Help With Thread Identification

[bigb]

Trying to find a nut for this screw but I don't think its Acme, the threads appear to be square cut. If my measurements are correct the major diameter is 7/8", T.P.I. is 5 and pitch is .2      .........I just don't know what kind of nut to look for that will work with the square cut threads, any ideas where to find one?

[Dogsoldat]

May have to get one machined.   Does look like a square cut single start thread though.  Somewhere in the forums there was a few different ways to repair a box on a vise.  May or may not help. 

[D.C.]

Most acme threads look nearly square when they're new/not worn. Technically they are trapezoidal threads...but definitely square at the top. We use ALLOT of acme in our shop.

[jimmy seale]

I don't know about solid rod except for acme, but, some tubulers are buttress thread that looks about the same profile.

 

[Anachronist58]

Please describe the vise it came out of - brand, model#?

[Smoggy]

It's a square thread, typical of a lathe feed screw, what is it from? What is it being used on? There may be options on where to look for or make a nut depending on what you need.

[Lionel h]

I know this has been posted before so I'm not claiming it , an old house screw jack has the same screw threads . They are the same on the two I've tried. 

[bigb]

It is off an old leg vise but most likely a replacement screw, not the original. There is no ID on the vise.There was no screw box, just an aluminum nut in bad shape,

[ThomasPowers]

More likely it will be easier to fab a complete replacement from something---like a house screw jack, that has it's "nut" already to hand.  Or you could check if the local VoTech will make one.  I used to use a VoTech in OKC that would do projects that "fit" the curriculum for a donation for their end of term party.

[Smoggy]

As it is most likely not the original screw thread for the vice, I agree with TP, easiest and most efficient to source a good replacement complete with nut/box, either from an otherwise damaged vice or a suitable alternate.

Having said that, as a machinist myself......I'd probably faff about and make one!

[ThomasPowers]

Smoggy; you should NEVER admit to that ability around other smiths; a lot of us have vises that could use a bit of such help...

[Anachronist58]

Smoggy - Some time ago I single-pointed a 1/2" - 10 Acme nut in brass - a lot of material removal, but quite rewarding.

With my limited time,  1" - 8 or 7/8" -9 all-thread and nut, or house jack would also be my choice.

Thomas, you chimed in whilst I was typing this - I wish I could start a business wherein one would send a plaster cast of his/her screw, and I would return a cast bronze nut <sigh>.

Robert Taylor

 

 

[ThomasPowers]

Well I remember reading about casting a babbett "nut" around a well smoked screw as a repair in a 19th century smithing book.

[Kozzy]

Square thread form as others have said.  Taps are really hard to find and expensive so you are looking at big bucks if you need a nut--and probably best to thread it on a lathe.

We make forming dies that are basically square thread form nuts in a variety of sizes--it's all lathe worth and a pain in the keester, taking LOTS of passes.  I wouldn't wish that on anyone.

So...again as others have mentioned, you'd be ahead of the game to start from scratch with ACME or similar instead.  It'd be nice if you could find some existing object to steal parts from but that too might be chasing your tail vs the ease of just switching to ACME.

There is a way to cast the nut using the existing thread as the form (as ThomasPowers mentioned regarding babbit)--One modern material is moglice which is theoretically supposed to be as strong as the parent material.  There is a little info on thread re-casting with the stuff at their site http://www.moglice.com/articles/replication_techniques/wrotethebook.html.  I haven't used it but I have spoken to several machinists who swear by the stuff for shaft build-ups.

 

[bigb]

OK sounds like I should start new and go with Acme. Any recommendations on where to order the parts? We do have a nut and bolt supplier locally I can check with for the Acme screw and maybe a bronze nut. I imagine I will buy a length of Acme rod and cut it to size.

Thomas, good idea about the VoTech, would have been easy when I was taking welding classes at the local community college in their machine shop.

 

I never see good old house jacks or RR jacks around here.

[bigb]

If I start with a new screw how can I make the part at the end that the handle fits into and what is it called? My present one appears to be zinc or some non ferrous metal, not sure if I can weld it.

[swedefiddle]

Good Morning,

Like Smoggy said, talk to your local machinist and ask him to make a nut.

It will be the LEAST expensive solution. Yes, you can make a nut, but by the time you are finished you will have wasted a few weeks.

Neil

[Smoggy]

bigb, If you are starting with a 'new' thread and nut.......get two nuts and weld one on the end and drill it for the bar.

 

" Smoggy; you should NEVER admit to that ability around other smiths; a lot of us have vises that could use a bit of such help... " TP, please note the strategicaly positioned wording in bold > "  Having said that, as a machinist myself......I'd probably faff about and make one! "

[BIGGUNDOCTOR]

I would make the nut from a steel alloy, not bronze. It will last longer, and take more force. Square threads can transmit more force than Acme threads that have a 29* included angle. 

Buttress threads have an angled (buttress) side. 

[ThomasPowers]

I have friends who were HSM and they tend to get weird...one offered to make be a threaded shaft to go into a headache ball so I could use it as a plannishing stake.  He told me that the threaded section was not concentric to the larger diameter hole leading to it, so he figured a way to make it work.  Me I'd have said "rats" and then shoved in a close sized shaft and poured lead around it and been using it when he was still indicating it in the lathe...