Precision Centreless Grinding

Tolerances as small as +/-0.0002” diameter are met and parts meet the straightness requirements for catheter manufacture. Finishes can get as smooth as 4-8 Ra microinches, rivaling polished surfaces.

Since the workpiece isn’t fixed, it “floats” and self-corrects, minimizing out-of-roundness (often below 0.00005 inches).

Inventory

We keep an inventory of spooled wire in the most common grades of 304 and 304V grade stainless steel wire and nitinol. This is available from our Componentshop.

For stainless steel wire, our precision straightening, cutting and deburring facility is used to produce a straight, spring hard wire, which is then either used in “as drawn” condition, coated with PTFE or parylene, or alternatively is centreless ground to produce a surface of impeccable quality and very close tolerance diameter.

PTFE coating or parylene coating of our wires induces greater lubricity, allowing release of catheters after manufacture.

Wire of impeccable straightness, surface quality and adherence to diameter required allows catheter production, using Pebax or other liner material, to proceed efficiently with excellent subsequent release of the finished multilayer catheter. Our mandrels are also used to check and ensure consistent inside diameters along long lengths of polymer or stainless steel tubing. Core pins for moulding and precision miniature shafts also require the precision tolerances resulting from our centreless grinder.

Process

Precision centreless grinding is a machining process used to remove material from a workpiece—typically a cylindrical one—without using a spindle or fixture to hold it in place. It’s a go-to method for producing highly accurate, smooth, and uniform parts, especially in high-volume manufacturing.

The workpiece sits on the work rest blade, sandwiched between the grinding wheel and regulating wheel.

The grinding wheel spins fast (think thousands of RPM) and removes material, while the regulating wheel spins slower, rotating the workpiece and pushing it forward.

The angle and pressure of the regulating wheel dictate the feed rate and stability.

Applications

Typical Applications

Automotive: Piston pins, valve stems, camshafts.
Aerospace: Landing gear components, turbine shafts.
Medical: Needles, orthopaedic pins, dental tools.
Industrial: Roller bearings, dowel pins, tool bits.