Finding an impossible blade

[BrianX128 107]

I need a new set of blades for my "Lawn Rov'r" which is proving to be difficult. There are only 3 mowers themselves that I've ever seen in existence online including mine. The blades themselves have a 5/8" center hole, and two outside bolt holes to keep the blade from rotating. Center to center those holes are 3 1/4" and the blades themselves are 12 7/8, maybe they were 13" and have just worn down this much as even if they were 13 there would be no way the blades would be able to hit each other and still wouldn't hit the frame of the deck. These are apparently not something that is made anymore for any deck, so I'm not sure what the best way to go about replacing them was. One is missing a significant chunk and can't be balanced and the other two are getting thin from sharpening over the years. I can find some other blades close to this size, is getting as close as I can and just drilling the outside holes since everything else has them closer to 1 1/2" center to center my only real option here? Thanks for any suggestions. I can post up a picture of the blades in a bit here.

[ranger 1,750]

If you have a local mower shop near you, they may have old blades kicking around you can compare before buying something unseen, which may or not be suitable. I would imagine as long as the blades are similar in length, centre hole size the same, and the pitch, ( angle of cutting portion of blade) is similar, they should work. Put an original blade on top of a new blade with a close fitting bolt or pin in centre hole to locate, then drill the other two holes, (you may need a drill bit for hardened steel, plenty of lubricant, slow speed, and keep the pressure on). Fitting a fresh set of matching blades, as close as you can get to the originals,  must be better than attempting to use the worn/damaged ones and risking destroying the bearings/deck.

Doug.

[rmaynard 15,436]

1 hour ago, BrianX128 said:

I can post up a picture of the blades in a bit here.

Waiting for the pictures. I just opened some boxes of parts that include some old, but usable blades. They appear to be a set of L/R blades that rotate in opposite directions.

[1995 520H+96+97 937]

[BrianX128 107]

 

 

[rmaynard 15,436]

Sorry, mine are not even close. 

[BrianX128 107]

So I've been able to find 2 blades online that might work with modification, but I'm not sure which "modification" will be easier for me to do.

 

These: https://www.lawnmowerpros.com/detail.asp?id=91-244

 

Are 13 7/8 long, I'll likely need to grind off a half a quarter of an inch on both sides roughly to make them not grind against the sides of the deck, and I'll have to drill the two holes outside of the center hole.

 

These: https://www.lawnmowerpros.com/detail.asp?id=91-636

 

Are slightly shorter than my blades which the longest one is 12 3/4, so I have a slight fear they might not "cover" the whole area of the deck, however all I'd have to do is drill the center hole.

 

What do you guys think might be easier? Either way I'm having to drill the two holes off the center, I have a drill press and some good bits I've had to use on hardened steel before, I'll probably ruin a couple to get through the blades but so be it. I'm just not sure how hard it would be to grind off enough of the sides of the blades on the top ones but I'd at least know for sure they would cover the whole bottom of the deck.

 

[ranger 1,750]

3 hours ago, BrianX128 said:

So I've been able to find 2 blades online that might work with modification, but I'm not sure which "modification" will be easier for me to do.

 

These: https://www.lawnmowerpros.com/detail.asp?id=91-244

 

Are 13 7/8 long, I'll likely need to grind off a half a quarter of an inch on both sides roughly to make them not grind against the sides of the deck, and I'll have to drill the two holes outside of the center hole.

 

These: https://www.lawnmowerpros.com/detail.asp?id=91-636

 

Are slightly shorter than my blades which the longest one is 12 3/4, so I have a slight fear they might not "cover" the whole area of the deck, however all I'd have to do is drill the center hole.

 

What do you guys think might be easier? Either way I'm having to drill the two holes off the center, I have a drill press and some good bits I've had to use on hardened steel before, I'll probably ruin a couple to get through the blades but so be it. I'm just not sure how hard it would be to grind off enough of the sides of the blades on the top ones but I'd at least know for sure they would cover the whole bottom of the deck.

 

If you have an angle grinder, fit a thin cutting disc and it’ll only take a minute or so to cut the excess off each end. Then switch to a grinding disc to finish and balance. As for drilling the holes, you say you have a drill press, use the slowest speed, form a small ‘Well’ From putty, or anything similar, fill with oil and keep the pressure on the drill bit. Don’t allow it to ‘Skid’ with low down pressure, that will blunt the drill in seconds, and probably ‘Work’ harden the blade in the spot where you’re drilling, making it even more hard.

[BrianX128 107]

Blades are finally in. Drill press none too happy about going through them - well the bit wasn't happy I should say. Slow and oil didn't matter much by the time I got to the third blade I had dulled the tip of the bit. So much for the fancy diamond tipped stuff Lowes had, not that they were crazy expensive either. Had to use a smaller bit on the third blade and then go back through with the correct size but they're all drilled. 

 

 

Going to cut 3/16 off both sides of the blades tonight and it looks like that will be enough to clear the other blades hitting or blades hitting anything under the deck.

 

Is there a special distance blades are to be away from the edges of mower decks normally for the grass to "stand up" as your mowing for the blades to cut into? I'm only going to have about 3/16 between the end of the blades and the deck itself.

[Handy Don 12,214]

Working hardened/tempered steel is always tough on tooling. I keep a set of cobalt bits I pull out only for hard metals. Lots of oil and short presses to avoid building up heat in the bit or the workpiece.

A bandsaw with a suitable blade may help on the blade tip cutoffs. I've been delighted with the utility of the Milwaukee M12 handheld bandsaw gifted to me at Christmas.

It may be worth your time (and tool wear and tear) to see if you have a welding or machine shop nearby that will cut the ends for you at a fair price. 

Edited February 22, 2022 by Handy Don

[BrianX128 107]

I got them done, my air fed cut off wheel actually went through them ok. The wheel isn't the same diameter it used to be by any means, but I have plenty more. Everything fits and works good.

 

[Handy Don 12,214]

1 hour ago, BrianX128 said:

I got them done, my air fed cut off wheel actually went through them ok. The wheel isn't the same diameter it used to be by any means, but I have plenty more. Everything fits and works good.

 

Are the ends of the blades showing heat marks or is it the angle and shadow?

[BrianX128 107]

47 minutes ago, Handy Don said:

Are the ends of the blades showing heat marks or is it the angle and shadow?

 

Just angle and shadow, there is a light over the work bench to the left. 

 

My only concern is I may have left the blades a little close to each other. There is only at most 1/4 of an inch between the blades if they line up square at each other but the deck doesn't flex at all and the spindles are tight so I think it will be fine. I fired it up and drove around with the deck on before we started getting all this rain and it seemed good. Deck is way less noisy with the 1 bearing repaired and a new grease fitting. Seems to have a lot more force throwing out of the deck as well, old blades were pretty flat and didn't have much "lift".

[Handy Don 12,214]

1 hour ago, BrianX128 said:

My only concern is I may have left the blades a little close to each other.

I was surprised when I overhauled my 42" deck how close together the blades came to each other. On the early 2-blade gear-driven decks the blade paths overlapped--hence the "double D" shape to the spindle hole to assure that they stayed 90º apart.