SMC Bulkheads use metric hole sizes and the bits are hard to find in US hardware stores. Use this perfectly sized metal drill bit for a clean installation of SMC DOT Bulkhead Unions or SMC DOT Bulkhead Female Straights.
Drill bit sizes:- 1/4" bulkhead - 15mm drill bit
- 3/8" bulkhead - 23mm drill bit
- 1/2" bulkhead - 26mm drill bit