www.ModulusArms.com
January 14, 2016
www.ModulusArms.com | Heavy-Duty Universal AR-15 80% Jig Instructions
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Installing the End Mill:
Loosen the router base so that it is as far down as it can go. Insert the end mill
into the router. Adjust the end mill in the router until it hits the bottom of the depth gauge slot “A”.
When the end mill is at the correct height, tighten the collet of the router locking the end mill in place.
Fire Control Group Milling
: Move the base of the router until the tip of the end mill is at the first line in
slot “C”, shown in Figure 15. Place the router into the opening labeled “C” and into one of the holes
previously drilled as shown in Figure 16. Be sure not to touch the sides of the holes when you start the
router. Start the router and allow it to come completely up to speed. Start to move the router removing
material. Start by moving in a semi-circular motion in small clockwise steps. Press down firmly to
prevent the router from lifting. Do not try to move the router in one straight direction but rather in
smooth half circles removing small amounts of material as you proceed. Join the drill holes together and
then start to widen the opening until you reach the template. When you reach the template, trace the
inside diameter of the template in a clockwise motion. Be sure to remove as much material as possible
before touching the template or tracing the template. Do not push hard against the template. A gentle
touch is enough. Mill the rounded corners in the template last, as they are most likely to chatter. When
the opening is the same size as the template turn off the router, wait for it to completely stop and
remove it. Adjust the router base so the end mill is at the next mark on the depth gauge as shown in
Figure 17. Continue in this pattern until you reach the bottom of the Depth Gauge. On the last step, start
the router in the hole you drilled for the trigger slot. This will prevent any need to plunge with the end
mill.
Note
: DO NOT INSERT OR REMOVE THE END MILL FROM THE TEMPLATE WHILE THE END MILL IS
SPINNING. THIS IS DANGEROUS AND THE MOST COMMON CAUSE OF BROKEN END MILLS OR
DAMAGED JIGS/LOWERS.
Note
: Be sure the end mill is very tight in the router. Tighten it as much as possible. Check
regularly
Note
: If the router begins to whine or vibrate during milling, turn the router off and remove it
from the template. Inspect the end mill and be sure there are no chips jammed into the teeth of
the end mill. If there is, use a tool to remove the stuck chips. A small screwdriver or pencil works
well. Be sure not to damage the teeth.
Note
: We recommend a mid-speed setting on most routers. Adjust as necessary for your exact
router.
Note
: If you have a shop vacuum, use it. Run the vacuum whenever you are milling. If you do not
have a shop vacuum, stop regularly are remove the chips. If they build up, they can become
stuck between the end mill and the template and melt. This build up can be removed from the
end mill with sand paper. Use of a cutting fluid or WD-40 is recommended.
