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I Forge Iron

Post vise restoration

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I have an old post vise which belonged to my Great Grandfather, so it is very dear to my heart. It has a stripped screw, and I want to restore and use it. While I have done alot of metal fabrication, tig and mig welding, I am new to the blacksmith scene. Anyway. I took the bell side of the screw to a machinist and had the old threads cut off in a lathe. I then had a new male screw made, with the same pitch thread as original, but a slightly fatter diameter to account for the metal lost in removing the female threads. I wrapped a length of 1/8 keystock around my new screw, and have a perfect spiral. My plan now is to use a thin layer of .007 brass shim material around my keystock spiral, and insert it into the tube portion of the bell and heat to melt the brass, brazing the keystock spiral in place so as to form the female thread portion of the screw.
Things I am not so sure about yet, as I really dont want to screw up great grandaddy's vise:
Fluxing-yes, or no-seems like it will take up some of the space needed to fit the keystock spiral and brass sleeve into the tube, and it is already a tight fit. Also flux type-borax powder or some liquid would take less space in the bell tube.
Also temper of the metal, after I braze this spiral in place, should I quench, or does anyone have any reccomendations. Also another concern- the keystock may expand upon heating throwing it out of kilter with my already cut male thread. I thought about drilling some holes in the tube and carefully tig welding the keystock in place. Also I dont really have a real forge. I have oxy acetelyne torch and also a homade propane jet burner which I have melted brass in a pot with before. I would proably use the propane jet burner to heat the bell. Will I mess up the bell by not heating in an oxygen free forge?
Thanks for any suggestions.

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Don't worry about trying to harden anything, it will create more problems than it might solve. The old vises were often completely wrought iron and so were not hard. Just grease the screw liberally and the whole box assembly should last many years.

Silver will melt at a lower temp so will be easier to control and heating from the outside with a burner won't hurt the screw box. Your idea of drilling and plug welding would also work.

I have also seen babbitt used for the box threads. The male thread form is coated with some sort of release agent (oil, grease, etc.) and centered in the box, which is then heated. The babbitt is poured and allowed to cool, then the screw is removed. The lead will shrink enough to allow a good working tolerance and a long length of lead provides plenty of strength. The only possible problem is if the lead core spins in the box so some folks run in a couple of machine screws to help with possible stripping. However, from a practical standpoint, the inside of the box is often rough enough to keep the lead in place. If I were rebuilding a vise, I would probably go this route rather than try to locate and fasten a separate screw form inside the box - just my $.02...

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Off hand I would say DON'T quench , as this may distort the keystock, warping your thread pattern and may break the brazed joint, as brass and steel expand and contract at different rates. When it cools slowly it's not a big deal because the mass will retain heat for a period of time lessening the distortion ( it would also help if you wraped your keystock hot rather than cold ) . Also I see no reason to harden your thread at all (almost all threads are never hardened ) , if you braze it in well and the keystock dosen't distort it should last you a lifetime or two depending on how hard you use it.
PS: Oh, and flux wont take up any room, it will just make the brazing or soldering work like it's supposed to.
Hope this helps

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