In-situ annealing?
In-situ annealing?
(OP)
Would heating up a cap-head until it is cherry-red and then letting it cool to room temperature reduce the hardness?
We were attending a breakdown up high on a crane the other day and found ourselves having to drill out a sheared caphead bolt (I'm a maintenance fitter currently doing my BEng in my spare time). As we already had oxy-propane equipment nearby I suggested that heating it up to cherry red and letting it cool in its own time would reduce the hardness and make it easier to drill. Obviously I got ignored because I'm under the age of 30, but does anyone know what the chances were of this helping at all? I'm happy to concede that I was wrong as long as there's a decent explanation behind it. As it turns out we ended up leaving the crane isolated and waited for some cobalt drill bits to come in.
Cheers in advance,
Ashley.
We were attending a breakdown up high on a crane the other day and found ourselves having to drill out a sheared caphead bolt (I'm a maintenance fitter currently doing my BEng in my spare time). As we already had oxy-propane equipment nearby I suggested that heating it up to cherry red and letting it cool in its own time would reduce the hardness and make it easier to drill. Obviously I got ignored because I'm under the age of 30, but does anyone know what the chances were of this helping at all? I'm happy to concede that I was wrong as long as there's a decent explanation behind it. As it turns out we ended up leaving the crane isolated and waited for some cobalt drill bits to come in.
Cheers in advance,
Ashley.





RE: In-situ annealing?
RE: In-situ annealing?
If it's any help this was just an M16 mild steel cap head, with 12.9 marked as the tensile. Regular HSS drill bits didn't show a lot of interest and it was sheared off under flush so we couldn't use a centre-pop to unscrew it.
I did wonder about sticking this thread in the, 'materials', section, actually.
RE: In-situ annealing?
Socket head cap screws to my knowledge are all high tensile, not mild steel. 12.9 is tough to drill. Heating it up to cherry red may have softened it but I'd say it might just as likely made it harder.
HSS drills with a small rake will drill them with difficulty and you will need a number of drills or access to a grinder to re-sharpen them. 16mm is big enough to weld a rod to it then bend the rod and unscrew it that way. It depends on why it broke.
RE: In-situ annealing?
How would heating it to a cherry-red and letting it cool in its own time make it harder? I don't understand that at all.
RE: In-situ annealing?
Use Kroil or other good penetrating oil (not WD40!!!)to make the job easier.
It is better to have enough ideas for some of them to be wrong, than to be always right by having no ideas at all.
RE: In-situ annealing?
The point is that in the field, you are aren't likely to have much temperature control ("cherry-red" is not a well-defined temperature) and you are not going to be able control cooling very well. The result is that you can't control the process very well, which is why TMcRally said you are just as likely to make it harder. We can't tell if you will make it harder or softer, but you are just as likely to do one as the other since you can't control the process very well. If you do get the capscrew hot enough to affect the hardness, you are likely to affect the surrounding material as well.
rp
RE: In-situ annealing?
RE: In-situ annealing?
TygerDawg
Blue Technik LLC
Virtuoso Robotics Engineering
www.bluetechnik.com
RE: In-situ annealing?
RE: In-situ annealing?
heating the bolt could make it also more difficult to remove.
heat seized threads. the opposite would be said if it where a nut.
Heating it would result in easy removal while it's warm.
due to thermal expansion.
drill, & easy out is the standard practice.
when a bolt is difficult to remove. using a punch with a blunt tip
and smack it with medium blows to loosen the the threads that have seized.
This has saved my ass many times. & prevents breaking the bolts or nuts.
The object is to loosen not yield the threads, thats why mild blows & not get carried a way with hammering. :>)
Mfgenggear