English Vise with Stripped Screw

[intrex]

I recently got my first leg vise from a craigslist find.  When I was getting it off the guys truck who was selling it everything looked good and seemed to work.  The Jaws were open pretty far and I tested closing them about an inch.  I didn't realize until I got back to my house that the screw was in good condition until you got to the section of threads were the jaws were about 2 inches apart.  The rest of the threads from there on out were completely worn out and you can't close the jaws anymore.  

 

I have read the topic about how to forge braze new square threads into the box.  If I want to go that route I think I am going to have to forge new screw threads and box threads.  I would really like to keep the original historical design of this vise and recondition it to be functional but am nervous about trying to take on this project.  I am a very novice smith and not sure if I will be able to tackle a project like this.  It seems like getting the original threads off the screw and out of the box is going to be a serious job in itself.  

 

Has anyone on here done this before?  What stock did you use for the threads?  What filler would you use for the braze?  Should I abandon the idea of forge brazing threads and just get a large acme threaded rod and bolt? Any ideas or pointers are greatly appreciated. 

 

 

[ThomasPowers]

Talk with your local VoTech; sometimes they will do odd ball things as a class project for a donation to the end of the term party fund.  Building a new screw and screwbox would cover several machining tasks.

 

And you have leaned that the most important thing to look at when buying the vise is the entire screw and state of the inside of the screwbox.  Pretty much everything else is easy to repair but that.  (and note that many sellers either cannot tell if a screw thread is mint or heavily worn; or chose to mislead folks)

[intrex]

Hey Thomas, 

 

Thanks for the advice. 

 

This has been a really good learning experience about leg vises.  The guy I bought it from didn't really even know what it was.  He just knew that it was a large vise that he could barely carry :).  

 

I am thinking about repairing the box and screw by chiseling away the existing threads and forge brazing new ones as shown in this post. 

 

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I am hoping that the threads on the screw are going to be brazed so I can chisel them off as well but I know there is a good chance they will be machined.  

[ThomasPowers]

almost 100% chance they are machined for that style of threads.  If you want a using vise in a moderate amount of time you may want to rethink that methodology.  (and if you do go that way look into say casting a babbit female threads in the cleaned out screwbox.)

[MLMartin]

It is possible to braze male threads onto a screw but I have never seen it done. Even on the old vices like the one I repaired the male screw was always cut into a solid bar. When I repaired the female box I re-brazed threads into the box and had the male screw to use as a pattern. Also even though I was repairing the box, the brazed in female threads was the original way the box was made. So I was just restoring the vice to original condition. 

 

 

I think you should carefully clean the screw box and look at the threads inside. If the threads are in good shape I would not try and chisel them out. Also your screw box is one piece of cast iron. I do not think chiseling the threads would be a good way to go. And like Mr Powers said above your screw is almost surely one piece of metal. I would guess mild steel because of the cast iron box being a later method in leg vises. 

 

If I am right and it is mild steel you could slowly build up the worn out threads with little electric welds then file the thread back to shape. This would be very slow and tedious work. 

[doc]

    I would take it to a machine shop, have the box bored out and the male thread turned off the screw. Then wrap the screw with a doubled over piece of stock large enough to to create a diameter equal to the ID of the box. Snip the wrap where it is doubled over and unscrew one spiral from the other. Then braze one in the box and the other over the the tenon to recreate the mail thread.

 

    Be warned the machining may well cost more than the vise is really worth!

[Fatfudd]

Repairing an existing leg vise box and screw is difficult at best as mentioned above, Here is a thread I posted a while back that I have used to fix lost or broken leg vises.

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[intrex]

Hey Fatfudd, 

 

Thanks for the link.  I have already found a few of these on ebay that are the exact same outer diameter as the existing screw on the vise.  I think I am going to cut the existing screw where the threads start and cut the screw off of one of those jacks then forge weld it to the original handle.  Using fairly new screw threads as a guide I feel pretty confident I can make the threads for the box and braze them in.  If all goes well this will allow me to keep the vise close to the original design without serious machine shop time or trying to recreate the screw threads by hand. 

[Fatfudd]

Sounds like an ambitious project but certainly worth doing. Best of luck.

[Awalker]

Mine was worn to the point of not holding. I simply cut off the acme screw and welded on a new screw. It has been holding fine in my fab shop, used every day for several years now. When the box finally wears enough that it won't hold the new screw I will bore out the box, turn down some acme nuts a braze them inside the box.

[Timothy Miller]

Mine was worn to the point of not holding. I simply cut off the acme screw and welded on a new screw. It has been holding fine in my fab shop, used every day for several years now. When the box finally wears enough that it won't hold the new screw I will bore out the box, turn down some acme nuts a braze them inside the box.

Leg vices don't have acme threads they have square threads.  New vices may have acme threads but this style of thread was not invented until the late 19th century.  Square threads are superior for vices because they do not exert bursting pressure on the box.  Just had to clear this up as it is a common misunderstanding.

[Dave Parker]

Not sure about yours but I repaired one by adding a large nut near the handle.  It slipped right over the screw and when the vice was reassembled it tightened fine.  The added one inch wide nut worked as an over-sized washer and allowed the jaws to grab a different/ not stripped portion of the screw.  Mine was stripped by over tightening.  Since it was a flea market find and did not work, I got it cheep enough and would have been happy to have it for parts.  I was pleasantly surprised to find most of the screw intact.  I should add the nut goes out side of the jaws.  Hope it helps.

[intrex]

Thanks for all of the sugestions. My options for the resoration were pretty slim after I left the box in the forge too long and melted half of it.

I ended up using a house jack that was the same diameter. I had to do some serious cutting and grinding to get the receiver to fit but everything is working well now.

After grinding all of the crud off I found an iron city steel mark on the vise.

Will post pictures next time I am at the forge.

[intrex]

Here is the final result.