In collaboration with Citizen Machinery Tech Center in Elmira, N.Y. Hardinge Inc. has developed and now manufactures standard TF-25 OG overgrip collets for Cincom M20 and L20 lathes. Overgrip collets — also referred to as over-the-shoulder collets — are used on a pick-off spindle when it is required to clear a shoulder and grip on a smaller diameter beyond. A good example of this type of part would be a screw. Extra spread is required to open the collet wide enough to go over the screw head or larger diameter.
Hardinge’s collet design incorporates teardrop slots and reduced wall thickness for maximum flexibility for the overgrip pick-off process. A double-angle taper reduces the contact surface to provide for quick opening of the collet. Hardinge hardened and ground collets provide high accuracy and repeatability with precision in the collet back bearing and concentricity at the gripping area. Order holes are finish-ground on a high-precision Tripet internal grinding machine. The grip diameter, grip length and the recessed part diameter are required to manufacture an overgrip collet for a specific part. A semi-finished stock program is in place at Hardinge to provide a quick order turnaround.
The Cincom M20 and L20 Swiss Turning Centers have extra stroke built into their sub-spindle to accommodate an over grip collet with a recessed part diameter (extra spread requirements) to 3 mm. Hardinge manufactures headstock collets, pickoff collets and carbide guide bushings for all Citizen machines.