# How much force in a vise?

• posted

How much force does a common shop vise develop in its jaws? Google was pretty unhelpful on this - the only reference I could find suggested up to 7000 lb. Another paper suggested that a minimum required clamping force for machining is much less - up to 1000 N.

I am interested because I am trying to guess how much force I can develop in this press:

Right now my answer would be "not enough" (see the following photos if you are interested in the process).

Can anybody suggest how such force could be measured?

Michael Koblic, Campbell River, BC

• posted

Looks a lot like a wine press. I know the small wine press I have will develop about 1000 pounds at the plate with a 2' lever on the handle.

• posted

Michael

Although not sure of the span dimension I am almost sure I could easily bend th 1/2" plate so any measurements would be questionable unless the bend of the span were taken into account.

And from many years of using presses in connection with photography I am not sure the heat requirements are at all dependent on the pressure. The pressure is probably needed to assure enough contact so the heat can do its thing for the mechanical connection of the media. The heat is probably needed to fuse the media and not completely dependent on pressure.

My two cents. Bob AZ

• posted

That's sort of like asking how fast a common car goes... Different vices have different thread pitch, different handle lengths, and different (stronger/weaker) humans operating them. So, unless an answer like "somewhere between 500 and 20,000 pounds" satisfies your curiosity, you may be disappointed.

You should be able to calculate (roughly) the force your press will generate using the thread pitch, length of the handles and how much force YOU can apply to the handles (which may be the hardest to measure)...assuming it's strong enough to hold together.

• posted

The formula to find the force exerted by your screw is F= 2*Pi*r*p*f

F is the force of the screw Pi is 3.14159 r is the distance from the center to the handle p is the screw pitch f is the force you exert on the handle

from the photo, I estimate the screw multiplies your force by a factor of

1. However, evenly applied force is not the way to remove bubbles. You will just trap them and compress them. The way to remove bubbles would be to run the plate and film between two rubber rollers with a rigidly-held, but adjustable gap. Another way is to apply the force through a slightly domed rubber pad so the center contacts first and the air is pushed to the outside. You have to make sure the rubber is compressible enough and the force is great enough that you make contact on the outer edge.

• posted

It's easy to work out. Let P = the pitch of the screw, and H = the length of the handle (this is measured at the point where you grip the handle and is generally a little less than the actual length). The mechanical advantage of the system is then 2*Pi*H/P

Assuming the pitch is, say, 0.1", and the handle is 12" long, then the mechanical advantage is 2*Pi*12/0.1 = 75.4/0.1 = 754 If you apply a force of 10Lb to the end of the handle, then the screw will exert a force of 7540 Lb, assuming no losses due to friction. Unfortunately, the frictional losses will be rather high, probably more than 50%, so the actual force would be more like 3000 Lb. IHTH

• posted

I just checked the bench and milling vises with a hydraulic load cell, which is a cylinder of 1 sq inch area attached to a 10,000 PSI gauge. At a 'reasonable' handle force without hammering the 4" milling vise reached 1500 lbs, the 3-1/2" bench vise 2000.

jsw

• posted

Use a trailer tougue scale or a Snap on brake force gage. I happen to have a snap-on brake force gauge set, they are only 1/2" thick and made to go in a caliper in place of the brake pads to check caliper pressure. Measure 0-5000 pounds.

• posted

Don't you have a 5 or 6" mechanic's shop vise, too, Jim?

I'd be willing to bet that one could do the 7k# force Mikey suggested. Wilton vises have 25kpsi castings. Another ad suggests 30kpsi. Tormach uses 80kpsi ductile iron bodies. Neither suggests jaw force.

Cool! I'd never seen an air over hyd vise before.

-- Learning to ignore things is one of the great paths to inner peace. -- Robert J. Sawyer

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I did but never used it and eventually traded it for a welding table etc. I can accomplish more through subterfuge than brute force.

The 4" brake 2805-0105 shown here bends thicker stock more neatly:

jsw

• posted

...

He used 1/4" plate, and in later picture says bending was a problem. I expect that 3/4"-1" plate probably is needed to avoid much bending.

Probably so. Unfortunately, the Press-n-Peel web page is a bit vague on requirements, merely saying "Temperature setting on the iron is critical, [...] Suggested starting temperature is 275-325 degrees F. [...] Iron until board has completely and fully reached the temperature of the iron. Time varies with the size and thickness of the board. Generally this is 1.5 to 10 min." They do offer a HIX Corporation Heat Transfer Press, on their information page.

