Instruction Manual Section Five
only a cup wheel, check the portion of the teeth back of the chamfer or
lead taper for any built-in back taper. This may be done with a hand
micrometer, since "feel" will reveal tapers of .001 inch per inch or less.
Set the reamer in place between the centers and locate a toothrest on
the machine Wheelhead (from above or below the wheel) and the blade
on center with the center of the reamer. Adjust the swivel table to equal
the known or desired taper on the reamer. If it is not possible to measure
the small taper accurately, a guess will have to be made and the adjust-
ments made when grinding the primary clearance or margin. The back
taper is usually on the order of 001 inch per inch, but it may go as high
as about .020 inch per inch, especially if it is not started immediately after
the chamfer or lead taper.
2. Using the short adjustable micrometer with a rounded blade as shown in
Photo 49 (or by raising or lowering the Wheelhead), consult the clearance
table mentioned above and "roll" the reamer up or down the required
amount, depending on the position of the rest.
3. Start the grinding wheel motor and traverse the reamer while firmly con-
tacting the toothrest. Care must be taken not to remove so much metal
as to lose the final desired reamer diameter just back of the chamfer or
lead table. It is desirable to contact the wheel very lightly with one
tooth held firmly against the rest and then to grind the entire peripheral
length of this tooth prior to checking or going to the next tooth. As
each tooth margin is ground, it is necessary to continually check the
diameter of the reamer. If a sizeable margin of .006 inch or larger must
be left, it may not be necessary to use the secondary clearance. If a
secondary clearance is needed to reduce the width of the margin created
by sharpening, adjust the Wheelhead or toothrest by the reamer table
values and grind the secondary in the same manner as the primary land.
C Sharpening the Lead Taper:
1. Sharpen the lead cutting taper by shifting swivel table to the desired
taper, usually on the order of ⅛ inch to ¼ inch taper per foot. The length
of the taper varies greatly with the length of the reamer, but it may
cover as much as one-third of the total flute length. This taper starts
immediately back of the lead chamfer if present.
D. Sharpening the Chamfer:
1. The swivel table is usually set at 45 degrees, but the existing chamfer
should be followed.
2. Consult the reamer clearance tables for "Rose Chucking Reamers for Steel".
Place reamer chamfer face on center with the center of the reamer by
means of the toothrest, which is placed on the grinder table. Raise or
lower the toothrest (or the Wheelhead) the amount necessary for the angle
desired. Grind the chamfer, holding the reamer firmly against the tooth-
rest, by traversing the table while advancing the Crossfeed. No secondary
clearance is placed on the chamfer. NOTE: It may be faster to merely
align the land width of the existing chamfer with the face of the grinding
wheel in order to obtain an adequate chamfer relief. If the grinder has a
tilting Wheelhead, it is equally fast to center a tooth horizontally on the
chamfer face with a rest and then tilt the Wheelhead to he desired clear-
ance angle.
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