K A Willey Posted September 18, 2012 Share Posted September 18, 2012 Anybody have a screw for a 7 inch jawed leg vise? Quote Link to comment Share on other sites More sharing options...
Bob S Posted September 18, 2012 Share Posted September 18, 2012 Anybody have a screw for a 7 inch jawed leg vise? it will be easier to find a replacement vice screw if you measure the major diameter and the number of threads per inch of your existing screw. there are no 'standards' when it comes to these vices. not that I know of anyway. unlikely that you will find a similar screw floating around out there without a vice. a shot in the dark. but nothing wrong with trying. Quote Link to comment Share on other sites More sharing options...
ThomasPowers Posted September 18, 2012 Share Posted September 18, 2012 Do you have a VoTech you can "bribe" into making one for you? Quote Link to comment Share on other sites More sharing options...
Fatfudd Posted September 18, 2012 Share Posted September 18, 2012 One just sold on ebay for $31. Sorry Quote Link to comment Share on other sites More sharing options...
K A Willey Posted September 19, 2012 Author Share Posted September 19, 2012 Thanks Quote Link to comment Share on other sites More sharing options...
Timothy Miller Posted September 19, 2012 Share Posted September 19, 2012 It is very unlikely that you will find a vise thread and box that will match what the vise came with. Ar far as replacement with a modern substitute goes you have a few problems. Leg vises use a square thread. This was used because it did not exert bursting pressure on the box. Vise boxes were normally made from wrought iron or cast iron not exactly the strongest stuff when that sort of pressure is exerted. Also a square thread is longer wearing than all other kinds. The thread count is normally about 3 threads per inch. This thread count results in a travel of about a 1/4 of an inch per turn of the handle. This makes hot work in the vise easy because the vise is quickly adjusted. I have never seen a improvised repair on a vise thread that worked as well as the real deal. You may find a vise screw for sale but I seriously doubt that it will fit a 7" vise. That is a very uncommon size of vise. A vise of that size is worth far more money as a complete vise rather than parted out on eBay. It is possible to repair the box in some cases new threads can be cut on a lathe though many lathes only cut 4 threads per inch or more. What is your level of commitment to this vise. Quote Link to comment Share on other sites More sharing options...
David Gaddis Posted September 19, 2012 Share Posted September 19, 2012 The repair is not so bad to accomplish. You need to be able to communicate with a machinist about just exactly how the thing works. There will be the problem as many machinist think themselve to be quite smart themselves, in that using modern approach is better! If they see another model and work with it just a little while then they will be more informed. Years ago when I worked in a machine shop a lot I rebuilt a leg vise screw myself. This is before I became interested in blacksmithing. The owner wanted it to work just like an original so that is what I did. After grinding the correct cutters, which is really not so hard, an appropriate piece of shaft was threaded. It still is operational today but not at a professional pace. Now this job may not be economical for all but with a lathe the job should be easily accomplished, square threads (modified buttress threads) and all. Carry on Quote Link to comment Share on other sites More sharing options...
ThomasPowers Posted September 19, 2012 Share Posted September 19, 2012 So are you totally missing the screw and screwbox or just have the screwbox or have both but they are worn out or damaged? Quote Link to comment Share on other sites More sharing options...
K A Willey Posted September 19, 2012 Author Share Posted September 19, 2012 Making it woun't be hard just thought I would ask incase someone out there had one, I have every thing to build one just need to find the time to make the whole assembly, the whole thing is gone. thaks again Quote Link to comment Share on other sites More sharing options...
ThomasPowers Posted September 19, 2012 Share Posted September 19, 2012 You can buy square thread and nuts for it and just weld up an assembly. Making your own allows you to lathe the pieces to look like the originals. Quote Link to comment Share on other sites More sharing options...
