The gear showed is not intended to mesh with a worm gear, however it can be done although not able to carry power as the meshing is not exactly correct. You need to measure the diameter of the bull gear and count the number of teeth to use an online gear module calculator which will give you the tooth pitch. The worm will have to be tilted to mesh with the straight teeth on the wheel. You will also have to choose the number of starts on the wheel you make.

We were given an Atlas 12 x 24 lathe which did not have its threading dial which works like a worm wheel on the leadscrew which is simply a straight worm of infinite diameter. I knew the number of teeth that the worm wheel should have and the TPI of the leadscrew and bought a gear that meshed correctly. The axis of the gear had to be tilted to match the leadscrew thread and the housing made to suit. The threading indicator works perfectly since it does not transmit more power than needed to turn it.

The bull gear on a Myford   is 16 DP   ,well it is on mine  checked against  16 DP hob   fits

perfect ,  Ivan law’s  book list the pitch as.1963 inch    5 mm = .1968 inch  so that would

do .Depth of cut =.135 inch.

20 deg  PA.

John

On 24 September 2026 at 18:52 old mart Said:

…as the meshing is not exactly correct.

Please could you expand on this statement and say what is incorrect. When you talk of meshing not being correct, in my head it implies that the required conjugate action does not take place.

We produce spur gears by hobbing and a hob is little different to a worm gear.

To me, the low power capability of the setup is more to do with the “quantity” of meshing (an hourglass worm and fully enveloping wheel is the other end of the scale) rather than some intrinsic geometric problem with the setup.

When the OP acknowledges the above advice I hope he will say something about his unusual Myford with its gold coloured knobs and flip-top oilers.