Mike- i had a local guy with a lathe turn it up for me.
i selected the 2" as my sleeve of choice- and built the collar to suit- it obviously doesnt spin, but then it doesnt wear out against the template either- i drilled the holes for the dust extraction.
i also had to shorten the sleeve about 1/2".
i keep meaning to do a more detailed build along- showing the whole process- just time is in short supply.
to disengage the oscillation- when you open it up- you will see its a pretty smart system.
there are two discs on the shaft, with nodes or bumps on them- they are driven off the same drive but one disc has more teeth on it than the other so it just rotates marginally faster than the other one and as these discs and the shaft spin at your grinding speed- the top disc rotates slightly, very slightly faster than the bottom one- so as these two discs spin, they rotate against each other- and when the nodes align- the rubber sleeve lifts, and when the to discs valleys align with the nodes on the bottom disc, the sleeve descends.
all i did was remove the top disc, and replaced it with a piece of copper pipe as a spacer so the rubber sleeve bottom washer and assembly sat against that . now there are no bumps or valleys to lift and lower the sleeve.
i should have had a better collar turned up- but it was late at night- and it was what was handy- and its worked fine.