Ask The Doctor
pros who know
Edge Crack Repair: Tools to Use
by Richard Campfield
Editor’s Note: The following is the second part in a series that began
on page 24 of the November/December issue of AGRR™ magazine.
Why should you repair cracks? Because your biggest competitor doesn’t.
In the first part of this article, we discussed the four stresses in the
windshield that the resins have to handle.
Following are descriptions of the tools needed to do a proper, fast and
easy repair and their functions. With the proper tools an edge crack repair
can be done in just 20 minutes. The consumer saves money and the profit
on a crack repair is about the same as a replacement. Here are the tools
Drill – The point must be drilled and a bullseye tapped or the
point will not hold.
Bullseye Tapper – Drilling and tapping a bullseye terminates the
crack into a cone-shaped hole, which you then fill with resin and cure
properly. This stops the crack permanently both mechanically (by tapping
and drilling the bullseye) and chemically (by filling with resin).
Suction Cups – The suction cups you utilize must be of proper durometer
and diameter or the crack will spread while being repaired. Pressure comes
from the suction cups and the control or lack of control is determined
by the suction cup(s). Suction cups that are too stiff and too large will
spread the damage.
Threaded Injector(s) – These must be equipped with a vacuum for the point
and must be able to hold at least 12 drops of resin. The average crack
uses 20 drops of resin. Finely threaded injectors also provide more control
of resin injection and do not spill or waste resin.
Tool Structure at the point – This is a chip repair tool with
an injector at the end so it can be placed close to the second tool.
Crack Repair Structure – You must be able to slide smoothly along
the crack and have no direct mechanical pressure over or on the crack
so as not to push the crack closed.
Crack Opener(s) – Size matters with a crack opener and the wrong
suction cups will spread damage. Size gives you leverage and a mechanical
advantage. The crack opener must open the crack symmetrically and the
suction cups are the key to doing this. Use longer (8-10 inches) crack
openers whenever possible, and shorter ones (5-6 inches) for cracks off
the bottom near the dashboard, because the longer ones will not fit. Also,
using multiple crack openers for tight cracks is easier than sliding just
Curing Light – Sixty percent of the repairable crack market is
comprised of cracks between 7 and 14 inches. A longer light is important,
as it saves time and eliminates multiple cures.
In conclusion, length should not be the determining factor for whether
a crack can be repaired. Rather, contamination is what should be considered—and
almost all cracks less than 14 inches in length have not been contaminated,
that is why the Repair of Laminated Auto Glass Standard (ROLAGS) encompasses
cracks 14 inches or less in length.
Richard Campfield is the founder and president of Ultra Bond Inc.
in Grand Junction, Colo. Mr. Campfield’s opinions are solely his own and
not necessarily those of this magazine.
© Copyright 2011 Key Communications Inc. All rights reserved.
No reproduction of any type without expressed written permission.