I have an older gun with a threaded head. It has a very chunky double flopper head which I'd like to replace with a pranger. It has been there a very long time and is frozen on. I have tried WD40 and heat but it is stuck solid. Any ideas on how to remove it?
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How to get a frozen screw-on head off a shaft
- Thread starter Mark77
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Thread Status: Hello
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Hold shaft with mole grips or vice put wet cloth on it to keep it cool heat up head with blow torch or cooker flame for a few seconds hasn't got to be red hot or any way near that hot turn head with spanner or grips with barbs out to give you leverage (if your not going to re use it) should undo easy.if all else fails put a grinder down one side to open it up.
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I tried everything but it wouldn't budge. A guy at the local dive shop showed me a good quick technique that worked (if you are not going to re-use the tip). He just hit around the outside of the threaded area quite hard with a hammer. It came off very easily and didn't damage the thread one bit!
Like Denian - until I read your post - I considered heat the ultimate way to free stuck threads (mainly due to differential expansion). I did come across another trick of my own though, after heating a stuck bolt in the back of my woodburner with a propane torch. The heat failed to free the bolt but when I sprayed a WD-40 like oil on the nut & bolt, the sudden cooling/contraction freed it up (differential contraction?) -- I hadn't expect that but it was quite a relief 
I have come across whacking before though: a professional motorcycle mechanic showed me how they routinely remove tough crankcase bolts from Japanese motorbikes, without damaging anything. They first whack the head of the screw-head bolts with a hammer to ensure the cross is nice & tight and to jolt the steel screws from the aluminum threads (i.e. to break any seal that has built up through oxidation, etc.) - much as the guy at the dive shop did - then they tap a Japanese T-bar screwdriver (which is similar to a Philips head but stubbier and ever so slightly different - they work well in Philips screws but not vice versa) into the tight cross and then they push hard while they twist the T-bar. T-bar screw drivers provide excellent leverage, I am surprised they are not far more common.
I have come across whacking before though: a professional motorcycle mechanic showed me how they routinely remove tough crankcase bolts from Japanese motorbikes, without damaging anything. They first whack the head of the screw-head bolts with a hammer to ensure the cross is nice & tight and to jolt the steel screws from the aluminum threads (i.e. to break any seal that has built up through oxidation, etc.) - much as the guy at the dive shop did - then they tap a Japanese T-bar screwdriver (which is similar to a Philips head but stubbier and ever so slightly different - they work well in Philips screws but not vice versa) into the tight cross and then they push hard while they twist the T-bar. T-bar screw drivers provide excellent leverage, I am surprised they are not far more common.
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I would think any form of shock to a jammed thread would help unlock it heat /cold expansion of different metals it's an age old method like train wheels have metal 'tyres ' have friction fit some ships propellers are heated and slid on to a shaft then cooled .WD40 is very flamible ! I wouldn't try it again unless you fancy blowing it to bits!.
differential expansion/contraction and a hammer jolt both work. You can make it easier by soaking the threads in Kriols or Blaster, both sprays designed to free up corroded threads. A couple of days soak, then try the first two. Almost always works unless crevass corrosion has so weakened the male end that it sheers off. If that happens, you did not want to reuse it anyway.