• posted

Age and treachery will always overcome youth and skill. (I know. I owned the t-shirt.)

I have this type, plus a shorty bender from HF.

-- Learning to ignore things is one of the great paths to inner peace. -- Robert J. Sawyer

• posted

Thank you and all the others for helpful information.

To answer some of the points that have been raised:

1) There is no question in my mind that two *heated* rollers would be the way to go. I have looked at several solutions including laminators but nothing fit the bill.

2) Up to now I have been heating the workpieces on the same 1/4" aluminum plate and then going over them with a hard rubber roller. Using a bathroom scale etc. I estimated the pressure developed this way at 21 psi. The results are reasonable with temperatures in the region of 160-170C but the bubbles are a problem as the pressure is applied *after* heating. No amount of rolling will get rid of them then. Often they are in a place where they can be re-touched but sometimes they are not and the piece is scrap.

3) The reason I do it this way after five years of experimenting is that I found the recommended method by Press-n-Peel quite useless. It works on PCBs. On anything thicker - not so much. There are others who have described successes with the Press-n-Peel iron-on method but the big question is always consistency. I did look at the Hobby Lite press from HIX but before I spent \$325 I wanted to make sure that the press is suitable for what I wanted it for. The company was not particularly helpful or forthcoming with information.

4) I jury rigged a press using two clamps. There is no question that on small pieces at least I develop higher pressures this way. This has reduced the number and size of the bubbles. However, the rub is that sometimes the pressure is too much and fine detail gets obliterated (I did this today with a 7 in2 piece which I only took up to 130C - one tiny bubble but I shall have to go over the details with a needle).

5) I knocked my version of the press together from whatever I had in the house. Frankly I did not expected it to last very long. Using the two clamps was a pain and sometimes there was a clearly discernible pressure gradient across the piece. I was hoping that the central screw will provide more even pressure distribution and better pressure control. I was disappointed at its performance but in retrospect I should have expected that as the whole area under pressure is 80 in2 thus to produce the same pressure as I do manually with the roller I would have to develop over 1600 lbs force. Of course the idea was to produce more.

6) The press reminded me today that the force developed is not inconsequential as it blew one of its legs off. Still, I learned a fair bit from the effort.

7) Thanks to the gentlemen who provided me with the formula. I found it independently in the Machinery' Book late last night after I posted. I should have found it much sooner if I fed "jackscrew" into Google. Such is life :-). The figures I got was 125x multiplier without friction. I tried to do the calculations with an assumed coefficient of friction of 0.2 and got a multiplier of 31.5. Seems kind of small. I haven't the foggiest what kind of force I put on the end of the lever (3" long, BTW, the pitch is 0.151" and the pitch diameter roughly 0.6").

8) Version 002 is in the works with many changes. I am still not sure how to achieve a consistent force (it is much easier to manipulate the temperature). I wonder if a torque wrench would be the answer if somehow incorporated in the top lever.

Michael Koblic, Campbell River, BC

• posted

On Jul 15, 10:01=A0pm, snipped-for-privacy@gmail.com wrote: The figures I got was 125x multiplier

My father tells me that anything that will not run backwards has an efficiency of less than 50%. You cannot spin the shaft on a vise by prying the jaws apart, or it would not stay clamped.

He once designed a vehicle with worm gear drive, that when the driver took his foot off the gas, the vehicle skidded to a stop.

• posted

I'm kinda' late to this discussion, but I just had an idea for a device that would excel in evenly-applied-force. That would be an air bag, fitted in a box. A reverse of the vacuum air bag, which is limited to

15 psi. I don't know how much more that 21 psi you'd want, but a bag-in-a-box could do much more than that.

For a bag, how about the bladder that's used in the storage tank for well water, or in the expansion tank of hot water heating system. The bladder itself is available as a replacement part.

Bob

• posted

Am I missing something? Is this business with the press all about getting rid of air bubbles under the sticky film? Pressing bubbles makes them smaller but they just, you know, re-expand when you stop pressing. And they migrate if you roll -- it's like spearing buttered green peas with a fork on a china plate.

Apply the film as well as you can. Maybe make an initial pass with a roller or iron to get it well stuck down.

