Cored Holes For Threads

Cut threads: standard tolerances

Tapped holes require special diaMetres, depth, and Draught to ensure production is cost effective. Draught may be retained, based on allowing 85% full thread depth at the small end and 55% at the large end. We recommend using a countersink or radius to provide relief for any displaced material and to strengthen the core in the tool.

Cut threads: critical tolerances

Greater dimensional accuracy is possible on tapped holes, but it comes at a higher cost. Draught may be retained, based on allowing 95% full thread depth at the small end and the maximum minor diaMetre at the large end.

Formed threads: critical tolerances

All formed threads require greater accuracy specified in these critical tolerances. Cored holes may be tapped without removing Draught.

Pipe threads: standard tolerances

Cored holes are suitable for both NPT and ANPT. NPT should be specified where possible, due to the additional costs and steps required. The 1°47' taper per side is more important for ANPT than NPT.

No standards exist for metric pipe threads.