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Re: Screw Thread Friction
Re: Screw Thread Friction -- RBPrice	Post Reply	Top of thread	Forum

Posted by: Kelly Bramble ® 08/30/2006, 12:39:56 Author Profile eMail author Edit

In general, what you are looking is challenging to calculate or estimate. Typically, to compensate for friction effects on torque and axial applied load, the tare or turning torque is measured. The final torque applied to a fastener is the required torque plus the tare torque. So, if you measure 2 in-lbs to turn a friction thread and your require 7 in-lbs. You would torque to 9 in-lbs (7 + 2).

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Re: Re: Screw Thread Friction
Re: Re: Screw Thread Friction -- Kelly Bramble	Post Reply	Top of thread	Forum

Posted by: RBPrice ® 08/30/2006, 13:24:47 Author Profile eMail author Edit

Hello Kelly and thanks for the response. My problem is that I am in the process of designing these items. I need to exert 8500 lbs force on a machine element and cannot use electical, hydraulics or pneumatic power. Hence the need to manually turn the threaded shaft. I really don't have the freedom to build one of these items and test it: I need to get it right the first time. Shigley and Roark and Hicks and some others really don't treat this problem very well. The folks at Nook industries have some values for their acme screws but that thread form is not a 60 deg. vee which is what I want to use. I would rather not have to use a lever (ratchet wrench, since that is a loose part) but just the operators hand. Even with the ratchet, it would be nice to have some sort of an educated guess as the the torque required. Which is a segue into the equally interesting question of the thrust load capacity of a 1.250-20UNEF thread in silicon bronze. Thanks again. Bob Price

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Re: Re: Re: Screw Thread Friction
Re: Re: Re: Screw Thread Friction -- RBPrice	Post Reply	Top of thread	Forum

Posted by: Kelly Bramble ® 08/30/2006, 13:30:28 Author Profile eMail author Edit

Unfortuantely, experimental data is always the best. Is your application static or dynamic (cycles)?

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