Slotting Saw Arbor
Slotting saws or Jeweler's slitting saws can be purchased in numerous diameters, thicknesses and tooth counts. Mounting the saws on the lathe requires an arbor. I have been wanting an excuse to make a collet shank, and since I needed an arbor to hold a set of small (1 inch) slitting saws, this was a good opportunity to do so. Malco saw produces a series of 1 inch diameter saws with a 1/4" bore, and in a variety of thicknesses. The arbor was made to fit these and expose about 4mm of blade for substantial rigidity. This arbor and saw combination would be suitable for slotting screwheads and for numerous slotting operations, that require only a relatively shallow slot.
I started with a section of 3/4" steel rod (12L14) and faced and center drilled an end. With tailstock support, the exposed portion of the arbor is turned down slightly, but not to the final diameter.
The rod is reversed and faced and center drilled. With tailstock center support, the 'collet' body of the arbor was turned to dimension. I simply used another collet as a guide for measurements.
Reduced to 12.5mm, and then to 8mm.
The 8mm body of the shank is turned down, the portion to be threaded was then turned to 6.85mm, and then the 20 degree angle can be turned using the compound slide.
The threads were formed using a B8 die in the tailstock die holder.
The milling spindle was setup on the cross slide. The centers were used in the spindle and tailstock to bring the mill on center. A 2mm endmill was used to form the keyway in the side of the shank.
The arbor can then be mounted directly in the headstock using the drawbar. The final diameter of the arbor head was turned, followed by another facing cut. The arbor was drilled 3.2mm, and tapped with a M4x0.7 tap. Finally the actual 1/4" arbor to hold the saws can be turned.
To secure the saws to the arbor a washer was made from the same 3/4" steel rod. A small section (from the scrap box) was faced and drilled 4mm to clear a M4 screw, and then bored. The boring is so that the washer will only apply pressure in the outer diameter of the washer. This provides a much more secure and concentric fastening. The washer is parted off, reversed and faced.