Post Vice Gave Up!

[tlreif]

Well I have a Steel City post vice that Im sure is much older than myseft. It finally called it quits this last weekend. The threads were very worn when I got it for 25 bucks about 6 years ago. The nut finally said enough and stripped what was left of the material. Oh well I have a back up vice but it is a 4 inch and I would like to have the 6 inch back up. So my queston to the fine people of the forum is have you fixed one before and what did you do? I have looked at acme rods and nuts and am not opposed to that. I also work at a machine shop but I personally dont have the experience of thread cutting. And neither do our machinists. But im sure we could figure someting out. If i did that what material would be recomended? I hate to retire the old gal it is otherwise in great shape. Thanks for your responces!

[Fosterob]

It seems the easiest repair would be to get acme threaded rod and a steel nut, cut off existing treads and replace with new. That is assuming you can make good welds, preferably a full penetration on the screw. Or even easier if you can find it would just be another screw and box in good shape. I have seen threads on here about repairing these you should search that.
Rob

[pkrankow]

Machining new shouldn't be too hard. Thread cutting on a machine that can cut threads is not difficult, just requires care. There are some very good tutorials for this on the net, so I won't try.

I assume the screw box is wiped out as well. This simplifies the thread choices as you can select an appropriate size, you will machine both parts. I would want to use a machinable alloy (1144 stressproof quite possibly) , but would settle with a36 just fine if I had no other cost effective choice.

Phil

[ThomasPowers]

Scrounged large vise repair parts have included: leveling legs from scaffolding, bottle screw jacks, trash compactors, etc.

Cleaning out and brazing in an appropriate nut from such items and then welding on the handle stub to the screw is then the repair.

[Timothy Miller]

If its just the nut known on blacksmith vices is known as the box you can braze in a new thread. Machine out all of the old thread and make a coil of square stock that threads on to the old screw. This is the blacksmith way to fix this problem. No fancy equipment needed just some braze and some square stock.

[Nakedanvil - Grant Sarver]

Enco and many others have acme threaded rod and nuts pretty cheap. Up to 1-1/2"

[BIGGUNDOCTOR]

What in the world has happened to our manufacturing base when a machine shop doesn't have the experience to cut a thread?

This would be a good project to learn on.

What is the condition of the screw thread?

I would cut the thread first with a standard 60 degree threading tool, then chase it with a square tool to complete it.

[pkrankow]

I would cut the thread first with a standard 60 degree threading tool, then chase it with a square tool to complete it.

I am going to try that, I have some 8 pitch lefthanded acme needing cut...

Phil

[tlreif]

What in the world has happened to our manufacturing base when a machine shop doesn't have the experience to cut a thread?

This would be a good project to learn on.

What is the condition of the screw thread?

I would cut the thread first with a standard 60 degree threading tool, then chase it with a square tool to complete it.

You are right. This is as good of a time to learn. Our machine shop consists of 2 guys that run cnc mills and a cnc lathe. but our needs for the company don't require thread cutting. They use taps and dies for everything. The young man that runs the cnc lathe is still learning but is willing to give it a try. But I would like to do it on the manual lathe. just because.

The condition of the screw is not much better. I would say 30 per cent of the thread width left in the middle where most of the work has been performed.

Thanks for the advice everyone.

[doc]

Well I have a Steel City post vice that Im sure is much older than myseft. It finally called it quits this last weekend. The threads were very worn when I got it for 25 bucks about 6 years ago. The nut finally said enough and stripped what was left of the material. Oh well I have a back up vice but it is a 4 inch and I would like to have the 6 inch back up. So my queston to the fine people of the forum is have you fixed one before and what did you do? I have looked at acme rods and nuts and am not opposed to that. I also work at a machine shop but I personally dont have the experience of thread cutting. And neither do our machinists. But im sure we could figure someting out. If i did that what material would be recomended? I hate to retire the old gal it is otherwise in great shape. Thanks for your responces!

Ask Glenn to give you the link to vise repair from the Blue Prints pages.

Doc

[ciladog]

Well I have a Steel City post vice that Im sure is much older than myseft. It finally called it quits this last weekend. The threads were very worn when I got it for 25 bucks about 6 years ago. The nut finally said enough and stripped what was left of the material. Oh well I have a back up vice but it is a 4 inch and I would like to have the 6 inch back up. So my queston to the fine people of the forum is have you fixed one before and what did you do? I have looked at acme rods and nuts and am not opposed to that. I also work at a machine shop but I personally dont have the experience of thread cutting. And neither do our machinists. But im sure we could figure someting out. If i did that what material would be recomended? I hate to retire the old gal it is otherwise in great shape. Thanks for your responces!

