Installation Guide

18
Polishing Drilled Holes
A properly drilled hole has a smooth semi-matte finish that can
be brought to a high polish. A wood or metal rod approximately
1
⁄
8 inch smaller in diameter than the drilled hole is split to a depth
equal to the depth of the hole plus
1
⁄
2 inch and mounted in a
drill press. If the inner surface of the hole is rough, steel wool or
strips of emery cloth or sandpaper are wound around the rod and
gripped in the slot. When the inner surface is smooth, a good
grade of flannel is wound around the rod and the compounds for
buffing are applied. Poor grades of flannel may throw lint and
require further cleaning.
Polishing Edges
In many installations, the edges of Plexiglas
®
acrylic sheet are
completely hidden in a mounting frame or channel and smooth
edges, free of chips and major irregularities, are entirely satisfactory.
Sometimes good machine-finished edges are used as a decorative
element in the design of a part made of Plexiglas
®
acrylic sheet.
Well-polished edges, however, may be required for household
accessories, jewelry, and other decorative items.
Saw marks can be removed from the edges of Plexiglas
®
acrylic sheet by scraping with a hard steel or Carboloy scraper
square-ground to a straight, smooth edge. After scraping, the
edges should be sanded on a wet belt sander with 320 grit then
400 grit sandpaper.
A fast method to polish Plexiglas
®
acrylic sheet is to make buffs
of layers of medium density 100 percent wool felt about
3
⁄
16 to
1
⁄
4
inch thick. The felt should have a specific gravity of about 0.27.
The wheels should be 10 to 12 inches in diameter and should be
held between hard faceplates about three inches smaller in
diameter than the buff. The wheels should be run at a speed
of 3,000-4,500 SFPM.
The edges are buffed on a felt wheel charged with abrasive
and tallow. The final polish is given to the edges with a soft cotton
buff. Felt wheels should not be used on large flat areas since
there is a tendency to burn and distort the sheet.
Whenever possible, a number of Plexiglas
®
acrylic sheet parts
should be locked together in a jig leaving only the edges
exposed, so that the edges may be planed, sanded, and polished
simultaneously. This technique is faster and gives better results
without rounding the edges. Lapidary wheels surfaced with
high-density felt may also be used for polishing flat surfaces.
To prevent heat buildup, the sheet may be buffed with a paste
or liquid wax with an abrasive.
Flame Polishing
Flame polishing is a fast, economical method of edge polishing
that is preferred by some fabricators, but it cannot be fully
recommended for use on Plexiglas
®
acrylic sheet, because of its
tendency to cause crazing – which is often not apparent until
sometime after the article has left the fabricator’s shop. This
technique is never recommended if other fabrication steps, such as
cementing, forming or painting, are planned after the polishing step.
Contact Altuglas International if additional information is needed.