Mowing why does a rotary mower have only 2 cutting edges?

[washita]

came across a ford push mower at a garage sale it had a x style mowing blade 4 cutting edges per revolution why do most lawnmowers only have 2 cuttting edges? is it a hp issue? cost issue? not effective? rough calculation on my push mower is 1135 mile per hour tip speed, I am just curious if any one knows why ?

 

[KentT]

came across a ford push mower at a garage sale it had a x style mowing blade 4 cutting edges per revolution why do most lawnmowers only have 2 cuttting edges? is it a hp issue? cost issue? not effective? rough calculation on my push mower is 1135 mile per hour tip speed, I am just curious if any one knows why ?

It requires more power to spin it... that's the only real reason.

I have a double-blade for my Snapper Commercial 21 trim mower. I think they called it a "Ninja" blade -- it's just for mulching. Likr you say, it's more of an X than a + since the cutting edges are about 30-45 degrees from each other, instead of 90 degrees. The idea behind those was that the first blade cut it, and the second chopped the clipping into pieces. That was before the decks were designed to create a vortex underneath them that would keep the clippings up in the air long enough for the blades to chop them repeatedly.

I've also seen aftermarket kits that would mount a second blade at 90 degrees to your original blade.

 

[MossRoad]

I wonder if it is harder to balance a 4 bladed blade VS a 2 bladed blade?

 

[J_J]

I have tried two blades at 90 degrees on my Dixie Chopper, and it did put an extra load on the engine. I have also tried putting edger blades with the single blade. Not much advantage. Someone also makes a disk with 4 small blades to retrofit on mowers. I have one somewhere in my stuff.

 

[BAGTIC]

Whyaren't mower blades sharpened on both edges so that when the becone dull they can be turned over and the other edge used for a while, like planer blades? Easy. The blade manufacturers would only sell half as many blades.

 

[Willl]

Why aren't mower blades sharpened on both edges

Is not the other edge turned up to act like a 'lift/suck' function ?

 

[ToolcatWonka5610]

Is not the other edge turned up to act like a 'lift/suck' function ?

I think thats why mowers don't have both edges sharpened.
If the edge wasn't turned up, I don't think the blades would get much lift.

 

[MossRoad]

To make the blades reversible the trailing edge would have to be shaped exactly like the leading edge. The leading edge is designed to cut flat, going under the cut off piece. The trailing edge is designed to lift the cut piece up higher. If the trailing edge was shaped the same as the leading edge, it would have very little lift and the clippings wouldn't be suspended in the air long enough to get chopped up more or blown out well.

That's my take on it.

 

[MossRoad]

Whyaren't mower blades sharpened on both edges so that when the becone dull they can be turned over and the other edge used for a while, like planer blades? Easy. The blade manufacturers would only sell half as many blades.

One more thing... I have two sets of blades. As soon as I change one I sharpen it, wipe it down with oil and put it in a bag for the next time I need it (which is about every 3-4 years!). It takes the same amount of time to switch blades as it does to change them. Put them on your wish list and the next time you order filters, etc... from PT add them to it to get your $50.00 minimum. Or, find some at a local lawn mower shop.

I've been tempted to find some high lift blades and converting my 60" rear-discharge deck to a mulching deck. I'm fairly happy with the current design, however in thick grass I get a windrow out the right side. I can eliminate it by going clockwise around the yard, but I like to "stripe" my lawn and cannot do that with the windrow.

 

[ToolcatWonka5610]

Someone also makes a disk with 4 small blades to retrofit on mowers

I know Lawnboy has them or used to have them on their walk-behinds.
Is that who your thinking of, JJ?