1st questions - always the doepiest

4112

Well, i need some lightweight alloy/carbon cranks -don't ask why
-ok for a micro bmx
-found some square taper 125mm -but steel and heavy -correct length tho

-anyway question, these hollow tech cranks -are the threaded bosses pressed in under a few tonnes?

-are they infact a boss pressed in? considering they are 'hollow'?

-ie can i get the threaded bosse, re-drill the cranks and press them in

-cos i have tried cutting down and re threading a few sets of cranks now, to no avail, heck, i even did a set and tapped them for a oversize helicoil -got the threads the right way around, they looked nice and straight, -BUT i then could't get the lh threaded helicoil


-oh well -

-the next set came out bad, then i gave up

are there 125mm alloy cranks available - off the shelf?

garage sale GT

Don't cut carbon. The direction the cloth laminations go in is crucial to strength.

Go to Mcmaster.com for left hand helicoils if you don't want to count on threads in aluminum.

I think, though, that your more lightweight alloy cranks will be forged and cutting them will also compromise their strength because part of the advantage of forging is that the metal grains flow in the direction you want.

Maybe while you're at Mcmaster, get some billets of 7075-T6 or 4130 and fabricate your own.