Measuring pressing force in a arbor press.

[atomarc]

I've searched and read several previous posts that asked this same question and gleaned some information. I have a different take on measuring applied force and want to know if the idea is totally bogus or not.

Place a small digital shipping scale on the base plate of the arbor press. Put the items to be 'pressed' on top of the scale and initiate the pressing process. Read the output of the scale at its highest value.

Would the readout of the scale equate to force, in pounds, that the press is applying to the object in the press? Am I confusing the terms 'force' and 'pounds' (weight) or am I missing some important point of physics or math!

I have a project that involves replacing an existing arbor press with some hydraulic or electro-mechanical unit and I need to get in the ball park on the approximate size to spec. If I can measure what is in use now, I can figure out what size is needed to replace, or replicate it. Make sense?

Stuart

 

[AA+]

The force read out by the scale is the same force that you are pressing down with. My degree is in physics.

Best wishes --- Allen

 

[jscpm]

Yes, this works as long as the force is applied straight down and does not exceed the capacity of the scale.

 

[rbent]

That would work, you can also use a enerpac or other appropiate hydraulic cylinder to get a good ballpark if you have a pressure gage.

 

[atomarc]

Great..thanks. I received my math and physics degree from the 'School of Hard Knocks' and may have been absent when that was covered.

Stuart

 

[rbent]

If you are using a scale put a spreader plate on top of it to make it an even distributed load and watch to make sure you don't exceed its capacity. Must be a small press.

 

[Chip Chester]

Well, sorta. Put items on scale, zero the scale, then press. Now, the scale shows the force exerted by the press, not the force plus the weight of the object(s). Probably a small point, if you're using a shipping scale.

Sherline has a hydraulic trailer tongue scale that will go up to 3 or 5k or so, for around $150. You can also make one with some chunks of material and a hydraulic pressure gauge, and some smarts.

Google up trailer tongue weight measurement for some ideas on how to multiply the capacity of your measurement setup without killing the scale.

Chip

 

[EPAIII]

If I were starting from scratch, I would definitely go with the pressure gauge. You need to know the effective area of the piston, in square inches. Then just multiply the pressure in PSI times that area and you have the pounds of pressure. This avoids the dangers of having an awkward scale in the mix.

You can probably find presses with a gauge already built in and with a custom scale that takes the area of the piston into account and reads directly in pounds or tons of pressure. Here's just the first hit in an internet search. Their least expensive press has such a gauge. I suspect all the rest also do and probably the same for many other brands.

Hydraulic Press - Presses - Metalworking | Baileigh Industrial

That would work, you can also use a enerpac or other appropiate hydraulic cylinder to get a good ballpark if you have a pressure gage.

 

[bryan_machine]

This is of course right, the small point is that a pound is a unit of force, not mass.

The "imperial" system unit of mass is called the slug (really) and converting kilograms to pounds is really converting kilograms at 1G to pounds.

 

[Illinoyance]

This is of course right, the small point is that a pound is a unit of force, not mass.

The "imperial" system unit of mass is called the slug (really) and converting kilograms to pounds is really converting kilograms at 1G to pounds.

A pound force (lbf) is the force required to accelerate one pound mass (lbm) at 1 g (32 ft/sec^2)

There are several mechanical devices for measuring force. The Dillon dynamometer is one that comes to mind. Morehouse is another.

 

[metalmagpie]

Make a simple hydraulic cylinder which has a rod sealed by an O-ring rather than a piston. Make the rod's cross-sectional area equal to exactly one square inch. Design your cylinder so that pressing down on the rod shows psi in pounds per square inch on a gauge. That gauge will read directly in pounds because the "piston" is one square inch.

 

[???]

There are gauges for measuring valve spring force. I've used them in a arbour press to calculate force.

 

[magneticanomaly]

I have an old screw-type press, and have always wanted to build a set of levers to amplify the stretch in the columns until it is readable on a gauge. If the max design stress in the columns is, say, 10,000PSI, a foot of column length will stretch roughly .004". One 25-to-one lever will give you enough travel to push a standard dial-indicator a full revolution. You will need a way to measure actual force, once, to calibrate your lash-up.

 

[gbent]

7 yo necropost

 

[Kallam]

7 yo necropost

 

[Kallam]

Here is a pressure gage I made years ago Its a 1.125 cylinder with an oring for sealing filled with oil . The 1.125 diameter is equal to 1 square inch .So 1 pound of downward force reads 1 pound on gage.

 

[awander]

7 yo necropost

Yeah, it's too bad the physics has changed in that time. LOL

 

[steve-l]

The path to your answer is arithmetic. Measure the distance travelled at the ram and the distance your lever traveled at a 1foot distance. then divide the first into the second to determine the ratio. Once the multiplication factor is determined, you can use a simple calibrated torque wrench rig on the handle or, as most of us do, just use feel.