Electric lawn mower blade replacement issues

[odd_duck99]

All we want to do is replace the broken blade on our electric lawn mower. It sounded simple enough... a month ago.

We braced the blade, but when we turn the bolt the whole blade assembly turns too. (not sure if blade assembly is the right word, but hopefully you know what I mean!) We are having a hard time finding anyone that deals with electric mowers, and are afraid it is going to be expensive.

I know this is not how mowers should behave. Could something be wrong with the thing? The blade broke due to hitting a rock.

 

[Joel_BC]

All we want to do is replace the broken blade on our electric lawn mower. It sounded simple enough... a month ago.

We braced the blade, but when we turn the bolt the whole blade assembly turns too. (not sure if blade assembly is the right word, but hopefully you know what I mean!) We are having a hard time finding anyone that deals with electric mowers, and are afraid it is going to be expensive.

I know this is not how mowers should behave. Could something be wrong with the thing? The blade broke due to hitting a rock.

I once had an electric lawn mower that I converted into a compost shredder. I've always only used gasoline-powered mowers. But I bought the electric mower second-hand, and I mounted it upside-down in a frame I made (& I covered the open bottom of the mower with a shaped baord, so the in-feed had a placement and was safe). But the mower motor burned out. And all this was years ago, and now I've forgotten details of how the blade was mounted.

BUT... If you can take a picture of a bottom view of the mower, and upload it here, I'll try to help you. :/

 

[odd_duck99]

Thank you Joel, I was hoping you would see this! I am worn out tonight, but will try and get you a picture tomorrow!

 

[odd_duck99]

OKAY! Here are the pics of the underside of the mower. We managed to get creative, get the old blade off, and get the new blade on. However, now the "creative solution" won't work thanks to replacing the black disc you see in the pics, and we can't tighten the blade down. We can wobble it with our hands easily.

You can't see much in the pics. Let me know if you need more to work with. Why is bracing the blade not working?!

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[Joel_BC]

Do you think the bolt that holds the blade in place has a common ("right-hand") thread? (IOW, does it tighten by turning it clockwise - as most screws or bolts do?) In my experience, most mowers have a right-hand-thread bolt there.

That's important to know. But beyond that, I believe your picture shows where the grass clippings stream out from under the mower... a sort of a channel or shoot. I believe your best bet - with common tools - would be to jam the blade with a piece of wood. A length of 2x4, 2X2... whatever will fit in through the channel that the clippings come through. Jamming the blade with wood (with most mowers) allows you to immobilize the blade. Then you need to get a socket onto the bolt head, and a long handle attached onto the socket. If it's a right-hand-thread bolt, you then need to torque the socket & bolt counterclockwise to loosen it off.

You may need extra leverage, if what you have for a socket-wrench handle is just a ratchet-type handle. Those often are not very long. People commonly use a piece of thick walled steel pipe as an extender (a "cheater") on the ratchet handle to lenghten it and increase the leverage. A piece maybe 14-18" long. However, depending on your tool kit, you may have a socket handle longer than the average ratchet.

To put the blade back on, of course, you reverse the procedure.

Good luck.

 

[odd_duck99]

Nope. That's what we have been doing. You jam the blade, and the bolt turns... but nothing unscrews. Everything above the blade turns too, and you just keep spinning things around with nothing happening. We have tried doing this both to the left and the right, just in case, but nothing changed. I know that is not supposed to happen, so I am wondering if perhaps something else is broken.

 

[Joel_BC]

Nope. That's what we have been doing. You jam the blade, and the bolt turns... but nothing unscrews. Everything above the blade turns too, and you just keep spinning things around with nothing happening. We have tried doing this both to the left and the right, just in case, but nothing changed. I know that is not supposed to happen, so I am wondering if perhaps something else is broken.

Okay... So the blade is not "locked" onto the shaft and fan assembly above it. See those fan-type fins above the blade? Can you jam something (preferably wood, not metal) in among them, and also onto the mower housing? Can you, in other words, immobilize that "fan" so you can turn the bolt and thereby get the bolt to loosen?

It's hard trying to brainstorm this by photos. I'm doing my best. But if the above suggestion doesn't help, I guess I'm out of ideas. As I tried to convey in my original reply post, I don't have much experience with electric mowers... and no recent experience.

 

[odd_duck99]

We ended up bringing it in to someone with the appropriate tools and knowledge. Even they had a bit of a struggle with it! However, it is now fixed. Thank God. If anything else breaks on any of my lawn equipment it is going in the garbage, and I am buying something of better quality!

 

[katemoore]

There are times that when you use things they break. Downgrading might be the best option than replacing or upgrading things. Well, it might be tempting to upgrade or even replace items that break with something better. It is wise to to think first whether you would like to replace and upgrade or not. There is a less expensive and of course a less difficult option that can be better all around. In fact downgraded items may also run on human power, which can also better for your health. It is said that "Quality is worth the price". If you are a bout to downgrade something such as your lawnmower, it is best if you spend the extra money to get a good-quality steel lawnmower instead of the cheap aluminum one. With a good-quality downgrades, it will always be less expensive in the end than a low-quality upgrade. You must consider the lifetime costs of an item rather than the immediate costs.

 

[OrbitSoldier]

I have been having exactly the same problem -- with the same unit. I can tell from your pictures that it's a Black and Decker MM875. The problem is that tightening the nut spins the whole electric motor and shaft. With a gas-powered mower, the friction between all the gears and valves and such provides enough resistance to allow tightening. To tighten this electric mower, I guess you need an impact wrench. The cheapest ones cost >$150, and it's annoying to take the mower to a repair shop just to use their impact wrench for 30 seconds. So today I had the bright idea to open the mower housing and clamp the shaft above the electric motor to provide the needed resistance, and I broke the outer metal sleeve around the shaft. It was pretty soft metal. The replacement part is cheap, but I still have a dilemma: buy a $150 impact wrench, or figure out a way to immobilize the electric motor shaft without damaging it.

Any ideas?