Extra-wide vice (vise) using linear motion components

Hi folks,
I want to build an extra-wide vice (excuse the British spelling - for the A merican guys, I mean a "vise"). Something with roughly the dimensions of a
Black & Decker "Workmate" (http://www.blackanddecker.com/en-us/power-tools/ project-solutions/workbenches/workmate-portable-project-center-and-vise/wm2 25), but mounted on a sturdy workbench.
Basically, I want to build a better version of the "Workmate" vice. This me ans a vice with jaws around 24 inches wide. The vice needs to be able to ho ld longer objects without additional support (e.g., wooden planks for plani ng). It will be used for both woodworking and metalworking tasks, but not f or welding.
My priorities are:
- The jaws should stay parallel - It should be operable using a single handle - It should be tough and exert a good clamping force - It should move smoothly and not jam
I've already built a workbench frame. It's made to the same pattern as the bench I built a year ago, but I haven't fitted a wooden top yet. Here are p ictures of the finished bench and unfinished steel frame: https://www.dropbox.com/s/ycbufnrkf54pzqs/Finished_bench.JPG?dl=0 https://www.dropbox.com/s/cpw9tw82kfdw1ab/Bench_frame.JPG?dl=0
I've thought hard about how to build the vice, and I've considered a bunch of ideas. Scissor mechanisms, linked screws, bell cranks, etc. I've only co me up with one concept which I consider good. I'd like to use a pair of bal l bearing slides under the bench frame to keep the vice moving parallel. Th ing is, I'm not sure what the right kind of slides would be, or if I could afford them. Are there any guys with experience in linear motion who could help me?
Here are a couple of rough sketches of my concept: https://www.dropbox.com/s/ci3a3aebm1ydvn9/Extra-wide_vice.pdf?dl=0
Two slide rails would be bolted to the underside of the bench frame (front to back). The bench frame is built from 100 x 50 mm steel channel section, so it's strong. Four ball bearing carriages (two for each rail) would be bo lted to a thick steel plate, which would form the moving part of the vice. A very heavy length of angle (from a transmission tower or similar) would f orm the moving vice jaw, and the jaws would be lined with hardwood. I would buy a ready-made threaded spindle. As everything would be bolted together, it would allow all the components to be adjusted to ensure parallelism.
So I have a few questions:
- If I want a decent clamping force (say 1000 kgf), this will place a large moment on the ball bearing slides if an object is gripped off centre. If t he object is right at the end of the jaws, this would create a moment of so mething like 3000 Nm on the base plate of the vice. That would create, at a guess, something like a 300 kgf sideways force on each of the ball bearing carriages. This is more or less an abuse situation, I know, but I want a s trong vice. Are there any affordable slides which could carry this load, or a reasonable fraction of it? What would you recommend?
- The simplest construction would require a 50 cm unsupported rail length. Is this easy to achieve, or do the rails need closely spaced attachment poi nts?
- Are there any simple alternatives I'm overlooking? Tracks for large up-an d-over doors might work, but I'm not sure. Small iron wheels and rails?
- Are there any likely problems? Is this going to work?
I'd be pleased to hear from anyone with experience of linear motion compone nts. If I can get the right components, I'm willing to spend a fair sum on them. I just want to build the ultimate extra-wide vice.
Best wishes,
Chris
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Hi folks, ....... Chris
============== Cam followers are a simple and reasonably priced way to run loads on standard structural shapes. http://machinedesign.com/linear-motion/selecting-and-applying-cam-follower-bearings --jsw
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Thanks, Jim. They look interesting and pretty tough. Ever seen cam follower bearings with a flanged wheel? That would be handy so that a follower wheel with a vertical axis could follow a horizontal rail without falling down.
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Loading needle bearings axially is asking for trouble. This is the geometry you need to support loads on a horizontal rail. http://www.harborfreight.com/1-ton-push-trolley-97392.html
When I asked about boring a recess to press in a ball bearing last spring I was making the wheels for a similar trolley with a frame that bolts to HF's 1300 Lb electric hoist.
--jsw
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On Sunday, February 7, 2016 at 6:01:57 PM UTC-5, Christopher Tidy wrote:

nents. If I can get the right components, I'm willing to spend a fair sum o n them. I just want to build the ultimate extra-wide vice.

