Arbor Press

I apologise for what I think is a daft question, and even my flakey maths suggests I know the answer....but to be sure.

I've bought a one ton arbor press. I don't need a bench that will take a one ton down-force on which to mount it, do I?

Thanks in advance

Martyn

Hi Martin, due to mechanical advantage between the fixed and moving part you should be able to generate a force of 1Ton, a normat bench will be quite adequate for mounting this device on. Good Luck, Noel.

The force on the bench will be:

The weight of the arbor press + weight of workpiece + the force of you pushing down on the press handle.

The "one ton" force will be generated between the jaws of the press.

I think that your bench will be OK.

JimB

Thanks Noel thanks Jim

Yes, I've just demonstrated this to my wife in the kitchen with an onion, whisky glass and my fist. The arbor (fist) delivers the ton to the bearing (onion) to push it into; for example a hub (the glass). Thus the force is on the onion not the bench.

Thanks again.

Martyn

SO ! The experiment was a success ? Noel.

Yes. And we didn't break the glass!

M

I'm easily confused. What's the difference between weight, force and pressure?

And what exactly does the 1 ton claim refer to? I assume, perhaps wrongly, it means the pressure exerted at the end of the ram is equivalent to loading it with a 1 ton weight, so a 1" square ram would put 2240psi on whatever fitted exactly between the jaws. Is that right?

Dave

But what was holding the glass up against the force from the fist?

The bench will be subjected to, as already said, weight of press m+ weight of workpiece, and whatever force is produced by the mechanical advantage to deliver a 1 ton force between the jaws of the press and the workpiece.

The latter is likely to be on a par with the first two, or maybe even less.

As long as the bench can safely withstand the total force, you should be O K.

For definitions

Pressure is force per unit area (Lbs per square inch for example )

Force will be (same units as weight) mass times gravity. (If you take a mass to the moon, where gravity is less the weight will appear to be less )

Howard.

It's much easier in SI, Mass is kilogrammes, force is Newtons, and pressure is force divided by area. One Newton is the force necessary to accelerate one kilogramme at one metre per second per second, and so has fundamental units of kg/sec^2. Pressure is Pascals, which is Newtons/sq m . This can be inconveniently small so we have MegaPascals, 10^6 Newtons per sq.m, which for engineering calcs is handy as it is numerically the same as Newtons per sq mm.

Imperial gets confusing as you have lbm (pounds mass) and lbf (pounds force) which are not the same as Howard points out. To overcome this we used to have poundals, which was the force needed to accelerate one lbm at one ft/sec/sec. It didn't really catch on, I wonder why?

A force is simply a push or a pull. We call the force pulling an object to the centre of the earth its weight - but this changes as gravity varies from place to place.

Mass is the amount of matter (stuff) in an object and doesn't change wherever it is.

Pressure is force per unit area so your assumption is quite correct.

As has been mentioned things can get tricky in imperial or pre SI Metric units. The force pulling a 1kg mass down is 9.81 Newtons on the earth as the Newton is the SI unit of force but in imperial the unit of force could be the Ton or the pound and the unit of mass is also called the Ton or the pound, even though mass is not a force and so not the same as weight. So if you took a 1 Ton mass weighing 1 Ton on the earth to the moon it would no longer weigh 1 Ton - even though there was exactly the same amount of matter there. My brain hurts!!

To be fair there are explanatory terms such as pound force and ton weight that clarify what is being talked about but these are not used as commonly as perhaps they ought to be.

The 1 ton force of the arbor press is only developed between the "jaws" of the press, in the same way that the force of a G-clamp is developed only between its jaws.

Owing to lever, (or hydraulic action, depending what your press uses), force is multiplied so you won't push the lever down with 1 ton, you will only push a small fraction of that, and this is all your bench will be subjected to - plus the static weight of the press itself.

The maximum force your bench will be subjected to is your own body weight, (since if you lift yourself off the floor, that is the maximum you can push down), plus the static weight of the arbor press; so if your bench can withstand you sitting on it next to your arbor press, then you are good to go.

Most important thing might be to bolt it to the bench so all that yanking on the handle does not tip it over, whence it falls upon your toes. They almost certainly wont stand up to it.

John

Suspected it was like that; but most graphically expressed. Almost poetry. Thank you.

Thanks too Hopper for the toe tip. Not only bolted to the bench but bench bolted to wall eh.

Best from Martyn in sunny France.