Ninja blade better?

12 years ago

Hello

This past Summer I bought a Snapper RE100 to make the mowing job easier on my old legs. The machine came equipped with a straight cutting blade. I found that I can not use it to mulch either grass cuttings or dead leaves without having to use the deflector. I've always mulched grass/leaves with every walk mower I've used and never needed to use a deflector. Material was just cut/re-cut and deposited on the ground. Having to use the deflector with the Snapper makes the job so much harder/longer having to deal with material blown away. I'm wondering if the Snapper Ninja blade will do the job better so that I don't have to use the deflector?
I use the machine is at it's highest cut, highest RPM and fastest speed (when room permits).
Thought I'd ask here before I spent any money on a Ninja blade.
Thanks
Dave

Featured Answer

mownie

12 years ago

The cute photo illustrates what happens to the end of each stem of grass when a dull blade is used to tear off the grass instead of "cutting" it.
The term "CUT" is something of a misnomer in itself (as applied to trimming a lawn).
If you could manufacture a mowing blade out of some otherworldly indestructible material that would never lose a razor sharp cutting edge...........that razor sharp edge would produce a near perfect cut.
But since all we have to work with is mere steel, a compromise must be reached.
So, the best profile for a typical mower blade is to provide a narrow, flat impact edge on the blade so that the edge can tolerate a longer period of use before it begins to "round over".
A mower blade does not actually CUT the grass like a razor.
Instead it is the high velocity at which the mower blade strikes the stem of grass, folding the grass stem over the leading edge of the mower blade in much the same fashion as you would crease a sheet of paper before tearing it in half.
Without creasing the sheet of paper, the paper will tear in an unpredictable and ragged manner.
The crease establishes a parting line.
The square edge of a mowing blade (and it is really the bottom edge that does the work) effectively "creases" a parting line on individual grass stems upon impact.
Then, the end portion of the grass stem is "broken off" because it folded over the mowing blade edge and cannot unfold quickly enough to slide off of the flat edge, so it is broken off cleanly and crisply at the sharp parting line established by the 90 degree angle on the bottom of the mower blade edge.
.030" is approximately 1/32". A squared edge of 1/32" to 1/16" wide is the range of effectiveness.
Anything narrower will round over quickly, anything wider is nearly the same as being rounded over right from the start.

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Comments (14)

twelvegauge
12 years ago
Hurt the OP's feelings, so post removed.

This post was edited by twelvegauge on Wed, Dec 25, 13 at 21:38
davestexas
Original Author
12 years ago
Not a helpful response. Don't need lecture on use of machines. Post was about Ninja blade.
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farmerdill
12 years ago
I have a Snapper Ninja. Does a good job of mulching if grass is not too high. Will windrow high grass. Never used a straight blade on it. Standard side discharge.
davestexas
Original Author
12 years ago
Thanks farmerdill for the help. What I'm hoping to accomplish is mulching grass and now dead leaves with the mulch-cover closed. My lawnmower has a mulching blade and I've never even taken the side-discharge chute off the shelf where I put it about 10yrs ago. I really expected this high-dollar Snapper rider to at least match my 10yr old 21" Yardman walk-behind lawnmower in mulching ability. Hopefully the Ninja blade will do the trick and I can keep the mulch cover closed.
I appreciate your response, thanks.
davestexas
Original Author
12 years ago
I've got a Gator blade on the way. From reviews I've read, it should do a better job on dead leaves. When grass starts growing again I may try a Ninja if the Gator doesn't do a good enough job. Thanks
davestexas
Original Author
12 years ago
Rec'd Gator blade Monday and installed it yesterday. Big difference from the straight OEM blade. I did not sharpen the new Gator. I looked for some info on that subject, but what I found was a 50-50 split on yes or no about sharpening.
I installed it as it came. The OE Snapper blade was definitely sharpened from the factory.
From the few short passes I made, it does the job and I was able to lower the deck 2 notches and keep the mulch door closed. Keeping the mulch door closed is exactly what I wanted, especially for dead-leaves. Grass cutting won't be happening here for about 3mths tho.
rcbe
12 years ago
best blade sharpening I ever heard from design engineers/blade suppliers was to keep about a 1/32 "flat" at the sharpened edge - supposedly limits fracturing/chips... but, many also swear best to get a knife edge.
Me, I'll stick with the former. Those people did a lot of testing to develop related specs for mfg such.
davestexas
Original Author
12 years ago
I meant to post this response I rec'd from the manufacturer:

"The Gator blade you purchased, and this may be hard to understand, IS sharpened at the factory although it may appear dull. Allow me to explainÃ¢ÂÂ¦ Our blades are sharpened to what we refer to as a 30 - 30 grind. The angle of the grind is 30 degrees while the edge has a .030 radius on it. The reason it doesnÃ¢ÂÂt appear sharp is that through our testing, we found that the typical Ã¢ÂÂrazor sharpÃ¢ÂÂ edge is quickly subject to nicks and dings almost immediately upon use. Also the razor edge has a tendency to Ã¢ÂÂrollÃ¢ÂÂ over as well. We found that the .030 radius provides an excellent cut, and stays sharper for a longer period of time"
wheely_boy zala
12 years ago
{{gwi:345045}}
davestexas
Original Author
12 years ago
wheely boy: cute photo. why post it?
davestexas
Original Author
12 years ago
mownie:

Help me understand: are you disputing the reply message received from the manufacturer of the Gator blade about sharpening a new Gator prior to installation? The Gator blade I installed is a rotary type blade. Your follow-up seems to be about a reel-mower blade?
Thanks
mownie
12 years ago
To the point: I am not disputing anything about the reply message you received from manufacturer.
If anything, my dissertation is a wholehearted agreement of the message you posted.
Reel type mowers do not depend on high velocity to break off the grass stems as rotary mowers do.
Reel type mowers cut by "shearing" the grass stems between 2 metal surfaces much the same way a scissors uses 2 metal surfaces to shear a sheet of paper. This type of cutting is also called "bypass shearing" wherein the 2 metal surfaces closely bypass each other (or actually touch slightly together).
Are you absorbing the point I was trying to make about the high speed impact of the blade edge striking the grass stem and folding the grass over the blade edge profile?
It is the velocity of the blade which makes all this possible in rotary mowers. Without sufficient speed to make the folding process happen almost instantly, very little "cutting" of the grass would take place.
User
12 years ago
Every Gator style mulching blade I've ever seen looked like it needed to be sharpened. In other words, no razor edge as both Mownie and the manufacturer stated.

Every Gator style mulching blade I've used worked great as it came from the package.