In response to a number of reported accidents involving abrasive cut off wheels used on
die grinders, we are publishing this safety bulletin to educate our customers, distributors
and employees about the dangers of this pairing. While die grinders and cut off tools may
look similar, they are by no means interchangeable. Several crucial differences exist between
the two handheld machines.
Cut off wheels must be used on guarded machines for the safety of the operator and
bystanders. Die grinders lack wheel guards because they are not designed for use with
cut off wheels. Cut off tools, to the contrary, are specifically designed for use with cut off
wheels and include proper wheel guards.
Cut off wheels must be used at or below their maximum operating speed, marked clearly
on the side of the wheel. Excessive speed can result in breakage and serious personal
injury. Die grinders often operate above 25,000 rpm and therefore are too fast for abrasive
wheels. The speed hazard is increased by the
absence of a guard to prevent installation of an oversize wheel. Untrained operators may
install large diameter wheels that cannot withstand severe RPMs, creating very high odds
of breakage and potential injury. Cut off tools, however, rotate at speeds compatible with the
abrasive wheels for which they are designed. What is more, their guards prevent use of an
Cut off wheels must be mounted between proper flanges, as described in the national safety
standard for abrasive wheels, ANSI B7.1. Die grinders make use of a collet for mounting, which cannot accept cut off
wheels, but some operators employ a mandrel adaptor to mount the wheel. This is not safe. The adaptor is
intended for low-speed machines like drills.1 Cut off tools, on the other hand, utilize flanges for mounting,
flanges designed according to the ANSI B7.1 safety standard. Now that you have learned the three crucial
differences between die grinders and cut-off tools GUARD, SPEED and MOUNTING be on watch for the
dangerous pairing of cut off wheels and die grinders, and warn your friends and colleagues of the same.