A 3/8" Endmill and Cutter Holding Arbor
For several different projects I required an accurate means of holding various 3/8" shanked tooling. I decided to make an arbor with a B-8 type shank to fit the Cowells headstock and bored to fit 3/8" tooling.
The arbor was started from 3/4" mild steel rod (type 12L14). The steady rest is used to support the rod for facing each end and center drilling for tailstock center support.
A 40mm length is turned to 14mm.
Next, a 27mm length is turned to 8.0mm.
The end is turned down to be threaded B8 (6.82mmx0.625).
The 20 degree head taper is turned with the compound slide.
The B-8 die is held in the die holder and the arbor threaded.
The work was too long to mill the keyway while mounted in the headstock. So it was setup in the milling vice and centered with the micrometer.
A 2mm endmill was used to form the keyway.
The arbor is mounted in the headstock and secured with the drawbar. With tailstock support, the diameter is reduced to true it and provide a clean surface.
The arbor was drilled 5.3mm for a length of 40mm.
This hole is then bored open to 9.525mm (3/8"). A boring bar of sufficent length is required, this is an Accupro 1801500 (0.180" minimum bore diameter & 1.500" maximum bore length). The boring is checked until a snug fit is achieved.
The work is transferred to the dividing head to cross drill (5mm) the securing screw hole. This was located 17.5 mm from the end.
The hole is tapped M6x1.0, and a socket set screw is used (M6 x 6mm length).
The arbor was intended for use with 3/8" shank mills. Shown are a couple of Whitney cutters, a 60 degree dovetail cutter and a 90 degree double angle cutter.