# Compute compressive forces necessary for thread rolling

Is there a mathematical method or reference source/handbook for computing the compressive forces necessary for thread rolling? I realize I could use FEM, but that is a lot of work, so I am hoping to avoid it if at all possible.

I am designing a frame that will hold two parallel radial rolls and gearing to drive the rolls into the workpiece while rotating and I need to know the approximate forces involved so I can (1) dimension the frame to be strong and rigid enough, and (2) accommodate appropriate gearing.

The variables are the material being rolled (typically annealed alloy steel or stainless steel), the diameter of the material (expected to be between 1/4" and 3/4") and the thread pitch. The type of thread is Acme.

I am not asking for an answer that computes the compressive force. I am looking for an answer that tells me how to do the computation myself, or at least explains the theory.

I know I can go to LMT Fette and they can just tell me off the bat, but I would rather not be going hat-in-hand to vendors every time I need to solve a problem.

• I would imagine this would just mean exceeding the force required for plastic deformation in the metal you intend to use, which you could look up anywhere that lists metal properties. Then it's up to you to decide how many threads you want to roll at once; the more threads you try to roll, the larger the contact surface area. I don't know for sure that's how that works, but that's where I would start (not knowing is why I'm not making this an answer). – Chuck Jan 29 '16 at 20:16
• The compressive force is dependent on the shape and size of the threads, so it is not a simple thing to compute. I assume however there is some method for doing the computation and I am hoping for an answer for someone expert in the subject. – Wallace Park Jan 29 '16 at 20:47
• As far as a reference, check the machinerys handbook. It's been a while since I dealt with roll threading, but if I recall correctly there are some basic formulas/guidelines in there. – CBRF23 Apr 29 '16 at 21:21
• Actually just looked at my copy, 28th edition, and there is nothing in there regarding pressure. They do provide recommended speeds and feeds for various thread sizes, so you may be able to work out the forces from the feed rate. – CBRF23 Apr 29 '16 at 22:25

If you have a vendor you work with, or even if you don't work with them but you're aware of their company, then I would ask them directly for the formulas/references you should use to spec the housing for their equipment.

I know from working with sales application engineers that they are very eager to help you design your system if it means you're (telling them you're) buying their equipment.

As a degreed mechanical engineer, this is the route I would take. Ask the people that know. If they seem unwilling to help, politely inform them that you'll check with other manufacturers - suddenly people are tripping over themselves to help.