Countersunk Tooling Screw M4 (SCM435 alloy steel, class 12.9, plain as machined, Torx head, countersunk) — L 8.3 mm

Overview

A countersunk tooling screw is a precision-turned fastener whose 60° conical head seats flush with the workpiece surface, leaving nothing protruding into the tool rotation envelope. On CNC tool holders, engraving seats and precision fixtures this flush seating is functional rather than cosmetic: a proud head changes the balance of a rotating assembly and can collide with the work envelope. Sizes in this range run from M1.2 upward, with head heights from 0.2 mm, and each size is defined by thread diameter, pitch, head angle, head diameter and drive size rather than by a single part number. This listing: thread M4, overall length 8.3, pitch 0.5, head angle 90°, head dia. 6, head height 0.45.

What sets this listing apart: Thread Dia. M (mm) M4 (series runs M1.6 to M8); Thread Length T (mm) 6.2.

Advantages

A TORX PLUS drive (5IP to 8IP across this range) engages with a larger contact area than a standard Torx or hex socket. Lower point loading lets the same recess carry higher torque without cam-out, the usual failure mode on M1.6–M2 screws driven by hand or by torque-controlled drivers.

SCM435 chrome-molybdenum steel hardened to class 12.9 reaches a minimum tensile strength of about 1220 MPa. At these small sections that headroom is what allows repeated assembly cycles without thread deformation or head shear.

The 60° countersunk angle matches the seat, so tightening draws the head into the cone and centres the screw. That self-centring reduces run-out at the tool tip, which matters when the screw also locates the insert or the cutting tool.

Applications

CNC tool holders and collet chucks, engraving and marking tool seats, precision cutting fixtures, EDM electrode holders, and 3C assembly jigs where the screw sits inside a rotating or sliding envelope. Also specified on optical mounts where head height must stay below the datum surface.

Specify the seat angle together with the screw: a 60° screw in a 90° seat will not sit flush and loses contact area. On DLC-coated parts allow for coating thickness, typically 2–4 µm, when head height tolerance is tight.

Product information is supplied by Toprecision. Custom parts can be produced to drawing — contact us for samples or a quotation.