CoilSert Free-Running Metric Coarse M3×0.5 × 3D

Overview

A metric CoilSert free-running insert restores or reinforces an internal metric thread with a diamond-section stainless coil. The coil is wound into a tapped hole and forms a new thread that is harder than the parent material, so the mating screw wears against stainless rather than against aluminium or cast iron. Nothing protrudes above the surface, and the screw runs in and out with no added resistance. This listing: thread M3×0.5, thread system Metric coarse, length 3D, material 304 stainless steel, finish Plain (cadmium.

Advantages

The coil's spring pressure distributes load along the whole engaged length, which raises the pull-out strength in low-shear-strength alloys far more than simply enlarging the thread would.

Stainless wire keeps the internal thread corrosion-resistant even in a carbon steel or aluminium host, so the joint remains serviceable after exposure to coolant or humidity.

Because the insert sits below the surface, the repaired joint is dimensionally identical to the original and needs no counterbore or extra clearance.

Metric coarse sizes from M2 upward follow ISO thread form, so an existing metric screw can be reused without change after a stripped thread is repaired.

Applications

Metric-thread repair in aluminium castings and die-cast housings, reinforcement of threads in magnesium and zinc alloys, machine frames where a thread will be opened many times over the equipment life, and export equipment that must retain metric threads after service in the field.

The tapped hole size for a coil insert is larger than the nominal thread and must be drilled to the insert manufacturer's table; using a standard tapping drill produces a loose coil. Length beyond 2D adds little pull-out strength in ductile alloys.

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