Locate any bubbles. Use a fine hypodermic needle to pierce the film and release the bubble, gently rolling the film down with a narrow steel roller as you do so.

Then use your iron or press or whatever to do the iron-on step and finish the heat transfer.

There used to be a product used by newspapers to produce cylindrical rotogravure plates, called IIRC "carbon film". I tried to get some 30 years ago and no one around here (very far from the NYT or the Chicago Trib :-) had ever heard of it. So I suppose it's no longer made or is hiding in some industrial niche somewhere. I wanted it to do stuff very like what you're trying to do.

BTW, "anorton" wrote that the axial force of a screw was:

force(out) = 2 Pi force(on handle) length-of-handle screw-pitch

which is apparently wr force(out) = 2 Pi force(on handle) length-of-handle --------------------------------------- screw-pitch

which agrees with Machinery's Handbook (P. 309 in 17th ed, 1972).

By that reckoning my cider press [1](which is a whole lot sturdier than the OP's press [2]) develops ca. 30,000 pounds (or ca. half that, if there's a 50% friction loss.)

- Mike

[1]
Ca. 2" Acme screw has a pitch of 0.42". "Handle" is ca. 40" and I'm guessing I put 50# on it as the pomace gets pressed down real hard. [2]
• posted

I think up to ~80% of the tightening force on a screw can be lost to friction. Compare the torque to tighten with that to loosen.

jsw

• posted

You would use my formula if the screw pitch is in threads per inch. Use the one in the machinery handbook if pitch is given as distance between threads. There also would be more than 50% loss due to friction.

I agree with what you say about bubbles. Evenly applied force will not work. Someone else suggested a vacuum bag which might also work.

• posted

Well ... just as a point of information, I clamped a short Enerpac hydraulic cylinder rated for 10 tons at 10,000 PSI in an old Bridgeport milling vise. (I have Kurt vises which I prefer to use.)

I connected it to an electric hydraulic pump intended for running large terminal crimpers.

That pump is designed to go up to 8400 PSI, and then release.

When I ran it on the Enerpac cylinder, I could *see* the frame of the vise bowing -- perhaps the center lifted about 1/8" above the line between the ends (this is without the vise being clamped to anything -- just resting on wood). So -- at 8.400 tons (16,800 PSI) it was bowing well beyond normal operation. so let's assume something much more reasonable in such a heavy vise -- say about 1 ton or less. (And I would have had to crank the handle a lot harder than I can physically manage without a long cheater pipe to get to that, I believe.

As the vise returned to straight, it was within the elastic range.

The first question is -- what force are you trying to measure? The easiest to measure is the force applied by the jackscrew to the middle of the plate. There are load cells which display the force applied as the frame deflects (and it is measured by a dial indicator).

However -- this is not measuring the force applied to the transfer labels, which is what I think you want. Just knowing the force applied by the rod is not enough, because both your backing plate and your top pressure plate are far from rigid enough.

For the top plate, you need something like forged steel with a platform in the middle (at a guess say 2-3" high) with ribs going out from there to the corners, and angling down to the corners. This will even out the force significantly.

However -- your aluminum plate on the bottom also bows, reducing the pressure in the middle and concentrating a bit more of it out to the edges.

What I would suggest is:

1) Triple the thickness of the bottom plate, and make it steel, not aluminum.

2) Go up to at least one inch thickness on the wood top plate, and ideally at least two.

3) Get a closed cell foam rubber to go between the wood pressure plate and your transfers. This will crush, and even out the force from center to edge significantly. At a guess, I would suggest perhaps an inch thickness or more for the foam rubber.

With this, you probably won't need as much force as you were applying in your tests.

Good Luck, DoN.

• posted
[...]

This would do fine. All I am after is something repeatable. The actual pressure applied across the workpiece can be calculated from the surface area.

There is one commercially available like that. I nearly bought it but it was 3x as expensive and quite big (the leg span was 18").

That I do not understand. The reason it bows in the middle is because the pressure is applied *there*.

Agreed except for the steel heat conductivity.

Probably also wise.

That's why I use the silicon pad. I wonder if ordinary rubber would withstand the temperatures. I know hockey puck does not!

I know I can develop forces well in excess of required for the small pieces (up to 16 in2). I suspect I shall never need to apply the same pressure over the whole of 80 in2. Right now I suspect consistency will be a bigger issue.

Michael Koblic, Campbell River, BC

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