Re: The Duchess Project: 1940 Super 8 Convertible Sedan

Posted by HH56 On 2018/1/16 10:12:25

I would be curious if the threads were all formed the same way thru those versions. Threads were originally cut on a lathe or with a die which actually cuts metal away from a round rod or blank. At some point pressure forming was invented and almost all mass production bolts are made that way today..

In the pressure rolling process a blank of material is rolled thru a grooved set of plates moving in opposite directions. Because of a slight taper, as the material rolls thru extreme pressure is generated to squeeze the rolling metal blank. The threads are fully formed by the time the blank exits the plates and machine. No material from the blank is lost in that operation but is rather compressed and displaced. Controlling the size, shape of the grooves and pressure of the plates determines the shape of the threads and whether they are slightly smaller or larger than the blank. After threads are formed then the hardening and plating is done.

It could have been a matter of cost or obtaining new machines was the reason for the changes.