STEMCO Aeris - Manual (Page 12)

Aeris Installation and Service Manual
Page 12 of 42

Use either an angle drill or standard drill where room permits. With drill fixture is in place (Figure 5) insert
the 5/16” drill bushing in fixture and drill a pilot hole using a 5/16” drill bit. Next insert the 7/16” bushing and
drill the hole using a 7/16” drill bit. Next insert the 9/16” bushing in fixture and using a 1/4-18 NPT, tap the
hole. Repeat procedure on all 3 holes in each trailer axle.
IMPORTANT: For some axle configurations, you may be required to remove the slack adjuster and or the air
brake chamber in order to access the drill locations specified by the axle manufacturer.

Tap ¼-18 NPT: Proper tap depth determination for a tapered pipe thread (NPT) requires an L1 Plug Gauge,
which Stemco highly recommends. If an L1 gauge is not available, an approximation of tap depth can be made
by using the actual fitting that will be inserted into the hole. Using only hand applied torque; the fitting
should screw into the hole so that 2 to 3 threads are inside the hole before it becomes too tight to turn. This
is a trial and error process to get the right depth, so use caution to prevent over-tapping. Once the tap depth
is verified, mark that depth on the tap (wrap tape around it, or mark with permanent ink) so the tap can be
driven to that depth on future holes.
 When finished drilling holes, use a cleaning wand connected to high pressure air to blow out shavings from
inside of the axle. Use safety glasses.
! WARNING: The use of a drill fixture is recommended. Drilling free hand can create oblong holes. Drilling
should be done at a drill speed 7/16” drill…262 rpm to 786 rpm or drill speed 5/16” drill…367 rpm to 1100
rpm. Keep drill straight when boring holes. Tapping should be done by hand only. Do not use a drill for
tapping. The use of a drill to tap holes can lead to threads being too deep or breaking the tap.
! WARNING: When drilling the 7/16” hole, be careful as the drill bit breaks through the inside of the axle! The
drill bit can hang up causing the drill to twist in your hands. When breaking through the inside of the axle,
apply less pressure and drill at a slower speed.