Seeking description of missing part of a vise (Gressel MHS 125)

Hello,

I have an old crummy milling vise Gressel MHS 125 for which I believe I am missing a part. I was thinking to remake the part, but as I am not familiar with this style of vise, I do not know how said part should look. Here is a picture of the vise:



Here is the nameplate:



This shows what I believe to be the vise handle. It is marked with the model number of the vise. It fits the bolts fastening the fixed jaw to the base plate, but it does not seem to fit the main clamping screw assembly of the vise:



The end of the clamping screw has a finely machined round recess Ø 30 mm x 14 mm deep, with a single Ø 4 mm cross hole:



The outer black piece is a sleeve. There is a needle bearing between it and the screw:



I'm thinking the missing part might be an interface between the Ø 30 mm recess and the handle. If I pin the sleeve and the main screw assembly together through the 4 mm hole, I can turn them by hand to close the vise. It seems to clamp, but I am not at all sure if it clamps securely. Furthermore, the needle bearing inside the sleeve confounds me. If the sleeve and the screw were meant to pin together, then what is the purpose of the needle bearing?

I contacted Gressel about a manual for the vise, which they provided. The manual is for a newer variant of the vise, some of whose parts look quite different to me. Below is a link to the manual. (I also asked Gressel about spare parts and jaw availability: They said they no longer provide spare parts for the MHS 125, and that jaws sold for the current model Grefors 125 would fit the MHS 125.)

https://forum.zerspanungsbude.net/download/file.php?id=209591&sid=d0a828acf7212b174d3325741d0662f3

Here is a similar manual:

https://forum.zerspanungsbude.net/download/file.php?id=209344&sid=d0a828acf7212b174d3325741d0662f3

These manuals describe a two-speed clamping system. Fast-ish feed through a screw until the jaws close around the work piece, and then an internal toggle lever to clamp the work securely. The manuals say that the outer, black sleeve would stop turning about a turn before final clamping, even as the handle continues. This seems to indicate that the black sleeve is not meant to be pinned directly to the main screw.

Anyone have a hint on how to proceed to get the vise working?

I removed the moving jaw to have a look at its underside:

Design appears to utilize two co-axial actuating screws. See if the outer one isn't multi-start for fast general placement.

Inner, finer one applies final pressure. A short portion of the stroke appears to be augmented by a cam-shape and knuckle-toggles as force multipliers.

Missing part would seem to have a female hex socket to mate to the vise handle. Even so, inner screw may have been sheared off?

Mind, I didn't read the text.

Seems a clever design for fast swap of repetitive work, otherwise overkill and not so helpful.

"Crummy" you can correct.

Right right, not crummy. Yet well rusted in some places.

I took out the screw assembly:


It is as you surmised. The outer screw has a 6 mm lead (two start thread). The inner screw has a 2 mm lead. They are connected by some friction clutch or so. The inner screw connects through a rotary coupling to a pushrod. That rod actuates the toggle mechanism. The black handle is fixed to the inner screw. The needle bearing supports the black handle against the main screw.

I made a bushing to hold a hex socket:




When clamping, the inner and outer screw initially turn together:


When some torque threshold is reached, the inner screw turns alone, about 1/3 a turn, driving the pushrod into the toggle mechanism:


It seems to work well now. Thank you for your help!

nitromarsjipan said:

Right right, not crummy. Yet well rusted in some places.

I took out the screw assembly:
View attachment 266309

It is as you surmised. The outer screw has a 6 mm lead (two start thread). The inner screw has a 2 mm lead. They are connected by some friction clutch or so. The inner screw connects through a rotary coupling to a pushrod. That rod actuates the toggle mechanism. The black handle is fixed to the inner screw. The needle bearing supports the black handle against the main screw.

I made a bushing to hold a hex socket:
View attachment 266310

View attachment 266311

When clamping, the inner and outer screw initially turn together:
View attachment 266312

When some torque threshold is reached, the inner screw turns alone, about 1/3 a turn, driving the pushrod into the toggle mechanism:
View attachment 266313

It seems to work well now. Thank you for your help!

Click to expand...

Figured you could do. More to the Norsk than "granITE", after all.



But thank not I, but an earlier Schwaben mentor - the late Herr Alfred Pelz, master "Mechanic", as they called themselves, not "machinists", in that bygone era, guru of 6-cylinder aero engines produced for the Kaiser's air farce, War One.

More to it than his legendary-precise hand and eye. It was his alert and fearless mind that first addressed challenges between his ears to magnify the gain off what then came between his capable hands.

"Anything a good man can make, a better man can understand, then improve."

Standing on the shoulders of giants isn't good enough, y'see.

One is meant to JUMP ... go even higher, yet!

Then lend yer own shoulder to the next round of Pilgrims...

You'd have to know humans... ?