Hello All,

Previously I posted about ER collet blocks in a 4 jaw independant chuck, and was having problems with the workpiece being parrallel to the spindle axis.

Well, having decided that they are not really designed for such a purpose I purchased a ER 40 collet chuck ,and hear is the outcome. Machined a new Rohm D1-5 backplate fitted the chuck grabbed a centerless ground bar 16mm dia 150mm long in a collet , elephants foot on the end of the Mitutoyo and runout at 100mm from the chuck face 0.019mm moved saddle towards the chuck by 75mm new reading 0.012 . Tried the same again with a Tungsten Carbide ground bar 20 mm dia and 200mm in length and readings at the bar end 0.015mm move 125mm toward the chuck new readig 0.011mm removed both bars, tried again and more or less the same readings, so great repeatability. Also tried a Rohm 20mm collet and results ever so slightly better. So im super chuffed with the chuck and is without doubt the best 49 pound iv'e spent in a long while.

The chuck came from Arc euro [ of which iv'e no connection, other than being a very, very happy chappy ]