(5) A spindle on which a threaded-hole wheel is mounted shall be threaded to
allow the abrasive wheel to be screwed flat against the back flange. In addition, all of
the following requirements shall be complied with:
(a) The direction of the thread shall be such that removing the abrasive wheel
requires rotation of the wheel in the same direction that it turns when in use.
(b) A spindle shaft shall not touch the bottom of a blind hole in an abrasive
wheel.
(c) A back flange that is specified in this rule shall be flat, unrelieved, and
square to the spindle axis.
History: 1979 AC; 1990 AACS.
GUARDING PROVISIONS
R 408.10121 General requirements.
Rule 121. (1) An abrasive wheel shall be provided with a guard, except as noted in
this subrule, which shall cover the spindle end, nut, and flange projections, as well
as the periphery, other than where work is to be performed (see figures). Exceptions are
as follows:
(a) Wheels used for internal grinding while advancing or retracting the work or
while within the work.
(b) Mounted wheels that are not more than 2 inches in diameter.
(c) Plug and cones that are not more than 3 inches in diameter or 5 inches in
length.
(d) A type l reinforced wheel which is not more than 3 inches in diameter and
1/4 inch thick and with which safety glasses and face shield protection are provided
and used as prescribed in Part 33. Personal Protective Equipment, being R
408.13301 et seq. of the Michigan Administrative Code.
(e) Lapidary grinding. A metal diamond lapidary blade which is
notched,
segmented, or continuous rim and which is used within a coolant deflector does not
require guards for speeds of not more than 3,500 sfpm.
(f) Tuck point wheel, masonry, or concrete saws may have the spindle end, nut,
and flange exposed as per figures 1 and 2 of R 408.10198.
(2) The guard shall be constructed of material that is capable of retaining
pieces of a broken wheel. See material tables. The guard shall be mounted so as to
maintain alignment with the abrasive wheel to contain wheel breakage, and the strength
of the fastenings shall exceed the strength of the guard. The guard shall be in position
before starting the wheel.
(3) Where flying particles or fragments are a hazard to employees other than the
grinder operator, an enclosure or barrier shall be provided to isolate the operation
from the remaining working area.
(4) When openings in the wheel safety guard assemblies are required for dressing,
a means shall be provided to protect the operator and other personnel from the
hazards of flying particles, sparks, or wheel fragments.
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