Dovetail cutter.
This dovetail cutter was constructed from a piece of 3/4" steel round bar and a TCMT insert.
The bar was chucked in the lathe and the shank turned down to 10 mm for a length of about 45 mm. With the top slide set over to 30 degrees the 60 degree angle on the conical face of the cutter was then formed. The piece was then parted of and faced.
The piece was then mounted horizontally in a vice on the milling machine and a triangular section milled from the cone as shown above. The depth of this cut must be such that the cutting edge of the TCMT insert is exactly on the centre line of the cone.
The bar was chucked in the lathe and the shank turned down to 10 mm for a length of about 45 mm. With the top slide set over to 30 degrees the 60 degree angle on the conical face of the cutter was then formed. The piece was then parted of and faced.
The piece was then mounted horizontally in a vice on the milling machine and a triangular section milled from the cone as shown above. The depth of this cut must be such that the cutting edge of the TCMT insert is exactly on the centre line of the cone.
This photo shows the insert mounted on the cutter shank. Note that the edge of the cutter lines up with the centre of the cone base. Once the milling was completed the cutter was stuck in place using cyanoacrylate adhesive so that the edges of the insert were protruding by about 0.5-1.0 mm. The hole was then drilled for the insert clamping screw. The cutter was warmed up to soften the adhesive and the cutter removed so that the clamping screw hole could be tapped. The insert was secured in position with the screw. The final operation was to mill a flat on the cutter so that it could be firmly secured in a holder. The scribed line on the cutter marks the insertion depth in the holder to line up with the holder clamping screw.
This cutter has only one cutting edge so there is much vibration when using it. It is important to keep the speed down, the depth of cut small and the feed slow, at least on my little Sieg X1 milling machine. However, it does a good job and it is much cheaper to make than to buy a purpose made multi flute dovetail cutter. It also has the advantage that the cutting tip can be turned around to provide fresh cutting edges and replaced when all the cutting faces are worn out. The surface of the cone becomes quite scratched in use due to swarf becoming trapped behind the cutting edge. This could probably be overcome by case hardening the conical end of the cutter. Another job for the "to do" list!