On 26 Aug, 19:21, T i m wrote:

I am tinkering with the idea of building a test jig and a basic bench
grinder could make the ideal platform.

Don't think I've ever seen a bench grinder with deliberate soft start.

Am I right in thinking you can make induction motors 'soft start'
(reduced starting torque) by the inclusion of a series resistor?

Make that a _big_ series resistor, ie chunks of old fire element wire.
You'll cook a little one. It also requires switchgear, either manual
or automatic (centrifugal)

What you might find handy is to look at a 1900-ish handbook of Modern
Electric Motors etc. (I've just acquired a copy of Rankin Kennedy).
In this period, the usual starter was a manual swinging lever across
an arc of copper studs with coils of resistance wire between them. As
life was simpler then, books of the period describe things with the
sort of shed-based technology we're likely to recreate with our
bodgery.

A cheap source of rotating machines with variable speed (shift while
spinnning) drives is a low-end woodturning lathe.