mechanical advantage-screw thread

[toolman87]

I am replacing a manual clamping procedure with a hydraulic cylinder.  I am working on sizing a cylinder and system pressure.  Currently we use a 1"-8 screw with a 15" wrench.  I estimate the we apply about 100lbs of force on the wrench to tighten.  I need to know the down force to pick a cylinder.  I have plugged the numbers into the formula on pg 150 of the machinery handbook.  but am unsure of the units.  The numbers seemed quite high from my experience.  I am a toolmaker/business owner.  I just signed up today this looks like a great idea!  

 

[MikeMilburn]

Toolman, I'm not an engineer, just a jack of all trades/master of none but if it was me, I'd get hold of an cylinder, put it in place of the actual item being clamped and read the pressure from a guage put in the cylinder. From this info you can work out the cylinder size and system pressure required...Mike

 

[DonLeffingwellPE]

I have calculated this to be about 6000 lbs force applied by your screw jack.<br>I assummed a coefficient of friction of .15 to be on the safe side. I would recommend you use a hydraulic cylinder for this application. Without knowing the stroke required or the speed you need to bend your tubing at I can't recommend a specific size. If you send me your e-mail address and what&nbsp;&nbsp;kind of software you have, I can send you the calculations.<br><br>Don Leffingwell PE<br><A HREF="mailto:dleffingwell@snet.net">dleffingwell@snet.net</A>