Thread-Cutting Screws

Thread-cutting screws have a cutting edge or flute that removes material to tap a mating thread as they are driven, producing low driving torque and clean threads in harder materials where thread-forming screws would crack the work or fail to displace. They suit thick metal, castings, and brittle plastics. We stock the full range of thread-cutting types, heads, and materials.

How Thread Cutting Works

A cutting slot or tapered flute at the point shears a clean internal thread, removing a small amount of material like a tap. This lowers driving torque compared with thread forming, making thread-cutting screws ideal for thicker or harder materials where displacement isn’t practical. The trade-off is a slightly looser fit and lower vibration resistance than a formed thread.

Thread-Cutting Types

Type 1 and Type 23: fine threads with a cutting slot, for general sheet and plate. Type F: machine-screw thread with a tapping point, for thicker metal and castings—the most versatile. Type 25 and Type D: coarse, widely spaced threads for plastics and die castings that resist clogging. The correct type depends on material hardness and thickness.

Head Styles and Drives

Available in pan, flat, oval, hex, and hex washer heads in Phillips, slotted, and hex drives. Hex washer heads provide high torque for thicker materials; flat heads countersink flush.

Materials and Finishes

Case-hardened steel with zinc plating: the standard, with a hardened cutting edge and tough core. 410 and 18-8 stainless: corrosion resistance, with 410 retaining better thread-cutting hardness.

Dimensional Standards

Thread-cutting screws conform to ASME B18.6.4 (inch), specified by type, gauge, and thread.

Selecting the Right Thread-Cutting Screw

Match the type to material: Type F for thick metal and castings, Type 1/23 for sheet, Type 25/D for plastics. Drill the correct pilot hole—thread-cutting screws need a properly sized hole to cut clean threads without binding. Choose a screw harder than the work, select head style for your flush or torque needs, and avoid repeated removal, which can degrade the cut threads.

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