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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
1 1/4 20 tpi thread dimensions
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<blockquote data-quote="Magnetoman" data-source="post: 116417" data-attributes="member: 2806"><p>I'm sure that sometime in the last 100 years someone calculated or measured the effect of this difference on the ultimate strength. A 20 tpi 60-deg. nut will dig into the root of a 20 tpi 55-deg. bolt by 0.008". Also, if the nut makes contact at the h/6 root of a 20 tpi 55-deg. bolt it will be 0.0024" away from touching at the h/6 crest when finger tight.</p><p></p><p>The fact the threads of a mismatched pair require an additional ~5% distortion of the metal (0.0024"/0.050") in order to make contact must have an effect on the strength. We already know it's possible to strip any of the threads of <em>matched</em> pairs by applying too much torque so a <em>mismatched</em> pair must be measurably weaker, and measurably easier to strip. Anyway, in answer to this question, yes, I think the nut will know the difference.</p><p></p><p>p.s. I have 55-deg. indexible carbide cutters for threading on my lathe so it's no more difficult for me to make a correct Witworth thread as is an incorrect 60-deg. one.</p></blockquote><p></p>
[QUOTE="Magnetoman, post: 116417, member: 2806"] I'm sure that sometime in the last 100 years someone calculated or measured the effect of this difference on the ultimate strength. A 20 tpi 60-deg. nut will dig into the root of a 20 tpi 55-deg. bolt by 0.008". Also, if the nut makes contact at the h/6 root of a 20 tpi 55-deg. bolt it will be 0.0024" away from touching at the h/6 crest when finger tight. The fact the threads of a mismatched pair require an additional ~5% distortion of the metal (0.0024"/0.050") in order to make contact must have an effect on the strength. We already know it's possible to strip any of the threads of [I]matched[/I] pairs by applying too much torque so a [I]mismatched[/I] pair must be measurably weaker, and measurably easier to strip. Anyway, in answer to this question, yes, I think the nut will know the difference. p.s. I have 55-deg. indexible carbide cutters for threading on my lathe so it's no more difficult for me to make a correct Witworth thread as is an incorrect 60-deg. one. [/QUOTE]
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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
1 1/4 20 tpi thread dimensions
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