No experience, but take a look on Ebay and Alliexpress. You can find linea r ball bearings and shafts of lots of sizes. I personally would use bronze bushing and not linear ball bushings. I think they would last longer with off center loads. And it is not as if you needed minimal friction.
Dan
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On Sunday, February 7, 2016 at 3:01:57 PM UTC-8, Christopher Tidy wrote:

American guys, I mean a "vise"). Something with roughly the dimensions of a Black & Decker "Workmate"...
- The jaws should stay parallel - It should be operable using a single handle - It should be tough and exert a good clamping force - It should move smoothly and not jam
I'd like to use a pair of ball bearing slides under the bench frame to keep the vice moving parallel. Thing is, I'm not sure what the right kind of sl ides would be, or if I could afford them. Are there any guys with experienc e in linear motion who could help me?
There's parallel left-right, and parallel face-vertical; the left-right can be handled with pulleys and wire rope (like Mayline parallel-moving straightedges used for drafting/drawing). For vertical tilt parallelism, most vises have heavy steel (and you don't w ant that to be wide). Force (compression) at vise-faces causes torque around the slide member (lower down) and you can only compensate that by two-member sl ides, the top slide member being in tension, while a lower one is in compression. Two or more force members, perhaps four hydraulic cyliinders; left and righ t top cylinders are the slides, and act in tension, left and right lower cylinders are for torq ue balance and act in compression.
Vise face verticality requires
F_work x D_work-to-slide = F_lower-cylinder x D_slide-to-lower
and compression balance with tension requires
F_work + F_lower-cylinder = F_slide_tension
... all of which can be arranged with hydraulic cylinders and some valves a nd a pump.
I'm thinking most 'slides' are not intended to survive maybe a quarter ton of imbalanced force, like a vise might exert. Balancing the forces is a light structure alternative.
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On Sun, 7 Feb 2016 15:01:46 -0800 (PST), Christopher Tidy

'sOK. We can deal with all your vices.

Lee Valley Tools has a twin screw vise which might work for you: http://www.leevalley.com/US/wood/page.aspx?pE114&cat=1,41637,45114 Chain drive for parallel operation/1-handle use.
Or go there and search for "vise" to see their large selection. http://www.leevalley.com/US/wood/Search.aspx?action=n
You could probably put longer jaw inserts in a little $700 Tucker vise. ;)
--
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who think decorating consists mostly of building enough bookshelves.
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Yes, but I want to build the vice myself. Know the feeling?
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On Mon, 8 Feb 2016 10:37:42 -0800 (PST), Christopher Tidy

Ayup. Gonna cast the flanges and mill the threads yourself, too? ;) If not, LVT has the basic metal parts. You build the vise itself.
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Am Dienstag, 9. Februar 2016 04:54:13 UTC+1 schrieb Larry Jaques:

No. I don't really have the time (or the thread-cutting gear). I've got my eye on a threaded spindle from Benchcrafted.
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On Tue, 9 Feb 2016 12:36:14 -0800 (PST), Christopher Tidy

I like LVT because they tend to have tried-and-true vendors with good products. Wow, Benchcrafted's tail vise costs $295-369? Ouch! For that price, they ought to be good, too.
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On Sun, 7 Feb 2016 15:01:46 -0800 (PST), Christopher Tidy

I think using a single screw and parallel slides will cause a lot of binding with any off center clamping. Also, the parallel slides will have to be really parallel to not bind. Using two screws and tying together with chain or timing belt would probably work better.
Pete Keillor
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On Mon, 08 Feb 2016 07:09:41 -0600
<huge snip>

The more expensive B&D Workmates use a loose belt to tie the two hand cranks together. Turning one crank then moves both until some resistance is met. Then you need to turn each crank individually for maximum holding strength. These usually have a mechanism to flip up one of the clamping boards to the 90 degree position too. A lot less throat capacity in that mode though...
I have three different tables like the basic Workmate. Two Wolfcraft models and a cheap one from Harbor Freight. The Wolfcraft are pretty nice and very similar to the basic B&D models. One of them has a table that can be tilted/turned to 90 deg and height adjustable.
The cheap HF is serving duty as a night stand in the bedroom right now though. Never got the chance to use that one as intended and probably never will ;-)
I would just copy any of the Workmate table mechanisms using stronger material rather than a plastic bearing & handles. It would be more than strong enough for Chris's purpose and easy enough to do. Harbor Freight has an assembly/part manual online that shows the gist of it...
--
Leon Fisk
Grand Rapids MI/Zone 5b
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Am Montag, 8. Februar 2016 15:46:30 UTC+1 schrieb Leon Fisk:

