Factoid: Nuts & Bolts

[Dave Stromberger]

"As nuts and bolts are not perfectly rigid, but stretch slightly under load, the distribution of stress on the threads is not uniform. In fact, on a theoretically infinitely long bolt, the first thread takes a third of the load, the first three threads take three-quarters of the load, and the first six threads take essentially the whole load. Beyond the first six threads, the remaining threads are under essentially no load at all. Therefore, a nut or bolt with six threads acts very much like an infinitely long nut or bolt (and it's a lot cheaper)."

http://www.gizmology.net/nutsbolts.htm

 

[catfish]

Good to know.

 

[cyclingday]

Which is why Titanium proved to not work out well for fasteners.
Titanium has tremendous elasticity, so it will coninue to stretch under load and has to be constantly torqued until it eventually breaks.
Titanium spokes and seat binder bolts were the worst for this application.

 

[TR6SC]

Good stuff! We've all heard of Joseph Whitworth, I think. 1841 thread standardization. There are a lot of British threads and head sizes some of us will run into. BSW=coarse BSF=fine CEI or BSC= cycle fasteners. You will know its a British thread if your American or Metric wrench won't fit. It wasn't until 1967 that the Brits started to retool. The reason the head sizes are off is the size of the shaft of the bolt became the length of one flat on the head. Go around the circle of 6 flats and you've got....Whitworth!
So here's the fun part. Whitworth standards at the time were for coarse threads, locomotive type nuts and bolts. These heads with the flats that he said developed the best torque delivery, were a bit overkill when the fine thread came along. The fine pitch required less oomph, so the head size was dropped to one size smaller. A British wrench (spanner) will be marked for instance 1/2W-9/16BS. These wrenches also work on the British cycle thread, most often 26tpi found on English bikes.
http://britishfasteners.com/index.php/

 

[bairdco]

That's the only thing I hate about older Brooks saddles. I had to make a 13.5-ish mm wrench for the seat clamps (or was it 12.5?)

Stupid brits...

 

[37fleetwood]

"As nuts and bolts are not perfectly rigid, but stretch slightly under load, the distribution of stress on the threads is not uniform. In fact, on a theoretically infinitely long bolt, the first thread takes a third of the load, the first three threads take three-quarters of the load, and the first six threads take essentially the whole load. Beyond the first six threads, the remaining threads are under essentially no load at all. Therefore, a nut or bolt with six threads acts very much like an infinitely long nut or bolt (and it's a lot cheaper)."

http://www.gizmology.net/nutsbolts.htm

Dave, you need to get out more...