For extreme accuracy in production bore finishing, there is only one way to guarantee precision. This involves a Helilaps and an abrasive lapping and polishing medium or Kemet Diamond Compound.

Manufactured from a uniform grade of annealed, close grained, grey cast iron, the lap incorporates a unique helical slot and external circumferential grooves. When the lap is slipped over the arbor and tapped gently with the lap expander, the internal taper in the lap and the taper on the arbor make contact, therefore allowing a precise degree of diametrical expansion to be achieved uniformly over the entire lap. This means that a Helilap gives a fast lapping action, perfect for bore roundness, exceptional straightness and superb surface finish. They are produced in a large range of sizes from 3/64" dia. to 3" dia as well as metric sizes.