The punch is small, the tolerance is tight and the wrong collet ruins both.
Punch grinding punishes shortcuts. A blank held in a near size collet runs out, a long blank cantilevered out of the chuck deflects, and a wheel chosen for steel will not touch carbide. None of these are difficult to avoid.
A collet gripping a diameter it was not made for contacts on a line rather than a surface, which marks the blank and lets it run out. Order the collet set that covers the punch diameters you actually work with, and treat a near size collet as a reason to stop rather than a reason to proceed carefully.
The WK22 has a 25 mm spindle through hole for exactly this reason. Feeding a long blank through it instead of letting it hang out of the chuck removes the deflection that otherwise appears as taper along the ground diameter.
Workhead swivel is plus or minus 45 degrees. Set the angle from the punch drawing rather than from the worn edge you are replacing, otherwise each regrind moves the geometry a little further from its original specification.
Tool steel punches take conventional abrasive. Carbide punches need a diamond wheel, a rigid setup and light infeed. Trying to grind carbide on an aluminium oxide wheel wastes the wheel and glazes rather than cuts.
Small bores need surface speed, and surface speed on a small wheel means high rpm. The WK22 internal spindle runs between 10000 and 20000 rpm on ER11 collets for this reason. A bore ground at too low a speed rubs rather than cuts and shows it in the finish.
The point of a CNC punch grinder is that the second regrind is faster than the first. Record the program, the offsets, the collet and the wheel against the punch part number, and the next time the press stops the job is a setup recall rather than a fresh problem.
CNC punch and pin grinding from 1 mm up to 150 mm, internal and external.
OD and ID grinding on one machine, for shafts, bushes, needle valves and plungers.
1 mm diameter, with the clamping range extending to 150 mm on both internal and external work.
Yes, with a diamond wheel and a rigid setup. Send the punch material and geometry and we confirm the wheel before you order.
Usually blank deflection from too much overhang. Feed the blank through the 25 mm spindle bore rather than letting it cantilever.
Whichever your maintenance team already supports. FANUC, SIEMENS, SYNTEC and GSK are all available.
Send the part, the problem or the photograph. A specific question gets a specific answer, usually the same working day.
