Metric Round Die (M4x0.7)

What a die actually lets you do is worth setting out, because people buy taps far more readily than dies and then find themselves stuck. It threads plain round bar, so you can make a stud or a screw of exactly the length you need rather than searching for one. It restores a damaged thread on an existing bolt — a bolt whose first few threads have been burred or crossed will often clean up perfectly and go back into service. It shortens a bolt: cut it to length, chamfer the end, and re-thread the cut portion. And it chases a thread that is fouled with paint, rust or thread-lock so the nut runs freely.

At M4 the work is fine: instrument and equipment assemblies, electrical enclosures, small brackets, model and precision work, and appliance repairs.

The material is 9CrSi alloy steel — a chromium-silicon tool steel chosen because it takes a high hardness at the cutting edges while retaining toughness. On a die that hardness matters directly, since it cuts the thread form and any dulling shows up immediately as a torn thread face that will not run smoothly into its mate.

A die needs a die stock to hold it concentrically and square; the die holder in this range covers M3 to M12.

The buyers are engineering and machine shops, instrument and electronics technicians, appliance and equipment repairers, model makers, maintenance fitters, and hardware dealers.

Three habits, and at M4 they matter because both the rod and the die are small. Chamfer the end of the rod first with a file — a square-cut end is difficult to start a die on, and forcing a start is what cuts a crooked thread. Check squareness after two turns from two directions ninety degrees apart, because a thread started at an angle cannot be corrected. And use cutting oil generously, backing off half a turn for every turn forward to break the chip.

Cut the rod slightly over length: the last thread or two a die produces are always incomplete, and trimming them off afterwards gives a clean start for the nut. Message us on WhatsApp for a price, or with the matching M4 tap.