Installation Guide

Routing and Shaping
Woodworking shapers (also called table routers) and overhead
or portable routers are used in edge-finishing operations and for
cutting flat or formed Plexiglas
®
acrylic sheet parts to size. For
edging small parts, the table router is convenient; portable
routers are useful whenever the acrylic part is too large or
awkward to bring to the machine.
Routers should have a minimum no-load spindle speed of
10,000 rpm. Higher speeds of 20,000 to 25,000 rpm are desirable
and should be used when possible. At slower spindle speeds,
cutters should have more flutes or larger diameters to produce
necessary surface speeds. Double or triple straight-fluted cutters
5
⁄
16 to
1
⁄
2 inches in diameter will produce good cuts. Smaller
diameter cutters should be used with care. If cutters larger than
1
⁄
2 inch in diameter are used, the material should be machine-fed
rather than hand-fed to overcome chatter. For safety, cutter
shanks should be as large as cutters in diameter. Single-fluted
cutters should not be used under any circumstances.
When machining thick sections of Plexiglas
®
acrylic sheet,
better-quality edges may be produced by using spiral-fluted cutters.
Spiral-fluted cutters always have a cutting edge in contact with
the material and chatter less than straight-fluted cutters. This is
done best when the material is held down securely.
Carbide-tipped cutters should be used whenever possible
since they stay sharp longer than high-speed steel cutters. All
cutters should be kept sharp and should have a back clearance
of about 10° and a positive rake angle of up to 15°.
The most common operations performed with routers are
deflanging and flange trimming. These cuts are illustrated in
Figure 3 (shown at right). Such cuts may be made with router
cutters or with veneer saw blades attached to portable or table
routers by suitable arbors. Typical deflanging cuts commonly made
on formed Plexiglas
®
acrylic sheet are shown in Figure 4A ( page 13).
When deflanging cuts must be made to close tolerances, fixtures
should be used to support the Plexiglas
®
acrylic sheet and index
the cut. Female fixtures are used for close tolerance referred to
the convex side of a formed part; male fixtures, to the concave side
as indicated in Figure 4B (page 13). The material should be clamped
to the fixture. In trimming close tolerance work, the part should
not be supported by its flange.
In contrast to deflanging where the entire flange is removed,
flange trimming is merely reduction of the size of the flange.
Table and panel saws can be used for flange trimming and will
produce a good-quality edge. For high accuracy trimming with a
table saw, place the part on a lightweight male shape with
runners to fit the saw table grooves. Another method is to install
a gauging device on the saw fence so that the flange is trimmed
by indexing from the outer surface of the return of the part.
These methods are illustrated in Figures 5A and 5B (page 13).
Portable routers or table shapers equipped with woodworking
router bits are also commonly used in this operation. Depending
on the equipment used, a template may or may not be necessary.
Figure 6 (page 14) shows deflanging cuts made with a table
router with and without a template. The lower illustration
shows a special router cutter tipped with a ball bearing pilot.
This cutter is useful in trimming cemented assemblies. The pilot is
the same diameter as the cutter and rides the guiding surface of
one part of the assembly as the cutter trims the other.
Another cutting operation using a portable router is shown in
Figure 7 (page 14). A template is cut to size and held to a work
table, along with the Plexiglas
®
acrylic sheet to be cut, by means of
air cylinder clamps mounted overhead. The router is fitted with a
bushing that enables it to follow the template, cutting only the
sheet.
12
Deflanging
Flange Trimming
Common Router Operations
FIGURE 3