Re: cam tailstock lock modifications for SB13

Steven H

Anyway, it’s all theoretical calculations. Variation in the bolt thread pitch, wear in washer thickness, wear on the mating boss, bolt stretch, wear in the tailstock, variation in the bed thickness, etc could require adjustments over the life of the lathe. If you have ever built a Quorn tool and cutter grinder, adjusting the washer thickness under each ball handle is how to get the handle to end up where you want it to be. 

Steve Haskell

On May 11, 2020, at 12:00 PM, Davis Johnson <davis@...> wrote:

But thread pitch (i.e. TPI) is what determines the thickness of the washer required to get a desired re-clocking of the nut. A 1/TPI washer will result in a 360 degree reclocking, back to where you started. If you want a 1/8 turn difference (1/8)*(1/TPI) washer will do, (9/8)*(1/TPI) will probably be more practical.

How to produce such an animal is probably more problematical than the math.

On 5/11/20 11:12 AM, wlw19958 wrote:
Hi There,

Talking about thread pitch (i.e. T.P.I.) is irrelevant.  What is a thread anyway?
It is a wedging action arranged in a helix.  So, what we're talking about is how
to wedge the tailstock so that it is secure against linear movement when needed.
And un-wedging it when linear movement is desired. So, those who insist that
it has to do with thread pitch are missing the big picture and are concentrating on
extraneous details.

The idea of re-indexing the square head bolt in the tailstock clamp is a viable one. 
It provides two more possible combination and it may be enough to work.  It will
provide a 30° rotational offset in relation to the flats on the nut (assuming a hex nut). 
When I got my first Heavy Ten, the tailstock clamp was a 1/2" block or steel with a
stud in it and hence didn't provide for the re-orientation of the bolt.  

Shaving the underside of the nut is of course possible but it make take several tries
to get it where the user wants and once it has been machined down, it is difficult to
put the metal back.  I learned a long ago to modify the cheapest part so that if one
screws up, replacement will be cheap.  That is why I suggested making some washers. 
They are easy to make; they don't require much machining skill (i.e. a beginner can 
do it) or tooling. And if it doesn't work, the person is no worst off that before.

Good Luck!
-Blue Chips-

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