Cooling Ports: The Threads That Keep Molds Dry
Specify the thread, not just the hole
Port spec is three decisions: thread type, size and depth — and they must match the fittings the shop actually stocks. Mixing straight and tapered threads on one circuit is a recurring source of weeps; each seals by a different mechanism and wants different install care.
Depth matters too: too shallow and fittings bottom out before sealing; too deep and the fastener runs out of engagement. Match the port depth to the fitting's thread length, and put both on the drawing.
Sealing practice
Tapered threads seal on the thread flanks and usually want a modest thread sealant; straight threads seal on a face or O-ring and need that face clean and undamaged. Overtightening tapered fittings cracks ports — a crack invisible until water pressure finds it.
Pressure-test circuits before the mold ships and again after any port work. Finding a weep on the molding floor costs hours; finding it at the bench costs minutes.
FAQ
Which thread standard should we use?
Whatever your maintenance shop and regional customers standardize on — consistency beats theoretical advantage.
Can a damaged port be rescued?
Often by re-tapping one size up or fitting a repair insert, provided wall thickness and cooling geometry allow it.
Why does one circuit always leak?
Usually a port face damaged by overtightening or a fitting style mismatch — fix the port, not just the drip.
All figures above refer to standard product data sheets; final confirmation is subject to written quotation.