RM48 and AHRM48 mulching blades

[MattA]

OEM mulching blades for the RM48 and AHRM48 deck have been no longer available for several years. Since I've had no luck finding a set, I've been doing some research on modifying a set of blades to fit. Basically I'd have to modify the blade hole to fit the RM series adapter. I've also thought about swapping in a set of Case left hand deck spindles. Moving to a different brand spindle may be possible but I'd like to keep it simple for now. Here is what I've come up with for blades so far:

Standard non-mulching blade Ingersoll C31572 (Oregon 91-117) (Stens 310-366)
Size: Length: 17"
Center Hole: 7/8" H, 1-1/4" W
Width: 2.50"
Thickness: 0.187"
Offset: 1/2"
Air Lift: 1"


Oregon 191-108
17” length
.164” thick
2.5” wide
Center hole 11/16”
Offset ¼”
Air lift 1”
https://www.oregonproducts.com/en/blade ... /p/191-108


Stens 302-438 Silver Streak Toothed Blade
Center hole 13/16"
Length 17"
Thickness 0.203"
Width 2 1/2"
https://www.stens.com/302-438-toothed-blade


Stens 330-719 Stens Hi-Lift Blade (similar to Oregon 191-108)
Center hole 11/16"
Length 17"
Outer Hole 3/8"
Thickness 0.164"
Width 2 1/2"
https://www.stens.com/330-719-hi-lift-blade


Oregon 91-586
17” length
.187” thick
2.5” wide
Center hole 11/16”
Offset 3/16”
Air lift 1 3/8”
https://www.oregonproducts.com/en/mower ... 2/p/91-586


Some blade options are thinner than the stock blades. Some are thicker. I still need to pull a blade off my RM48 deck to see if the thinner blades will work ok.


General blade adapter info:
Blade and adapter info:
https://www.reddogsupplies.com/blogs/ne ... wer-blades
https://www.lawnmowerpros.com/diy/index ... ole-types/


8ten stocks lots of spindles, blades, pulleys ect…
https://8tenparts.com/

[MattA]

Anyone have any opinions on standard mulching blades vs gator mulching blades?

I'm thinking of ordering Oregon 191-108 and modifying them to fit.

[DavidBarkey]

Anyone have any opinions on standard mulching blades vs gator mulching blades?

I'm thinking of ordering Oregon 191-108 and modifying them to fit.

I live in a very sandy area . Gator don't seam to stand up as well in sandy areas . Heavier soil areas they seam to do fine . The sand seams to ware the lift fins off quicker than standard .

Dave

[Timj]

I have not tried any of the mulching style blades. I have 3 good sets of old OEM blades I alternate through. I have the same issue of sand cutting the lift fins off. Though it has gotten much better here as the quality of the lawn has greatly improved.
Been curious about the mulching blades as I usually blow the cuttings inward, recutting them and essentially mulching the grass. I attribute a lot of the improvement in the lawn to this. I don't fertilize.
Tim

[MattA]

I measured one of my RM48 blade drive adapters and the blade drive portion is 0.183" to 0.185" tall. The blade is 0.187" thick. Adding the dust cups reduced the drive portion's height to 0.118". The Oregon 191-108 blades I ordered this morning are 0.164" thick and should work just fine.

[Timj]

@MattA we'll be waiting for the full report. or

[MattA]

The Oregon 191-108 blades arrived today. First thing I noticed is the blades are fully sharpened on the leading and trailing edges.The trailing edge might help with the 1.5db noise reduction Oregon claims???

Would be nice if the RM38, RM44 & RM48 decks still used the older Case style spindle shafts. All I would have to do is drill out the center hole and drill the two bolt holes and I'd be done. I'll get to work on marking up the blades and creating the new blade adapter hole soon.

[MattA]

I tried drilling out the blade center hole on a small drill press at work. The blades appear to be hardened steel and I wasn't able to make much progress I'm also not able to hold the blades in a vice very well due to both sides being sharpened

I did come across some cool blade adapters called X-Blades. Basically its a blade adapter that allows you to mount a second blade at 90° to the first blade on the same spindle. Seems to be for commercial use only... I'm not sure my 16HP vanguard engine would do very well running a 48" mowing deck with 6 blades.

[Eugen]

I tried drilling out the blade center hole on a small drill press at work. The blades appear to be hardened steel and I wasn't able to make much progress

Matt, I don't know if there's value in having hardened steel in the middle where you want to drill the hole. That is, assuming that you want the hole in the middle. A trick to soften the steel is to get it cherry red with a torch and let it cool down slowly, naturally in the air. Depending on the area you want, this can be done without an oxy-acetylene setup. Map gas or even propane with a turbotorch and enclosing the heating area among some bricks can achieve that. I know because I did it.

I haven't followed this discussion in detail but if the hole needs to be near the tip(s) then you don't want to soften the steel near the cutting edge.

I don't recall where I heard that many current blades are only hardened along the cutting edge.

[Spike188]

@MattA increasing the hole size would be fairly staight forward on an EDM.(Electrical Discharge Machining) if you can find one with a large enough bed to hold the blades.

These will easily cut hardened steel to 0.001" tolerance.

I repaired an EDM last week. Just another reason the 646BH isn't finished.

Spike