[garymck (Gary)]

"I think you mean lapped. Hobbing is only a special type of milling operation."

What I mean is that the worm and worm gear are not matching profiles, this means that the angular contact area is small and exaggerates the small random errors. This is not uncommon My understanding is that gears are hobbed, worms are cut - I probably wasn't as precise as I should have been :-)

"It might pay me to have a new worm and wheel precision ground and lapped if the existing ones are easy enough to duplicate. The PE errors are really quite abrupt; worse that your bad one, though not as extensive."

I've already checked this out, having a worm precision ground costs about $150 on mates rates, and that is after having one made with a matching new worm gear !!!! You might want to check out a set of Gerlinger gears from Germany - these will cost about $500 to get here. Have not seen any real reports of the results of fitting, but they were popular in Europe. They have matching profiles and are supposedly much smoother than the originals, but require VERY precise set up.

You might want to check and adjust the mesh and alignment of the gears - I was able to reduce the pe from about 55 arc secs to that shown, and at the same time the small jigglies shrank as well.

I also am not sure that the pec routine works properly as I have had strange results with it as well....

cheers

Gary