Friday, Apr 7 2017
The mill is working well and meeting my needs. I also use the mill for drilling. It’s slower to crank on the Z axis than a drill press (or larger mill) with a quill that can be lowered) but it gets the job done. I do, however want some spotting drills to start holes and keep drill bits from wandering. Since most of my drill bits have 118° angle points a 120° spotting drill would be perfect. Hmmm.
Truing stock in the 4-jaw
That’s some 3/8” W-1 tool steel being centered with the 4-jaw chuck in the lathe. Once centered I cut a 60° taper on the end for a 120° included angle. When that was done I cut off a small (but large enough) section of the tool steel and moved to the mill.
Milling the bit
Ready for hardening
I used the collet block I made to hold the piece and milled off just under 1/2 the diameter. That leaves a bit of material to grind off after the bit has been hardened. The collet block was then rotated 90 degrees and a slight radius milled along with a relief under the cutting head to make sharpening a bit easier. It’s ready for hardening.
Hardened and tempered
The above was done yesterday. Today I picked up some Map gas (I was out). I put the part on some bricks and got it cherry red before quenching it in water. I cleaned off the resulting scale and heated the part again, this time slower and not as hot. When my thermometer said the part was about 500° I turned off the torch and let the part cool.
It works
Once cool I honed the face on a stone. I didn’t think I needed to use the grinder at this time. As the picture shows, it works. At least it works in aluminum.
If I had use of a D-bit grinder I could have made this out of HSS and got a proper relief ground behind the cutting surface. No matter. This is likely good anough for my needs.