How much force in a vise?

I guess they are different :-) ??

I re-did the calculations using the 2 formulae in the Machinery's Handbook: One for when the motion is in direction of the load (assisting it) and the other in the opposite direction (opposing).

With the same data I got the force necessary to move a load of 1000 lb to be 6.66 lb in the first case and 9.68 lb in the second case. This time the multiplier is 103 and 150. GOK where that 31.5 came from. The multiplier without friction is smack in the middle. That makes sense, does it not?

Michael Koblic, Campbell River, BC

Not by much sometimes. AFAIK the torque to loosen is mainly from friction. In a simple system like sliding a load up a ramp the force going up is the friction + the load, going down it's the friction - the load.

My 10,000 # load cell is a pressure gage on a cylinder like this:

You might find a spring scale for weighing fish/deer/moose in a sporting goods store. jsw

This seems too obvious to mention, but I will anyway. The friction depends on the lubrication. A ball bearing thrust bearing or a roller bearing would also help.

You can find a lot of the type of information you want in web sites that are about torquing bolts. Especially on the effects of lubrication.

Perhaps you could incorporate Belleville washers to give you an idea of the force applied. Belleville washers can be stacked to increase the force necessary to flatten them.

Dan

=A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 Dan

IIRC experiments on torqueing aircraft fasteners showed a 2:1 variation in clamping force vs torque from surface roughness etc under the best conditions. A skilled mechanic's judgement was as good as a torque wrench. The best way to torque a fastener to a large fraction of its yield point was to measure the change in length, though that's not always possible. I saw that in print a long time ago.

The bottom line is you have no good way to predict what's happening and should measure the forces.

jsw

Just this week I did an experiment [for Mosin Nagant scope mounting] that compared torque to strip out three turns [.1" thick steel] of

10-32 female threads in mild steel:

a) waxed: calculated 17.8 in lb, but got a 15 and a 16 inch pound yield b) lubed: calculated 26.5 in lb, but got yield at 28 in lb c) dry: calculated 34.7 in lb, but got yield at 34 in lb

What does it all mean? Close to 2:1

I had to go to YouTube to see what this does. Is there much call for moving 10-ton objects 11 mm? However, I can see the use to measure the load exerted. Do you have a special pressure gauge filled with liquid?

Oddly enough that was the only bright idea I had myself. It may be the only practical one, too :-)

Actually, maybe not. Don N gave me another idea: Rather than strengthening the bar that holds the screw use the same one and measure its deflection by a dial indicator.

Michael Koblic, Campbell River, BC

I saw the same data which is where I got the idea to incorporate a torque wrench into the design. Then I got completely confused looking at the recommended torques for tightening bolts - the figures seemed to exceed the tensile strength of the bolts.

Even some sort of indirect method would be useful to achieve consistency. Stick a lump of rubber in the press and measure its distortion?

Michael Koblic, Campbell River, BC

It's like a crowbar for cramped spaces. The kit it would go with is for straightening vehicle crash damage.

I do, and you can too:

jsw

This is a good geometry for a homebrew mechanical force gauge:

I don't have any data on dimensions or a suitable source of tubing.

jsw

Not just the inside of the gauge, but also the area behind the glass -- presumably to both add damping to the movement, and to reduce the shrapnel if it fails.

This was not to measure the deflection of the screw or the frame, but rather the deflection of the frame built around the dial indicator. A simple example is a short length of steel pipe large enough to hold the indicator, with the indicator mounted to one side, and the point pressing against the space to the opposite side. You either apply force between the mounting point of the indicator and the opposite wall, or at 90 degrees to that -- in which case the measured diameter increases instead of decreasing.

The trick is calibrating it -- which requires known forces to measure.

Others would be a heavy chunk of steel machined to be an open 'C', with the indicator measuring the distance between the ends of the 'C' -- and the force applied to lips of the 'C'. Again, you will need some way to calibrate it.

Here is one on eBay -- but one without a dial indicator built in. You have to have some special electronics connected to it to measure the output -- or know enough about electronics and have enough test equipment to build your own -- and be able to look up the connector pinout and such from the maker (if still in business).

eBay auction # 380337072665 -- $299.99

Enjoy, DoN.

Here's a newer model of mine:

were missing the shackle attachments, likely the reason they were sold cheap.

The indicator point slides on a ~45=B0 ramp on a rotatable plug which is the gain adjustment. The indicator mounting clamp is the coarse zero and the scale can be rotated for the fine zero trim.

As a chrome plated factory-made product it's nice and compact but I think a ring would be easier to machine smooth enough to remove surface defects at home, and a hydraulic cylinder with gauge easier to calibrate from measured dimensions.

You could weigh the front axle of your vehicle on the truck scale at a scrapyard and then use it for your calibration weight.

jsw

I have the short Standard-Hydraulic model without the red peak needle. The gauge is thicker than the cylinder body so I had to stick a 1/4" spacing plate on the back to use it lying flat, as it was meant to go between spotwelder tongs. It was last calibrated in 1992.

Instruments that require calibration to be commercially useful can go quite cheap as surplus. I have enough to cross-check them, to see if any are broken. So far all have worked fine, they're simply old and analog.

Sadly Harbor Freight no longer offers the 65613 Big Game Scale which weighed to 440 Lbs. When I checked and reported on it last August it agreed with a doctor's scale to one division at 248 Lbs. Y'all just didn't run out and buy enough of them.

jsw

Gunner Asch fired this volley in news: snipped-for-privacy@4ax.com:

So, make a new dial face!

LLoyd

In practice I've needed to pull about 3000 lbs max on jobs around the house, like extracting small stumps or winching down a tree that hung up on others when it fell. I had no real idea how much force a manual cable or chain hoist could apply, and if it was overloading the chains and ropes, until I measured it once for each device.

I don't think it matters that the instruments are long out of calibration. A 3/8" grade 70 transport chain rated for 6600 Lbs was proofed at 13200 and supposedly breaks at >26000. I doubt I'll ever damage it. The risk is with smaller gear that is light enough to carry all in one trip.

jsw

A kilogram is roughly two pounds, or almost exactly 2.2 lbs, ie pounds =3D double the Kg and increase by 1/10. For my transport chain 3000 Kg =3D

6000 + 600 Lbs.

jsw

Follow up:

Version 002a is up and running while waiting for a thicker aluminum plate to arrive:

The results are shown in the next few photos. Low tech approach works just fine. How it works with larger pieces, steel and possibly half-tones remains to be seen.

Michael Koblic, Campbell River, BC