The S&G combo lock on my old Treadlock safe (cheap gun safe) was getting flaky. I had a locksmith out to fix it, but he declined, saying Tread had modified the S&G bolt by drilling and attaching the bolt operating mechanism, and any replacement lock would likely wear out as well.
I didn't feel like buying a new safe, so I made an operating bolt and installed, plus a new electronic lock. Took several hours one day to fab, part of another to assemble and test. I bought the lock and the handle. The rest was on hand.
Pete Keillor