Roll form die head question..

[niggle21]

I was at work today (Apprenticing toolmaker), screwcutting a thread on a lathe, the boss comes up to me with a roll form thread die wheel and a small brass part with a thread that's been made with the die wheel. The die wheel is multistart (4 starts), but the part is only single start.

He wants me to tell him how / why a 4-start die wheel can produce a single start part. I have absolutley no idea!

Does anyone know how this is? I've had a bit of a look on google but google doesn't know much about roll form thread die wheels

He said they made die for a special thread for a job they were doing. It's OD is about 40.5mm and the part is approx 11mm. (almost 4x.. this relates to the 4-start thread?)



I anyone's intersested.. I work here

http://www.tpenz.com

Thanks, Nigel.

 

[MikeHalloran]

If the forming wheel had only one start, it would have to be the same diameter as the formed part, and it wouldn't last long.

Think of the finished formed part as a gear with a helical thread, and think of the forming wheel as an infinite rack (with teeth at a rather extreme angle) that engages the formed part without slipping. Think of cutting off four teeth of that rack and rolling the segment around on itself, teeth out, and magically bonding the ends. There's your forming wheel.




Mike Halloran
Pembroke Pines, FL, USA