On May 16, 4:42*pm, stuart noble wrote:
John Rumm wrote:
Multiply by the blade circumference... so for a 190mm blade at 4500 rpm
that is 4500 x 0.19 x pi = 2686 m/sec

Heh-heh, blade tip travelling at beyond even rail gun projectile
hypersonic speed would be fun.

I knew I could count on you :-)

RPS = 4500rpm / 60 = 75
Circumference is 2*Pi*R = 2 * 3.14 * 0.19/2 = 0.59m
Circumferential speed = 75 * 0.49 = 44m/sec.

At 4,500rpm you have almost 100 miles per hour. At 10,000rpm you have
200 miles per hour. Quite a few angle grinders run 12,000rpm, still
far below the sound barrier.

Due to the way an angle grinder is mechanically driven, stopping one
in motion as with a tree root will hurl the saw at speed. A chainsaw
will not do this hence eminently less dangeous than a freakin angle
grinder.

Alligator saw is expensive but handles both demolition & general
precise wood cutting, a jigsaw with a wood ripping blade is cheaper.