Just a guess, but someone probably thought they would protect you from
using a bit 1" dia in freehand-like (non-router table) tasks.

Robatoy wrote:
For some reason or another, I cannot find a router guide bushing bigger
than the normal 1" or so.
I bought some many years ago. Two of them. One was 1-3/4" OD and one
was 1-5/8" OD.
They are used in conjuction with either a 3/4" or a 5/8" bushing along
with a 1/2 bit in order to make inside-outside parts for inlay work.
I have a kit for a 1/4" bit from Lee Valley, which achieves the same
thing, but doesn't have the utility to be plowing out 1/2" acrylic. For
that, I want to use a 1/2" single flute up-spiral.
I suppose the option is to have a machinist make me a sleeve that steps
up a 3/4 bushing to 1-3/4".
But I KNOW the larger ones exists, but just can't find the things
anywhere.

HELP??

TIA

r