Things are Hobbing along... Yesterdaay I showed the setup for hobbing the teeth on the worm wheel. Here is what pre-cutting the teeth looked like. I ran the table straight in to cut the teeth in the center of the blank, not running it left to right like cutting normal teeth, since all I wanted was a start to the teeth for the spinning tap to grab onto and spin the blank as it cut.
Then the actual hobbing. The rotary table was set down flat on the mill table again, and the involute cutter replaced with the Acme tap. The blank was put into the arbor set up for letting it spin freely but not move side/side, with some oil on its shaft to ensure it didn't grab. The cutter was set up so that it was in the middle of the blank, with the full teeth at the shank end of the tap in line with the center of the blank. Then, moved in the table so the teeth were started in the cuts, verified that by hand-spinning the mill spindle. This video shows what it looked like in near the start of the process. It takes a few seconds for the blank to make each rotation, so after every couple spins I moved the table in another 5 thou or so, gradually taking more off the teeth.
This one shows it near the end of the process, you can see the teeth are deeper/wider in the center
Here its about down to final depth, you can just make out how the tops of the teeth have some hollow to them:
And checking with a length of the Acme threaded rod:
Next, moved the chuck back to the lathe and used the compound slide to angle both of the sides in to where the shaped part of the teeth start. The cap on the arbor was switched to the one that holds the part rigid to the arbor, and the oil was cleaned off the shank of the arbor too.
Then trimmed in the sides to form the hub that sticks out in the middle. That required a smaller arbor cap.
Then moved back over to the mill with the horizontal rotary table, and laid out the holes at the corners of the spokes, using measurements for distance and angle from the CAD drawings. The blue lines are just to keep me oriented for where the openings will be.
Started out by milling the inner and outer arcs - first passes were in a little from the outer arc, then finish passes to dimension. Same on the inner arc of each opening.
Then moved on to the straight line cuts for the sides of the spokes. Again, first cuts in from the spoke, finish light cuts at the spoke edges:
And final cuts were to recess the spoke sides and the rim on both sides of the wheel:
And the finished gear! Only took a couple hours start to finish, came out looking great.
Next time I can start in on the set of shafts and bearings for the main control shaft, and then get the bearing blocks to hold that assembly in place. The next few days are shifting into some real summer weather, clear and upper 80s all of a sudden, so may not get much shop time in.
