Andy Pugh wrote: > 2009/6/12 Douglas Pollard <dougp...@verizon.net>: > > >> The Germans have have a set of metric standards the English have >> ISO standards and the Spanish have still another. >> > > I _think_ that DIN (German) BS( British) JIS (Japanes) and the rest > have all converged on ISO (Inrternational) but I might be wrong. > > >> Imperial bolts are designed to break before the threads pull out >> of the parent metal. The best thread pitch is picked for the bolt >> diameter to achive this partially by having a smaller or larger root >> diameter. >> > > Ah, but you eschewed the One True Thread angle (Whitworth 55 degrees), > rounding up to 60 degrees, which has a fractionally less optimum ratio > of self-locking to tension. > > The least useful standard I have come across is UNF, which seems > designed to seize irretrievably at the first hint of corrosion. In > contrast I have dismantled bits of old commercial vehicles left in > fields for 70 years where the hexes on the (Whitworth) nuts were half > their original size, and they just unscrewed like normal (once we > found a random socket that nearly fitted) > > This might be a good time to point you at my "Thread identification > table" which lists all the threads from all the standards I could find > at the time in the same table, in size order. In retrospect I omitted > the metric sizes below 3mm, and similarly many of the smaller American > sizes. > http://www.bodgesoc.org/thread_dia_pitch.html > (You can click the headers to link to lists sorted differently) > > Andy that's a nice chart I will bookmark it on both of my computers. I notice the ISO metric threads are also 60 degrees which was kind of surprising since as far as I know Britain came up with it in the first place. Someplace in the Machinerys hand book, I think there is a notation on why 55 deg and why 60 degrees. I just looked but can't find it. Maybe it was in an older version. I would have never considered that either angle would be locking. I always thought down around 7 degrees might be locking. Any way haven't thought about it in long time, so I don't know. Now, I am now curious. Doug
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