Drill Bit for Self-Healing Injection Ports

This 7.1 mm cobalt steel drill bit is the workhorse tool for any serious mushroom cultivator who modifies their own substrate jar lids. We picked 7.1 mm because it is the universal standard size for the two essential modifications a mycology jar lid needs: a self-healing injection port for sterile inoculation, and a self-adhesive filter patch for filtered air exchange during colonisation.

Why every jar lid needs two 7.1 mm holes

A properly prepared substrate jar lid has two holes — both 7.1 mm:

• Hole 1 — Inoculation port: a self-healing butyl-rubber port snaps into the 7.1 mm hole. You push a spore-syringe or liquid-culture needle through it, inoculate, and the rubber re-seals on its own.
• Hole 2 — Filter for FAE: a self-adhesive 18 mm filter patch sticks over the second 7.1 mm hole. The mycelium needs to breathe — the filter lets CO₂ and O₂ exchange (FAE) while blocking mold spores and bacteria at 0.22 µm.

Why 7.1 mm cobalt steel?

• Universal port & filter size — the snug 7.1 mm hole holds the rubber port tight and is fully covered by the 18 mm filter sticker. No oversized leaks, no undersized choking.
• Cobalt steel — drills cleanly through PP plastic mason-jar lids and tougher metal canning lids without dulling.
• Standard 1/4" hex shank compatible with any cordless drill.
• Specifications: diameter 7.1 mm, total length ~ 80 mm, cobalt steel (M35/HSS-Co).

Use it for these compatible products

Self-Healing Injection Ports | 10 Pieces

Self-Adhesive Lid Filters 18 mm — 50 Pieces

How to drill

1. Mark two spots on the jar lid, well apart from each other and away from the rim.
2. Drill straight through at low/medium speed; let the bit do the work — don't press too hard.
3. Deburr each hole — run your finger, a utility knife or a folded paper towel around the rim to remove any plastic or metal burrs.
4. Wipe the lid clean with 70 % isopropyl alcohol.
5. Press a self-healing port into one hole; stick a self-adhesive filter over the other.