“In our opinion, backlapping should be banned as the carborundum paste is environmentally unsound”
is to keep that zero contact at all times and also to keep a superior quality cut. Relief has nothing to do with cutting grass. It is all about making the mower work easier when running contact. We have found that sharpness of the
reel has nothing to do with relief whatsoever. Sharpening reels need only take place when the quality of cut deteriorates.
The true answer to relief is to keep a good sharp edge on the bed-knife and never allow the reel and bed-knife to touch - 100% relief.
So how does your reel mower really work?
Is it a Scissor? As a scissor, the cutting unit will be set-up with contact between the reel and the bed-knife.
This is how the mower unit will be set if you backlap at any time during the cutting season, because, once you have back lapped, you will have made the blade surfaces match each other by rubbing them together with a carborundum lapping paste. The blades will then only work as a scissor, which
requires reel and bed-knife contact. The lapping process will not have sharpened the bed-knife’s front edge, so you have not improved the quality of cut, you will have just smoothed out the action of the reel blade and bed-knife working in contact, which will show a temporary improvement in cut. Have you noticed that lapping becomes more frequent in order to keep a barely acceptable quality of cut? With a scissor cut, grass blades are torn off when they are trapped between the reel and bed-knife. As you can easily see with a magnifying glass (or macroscope), the torn edges of cut grass blades look ragged and suffer agronomically from this tearing action. In fact, bearding of grass underneath the bed-knife, or a build up of grass resins on the face edge of reel blades, are visual symptoms of this tearing and bruising action. This is a scissor cut.
A few facts about backlapping
Whenever you see evidence of sand wear grooves on the reel blades, there will always be opposite and matching grooves
on the top face of the bed-knife. After back-lapping, take a magnifying glass and you will be able to see similar, but finer grooves on the reel blades, your bed-knife top face will be the same. No sharpening has taken place, you have only matched the faces of the reel and bed-knife together, the blades will now only cut when set in contact. You should understand that
backlapping paste is just a finer form of sand.
Understand, therefore, that it is absolutely essential to continually relief grind (blade thin) the reel blades, by at least 75% of their thickness, if you are going to continue to backlap and run contact, thereafter setting up as a scissor. It is the only way this lapped mower will work without major stress to the transmission, reel bearings and power unit.
In our opinion, backlapping should be banned as the carborundum paste is environmentally unsound. In addition, backlapping damages your mowers in several ways including, most notably, it
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