I realized that some Avid Single Digit v-brakes for bicycles come with retaining bolts with the socket head sunk into the body of the screw itself:
Monday, June 10, 2013
Lathe: Crank Retaining Bolts
The stock retaining bolts for the cross slide and compound cranks are socket head cap screws. I was constantly hitting my knuckles on them and was annoyed by them whenever I used my lathe.
They sit the lathe's cranks perfectly. The only issue is you need to put a pair of washers between the crank and dial to space it correctly. The new bolts almost sit flush with the cranks and I have yet to hit my knuckles on them again. The bolts should be available in most bike shops.