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| How to test the gripping force of a chuck? |
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| Jonny:
Beat me to it Pekka. A simpler idea though never tried it can be to make up a self contained container thats held in the jaws that will collapse. Link this to a pressure guage just make sure you take a reading from a designated point ie 0 psi or 34 psi or whatever. As cylinder compresses so will the internal pressure, sure I am missing something? To pressurise could use oil or air, its low pressure so no harm should things go pear shaped. Standard nitrile O rings will take in excess of 10000psi and operate for years at 300 bar in a static arrangement. On moving pistons have had several Viton pieces last 8 1/2 years running 120bar at about 140 cycles per week with just one o ring 1mm cross section. I prefer to expand up on inner bore and compress o/d with minimal width guaranteed to work from zero psi. Some specs rely on pressure against the o ring to create a seal either on I/d and face they always pack up and distort. Unless its a 1mm cross section o ring I usually go for a compression on o/d around 0.3mm for sub 1 1/4" bores, still nice and easy to screw 1.5 to 2.4 cross section together by hand. |
| hermetic:
Do you want to know the pressure exerted, or the grip? a test of the actual gripping capacity could be done by gripping the plain part of a bolt in the chuck and using a torque wrench on the hexagon. you could then work out the surface area of the chuck jaws, and extrapolate mathematically from there (don't ask how, I leave that to the wife, she has a maths degree:-) Or have I missed the point? |
| awemawson:
Basically I want to check that the way I've fitted it allows it to apply the force specified by the manufacturer (Schunk). I need to adjust the operating hydraulic pressure to get the right amount of grip without exceeding the maximum pull on the chuck (22kN) Researching (googling) this I've come across all sorts of interesting things. For instance I found one site with a video demonstrating how the grip reduces HUGELY as the speed increases due to the centrifugal force on the jaws. Sadly I now cannot find the link ! |
| PekkaNF:
--- Quote from: awemawson on September 14, 2014, 08:18:06 AM ---..... Researching (googling) this I've come across all sorts of interesting things. For instance I found one site with a video demonstrating how the grip reduces HUGELY as the speed increases due to the centrifugal force on the jaws. Sadly I now cannot find the link ! --- End quote --- Anything like this? Pekka |
| hermetic:
Right Andrew, see what you mean, not straightforward at all, what is needed is a link between rpm and pressure so that as rpm increases, pressure rises Subject to the max safe working pressure, I am skating on thin ice at the very edge of the abyss here, so I will leave it to "them as knows". I will watch and hopefully learn. Phil |
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