Anyhow I dont know what is in Shops in Helsinki Finland, or Latvia .. only in my Town ..

bike BB are threaded in 34 to 36 mm so the welding in a sleeve machined to do the job is possible.


then threading it with a Bicycle BB tap set. its a specialty tool..



a pair of sleeves with 3 compression bolts have been machined threaded to adapt American OPC to use a conventional Threaded BB..

You may find a Thompson equivalent.. or maybe the axle has a square taper equivalent ..

got any bike shops that have run in the same location since WW2?