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34tpi works out at 0.747 mm crest to crest - near enough 0.75mm

 

""4mm x 0.75mm Common derailleur limit screw (JIS standard)"

http://www.parktool.com/blog/repair-help/basic-thread-concepts

Edited by Peter Cobbold
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Hi Peter,

one of Bob's earlier posts said it was 0.196" diameter !!

 

Roger

= 4.98 = 5mm

 

5mm and 0.8mm pitch is here, also 4.5mm and 0.75mm pitch:

http://www.osg-global.jp/products/technical/pdf/drillholesize.pdf

 

- perhaps Smiths bought Japanese?

 

Peter

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A dozen years back I acquired a couple of boxes full of assorted old used Smiths/Jaeger instruments and parts, remnant stock of a restoration outfit that went down the tubes.

 

Trying to sort knurled, and any other, nuts to fit was a ruddy nightmare, I hate to think just how many variations Smiths must have used over the years.

 

For sure there were rather more than just three thread variations of knurled nut, and heaven knows how many overall size variants.

 

No I don't have any left before you ask, the little bits of nuts, brackets and suchlike all went to an instrument repairer along with several gauges - the man was well chuffed, evidently some of those little bits were unusual sizes. He reckoned Smiths came up with oddball fitments for certain vehicle manufacturers, to maintain exclusivity as it were . . . . .

 

Cheers

 

Alec

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