Steel square taper cranks with 1/2inch female

Hi,

Asking for help if anyone knows where to buy cranks: I am converting a vintage military bike to electric, using the BBSHD mid-drive and the shaft of the BBSHD demands square tapper cranks. It seems like all square tapper cranks on the market use the modern 9/16" threads for pedals, but I want to use the vintage union pedals with the 1/2" male threading. Is it possible anywhere to find steel square taper cranks with 1/2" female for these 1/2" pedals??? Can´t find these anywhere, and if anybody knows give me a tip.(Now I use 9/16" to 1/2" adapters to make the old pedals work). Thanks!

Never heard of the adapter you speak of until now
9/16 to 1/2 adapter
https://www.bicycledesigner.com/bike-parts/pedal-adapter---convert-9-16-to-1-2.html

But you want crank arms with 1/2" I have not been able to find nothing.

I got no clue, but I found this website LINK
not sure if 14-1.25 is 1/2" or not.
Oops no go, that is French.

Pedal threads: Most bicycle pedals have either 1/2-20 or 9/16-20 threads. But some vintage bicycles use “French thread” pedals, which is metric 14 – 1.25. The 14.0 mm thread is slightly smaller than 9/16″ (14.3 mm), but bigger than 1/2″ (12.7mm).

14mm pedals screw into 9/16 cranks all the way but fit loosely. Then later they break off or strip out easier.

9/16 pedals screw into 14mm cranks so tight they stop half way. Then later they break off or strip out easier.

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Weld the pedal hole in, and use this 1/2" pedal tap
https://www.ebay.com/itm/Park-Tool-TAP-3-Bike-Bicycle-Cycling-Pedal-Tap-for-Crank-Arms-1-2/111846504698?epid=691316009&hash=item1a0a9238fa:g:UxcAAOSw8-tWaR~p&frcectupt=true

Just use an helicoil

markz said:

Weld the pedal hole in, and use this 1/2" pedal tap
https://www.ebay.com/itm/Park-Tool-TAP-3-Bike-Bicycle-Cycling-Pedal-Tap-for-Crank-Arms-1-2/111846504698?epid=691316009&hash=item1a0a9238fa:g:UxcAAOSw8-tWaR~p&frcectupt=true

Click to expand...

That's a good idea, but I think the weld will not be strong enough for the SIS steel number.

MadRhino said:

Just use an helicoil

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Thought of that, but I have only found pedal insert thread for repairing damaged threads in cranks like 9/16" x 20 tpi (inner diameter) to 5/8'' x 24 tpi outer..

Do you have a link where to buy the 9/16" to 1/2" helicoil or anyone else that knows? Perhaps I have to drill the hole in the crank somewhat bigger, to be able to find a helicoil that reduces to 1/2"?

9/16 to 1/2 is a standard size for helicoils. If you can’t find them locally, you should inquire with the manufacturers. You might have to contact them anyway, since it is very unlikely that you will find them counterclockwise on the shelves.