have the hang of it.

In all seriousness left hand bits ROCK for broken bolts, add a little heat if you think it’s going to be really tough
 
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Yes, centering punches help, i rarely use them, set in my ways I guess. it also helps to have a milling machine 😉

I got these out of a 4bt Cummins manifold fairly easy

Not the drill I used just what was in the spindle

037F9169-C9FF-453F-8E89-579AC1A67BA8.jpeg
 
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Stainless steel bolts are the worst choice to screw into that aluminum housing. Or any aluminum. Cadmium plated Toyota bolts are best. Just replace the housing bolts every time the thermostat is replaced (every 10 years) and the bolts won't ever seize in the threaded holes again (if antiseize grease is used)
Thanks for the tip. The Japanese bolts I ordered say they are “stainless steal “, lol, I get it. Anyway, I was just at the hardware store getting a gate latch for a stallion we have, and started looking at the wall of fasteners. I found the 8mm x 1.25 bolts, with a variety of heads, hex, metric bolt , etc. I’m wondering if any of these might be good replacements for the thermostat housing.
 

OSS

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Actually, zinc plated hardware store bolts are hands down the worst choice - worse than stainless steel.
The problem with zinc plated hardware store bolts is that the plating is zinc and it's super thin. Those bolts are rust magnets in aluminum threads.
The problem with stainless steel screwed into aluminum threads (and I'm a die hard fan of stainless steel) is that the aluminum corrodes very quickly when in contact with stainless steel - creating galling of the threads interface.

I suppose an acceptable workaround is the use stainless steel bolts with lots of antiseize grease on the threads and remove and inspect and regrease the threads every 7 years or so (as a timeline guess). I'd inspect them after 5 years, and if fine, extend the interval further. What we're trying to avoid is screwing in new bolts then forgetting about them for another 20 years.
 
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Use studs, I like studs, if they go into aluminum especially.

I know folks on here like the factory look and all, I do too, but this would be harder to spot.

Like OSS said anything left in aluminum threads for decades is gonna be tough to extract without pulling the threads out with the hardware.
 
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Here are a few tools of the pros for bolt removal

solid carbide spade drill, will drill extremely hard material, very $$ , useless in a hand drill will shatter quickly!
6AA5B021-FE70-44B6-8120-E940B51FBC1F.jpeg


these are broken tap removal tools, you can also drill 4 holes in a broken bolt and use them as a ease out tool.
46413731-7C85-45F3-B51A-3AC869B4EE25.jpeg


old fashioned ease out on the left

Honestly, a broke bolt in aluminum is a crapshoot even with good tools. Especially the size we are talking about here. The bigger the bolt the better your odds are of extracting it. Aluminum is weld able so you can always drill oversize to clean hole out, and weld Up hole, drill and tap to OEM size
 
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Here are a few tools of the pros for bolt removal

solid carbide spade drill, will drill extremely hard material, very $$ , useless in a hand drill will shatter quickly!
View attachment 2726405

these are broken tap removal tools, you can also drill 4 holes in a broken bolt and use them as a ease out tool.
View attachment 2726406

old fashioned ease out on the left

Honestly, a broke bolt in aluminum is a crapshoot even with good tools. Especially the size we are talking about here. The bigger the bolt the better your odds are of extracting it. Aluminum is weld able so you can always drill oversize to clean hole out, and weld Up hole, drill and tap to OEM size
I seem to be behind the times in technology.
 
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Here are a few tools of the pros for bolt removal

solid carbide spade drill, will drill extremely hard material, very $$ , useless in a hand drill will shatter quickly!
View attachment 2726405

these are broken tap removal tools, you can also drill 4 holes in a broken bolt and use them as a ease out tool.
View attachment 2726406

old fashioned ease out on the left

Honestly, a broke bolt in aluminum is a crapshoot even with good tools. Especially the size we are talking about here. The bigger the bolt the better your odds are of extracting it. Aluminum is weld able so you can always drill oversize to clean hole out, and weld Up hole, drill and tap to OEM size
I tapped the surface of the broken bolt with a pritzel, hardened tapered square farrier tool. Also let break free liquid sit overnight. Next day, I got it out with the vise grips. I got lucky. It could’ve easily broke. Thanks for posting the cool tools.
 

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