Bob S Posted September 19, 2012 Share Posted September 19, 2012 You can buy square thread and nuts for it and just weld up an assembly. Making your own allows you to lathe the pieces to look like the originals. I have seen 'acme' threaded rod and acme nuts but never 'square' threaded rod or nuts. Can you provide a source? The thread count is normally about 3 threads per inch. This thread count results in a travel of about a 1/4 of an inch per turn of the handle. not to quibble but... three threads per inch would be 1/3 = .3333 etc. closer to 5/16" (.312) per full turn. or 21/64" (.328 to be completely ridiculous.) sorry. :wacko: Quote Link to comment Share on other sites More sharing options...
r smith Posted September 19, 2012 Share Posted September 19, 2012 not to quibble but... three threads per inch would be 1/3 = .3333 etc. closer to 5/16" (.312) per full turn. or 21/64" (.328 to be completely ridiculous.) sorry. :wacko: Are you thinking the jaws close the exact same as the threads advance like a machine vice? Leg vice moves on a pivot and since the jaws are farther from the pivot than the screw they will move farther. My 7 1/2" vice with 2" dia thread with 2 threads per inch moves the jaw from closed to 11/16" open with one revolution of the screw. Not the 1/2" that your method of calculation would have given. Hope this helps with what you need. quibbling smith out Quote Link to comment Share on other sites More sharing options...
Bob S Posted September 19, 2012 Share Posted September 19, 2012 Are you thinking the jaws close the exact same as the threads advance like a machine vice? Leg vice moves on a pivot and since the jaws are farther from the pivot than the screw they will move farther. My 7 1/2" vice with 2" dia thread with 2 threads per inch moves the jaw from closed to 11/16" open with one revolution of the screw. Not the 1/2" that your method of calculation would have given. Hope this helps with what you need. quibbling smith out I was replying to Tim's comment that.... "This thread count results in a travel of about a 1/4 of an inch per turn of the handle.' He did not say *jaw travel" but *travel*. In this case 'travel' would be assumed to be 'travel' of the thread since that's what we were 'talking' about. Jaw 'travel' is another issue. Quote Link to comment Share on other sites More sharing options...
ThomasPowers Posted September 19, 2012 Share Posted September 19, 2012 Don't know squat about them but they claim to sell buttress threads: http://www.indiamart.com/rolexengineers-pune/search.html?ss=buttress I've usually not bought vises without good threads as that's a deal breaker for me. (Though I once bought a good screw and screwbox that was in a trashed vise; ended up trading it as part of a deal for a 400 pound anvil...) Quote Link to comment Share on other sites More sharing options...
r smith Posted September 19, 2012 Share Posted September 19, 2012 I was replying to Tim's comment that.... "This thread count results in a travel of about a 1/4 of an inch per turn of the handle.' He did not say *jaw travel" but *travel*. In this case 'travel' would be assumed to be 'travel' of the thread since that's what we were 'talking' about. Jaw 'travel' is another issue. I read his post differently and took "travel" to mean jaw travel because of doing hot work it needs to close quickly. It meaning the jaw. ;) I also would think that he is smart enough to know that 3 threads per inch does not equate to 1/4" screw advancement. Maybe he will chime in? At any rate you (KA) should look for something close to 2-3 threads per inch 1 3/4-2" dia. Quote Link to comment Share on other sites More sharing options...
Bob S Posted September 19, 2012 Share Posted September 19, 2012 Don't know squat about them but they claim to sell buttress threads: didn't think you would find any square threaded rod and nuts. Quote Link to comment Share on other sites More sharing options...
Timothy Miller Posted September 20, 2012 Share Posted September 20, 2012 Ok, I seem to have a talent for being confusing sometimes. What I meant by travel was how much the jaw moves by turning the handle over a half revolution of the vise screw. I say it in these terms because that is about how much one can turn the vise handle easily with out changing their grip. I took the time to remeasure some of the vises in my shop. I used a tape because blacksmiths typically work to fractional tolerances not .001. Giving numbers in thousands for something as imprecise as a leg vise is just silly in my opinion. Lets say my measurements were +or- 1/32" remember many vise boxes were made by brazing in a coil of square wire in to a iron tube. I own 3 vises made this way I would be surprised if they were within .020 along the whole thread. I have 3-6" vises two measured at 2 Threads per inch this resulted in approximately 5/16 of travel for a half turn of the screw. The other vise was 2 1/2 threads per inch and it has a broken box I could not measure the travel of the jaw. I also have two 4-1/2" jaw vises they were more or less 3 threads per inch. This resulted in about 1/4" of travel when you turn over the handle. I also have a small forged bench vise with a brazed box probably from the early 19th century it has 2 1/2" jaws it had 5 threads per inch. You need that fast thread to get a quick grip when your working hot. Also its nice to be able to rapidly change grips on a piece that one is filing. if you had a large vise with 7 or even 5 threads per inch it would be a chore to use lots of handle turning in an 8 hour day. I would think for a 7" vise 2 threads per inch or less would be the ticket on a 1 1/2" or 1 3/4 diameter vise screw. I also have a 7" double screw fisher vise it has 3 threads per inch and it is a task to use some times it feels slow and clunky when compared to my normal 6" vises with 2 threads per inch. My lathe won't cut less than 4 threads per inch and many makes of lathes do not go lower than that. My forging skills are the strongest over over ability as a machinist. If It were a job I needed to do I would probably braze on both the internal and external threads. I would use the lathe to cut off the old threads. I would wrap two square bars around the now smooth vise screw together. One would become the new thread for the vise screw and the other one becoming the internal thread for the box. Forge brazing is really an easy and simple method of joining things all you need is borax some small bits of brass and a forge to heat it in. The other advantage is that the vise will look and work right when your done. Quote Link to comment Share on other sites More sharing options...
