Andy Dingley responds:

There is _no_ UK law against dado sets. There is a law (part of PUWER
98) that requires a rapid stop. As this is awkward to achieve with a
heavy dado set (you'd need to fit electric braking, which is
expensive), the cheapest fix for new retail machines is to shorten the
arbor.

If you have a long arbor you can still use it.
If you have a long arbor you can still sell it.

If you want to use a machine in a commercial workshop - any age of
machine - it now needs to comply to this spin-down regulation, even if
that requires retrofitting a brake. OTOH, we did get 5 years warning
of this ruling coming into effect.

What's the spin down time. If it isn't instant stop, a la Saw Stop, it seems
useless to me. A hand stuck in a dado blade is going to get chewed up about as
much as possible in 30 seconds as compared to 60 seconds.

Spin down time and the use of electric brakes on power tools have always seemed
to me to more beneficial in stopping the blade quickly so the next operation
can be started, not as a safety measure, though it might also serve as such on
some circular saws (Skil type) and one or two miter saws, always assuming those
don't have guards.

Charlie Self
"If a politician found he had cannibals among his constituents, he would
promise them missionaries for dinner." H. L. Mencken