Does heating stuck bolts harden them so you can't drill?

[Tinkerer]

I arc welded nuts and rods to stub of broken water cover bolts on cylinder head of 1967 60HP V4 Evinrude, partly to try to get heat in to loosen them and partly to give me something to hold on to to remove them. Worked on one, not on next three, and left next three alone. Couldn't get drill bit into the three I'd weleded. Same drill bit went easily into the other three and into a test bolt I'd removed without heating.<br /><br />For future reference, as I'm expecting to be doing more of this, I'm wondering if heating hardened the bolts. <br /><br />If it did, I'd be better off just drilling them out to begin with rather than having to spend lots, lots more time drilling beside them and then refilling and inserting studs etc and generally making a disgusting mess of the job.

 

[andrewkafp]

Re: Does heating stuck bolts harden them so you can't drill?

Or use a tungsten carbide bit ...

 

[Hooty]

Re: Does heating stuck bolts harden them so you can't drill?

I would have thought it would make them,if anything, softer. Tempering steel is usually done by heating it cherry red and then quenching in rapidly. I would think cooling slowly would remove the temper. Guess that's what I get for thinkin' huh.<br /><br />c/6<br /><br />Hooty

 

[SeaMasterZ@aol.com]

Re: Does heating stuck bolts harden them so you can't drill?

or titanium, or cobalt, or diamond tipped bits ... <br /><br />what ive heard works is a TIG welder, hotter I guess, puts blast furnace heat on the bolt and spares the motor ... Ive never done it, dont have one, but a buddy of mine does and its just about time to call in a favor - let me know how you make out

 

[basser289]

Re: Does heating stuck bolts harden them so you can't drill?

I work in a automotive machine shop and remove a lot of broken bolts by welding a flat washer on and then a nut. I use a wire feed welder to do this. After welding the nut and while still red, I spray WD-40 under the washer. As the bolt is cooling, It sucks in the WD-40. This works about 90% of the time. Also, cobalt drills will work when normal drills won't.

 

[wayne h]

Re: Does heating stuck bolts harden them so you can't drill?

good left handed drill bit always works for me

 

[SeaMasterZ@aol.com]

Re: Does heating stuck bolts harden them so you can't drill?

wire feed ... TIG welder, lol, I win!<br /><br />and he likes cobalt too, wierd thing, was drilling a busted intake manifold bolt on a 390 Ford, and it slipped off and drilled into CAST IRON like it was butter, lol, amazing ... I stopped drilling, and had pretty fast reflexes, but that thing was heading for china in an instant - cobalt ROCKS!