is it still safe to use?

my machinist told me I can use standard bearing just to check my clearances with plasticgate

 

No, .5mm under is an increase in clearance of .020". Your clearance should be around .0015-.0025 on stock parts. So with the crank undersized you would likely by around .0215-.0225" bearing clearance. Which is way far and beyond too much. You most definitely need oversized bearings.


Unless you machinist isn't quite as dumb as your post implies, and he said .5 thou, as in .0005". Which should be OK to use as long as you check the clearances.


But if he is truly saying a .5 MILIMETER cut crank is good to use with standard bearings, find a new machinist.

 

Thanks i will double check if its .0005 or .5MM

4G64 cranks are cheap so not worth risking my build