HWooldridge Posted September 20, 2012 Share Posted September 20, 2012 Kevin, I have a modified Acme screw and box I can send you. I made it on the lathe for a vise screw replacement that never got done. The male side would need to be cross drilled and a handle added. I also have an old screw/handle assembly but it doesn't have a matching box. Email me if you want to discuss...Hollis Quote Link to comment Share on other sites More sharing options...
ThomasPowers Posted September 20, 2012 Share Posted September 20, 2012 Squareish threads are pretty easy to find, look at acme threads, buttress threads are different more of a | thread form so they take a lot of pressure in one direction. Quote Link to comment Share on other sites More sharing options...
David Gaddis Posted September 20, 2012 Share Posted September 20, 2012 Most times when I needed to use ACME threads the problem came from the nut and not the threaded shaft. All sorts of places stock and sell the stuff but again the nut is where the problem occurs. One of the writers is so correct about brazing on the stuffing box end. If one decides to machine the box then he is going to be sorely surprised about the amount of time required there. But again if someone was to purchase a threaded rod, ACME, BUTTRESS, Mod BUTTRESS or whatever, he can pretty easily forge or braze the beginning to a box, then braze that box to a steel forging that fits the frame. It will be slow in action...very slow. Okay for machinist ...too slow for hot work. How about posting some pics of what you do have so you can get a thousand more opinions. I would like to see what you have though. My lathe only goes down to 3 1/2 threads per. carry on Quote Link to comment Share on other sites More sharing options...
RGraff Posted September 20, 2012 Share Posted September 20, 2012 I've got several sections of "acme" type lead screws and nuts. I'm happy to give you a set if you wanted to cover the shipping. Quote Link to comment Share on other sites More sharing options...
utaholdiron Posted September 28, 2012 Share Posted September 28, 2012 http://armyordnance.tpub.com/Od1645/Od16450132.htm Now can someone tell me in layman's language what they are talking about? Quote Link to comment Share on other sites More sharing options...
John McPherson Posted September 28, 2012 Share Posted September 28, 2012 Just as there are basic and advanced blacksmithing skills, so too with lathe and milling operations. How to choose, make and sharpen the tool to make the cut is as important as the cut itself. Yes, you can now buy some wonderful stuff made out of miracle materials in 10,000,000 different shapes from vendors that are only an overnight shipping away. Or you can do it yourself, now, with whatchagot©, in the time it would take to get a cup of coffee, page thru the catalog, and place an order. Back then, it was an expected journeyman skill to know how to forge, grind, and heat treat your own tools. Standard wood and machine screw threads are an equilateral triangle with 60 degree angle sides, and a sharp pointy top. There is a standardized protocol for grinding the required cutting tool profile out of a block of tool steel. That is something every newbie learns in order to cut threads on a lathe in basic shop class. Cutting other thread profiles, such as acme and square threads, calls for superior operator skills and specialized cutting tool profiles. That page shows the desired square thread tool profile and reasons behind grinding it that way. Quote Link to comment Share on other sites More sharing options...
Timothy Miller Posted September 28, 2012 Share Posted September 28, 2012 So not only do you need a to know how to cut a square thread. You need to have a lathe that can cut it at 2 threads per inch or less to get the vise back to proper function. my south bend only goes to 4 tpi this seems to be common to many lathes. I think the only viable option to most is a wrapped and brazed thread. It can be done in an ordinary forge with out any special tools. all you need is borax and brass filings. Quote Link to comment Share on other sites More sharing options...
ThomasPowers Posted September 28, 2012 Share Posted September 28, 2012 And *SKILL* from practice! Quote Link to comment Share on other sites More sharing options...
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