Post vise Spindle & box repair

[BartW]

Hello Guys;

 

 

I revieved this tiny (well small compared to the other ones  ) post vise, but it's in need of repairs.

It needs a new spring, but that's easy. And I wanted to make it a low free standing vise, since every other vise I have it much higher.

The spindle and the box is of more concern to me. I'll attach a picture of the trapezoidal thread spindle. Having measured it; it's standard TR40 x 7. (40 mm outer diameter, 31 mm inner diameter, 7mm thread ) That's good news, I should be able to make something like that. What bothers me more is the quality. When I was removing grease from the box, I took 2 or three piece of thread out. Simply broken of inside the box. As you can see in the picture, the first 10 cm of thread is severly worn down. Now the question is fairly simple. 

Is this damaged enough for you to replace it ?

I can replace it - costs me about 100 €, just put a new threaded rod TR40 x 7 in the handle and weld it solid; chop of the part of the box the size of the fitting nut, and weld that on. But it will take me a lot of time at the lathe, and it still works as-is.

 

[ThomasPowers]

The old ones had the thread brazed into the screwbox and are prone to failure if over tightened.  

However: if it's working for what you want to use it for and the repair will be the same as it is or if it's used more.  Why not use it?

If you have the skills and access to the equipment; making a new screw & screwbox that can be used when done or catastrophic failure occurs could be a "spare time project".

[caotropheus]

Just saw this today.

https://www.youtube.com/watch?v=IQcBC1Nf7qg

 

[ThomasPowers]

Not the way I would have done it; but within tolerance---save for that he used all thread for the pivot bolt and so the thread edges will be impact points when the vise is in use.  Why didn't he just use a bolt with no threads for the bearing section???

Very "blacksmithy" use of machine tools!

[BartW]

Nice video, and the box repair part was pretty much what I had in mind. Except one thing ... I just checked my other (normal) vises; and they use trapezoidal thread but size TR24 (about 1 inch) or TR30 (I have both on supply with nuts) ; While my post vises use TR40 (like the one in the picture); I even found one that uses TR44 (almost 2 inch). Why does it has to be that heavy ? Those normal vises can squeeze fairly hard, and really the limiting factor is the human using it.  What if I replace it with basic TR30 trapezoidal threaded rod with matching nut ? I'd have less work, no purchases; but I wonder why they'd use threaded rod that heavy. Especially if you are going to braze on the thread in the box; I'm fairly sure the precision machined TR30 threaded rods and nuts from medium hardened tool steel are FAR stronger, even tough they have a smaller diameter 

The amount of rotations needed / travel distance is almost the same.

 

If I had to use allthread for the pivot; I would have made a threaded sleeve to go over it to serve as pivot point out of bronze or brass. Unprotected threaded rod as a pivot will wear out fairly quick.

 

 

 

[ThomasPowers]

I suspect that some of the original screw/screwboxes were not high grade metals and so went big to avoid failure.

I know on my oldest postvise the screwbox was forge brazed out of a number of forged parts and would definitely date to the real wrought iron era.  The screw thread in the screwbox had been wrapped around the screw and then unthreaded and forge brazed into the screwbox.  It's lasted a couple of centuries so far; but I don't let students touch it! (I use it gingerly every once in a while because tools *should* be used!)