[SOLVED] B&D lawnmower. How to remove blade from electric lawnmower?

[mm]

Black & Decker lawnmower. How to remove blade from electric lawnmower? Model MM525 which is very much like the MM575.

Is there a simple, or complicated, way to keep the motor shaft from turning, when trying to loosen the nut on the end of the shaft?

I have to remove the blade to replace the fan and the manual says to use a 2x4 to keep the blade from turning. I do keep the blade from turning, but the nut and shaft turn together anyhow, so there is no unscrewing.

I figured if I broke the plastic fan off, I might have enough room for vise-grips. Do you think they could nick, whatever, the shaft enough to unbalance it?

(FTI, a third of the plastic fan was broken off so I tried to knock off the rest with a hammer. It cracked easily and fell off in suceessive pieces. Unfortunatately, that was stupid because I also cracked the blade spacer, a cast metal piece, that now I have to replace. :( 3 dollars and a trip to the store, 10 miles away. Fortunately I have to drive by there next week anyhow.)

Thanks a lot.

[Jon Danniken]

Yes, with an Impact wrench; you'll have that nut in your hand faster than you can say, "wow, that's pretty cool".

Jon

[mm]

Thanks for replying.

Do you mean the impact wrench one hits with a hammer**, or the kind that usually uses compressed air, but comes in electric also?

**I have a manual impact wrench and I did think of it, but I figure it might put too much longitudinal force on the bearings, and I wasn't sure there was enough mass in the shaft and armature for it to work anyhow.

[Big Bob]

Make sure that they do not use reverse threads or you will be tightening instead of loosening

[Jon Danniken]

Aye, sorry, not the manual one (I have one of those too). You can get the pneumatic kind that requires a compressor, which are the most common, but they also sell electric ones.

If you don't have a compressor, I have heard that the electric ones from harbor freight do an acceptable job.

Jon

[Rudy]

Wedge a piece of 2 by 4 or such against the blade/deck housing so it can't turn.

Undo the nut with a socket wrench

[William Munny]

When all else fails, RTFM or call the mfg.

[tim birr]

Not sure of the problem. I have a similiar model....or used to ...the CM1000...you used the wood to jam the blade and you just "unscrewed it." It was pretty simple. If you are having problems, there may be more wrong than something simple, because it is really pretty simple. Wear gloves though when doing this.

[mm]

Thahks again.

Yeah, I see they have a 12 volt Harbor Freight model for 25 dollars. It says it has 150 foot pounds with a good battery, and 30 to 40 blows per minute (BPM).

Then there is for 50 dollars an AC model withe 240 ft.pds and 2400 BPM.

And for 40 dollars an 18 volt battery model, 3/8", 87 foot pound, 1700 BPM

Rudy, Tim, I can't just use a socket wrench because even when I hold the blade still, the nut and the shaft turn.

Thanks Bob and William, the manual said nothing about being left-handed, and based on the direction the blade turns, I don't think it is.

[Don Young]

You can try a short box wrench and small hammer. The inertia of the rotor should enable you to use them as a primitive impact wrench. The type impact driver you strike on the end with a hammer would also likely work with a little patience and skill. Of course, a power impact wrench would be the best.

Don Young

[dpb]

mm wrote: ...

...

The possibility is that sometime you hit something and that impact stretched the bolt (or shaft if it really is a nut on a shaft; that would be unusual for anything but electric but I've not had an electric so perhaps they do).

If that is so, the impact wrench is probably about the only hope. If that is the cause for it being so tight, you're looking at a replacement shaft/bolt/whichever.

Had it happen on one of the blades on the 6-ft belly mower; took a 3/8" pry bar through the upper drive pulley as a backup and that bar simply bent rather than the bolt coming out.

--

[sligoNoSPAMjoe]

I don't recall the model I have (it is battery powered), but I just sharpened the blade for the first time a few days ago. A gloved hand held the blade while a box wrench turned the bolt holding it on. It was threaded normally and did not require an unusual amount of force.

[Stormin Mormon]

Impact wrench is your friend. Often you can rattle loose a bolt that's not responding to steady pressure.

[dpb]

What, precisely, about

"If that is so, the impact wrench is probably about the only hope."

did you fail to comprehend???? :(

[tnom]

If stopping the blade doesn't stop the shaft then what drives the blade?

Something is wrong. Somehow the blade is slotted, flat sided, or some other means of coupling is suppose to take place. Push the blade down onto the shaft while turning the nut.

[Stormin Mormon]

Hmm. Maybe it was the part where blurred togther in a scsrouieorjenrble of letters?

[mm]

The blade is on tight enough that the motor will spin it, and it cuts well. But it's not on tight enough to hold the shaft in place when trying to unscrew the nut on the end.

There was a picture which was about balancing the blade after it is sharpened, and it showed the center hole as round.

I broke a part on Friday, and just got it today, Monday. I'll probably work on it tomorrow and I plan to let you all know tomorrow night, if the thread hasnt' gone up into the wild blue yonder.

I

[tnom]

It may be round but I believe it is splined. Don't damage the spline on the motor shaft by letting the blade spin.

[tnom]

Look at this picture of the armature. Notice the flat spots on the shaft. At the very least attempt to hold the armature on the flats.

[clare]

On many (at least some) cheap electric mowers the blade is sandwiched between 2 big washers. The washers have "D" holes but the hole in the blade is round - makes a "slip clutch" to protect the motor shaft.

Usually not worth replacing a blade on them either.

Some motors have an "allen" end in the shaft - you hold the shaft with an allen wrench and turn the nut - never seen it on a mower, but it's possible.

Also, are you sure it's not a left hand thread???