metal must be removed from the bore of new wheels by
nearly the same diameter as possible and must not vary
2 or more separate cuts; that is, 1 or more roughing cuts
more than half tape size when measured with a standard
and 1 finishing cut.
A radius or chamfer of
In selecting wheels for mating, in
approximately 1/8 of an inch must be turned at the entry
machining wheels and axles, and In mounting them for
or back end of the hub after the finishing cut The
interchange service, the following points must be
finished wheel bore must be within the limits for
rotundity and taper and must be smooth and concentric
with the tread.
New wheels must not be mated with
necessary for the measurement of wheel bores and
One-wear wrought-steel wheels must
axles wheel seats to insure consistent results. On each
not be mated with multiple-wear wrought-steel wheels.
wheel bore and axle wheel seat, a fine, smooth machine
finish is required and must be checked at not less than
Double-plate cast iron wheels and
three points in its length, and on two different diameters,
wheels and single-plate nonbracketed-design cast iron
at each of these points, to insure rotundity and absence
wheels must not be mated.
The variation for any two of these
measurements must not exceed 0 002 inch. The bore
Cast iron wheels varying over 25
should be smaller than the wheel seat diameter, with a
pounds in marked weight must not be mounted on the
tolerance of 0. 0. 01 inch per inch of diameter of wheel
seat for wrought-steel wheels. For cast iron wheels, the
tolerance should be equivalent to 0.005 inch per inch of
Cast iron single-plate nonbracketed
wheel seat diameter and a maximum of 0.102 inch.
wheels must not be mated with iron single-plate
Permissible variations in dimensions for
cast steel wheels not shown by tolerances on individual
Heat will not be applied to the hub of
a tight wheel with a torch to assist in disloading it.
show dimensions for machining 33-inch one-wear and
Wheels bearing any evidence of such heating or which
have holes burned in the plate by a torch must be
Inside diameter-back face of rim. The
inside diameter of the rim at the back face of the wheel
In handling pairs of mounted wheels, wheel
shall not vary more than 3/8 inch under the nominal
sticks must not be used on the journal surface. Journals
dimension. The maximum diameter at this location is
of mounted axles must be coated with rust preventive,
governed by the rim thickness and the tape size.
unless they are to be placed directly in the trucks.
Before placing wheels with coated journals in a truck,
Inside diameter-front face of rim. For
the coating must be carefully removed with a suitable
narrow flange wheels, the inside diameter of the rim at
the front face of the wheel shall not exceed that at the
back face of the wheel and shall not vary under this
18-25. Boring-Mill Practice
dimension by more than 1/4 inch. For wide flange
wheels, the inside diameter of the rim at the front face
Boring mills must be maintained with the
of the wheel shall not differ from that at the back face of
table running true and with the boring bar held true with
the wheel by more than 1/4 inch.
respect to the center and the plane of the table, and
must not chatter.
Thickness of rim. In any wheel, the
radial thickness of the rim shall not vary more than 1/8
Chuck jaws must be properly alined radially
inch around the wheel.
and vertically. Contour of the chuck jaw may have a
taper of 1 inch in 20 inches to correspond to the wheel
Corner at inside diameter of back
tread line or it may be maintained vertically The boring
A sharp corner is preferable to facilitate
bar must have a position micrometer adjustment for the
measurement. In any case, the radius of the corner
cutters accurate to 0. 001 inch.
shall not exceed 1/8 inch.
If roughing and finishing cutters are carried
Plane of back face. When wheels are
on the boring bar at the same time, they must be
gaged with a straightedge applied to back face of rim,
separated by a distance greater than the length of the
no point on back face of narrow flange wheels more
hub, unless the roughing and finishing cuts are separate
than 1 1/4 inch from inside edge of rim shall be more
operations With the wheel properly alined in position on
than 1/32 inch from the
the mill with regard to concentricity and to plane, the