Eisboch wrote:

Scag dealer and also confirmed by our landscaper who obviously only buys
commercial equipment. He's the one who recommended that I buy a
commercial mower for the purpose I needed (mowing large horse paddocks).

The residential tip speed limit is a federal regulation. I forget what
it is exactly, but something like 1750 feet/min rings a bell.

I couldn't find anything specifically regulating residential mower blade
tip speed, but did find that there is a federal regulation concerning
all mowers at 19000 fpm top blade tip speed. Most commercial mowers
appear to advertise at between 18000 and 19000.

Shamelessly cut and pasted:
---------------
American National Standards Institute (ANSI)
ANSI standard B71.1, Walk-Behind Mowers and Ride-On Machines With Mowers
- Safety Specifications, is the primary safety standard for homeowner
riding mowers and small tractors. This standard requires the use of an
operator presence control, a device that will stop the mower blades if
the operator leaves the seat without disengaging the blade drive (PTO).
This prevents an operator from being down on the ground around a mower
while it is running.

One of the most important features of this standard is a requirement
that the blades must stop turning within 5 seconds when the PTO is
disengaged or the operator leaves the seat. This requires an automatic
brake on the blade drive. ANSI also requires that mowers be tested to
strict performance standards for thrown objects.

A seatback height of at least 4½ inches is required to keep operators
from falling backward. There are requirements on dynamic turn and sudden
traction performance to improve machine stability. There are
requirements for braking performance. There are also requirements on
guarding and safety labeling. The blade tip speed is limited to 19,000
feet per minute.
----------------

That would seem to indicate that there is no specific lesser top blade
tip speed for a residential mower.

It still could be true, I suppose, that the manufacturers of residential
mowers spin the blades slower, but that may not be necessarily true in
all residential machines.

Johnson.