Justor JeiGallo Posted January 31, 2022 Share Posted January 31, 2022 Hello all, I have an unknown (to me) type of small post-mount vise that I've been pretty happy with until I ended up snapping the screw in half a week or so ago. As you can see from the attached images, it looks like there might have been a stress crack or something that allowed moisture to get into the screw and corrode it. Of course it probably didn't help that I was chiseling a groove into a tong blank at the time either. The screw seems to be somewhere between 5/8 and 3/4 and 11 tpi, but neither size of threaded rod diameter matches up, so I assume that it is metric. I'd have to source rod for it outside of my area, but I'm also concerned about the quality of the rod originally used for the vise, as it seems to be a standard coarse thread instead of a square, trapezoidal, or Acme. I'd also have to figure out how to reuse the handle on the new rod as I don't have a welder. So I have what may be a hare-brained idea, and wanted to run it by you folks to see if it was feasible. I have a scissor jack that could be stripped of its screw and end box. The existing box threads on the vise could be drilled out to a smooth hole and the jack box fastened to either the front or the back of the rear hole. Instead of the existing handle, I could fasten a hex socket to the near end of the screw and use a small breaker bar as a handle. As far as fastening the box to the vise, I don't own a welder, so would it be possible to braze the box to the vise using silver or other suitable rod and a propane forge burner? What am I not considering here? Thanks in advance for any guidance. Quote Link to comment Share on other sites More sharing options...
ThomasPowers Posted January 31, 2022 Share Posted January 31, 2022 Older screwboxes had the screwthreads forge brazed in. Any friends with a lathe that would turn and thread an insert to convert the threads in the stationary arm to the threads in the screwjack? Quote Link to comment Share on other sites More sharing options...
Irondragon Forge ClayWorks Posted January 31, 2022 Share Posted January 31, 2022 I was looking at the broken screw. Wonder if a "good welder with the correct rods", could weld the screw back together, where it's broken doesn't look like the threads get used. Quote Link to comment Share on other sites More sharing options...
Justor JeiGallo Posted January 31, 2022 Author Share Posted January 31, 2022 Thomas - unfortunately no, although thinking about it, there may be someone at work that I could ask about that. I would just have to track down an insert, unless the threaded part of the jack box is possibly removable from the housing? Irondragon - I could check with my steel supplier about welding the original screw back to the handle, as they have on-duty welders. Would you have any concerns about the screw being rotted further up the shaft from where it broke? The other end that inserts into the screwbox is bubbly on the non-threaded tip. I figured that if I took it to someone professional, either the cost to weld it would be outrageous, or they would just tell me that it couldn't be welded, but if you think that it would be ok I can certainly inquire about it. That being said, I could also check into a matching new rod with them, but they only deal in mild steel and hardox, so I'm not sureI could get what might be a 'proper' screw material from them, unless I'm over thinking it. Quote Link to comment Share on other sites More sharing options...
Irondragon Forge ClayWorks Posted January 31, 2022 Share Posted January 31, 2022 Without inspecting the screw in person, it's hard to tell if there are other weak sections. However if it were mine I would grind tapers on the broken section to get a deep penetrating weld then put a brass washer on the screw to move it back a little bit. It really should not cost too much for that type of repair. Quote Link to comment Share on other sites More sharing options...
ThomasPowers Posted January 31, 2022 Share Posted January 31, 2022 OK if there is room I would brad in a section of copper pipe to protect the old screwthreads and just weld the jack screw "nut" to the back of the stationary arm allowing for removal and restoration if you happened to discover a replacement piece later. Quote Link to comment Share on other sites More sharing options...
Frosty Posted January 31, 2022 Share Posted January 31, 2022 How much do you think it'll cost If the welding shop tells you it can't be welded? Perhaps they'll tell you it can but will probably cost more than a new screw and box. It's unlikely a welding shop will know what a screw and box for a leg vise will cost but you'll have some hard numbers with which to evaluate your situation. I've walked in the door to many welding and fab shops to ask this kind of question and been pretty well received. It was easy to tell when I'd talked through my welcome, they said so or told me that if I wanted to take up more of their time they'd have to charge me an hour shop time. Thank you, have a nice day. Your next step is at a machine shop and ask for a ball park estimate for turning and threading the screw and tapping the screw box. They might want to charge for a hard bid but most will give you a ball park estimate, say. Oh, $100 give or take $25. Nice looking little vise. Frosty The Lucky. Quote Link to comment Share on other sites More sharing options...
BIGGUNDOCTOR Posted February 2, 2022 Share Posted February 2, 2022 I'd weld it. 7018 would be my rod of choice. If I was to do it I would turn the threads off for a bit, drill a hole in the handle to fit the turned section to keep it straight and centered, then weld. Keep it simple. Quote Link to comment Share on other sites More sharing options...
BartW Posted February 27, 2022 Share Posted February 27, 2022 I wouldnt weld it. Chance of brittleness is too high. Well... with my welding skills at least: D I had a similar problem once, and i fixed it with a m20 screw box, a piece of pipe to protect the threads and a key to build this: the bar was made from another piece of m20 wire Rod and 2 nuts . The box and front part and salvaged from a truck spare part mounting. Quote Link to comment Share on other sites More sharing options...
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