Tap and drill selection starts with process data. A thread size or drill diameter alone is not enough. Material, hardness, hole depth, hole type, machine, coolant, tolerance, and current failure mode decide the tool choice.
Why suppliers ask many questions
Drilling and tapping are closed cutting operations. The cutting edge is inside the workpiece, chips must leave through limited space, and failure can break a tool inside the part. Without enough data, a recommendation becomes a guess.
Minimum data for drill selection
- Material grade, hardness, and whether the surface is cast, forged, hardened, or plated.
- Hole diameter, depth, tolerance, surface finish, and through or blind condition.
- Machine type, holder, runout, coolant method, and coolant pressure if through-tool coolant is used.
- Current speed, feed, chip shape, burrs, hole size, and tool wear photos.
Minimum data for tap selection
- Thread size, pitch, thread class, full thread depth, and bottom clearance.
- Pilot-hole size and whether the hole is drilled, reamed, cast, or formed.
- Blind or through hole, chip direction, lubrication, and tapping cycle.
- Failure mode: breakage, chipping, tight gauge, oversize thread, or poor finish.
Better data saves trial cost
A shop may spend more time and money testing random tools than it would spend collecting the right information. Photos of chips, broken edges, hole finish, and machine setup are often more useful than a long verbal description.
For a broader starting point, see HEYI’s hole machining tool selection by material. For special holes or nonstandard threads, HEYI can review custom tooling options through the RFQ form.