Burnished Pitch Hole Advantage

Webster Industries utilizes a variety of manufacturing processes to ensure the highest quality solution is delivered to our customers. Burnishing is a unique cold forming process used by Webster where a graduated mandrel (punch) is used to punch the sidebar pitch holes.

First the punch pierces the sidebar material producing a heavy tapered slug:

Then the mandrel rubs the metal surface of the pitch hole with sufficient force to cause plastic flowing of the metal. This rubbing or smearing (burnishing) action of the metal fills the break out or tapered portion of the hole that was caused in the initial piercing operation:

This results in a high quality, high tolerance, fatigue resistant, work hardened sidebar hole; all primary keys to extended chain life.

The major advantages of burnished pitch holes are the amount of bearing surface, accuracy of hole size, consistency of press fit and cost control (one-step operation).

A single-punch hole typically has a bearing surface of 15% to 20% of the sidebar thickness. Punch and shaved holes typically have a bearing surface of 75% to 80% of the sidebar thickness. Webster’s burnished holes achieve 85% to 90% bearing surface. Compared to single-punch holes, this is at least five times more surface for the pin to rest against, which means at least five times the material to resist deformation of the hole under heavy loads.

The increased bearing surfaces and accurate hole sizes lead to consistent and more controlled press fits, particularly when used in combination with Webster’s Duralloy pin. Our consistent and increased press fits give our chain an improved fatigue life, prevent the pins from wallowing out of the sidebar holes (elongation) and provide superior customer value.