Home Grown Precision Grinding Vises

[OldCarGuy]

Precision vises are a great accessory to have and makes setting up work pieces fast and easy. Here's a few that I was able to make over the past 60 years. I was a mere four teen years old on this pair of vises... They are made of O-1 oil hardening tool steel hardened to 60 RC. This design is far more difficult to make; but has its' advantage in use. Note the two piece screw design,, the smaller one is a LH thread. While the bigger one is RH. Turning the handle moves the jaw twice the distance, yet a stronger holding power than a coarser single thread... And has a nice flip up "speed Lever"added to the knob...

All the other are made from low carbon steel and case hardened. Called Nitriding Where Nitrogen is diffussed into the surface making it 70 RC. . Leaving the core soft and more stable. Baby one, And a sine vise.. All are still within tents of being square.

Here's a setup using my vise on a magnetic sine plate to grind the ends of a blade for a Precision Protractor.

Here's where the two grinding vises of the exact same size came in handy. Two vises vises and a parallel on either end to grind the edge of an 18" long blade.

 

[Rex Walters]

The differential screw is a neat touch. I've not seen that in a grinding vice before.

 

[OldCarGuy]

The differential screw is a neat touch. I've not seen that in a grinding vice before.

My design of using a thread within and on the same centers is not actually a differential thread as I understand the terminology. My design uses two different threads (one RH & the second LH). When the handle is turned clockwise the jaw travels forward the pitch of the larger RH thread,, Plus the distance of the smaller LH thread. Therefor the jaw travels twice the distance per turn. While the handle travels half the distance of the jaw. Making the overall length of the vise less when wide open.. Giving more clamping force compared with the movement of a much coarser single thread.. Hope that makes sense,,,

 

[Rex Walters]

It makes perfect sense. To my mind, it was still "differential," it's just that it was addition rather than subtraction.

Although I think a normal differential screw needs different screw pitches or you won't get anywhere!

 

[WesPete66]

Very nice!
Rookie question here, but what is the theory on vises like these to keep the moving jaw from lifting or tipping when tightened?

 

[whitmore]

It makes perfect sense. To my mind, it was still "differential," it's just that it was addition rather than subtraction.

Although I think a normal differential screw needs different screw pitches or you won't get anywhere!

When calculating effect, a positive (right hand) screw pitch and negative (left hand) screw pitch are
certainly different!

And, when trying to match screw and nut, such a difference dominates.

 

[Rex Walters]

When calculating effect, a positive (right hand) screw pitch and negative (left hand) screw pitch are
certainly different!

Yup.

To continue beating the poor dead horse, I think a normal "differential screw" has the same handedness for both the external thread and the internal thread. Assume RH: turning the outer thread clockwise moves it forward through its nut. If the inner thread is prevented from rotating though, the same clockwise turn RETRACTS the inner screw.

The difference between the two pitches determines the overall movement. If they both had the same pitch, then there would be no overall movement at the end: the inner part would retract the same amount as the outer part moved forward. You can control whether the overall length increases or decreases by changing which part has the larger pitch, but a typical differential screw changes in length by the difference between the two pitches per rotation.

By changing the inner screw to a LH thread, @OldCarGuy cleverly made his vice jaw move forward by twice the rotation (assuming they both had the same pitch: addition, not subtraction). Turning the outer screw clockwise moves the outside forward AND extends the inner screw at the same rate.

Again, to my mind, these vises still have a "differential screw" of sorts. With identical pitches, the length changes by exactly 2X the pitch per rotation. If you changed the inner pitch, or even the number of starts, you could make the overall length vary by more or less than 2X the outer pitch per rotation.

 

[Winegrower]

Instead of a "differential" screw, it's an "integral" screw.

 

[OldCarGuy]

Very nice!
Rookie question here, but what is the theory on vises like these to keep the moving jaw from lifting or tipping when tightened?

The movable jaw is guided in the vise's main frame by a tang below the jaw. And a small hardened steel plate stops the jaw from picking up. All guided surfaces were precisely ground and fitted after heat treating.

 

[Parlo]

The tenon slots in the base are really handy for setting up on a rotary table, enabling the vise to be slid along at the same setting to another offset while keeping parallel.
Mine are also ancient but still going strong, the smaller ones use a fine l/h thread.