Preface: In the shop I worked in years ago, we had a non-Varimatic Hamilton drill equipped with a DC motor that we used to control the speed. It was a great machine for small-hole drilling.
Skip to the present: I recently picked up a Varimatic version of the same drill, which uses a female cone on the motor and a male cone on an idler shaft. The idler shaft is belt coupled to the spindle. As the center distances and vertical displacements of the two cones are varied, different sections of the cones bear on each other, varying the speed of the idler and thence the spindle. The problem is that on mine, the cones make a horrendous moaning noise that changes in pitch and volume as the speed is varied. Both motor and idler bearings seem fine, since decoupling the cones and running either alone does not produce the noise.
The female cone on mine is made of cloth based phenolic. It may or may not be original. I've heard others talk about this component being made of rubber. Can anyone with one of these machines enlighten me? One would expect that a hard rubber might not be susceptible to the soft of vibrations that I'm experiencing.
-- Greg