AMMCO 3860 Drum & Disc Brake Lathe - Manual (Page 12)

6 • AMMCO 3850, 3860 Brake Lathes
Brake Lathes
Mounting Drums
Hubbed drums are mounted with tapered adapters
that contact the drum near the middle of the bearing
races for accurate mounting. Hubless drums are held
in place on the arbor by the hubless adapters and cen-
tered by a cone adapter. The hubless adapters should
contact the bolt hole surface of the drum while strad-
dling the lug holes if possible.
Note: Clean the drum mounting surfaces before
mounting the drum. Use a wire brush (or a drill-
mounted brush) to clean all mounting surfaces of
burrs and rust. The inside diameter of the center hole
must be thoroughly cleaned as well. Brush these sur-
faces down to clean, bare metal to ensure accurate
mounting.
After mounting the drum, it may be necessary to use
adapters to fill out the arbor so the arbor nut can be
tightened down securely. The self-aligning spacer
must always be used next to the arbor nut.
1. Determine the correct mounting configuration
from the samples shown in Figure 4.
2. Install drum and adapters according to the con-
figuration.
3. Add adapters as necessary to fill the arbor out to
the threaded section.
4. Place the self-aligning spacer on the arbor.
Tighten the arbor nut either by rotating the drum while
holding the nut until they lock up, or by using the
wrench to turn the nut until the drum begins to turn,
and then continuing to advance the wrench 1/16 of a
turn.
Figure 4 - Typical Drum Mounting Configurations
Reconditioning Brake Drums
1. Before mounting the drum on the lathe, set it on
a stable surface and measure the diameter of the
brake drum with a brake drum micrometer. Determine
if the drum will be within maximum rebore limits after
reconditioning. Inspect the drum and verify that it is in
good general condition. Remove dirt, rust, and burrs.
Note: In most cases, the number cast into the brake
drum is the DISCARD diameter, not the maximum
MACHINE-TO diameter (which is always less).
Figure 5 - Measure Drum Diameter
2. Mount the drum on the arbor using the proper
adapters, cones, and spacers. Refer to Figure 4 for
mounting instructions and typical mounting configura-
tions.
3. If a boring bar is already installed on the lathe,
loosen the self-aligning nut slightly to allow for reposi-
tioning.
If a twin cutter is installed, remove it and install the
boring bar. Hold twin cutter and remove self-aligning
nut. Lift twin cutter off lathe. Clean the slide and bot-
tom of boring bar clamp. Install the boring bar and bor-
ing bar clamp onto slide, over the T-bolt and secure
with self-aligning nut. Handtighten the nut only at this
point. Make sure the tool bit is clean and sharp.
Replace as necessary to ensure smooth reconditioning.
ạ Ả
Ả
ạ
ẩ
Ạ
Ẩ
Ạ
ả
Ầ
ầ
Ấ
ấ
Ạ - 1” Arbor
ạ - Arbor Nut
Ả - Self-Aligning Spacer
ả - Spacer
Ấ - Spring
ấ - Small Hubless Adapter
Ầ - Large Hubless Adapter
ầ - Centering Cone
Ẩ - Small Double Taper Adapter
ẩ - Large Double Taper Adapter
Hubbed Drum Hubless Drum