If you are using 608's and you have 4 bearings in the stack, that would use up 28 mm of your 40 mm. A thin 8mm nut will add 2.7 mm. You are down to about 9.3 mm for spacing and what ever you are attaching to on the bottom of the stack.
These guys:
[onlinecatalog.tpa-us.com]?
Will sell you 5 pcs that are 60 mm long for only $97.07.....
These guys go to 50 mm for $15.19
[barnhillbolt.com]
These guys:
[onlinecatalog.tpa-us.com]?
Will sell you 5 pcs that are 60 mm long for only $97.07.....
These guys go to 50 mm for $15.19
[barnhillbolt.com]