Help With Prentiss Vise Nut

[Ecosta777]

Hi everyone,
So I'm making a new vise nut for a customer's Prentiss vise and I need some confirmation on one aspect of it. It's seen some abuse, and I want to make sure it was manufactured a certain way vs. it wore out this way.

You'll see from the photos that he dovetail is tapered along the length of the nut. The side of the body is not square to my square, but when a .050 - .060" shim is placed under the low end, it makes the side square. This also coincides with measurements I'm getting from the threaded hole. From the dovetail to the edge of the hole is about .050 - .055" difference. High side being zero, and low side being about .055" less. Which confirms the hole is square to the left edge (where my square is).

So I'm assuming that that is a little much for wear, since the nut doesn't move at all. I believe it is tapered to lock into place in the vise body? Is that correct? Just wanted to confirm before machining it incorrectly. So if that's correct, all I'll have to do is machine the entire thing as though the dovetail were straight, and them machine the underside at an angle after it's completed.
Thanks
Eric

 

[Maui]

The nut does move. Its motion is restricted but it can move back and forth as the vise is alternately tightened and then loosened. From the damage that is visible, it looks like that one was abused.

 

[Ecosta777]

The nut does move. Its motion is restricted but it can move back and forth as the vise is alternately tightened and then loosened. From the damage that is visible, it looks like that one was abused.

Ah, ok - that makes sense. So I'll assume its not supposed to be tapered then?
I thought perhaps it was to wedge it in as I said before, but if it does move then I would guess its do to wear considering how badly this one was damaged.

 

[KMScott]

The important number is from the center of the Dynamic spindle hole to the center of the dovetail nut threads. The dovetail should float a little from side to side and a little up and down .03. The pin that holds the nut in should be pretty close so the back of the nut so it does not travel forward or backward to help with backlash. This is how I set up the dovetail nuts in my vises. Hope this makes sense.

 

[thehorse13]

I am the mystery customer.

For about two years I've searched for a suitable donor main nut for my Prentiss 21 vise. I've discovered through disappointment that Prentiss changed the thread and spindle diameter on the model 21 sometime after the late teens. This makes sourcing a 100+ year old main nut especially difficult. As a side note, you can tell the early model 21s from the later models by the fixed jaws. Only the early ones have fixed jaws while the later years have removable jaws.

Through word of mouth from another GJ member, I found myself with the right guy for the right job. Eric has done a superb job of fabricating what I could not find in the wild.

Attached is the picture he sent along when he finished the job.

 

[maleko48]

Hi everyone,
So I'm making a new vise nut for a customer's Prentiss vise and I need some confirmation on one aspect of it. It's seen some abuse, and I want to make sure it was manufactured a certain way vs. it wore out this way.

You'll see from the photos that he dovetail is tapered along the length of the nut. The side of the body is not square to my square, but when a .050 - .060" shim is placed under the low end, it makes the side square. This also coincides with measurements I'm getting from the threaded hole. From the dovetail to the edge of the hole is about .050 - .055" difference. High side being zero, and low side being about .055" less. Which confirms the hole is square to the left edge (where my square is).

So I'm assuming that that is a little much for wear, since the nut doesn't move at all. I believe it is tapered to lock into place in the vise body? Is that correct? Just wanted to confirm before machining it incorrectly. So if that's correct, all I'll have to do is machine the entire thing as though the dovetail were straight, and them machine the underside at an angle after it's completed.
Thanks
Eric

@Ecosta777 I have a Monarch 218 vice that is in need of a similar dovetailed vice nut like what you showed here. Mine unfortunately cracked diagonally from the dovetail today. My first thought was to get it machined out of steel since the cast parts are probably long gone. I use my vice regularly, and of course it went down in the middle of a project on me. I found this site here with some additional info on it:

Replacement Prentiss Vise Nut

Recently, a reader commented that he had a Prentiss vise with a broken vise nut. He asked if I knew of how to find a replacement. I said recommended a few places but said he’d probably have…

somanyhobbies.wordpress.com

I would need to double check, but I am pretty sure my vice's nut has the same number 20 on its side as the pic here: https://somanyhobbies.wordpress.com/wp-content/uploads/2018/10/vn1.jpg?w=640&h=337

Please let me know if you might be able to help or know someone else who can.
In the meantime, I guess I am off to the big box store