Re: 1KW, 30KRPM Router as a Spindle/Motor?

For a BP type mill, why not use an Erickson collet extension in
either a small DA or ER size, and some good bearings, to build a
spindle to clamp on the quill and run coincident with the spindle
centerline. Spindle could drive an integral jackshaft at 1:2 and
the jackshaft could drive the collet extension at another 1:2
ratio. Designing and building the housing itself would be a
challenge, but the only critical part would be bore alignment and
sizing. The rest of the accuracy would be purchased for
surprisingly little $$. IMO, there's no need to own machine tools
and then be afraid to try building something that has to be
accurate. About 20 years ago, using a manual bridgeport, manual
lathe, and cylindrical grinder, we built a 3 axis force measurement
hub for tire testing with error and inter-axis crosstalk less than
half the stated specs of the best similar device on the market at
the time. We could have purchased for about $220,000 but we built
it for less than $30K including all design and building time. With
a CNC mill, we could have easily shaved another $5K off the cost.
Patience and forethought are the two main requirements for building
accurate rotating devices.

Cliff