Installation Guide

9
Scroll Saws
Scroll saws may be used for cutting sharp radii and closed holes
in thin pieces of Plexiglas
®
acrylic sheet, but are less suitable for
cutting thick sections or multiple sheets. Because of the short
stroke, scroll saw blades do not clear the chips and tend to gum
up. When this happens, the plastic softens and welds around
the blade. Scroll saws must be used with a light feed and without
forcing the work. The teeth should be cleared often. As soon as
the blade stops cutting cleanly, it should be backed out, the
chips removed, and the sheet cooled. Welding of the plastic
behind the blade may be alleviated by using two blades mounted
side by side, or by using an air blast to remove chips and cool
the Plexiglas
®
acrylic sheet. A coolant may also be used. Masking
material should always be left intact to provide lubrication in addition
to protecting the sheet. Blades should be sharp with 10 to 14 teeth
to the inch. Hold-downs are necessary to prevent vibration.
Saber Saws
Portable saber saws may also be used for making either straight or
curved cuts in Plexiglas
®
acrylic sheet. When using this type saw,
however, it is necessary to provide adequate support for the Plexiglas
®
acrylic sheet, since the vibration caused by the reciprocating action
of the saw blade may chip or crack the sheet. Chisel-type sabre
saws should be adjusted so that the cutting chisel stroke is about
3
⁄
16 inches greater than the thickness of the work to be cut. Two
thicknesses of corrugated fiberboard should be placed on the
working surface under the Plexiglas
®
acrylic sheet. The stroke of
the chisel should clear the upper surface of the sheet by about
1
⁄
16 inch and penetrate into the corrugated fiberboard about
1
⁄
8 inch,
thus driving the plastic chips into the board. The blade should be
the same type used for scroll saws.
Veneer Saws
Veneer saws are small circular saws mounted on arbors and
powered by high-speed electric or air motors. They are available
as stationary or portable models. The saw blades are made in
3-inch and 4-inch diameters with several teeth per inch and have
considerable set. They should be driven at 10,000 to 15,000 rpm
to give a surface speed of 8,000 to 15,000 feet per minute. Veneer
saws cannot be easily guarded and must be used with great
care. Carbide-tipped blades should not be used unless designated
for high-speed operations.
Portable veneer saws are most often used to trim large formed
parts of Plexiglas
®
acrylic sheet held in trimming fixtures. (See
Machining Plexiglas
®
Acrylic Sheet, page 11.) Stationary veneer
saws can be used in woodworking shapers or routers for trimming
the flanges of compound formed parts when the flange is on one
plane. The height of the saw is adjusted to the proper distance
above the table and the work is moved past the revolving blade.
Hole Saws
A hole saw is a tubular tool with teeth filed on the lower edge
of the tube. The teeth are set to cut a groove wider than the
thickness of the tool wall. A shaft is fastened to the top of the
tube so that it can be mounted in a drill press to drive the saw.
Usually a pilot drill and guide are provided to locate and center the
hole saw. Knockout holes are located in the top of the saw to allow
removal of the discs. Hole saws are stocked in sizes from
5
⁄
16-inch
to 4-inch diameters. Large-diameter hole saws may be made by
inserting a piece of band saw blade in a groove machined in a
steel disc and holding it with set screws. Coarse-tooth saws
should be used for cutting Plexiglas
®
acrylic sheet.
The Plexiglas
®
acrylic sheet should be cut halfway through, turned
over, and the finishing cut made from the other side. When cutting
sheet greater than 0.236 inches thick, a detergent/water lubricant
and coolant should be used. A saw-cut hole is typically rough and
often melted, requiring a post-finishing operation. Better quality
holes can be achieved by machining with a router or circle cutter.