edweitz wrote: ↑Fri Jun 11, 2021 2:26 pm
As you know, the misalignment of the steel worm screw chews away the softer part that causes the speed to change by spreading the sheaves. That softer part is what I need again. The softer part gets worn during use. I believe it is an aluminum cast product. I will check for new replacement from SS.
The speed control quadrant, aka porkchop, is usually readily available from SS:
https://www.shopsmith.com/ownersite/ite ... tem=504221 It is also available as part of the speed control assembly, 504198. Both are popular replacement parts. Consider reviewing the Bill Mayo headstock improvement document accessible from the first entry in this thread:
viewtopic.php?f=10&t=16113 Bill had a modification he made to the speed control assembly that provided a measure of improvement in the life expectancy of these parts. My interpretation is that his changes make a couple of significant improvements:
1) As designed, the quadrant 'hinges' on a spring tension pin that is a tight fit in the quadrant and a loose fit in the legs of the control. Over time these pins can wear a larger hole in the casting assembly, allowing misalignment which then accelerates the process. Bill's solution locks the new hinge pin to the legs and the quadrant rotates on the 'pin' instead. Unlike the tension pin, the new pin does not have any 'cutting edges' to expand the hole. Note that if these holes are enlarged from past use that installing a new quadrant is only a temporary solution because the enlarged holes won't keep the new quadrant aligned and its wear-out will be accelerated. In this case the whole speed control assembly should be replaced or another solution installed.
2) It strengthens the whole assembly by tying the two legs together so they cannot spread apart as easily, also a source of misalignment of the quadrant with the worm screw.
These improvements, along with keeping the two moving sheaves lubricated so speed change requires minimal effort, are meant to increase the life expectancy of the parts by keeping the quadrant aligned with the worm screw. Bill also advocated that the user should slow down speed change rate, especially when transitioning to a slower speed, the idea being that giving the machine more time to respond to the change reduced the amount of force needed.
- David