How to test the gripping force of a chuck?

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Meldonmech:

Andrew I do like the little gizmo you have discovered, do you intend making one?

Cheers David

awemawson:
David,

I'm not yet committed, but it's on the list of possible little projects for winter :thumbup:

PekkaNF:
Do you know Poldi hardness measurement system? Anyway the big idea is that you strike a plunger that presses a specimen of known strengt and a hard ball againsta unknown specimen. Indentations (of the ball) are measured from both specimens and hardness is deducted from the table. Anyway, this is pretty simple method and it produces results that are not 1:1 brinnel etc. hardness.

http://www.measureshop.biz/images/products/ultra/Ultra_tisk-193-i2.jpg

Now, we are not measuring Brinnell hadness here, but only a force. Just incidently same method:
http://home.iitk.ac.in/~kamalkk/Image10.gif

Could this idea work in sort of reverse engineering manner here? If a bush that has holes squarely against the jaws. Holes accomondate one ball bearing "ball" each. In the centre there is a round rod. When jaws are closed, an indentation is made. Now. If you have a shop press, or something close to it (I would not be surpriced, if someone had a deadweight calibrator) and you would use same size ball bearing to press indetations on the same rod. When you get close to same size indentation, you have pretty close the same force than the jaw?

Right or wrong?

I'm a little handicapped mechanically (I'm electrical engineer we did not read that much ironbashing). So, if I'm completelty off I don't mind corrected.

Pekka

awemawson:
Pekka,

That sounds a nice simple thing to make and use, thanks for the suggestion I may well try it out.

The '3 hydraulic piston' one has the advantage of giving a reading that can be watched as the jaw pressure is adjusted.

I can see a series of mini projects being spawned here :ddb:

PekkaNF:
Happy if you find that idea usefull.

That meter surely looks spiffy and it's a instant reading.

My line of though was that you probably have a meter or set value for the pressure setting. Now, if you make a table of the pressure vs. force (indentation) you can set it later easy and if something does not check you can allways fall back known rod/ball/indetion size to check system up.

I saw once a measurement station for load cells, they had a really nice system to minimize frictions and enviromental effect. one thing that I found genious was that they were rotating the cylinder piston - all friction was sliding friction, static friction would be very much bigger loss.

Pekka

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