Open the PDF file and scroll down to page 3 for directions on rethreading the vise box.

[pkrankow]

Many CNC lathes are not capable of thread cutting in the way a manual lathe is, they only use taps, and dies (and some other special tooling), and are unable to chase a thread repeatedly. If you have the tooling to cut appropriate matching threads on CNC it will take "no time" to run the job.

Learning to chase threads on the manual lathe may save the bacon on a job in the future because you can chase existing threads if necessary. Knowing what to do, and where the directions for how are can be very helpful.

Phil

[Spears]

Cutting square or Acme threads on CNC or manual equipment can be a bit of a setup depending on what the shop owner has on hand to work with. I have seen full blown machine shops stocked with everything under the sun that didn't or wouldn't purchase the proper tools to do the simplest tasks. Considering the availability of ACME threaded rods and nuts and the legitimate pricing like what was mentioned by Mr Sarver, I would probably weld together some sort of new assembly. That stuff welds like a dream and not having to mess with thread fits is like having the hard part already done. Just my two cents and good luck with the route you take on your project. Peace, Spears.

[BIGGUNDOCTOR]

The Tornos Deco screw machines we have at work are pretty amazing at times. We do a lot of threads, and a lot of the time they are either single pointed (exterior), or thread whirled/milled (interior). With the servo motors that they employ threads can be timed, and rotated exactly where we need them.

One electrical connector we make has a .040 square shank that is made while it is spinning at 7,000 RPM. The computers time the four rotating inserts in the cutting head to form the square as the part is also rotating. Each carbide insert cuts one side of the part.

As for me, I run the regular machine tools to make tooling for the machines.

[maddog]

I replaced the thread and nut on a 5" vise with a large dia acme threaded rod and nut. The threads were very worn and the box (nut) was cracked. The acme thread is a higher pitch than the original thread so the jaw action is slower but it closes very tight.

I cut the boss off the original thread and welded it onto the acme rod. That part is tricky. Acme threaded rods are something like 4140. The original thread and boss were a casting. I used SS rod with pre and post heat and peening. So far it has held fine. Frank Turley did a similar repair and the weld broke after a year. So its an iffy weld. If I were to do it again, I would probably use nickel rod or some other rod designed for CI. I could post a picture if there is interest.

I chosed a 4" long acme nut, I think these are meant to be couplers, rather than the standard size nut. The nut fit in the eye of the fixed leg easily so I welded a ring of 1/2" rod around one end to hold it from the back side.

I decided to use the original boss together with its spherical washer because the head of the screw needs some way to accomdate the changing angle of the the moveable leg as it pivots. This seemed easiest and it retains the original look.

There is a traditional method for this repair that involves wrapping two pieces around a rod to form matching threads and brazing one onto the rod and the other to the inside of the box. I think there was a BP for this once.

Did you mean "Iron City"? I have a 4" vise stamped with the legend Iron City inside a six pointed star. That too was in bad shape when I got it, but the threads were fine. I keep it next to my forge.

If you decide to scrap the vise, keep it as a source of wrought iron.

[tlreif]

I replaced the thread and nut on a 5" vise with a large dia acme threaded rod and nut. The threads were very worn and the box (nut) was cracked. The acme thread is a higher pitch than the original thread so the jaw action is slower but it closes very tight.

I cut the boss off the original thread and welded it onto the acme rod. That part is tricky. Acme threaded rods are something like 4140. The original thread and boss were a casting. I used SS rod with pre and post heat and peening. So far it has held fine. Frank Turley did a similar repair and the weld broke after a year. So its an iffy weld. If I were to do it again, I would probably use nickel rod or some other rod designed for CI. I could post a picture if there is interest.

I chosed a 4" long acme nut, I think these are meant to be couplers, rather than the standard size nut. The nut fit in the eye of the fixed leg easily so I welded a ring of 1/2" rod around one end to hold it from the back side.

I decided to use the original boss together with its spherical washer because the head of the screw needs some way to accomdate the changing angle of the the moveable leg as it pivots. This seemed easiest and it retains the original look.

There is a traditional method for this repair that involves wrapping two pieces around a rod to form matching threads and brazing one onto the rod and the other to the inside of the box. I think there was a BP for this once.

Did you mean "Iron City"? I have a 4" vise stamped with the legend Iron City inside a six pointed star. That too was in bad shape when I got it, but the threads were fine. I keep it next to my forge.

If you decide to scrap the vise, keep it as a source of wrought iron.

