Will use the largest size (for a 5/16" bolt & 25 mm deep).
Drew the location of the four bolts.
Used a center-punch to make a depression at the bolt location.
Used a tapering bit to enlarge the hole locations so that the 5/16" drill bit will self center as it goes down...
Drilled 5/16" holes through the leg and into the bench.
Used a piece of tape on the drill bit to make sure I go in the right depth (don't want to go through!).
All 8 holes drilled.
The threaded insert needs a drill bit that's about 0.05" less than the thread diameter, so about 0.45". Not an "even" size... In metric, it's about 11.4 mm. An 11 mm drill bit is 0.433" which may be close enough. 7/16" is 0.4375", which will probably work. I don't have a 7/16" drill bit! Will have to see if I can find a 7/16" drill bit at the local hardware store (if not, I'll have to order it online)...
