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I removed the pedals of a Göricke bike from 1934 or 1935 (according to the bike number). It has a Glockenlager (What is that in English? Bell shaped bottom bracket?) as seen in the picture. The crank threading for the pedals however is quite messed up and I would like to re-cut it. I measured 4 threads at about 4,8mm (or 4,9mm) with an 14,2mm external diameter on the pedals. The diameter is a tipical 9/16 pedal threading, but the thread steapness only results in about 20-21 threads per inch, and not 24. 24 is the normal amount of threads per inch for pedals.

EDIT: I noticed 20 tpi is normal and not 24 tpi. Therefore it should be a normal threading.

Is this some other threading they used in these days or shall I just cut it with a normal pedal thread cutter? The pedal make is K&B (the logo is in a cloveleaf) Bottom bracket

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It may be "old French": sheldonbrown.com/gloss_p.html#pedal – Daniel R Hicks Mar 17 at 13:30
If you go to a decent machine shop, they can measure the pitch/depth/diameter/threading of anything - that'd be your safest bet considering the age of the bike. (In fact, if they are good they'll likely have taps and dies to fit it.) – WTHarper Mar 17 at 13:59
Thanks for the ideas. It might actually be a normal thread. It is fatter than 14mm, more like 14,2mm, therefore it can't be French. After measuring again it could be 20 tpi. Somehow I though 24 is normal, but it is actually 20 tpi. Some shop was selling 24 tpi drills, that must have thrown me off. Because I can only there 4 threads it isn't very accurate, but I will just try my luck. – Franz Kafka Mar 17 at 16:54
If you try threading the wrong size tap into your crank, you run the risk of cutting out the original threads. If you can't get a hold of a pitch gauge, look into heli-coil or some other sized thread repair slugs for pedal threads (if you do indeed cut out those out threads.) – WTHarper Mar 17 at 23:30
I don't know much about old cycles and have limited knowledge of German but I do know 'glock(en)' pertains to bell(s) and 'lager' in a technical sense is bearing The Germans love compound nouns so this could be the translation you are looking for. Sorry I can't shed any light on the engineering side of this topic – stew Apr 25 at 7:34

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