how are bolts manufactured?

chuck2015

Member
I was just wondering about this today because I noticed as this particular bolt was threaded in it had a wobble that was noticeable. Enough so that a certain tolerance for an assembly of which this bolt was a part could not be met.

On a TV show "how its made" segment it showed how the threads are rolled on by a set of dies. But does the threading go on equally around the bolt or is it possible for the bolt to have non concentric threads?
 
Many years ago I ran an Automatic Screw Machine. This was a automatic lathe. You started out with a 20 foot piece of metal the same size as the head of the bolt. A tool came in from the side and formed the body of the bolt Then a die came in from the end and threaded it. When the die goes in to a preset length it opens and pulls off. Of course the machine must turn in the opposite direction to thread over the other functions. A tool comes in from the side to cut off the bolt at the head end.
 
It goes all the way around. I?ve seen these machines working, and the bolts come off so fast that it?s just a blurr. Some very high quality
aerospace fasteners are cut but they are usually made out of something other than steel. The best.are actually ground threads.
 
I could tell a true story about one of those machines, but it would probably get this thread poofed.
 
yes--i believe a rolled thread root diameter is larger than a cut thread---thus making the area for tension larger---A sub t
 
Maybe it's not too bad, it was on the old Art Linkletter show.

He had a lady on who had like 6 kids, no more than a year apart. Art asked her what her husband did. In all innocence, she replied, "He runs an automatic screwing machine".
 

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