PDA

View Full Version : Rolled Threads Designation



sbmathias
03-12-2010, 12:13 PM
Is there a standard designation for threads to be produced by rolling instead of cutting? Or, is it just stated in plain old english "rolled threads"?

lazlo
03-12-2010, 12:26 PM
I don't think there's an ASTM designation, but almost all commercial fasteners are rolled these days. A rolled bolt will have a slightly reduced body diameter: i.e., a 1″ diameter bolt is manufactured from .912″ diameter round bar.

The other, more confusing thing is that most rolled bolts are rolled before heat treat, which doesn't help thread strength. Very few bolts are cold rolled after heat treat, but the one's I have (Holokrome) are marked on the box.

According to Carol Smith's book, all NAS (aircraft certified) bolts are cold rolled after heat treat.

Here's the How It's Made video of a French Canadian company making high-quality bolts. The threads are rolled at 2:17, and the heat treat process starts at 3:30. The bolts are heated to 870 C, quenched, and then annealed, after they're thread rolled:

http://www.youtube.com/watch?v=3kxcw08p_oY

knedvecki
03-12-2010, 05:58 PM
UNJ if i am not mistaken. Per H-28 Handbook

lazlo
03-12-2010, 06:19 PM
UNJ is different thread form with a rounded root.