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CONCENTRICITY:
(Total indicator reading) Bushings 1/8"
to 1" I.D. - Concentricity 0" to .0003"
(Max.) Other sizes - Concentricity 0" to
.0005" (Max.) On counterbored bushings above
tolerances will be met at the drill exit
end.
RADIUS:
All bushings feature a blended radius at
drill entrance unless otherwise specified.
LEAD:
All bushings feature a concentric
ground lead in addition to a chamfer on
exit end of bushing.
STEEL:
Our bushings are manufactured from
selected steels known for their long wear
and stability. Bushings are also available
from other materials at extra cost (bronze,
M-2, D-2, stainless steel, etc.) (see also
page 2)
HARDNESS:
Rockwell C 62 - 64 in the hole.
APPLICATION
DATA
The head liner, type HL, drill bushing is
used with our renewable drill bushings and
is permanently pressed into the jig plate
or fixture. The headliner bushings are preferable
when heavy axial loads are anticipated.
The head liner, type HL, drill bushing is
similar to the liner drill bushing except
that it has a head or shoulder on the drill
entry end and the fixture may be counterbored
for flush mounting.
INSTALLATION
DATA
(Cast iron or unhardened steel jig plates)
To maintain accuracy in the production operation,
extra care must be taken in mounting hole
preparation for head liner bushing installation.
Factors to consider are diametral interference
fits, alignment, chip clearance, and proximity
of bushing to work piece.
a) INTERFERENCE FITS
In any press fit installation, metal is
displaced. Usually, a combination of bushing
closure and jig plate distortion results;
therefore the best practice is to use the
minimum interference necessary to retain
the bushing in the jig plate. In most installations
diametral interference of 0.0005 to 0.0008
inch is adequate for installation of head
liner bushings.
b) MOUNTING HOLES
An important point to consider is the roundness
of the mounting hole. Because bushings tend
to assume the shape of the hole into which
they are pressed it is recommended that
all mounting holes be jig bored or sized
with a reamer to assure roundness. An ordinary
twist drill will seldom produce a hole that
is accurately sized and truly round.
c) BUSHING INSTALLATION
Before installing a head liner bushing always
lubricate the inside diameter of the mounting
hole and the outside diameter of the bushing.
Bushings installed without lubricant may
pick up metal and score the mounting hole
during installation. Lubricated bushings
are more easily removed for replacement
with less chance of damaging the jig plate.
Use a hand arbor to press the head liner
bushing into the jig plate whenever possible.
If not, use some other means such as drawing
the bushing into the jig plate with two
steel plates and a nut and bolt. A hammer
should be used only if no other methods
are possible and then never strike the bushing
directly; use a block to take the hammer
blows. Whichever method is used, care should
be taken to maintain centerline perpendicularity,
otherwise inaccuracies may result in the
production operation.
NOTE:
Chip clearance: Due to the abrasive action
of metal particles sufficient clearance
should be provided between the drill bushing
and the workpiece to allow for removal of
chips. Careful consideration of this point
will aid in producing accurate holes. (A
rule of thumb is, the greater the clearance
the greater chance of error.) Example: The
recommended chip clearance for metal producing
small chips, such as cast iron, equals one-half
the drill diameter. The recommended chip
clearance for metals producing long chips,
such as cold-rolled steel, equals one to
one and one-half times the drill diameter.
Maximum
Accuracy: Use drill bushings of
different lengths to obtain the combined
advantages of adequate chip removal and
precise accuracy.
Example: Use a drill bushing that is short
enough to provide chip clearance during
the drilling operation. Next, use a drill
bushing long enough to contact or closely
approach the work piece for the reaming
operation. |
