One of the problems with using a treadmill motor is that they're often
made overseas, and often have metric-sized shafts. Mine is 17mm, which
I think isn't uncommon. I tried a couple of times to get a 2" pulley
with a 5/8" bore bored out to 17mm -- the first time didn't work
out due to lack of the appropriate cutting tool, and the second time
(different place) I ended up with a 17.4mm bore. Oops. Happily I
didn't have to pay for that. Also happily, the pulleys only cost
$5.50, shipped, from Amazon.
I got a second pulley, this time with a 3/4" bore. 3/4" is almost
exactly 19mm (19.05), so I needed to shim it by 1mm all around to fit
the 17mm shaft.
It turns out that the walls of 1/2" EMT electrical conduit are just
proud of 1mm thick -- the nominal wall thickness is .042", or 1.07mm.
It also happens that 1/2" conduit is just about 5/8" diameter I.D.
So I was able to take a 5/8" shaft I have lying around (part of my
Shopsmith accessories), and wedge a short length of conduit onto it. I chucked
the shaft into my drill press, and used a hand file while it spun to
thin the walls of the conduit a bit.
One of the problems with using a treadmill motor is that they're often made overseas, and often have metric-sized shafts. Mine is 17mm, which I think isn't uncommon. I tried a couple of times to get a 2" pulley with a 5/8" bore bored out to 17mm -- the first time didn't work out due to lack of the appropriate cutting tool, and the second time (different place) I ended up with a 17.4mm bore. Oops. Happily I didn't have to pay for that. Also happily, the pulleys only cost $5.50, shipped, from Amazon.
I got a second pulley, this time with a 3/4" bore. 3/4" is almost exactly 19mm (19.05), so I needed to shim it by 1mm all around to fit the 17mm shaft.
It turns out that the walls of 1/2" EMT electrical conduit are just proud of 1mm thick -- the nominal wall thickness is .042", or 1.07mm. It also happens that 1/2" conduit is just about 5/8" diameter I.D.
So I was able to take a 5/8" shaft I have lying around (part of my Shopsmith accessories), and wedge a short length of conduit onto it. I chucked the shaft into my drill press, and used a hand file while it spun to thin the walls of the conduit a bit.