That's interesting. Anyone got a link to the picture of the loose belt arrangement? I'd link to see that.
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    Not a picture -- but I have one of those WorkMates. The belt is sort of a flat belt with holes punched in it going between the two cranks, with the right crank preferred by shape for the general default use.
    The belt goes through the metal channel just behind the cranks, and beyond a certain torque will climb over the gear on each screw and slip one hole at a time. The belt is loose enough so the center is sort of pinched together between the two screws.
    I would love to have one built to better standards, but the WorkMate has some nice features, such as a base that it folds down to, and some extra folding legs, so you can raise it by about 8" or so. There is a step on the front, so you can use a foot to hold it down while sawing something held in it.
    But the table top sections are made of laminated cardboard and have drooped between the rails somewhat. My other (older) WorkMate appears to have Bakelite for the table top sections. That one came from Home Despot, while the fancy one came from an estate sale. Looking up the manual PDF files on the B&D site shows only one early version had the belt connecting the two screws.
    O.K. The following site has an exploded diagram. Note that the belt/chain is twisted, so you see only a loop at the ends. It is part 26 in the drawing.
<http://www.ereplacementparts.com/black-and-decker-wm225-type-workmate-parts-c-4167_4340_4342.html
    The "WM225 Type 1".
    Good Luck,         DoN.
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wrote:

The linked screw drive I made for my sawmill might be easier to make. The two leadscrews that raise the bandsaw head hang from flanged ball bearings in loose-fitting holes. They are normally connected by bicycle sprockets and chain. To disconnect them and reset the blade parallel to the log supports (which shift) I lift one side so the bearing comes out of the hole and the lead screw can move closer to the other one, then pop the chain off the sprocket.
If you have a metal lathe a similar flange mount is easy to make for a thrust bearing, as I did to adapt an extra long collet closer tube to my lathe.
--jsw
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Thanks for all the ideas. Jim's suggestion of the cam follower bearings and Dan's comment about the friction gave me some fresh inspiration. I have a long length of 75 x 12 mm flat steel bar lying around. How about a design u sing flat steel bars as rails? Something like this sketch:
https://www.dropbox.com/s/khx7rdw5odcm3wh/Extra-wide_vice_using_flat_steel_ bars.pdf?dl=0
The idea of turning up the eccentric bushes to permit adjustment came from Jim's cam followers (they are nice, but too expensive).
As with the other sketch, the width isn't to scale. It would be almost twic e as wide. What do people think? Would it work?
Chris
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On Monday, February 8, 2016 at 1:36:14 PM UTC-5, Christopher Tidy wrote:

nd Dan's comment about the friction gave me some fresh inspiration. I have a long length of 75 x 12 mm flat steel bar lying around. How about a design using flat steel bars as rails? Something like this sketch:

l_bars.pdf?dl=0

m Jim's cam followers (they are nice, but too expensive).

ice as wide. What do people think? Would it work?

I think it would work. I would not bother with the eccentric bushings. In any case you need the sides of the middle plate parallel. So you could ju st put a shim made of paper ( so you end up with a little clearance.) clam p the bars to the plate and match drill.
If you do use the eccentric bushings, you really only need the adjustment o n one rail.
Dan
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Am Montag, 8. Februar 2016 22:14:51 UTC+1 schrieb snipped-for-privacy@krl.org:

In any case you need the sides of the middle plate parallel. So you could just put a shim made of paper ( so you end up with a little clearance.) cl amp the bars to the plate and match drill.

on one rail.
My thinking with four eccentrics is that I could ensure the first rail is p erpendicular to the front of the bench, then adjust the second rail to get it parallel to the first, and correctly spaced.
I'm not sure if the eccentrics are necessary. If the whole frame was perman ently welded together, I'm sure they'd be overkill. But as the frame will b e dismantled and reassembled from time to time (when I move house), there's a chance the rail attachment holes will move slightly.
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On Monday, February 8, 2016 at 10:36:14 AM UTC-8, Christopher Tidy wrote:

nd Dan's comment about the friction gave me some fresh inspiration. I have a long length of 75 x 12 mm flat steel bar lying around. How about a design using flat steel bars as rails? Something like this sketch:

l_bars.pdf?dl=0
The steel plate is very ineffective in that orientation; it is stiff agains t vise left/right twist, but not against vise top/bottom twist. A deeper structural member (maybe just a few sections of C-shape stuff: unistrut/superstrut is inexpensive and available ) would be preferable. Recall that 'bar clamp' devices always have the bar in the up-down orientat ion, not left-right.
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