In My Humble Pinion
While I am in the mode of making gears, I thought I would make the last two, the oil pump pinions. They are .375″ in diameter, 32 DP, 20 degree pressure angle, and have 10 teeth. I am going to make them in brass so I figured I could get away with a single flute fly cutter to cut the gear leafs. I am making the cutter from 01 tool steel on the CNC router. I use a gear profile spreadsheet I have for the cutter design, then capture the cutter in SolidWorks with an 8 degree clearance angle. To cut this clearance angle I clamp the 01 tool steel blank at an 8 degree angle as seen in a few photos below. So I take a section of the cutter in the following CAD model to present this tilted cutter blank to the mill.
Above is how the cutter will sit in the vise and how it will be cut. The blue area is the remaining part to be used, the rest of the model is trimmed away. This CAD model is then transferred to Fusion360 to generate the tool paths
I am using a two flute 3/32″ flat end mill because I have an internal radius of less than.125″, otherwise I would have used my go to 1/4″ end mill. I am making lots of tiny little cuts. Above is a simulation of the tool paths.
Above is the completed cut in the CNC router vise. I have used a second scrap cutter blank to even out the vise clamping force. You can see that it is clamped at the 8 degree angle.
This is the standard heat treating kit with the MAP gas torch, boric acid to eliminate scale and quenching oil. The tin can is used to hold boiling water to remove the boric acid after heat treat. I warm the cutter tip and roll it around in the boric acid which adheres and melts. Then I bring the cutter tip to a bright red hot and plunge in the quench oil.
After removing the melted boric acid by rinsing in boiling water, I temper the cutter by heating it with the torch on low. I aim the heat at the middle of the cutter and watch the color change propagate out toward the tip, when I see the light straw color I am aiming for, I again plunge it into the quenching oil. Finally I sharpen it on the Arkansas stone.
Above is the mandrel used to hold the cutter.
I prep the pinion blank by bringing the OD to size, drill and ream the 1/8″ hole down the middle. Then I transfer the blank and chuck to the 4th axis on the mill.
I set my gear cutting rig up with a tail post, but the pinion is so small the cutter hits the dead center in the tail post, even though it was relieved. Cutting the pinion hanging into space like above causes the blank to vibrate and there are slight machining artifacts on the teeth. since this is not a set of power train gears, these should have no effect on the function of the oil pump.
Once the teeth are cut, it is back to the lathe to part them off and finish the ends.
Done with gears, whew.