Yes sorry I did mean Iron city. Pictures would be great. thanks for your input.

[peacock]

My 100 year old American tool & machine lathe cuts acme and square threads just fine. If you know how to cut standard threads the hardest part is grinding the tool bit. If it is a square thread the compound must be set to 0 degrees instead of 1/2 the thread angle. You must go slow as you will have alot of toolbit contact area. Backup follower rest can also be helpful on smaller sizes

[Sask Mark]

There is an article posted in this thread that might interest you:

[Frosty]

My 100 year old American tool & machine lathe cuts acme and square threads just fine. If you know how to cut standard threads the hardest part is grinding the tool bit. If it is a square thread the compound must be set to 0 degrees instead of 1/2 the thread angle. You must go slow as you will have alot of toolbit contact area. Backup follower rest can also be helpful on smaller sizes

And once you have cutting square or acme threads down make the tap by cutting threads in tool steel and grinding the flutes.

Frosty the Lucky.

[BIGGUNDOCTOR]

My 100 year old American tool & machine lathe cuts acme and square threads just fine. If you know how to cut standard threads the hardest part is grinding the tool bit. If it is a square thread the compound must be set to 0 degrees instead of 1/2 the thread angle. You must go slow as you will have alot of toolbit contact area. Backup follower rest can also be helpful on smaller sizes

That is why you cut it first with a 60 degree tool, then again with a square tool bit. A lot less surface area in contact with the bit. On big threads you can have the compound set at 90/180 (whichever is parallel with the ways,not all lathes are marked the same), rough with a 60, then cut the front, then back of the thread with the square tool. This is a much easier for a lighter duty lathe to cut big square threads. It also allows you to tailor the fit.

[maddog]

Here are pix of my vise thread repair with an acme rod & nut.


I wanted to keep the original boss with it's spherical washer. The handle was a wimpy short piece of wrought so I replaced that with a longer heavier MS rod.


The acme rod is welded on to the stub left on the boss. I used SS rod for this.

The acme nut is 3" long. Perhaps it was a coupler. I dont recall. I welded a retaining of 1/2" round on to one end. I was going to add ears to stop it spinning but there was no need




The acme thread is slower than the original but it gives tremendous clamping pressure. So far the weld has held. I am sure a short nut would do as well. Modern precision cut 4140 threaded rod is far superior to the original. But a long nut fit the style of the vise better. I have plans to at a piece of black pipe fore and aft to keep crud off the threads and make it look more consistent with the original style. A piece of 1.5" pipe, necked down to a nice round ball at the end would look good IMO.

[tlreif]

Thanks for the information Maddog! It looks like a nice job! I will most likely go that route in repairing mine. Do you happen to know the tread pitch? Like was it 4 turns per inch or 5? Thanks again!

[maddog]

Thanks for the information Maddog! It looks like a nice job! I will most likely go that route in repairing mine. Do you happen to know the tread pitch? Like was it 4 turns per inch or 5? Thanks again!

Looks like 4TPI x 1.25" dia. I chose the biggest dia that would fit with the lowest pitch available from McMaster Carr. The 3" nuts have a smaller OD than the regular short ones. I have it in my head that acme rods were 4140 or similar but I can't recall where I got that info. In any case, I have clamped the vise very tight many times without any sign of distress.

I took as much care as I knew how with the weld. I veed the weld, preheat & postheat. I kept it warm while welding with the rosebud and peened the heck out of the weld. Then stuck it in the lime bucket for a day. Frank Turley did a similar repair and the weld eventualy failed. I think he used 7018. My guess is that its something of a crap shoot. They probably made those castings out of whatever. I got lucky, Frank didn't. The retaining collar on the 3" nut was done with 7018, pre & post heat.


I did the final alignment of the boss with the acme rod by installing it in the vise, clamping it tight on a spacer block and heating up short section of the acme rod so that the tension straightened any kink. As a machinist you will probably be more accurarate in the first place. :)

[Timothy Miller]

Please take no offense by my comment but having that fine a thread may hinder you wile doing hot work. When you need to move fast with hot metal. If you are not doing a lot of hot work in it then it should work fine.

[maddog]

Please take no offense by my comment but having that fine a thread may hinder you wile doing hot work. When you need to move fast with hot metal. If you are not doing a lot of hot work in it then it should work fine.

Yes the slower action is definitely a downside of this method. It has turned out to be less of a problem than I expected when doing hot work as long as I remember to set the jaw gap close to its final position before pulling the piece out of the forge. OTH it is nice to have the extra clamping pressure from the finer threads.