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

Posted by on June 30, 2009, 10:32 pm

On Mon, 29 Jun 2009 12:45:29 -0400, tnom@mucks.net wrote:

>wrote:

>>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.

>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.

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???

Posted by on July 1, 2009, 12:45 am

On Tue, 30 Jun 2009 22:32:13 -0400, clare@snyder.on.ca wrote:

>On Mon, 29 Jun 2009 12:45:29 -0400, tnom@mucks.net wrote:

>>wrote:

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

>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.

I take it the flat part of the "D's" mate with the flat on the shaft.
If this is so then this set up would more accurately be described
as a cheap design.

>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.

The motor shaft on the MM525 has at least one flat machined into the
motor shaft that a wrench can secure.

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

The picture of the armature does appear to have left hand threads.

Posted by mm on July 1, 2009, 5:41 pm

On Wed, 01 Jul 2009 00:45:18 -0400, tnom@mucks.net wrote:

>On Tue, 30 Jun 2009 22:32:13 -0400, clare@snyder.on.ca wrote:

>>On Mon, 29 Jun 2009 12:45:29 -0400, tnom@mucks.net wrote:

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

Thanks for all the help.

Well, I got it off by putting a little liquid wrench type stuff on it,
putting on a 3/4" end wrench and hitting the wrench with a hammer 10
to 20 times. The shaft just turned with the wrench, but it must have
done something, because the last time I hit it, the wrench turned more
than the shaft. After that the whole job was quick and easy.

>>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.

I was trying to write a post last night to explain this, but I got
stymied and didn't finish it. You do a pretty good job and I may not
bother to finish it. (Although in this case one piece of bread of
the sandwich is the fan, and only one washer, the one at the end has a
D hole (in this case, with flats on two opposite sides) and it has two
slip clutches, between the metal washer I desribe and a plastic washer
of the same size, and between the plastic washer and the blade.

The washers are square and the plastic one has ridges on each side,
two pointing to the blade and two pointing towards the drive washer,
the one with the double-D hole.

The ridges break off when something hard is hit. But the mower still
worked fine. The problme in my case was that the fan also broke,
maybe in the same incident, and the whole thingg was no longer
balanced. I figured the bearings wouldn't last as long with the
imbalance, and it might be more tiring to use the mower, and the fan
wasn't as effective with 3 out of 8 blades missing. (Indded on the
fan is embossed, Don't run mower without fan, so maybe it helps in
cooling. There were some ventilation holes just above it come to
think of it.

>I take it the flat part of the "D's" mate with the flat on the shaft.
>If this is so then this set up would more accurately be described
>as a cheap design.

What would be better? How much better and how much would it add to
the price of the mower, and the weight?

All the B&Decker use the style I have and the Sears look like they're
made by B&D and I haven't seen electric mowers from any other company.

>>Usually not worth replacing a blade on them either.

Well, a blade acan be sharpened and even if a chunk of blade is
missing, the other end can be ground to balance the blade, But if the
blade is ruined, it sure seems worth replacing the blade to me. A
blade costs xxxx and a mower like mine** costs about 220 dollars plus
tax.

**(the newer model which is the same except for the height adjustment)

>>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.

>The motor shaft on the MM525 has at least one flat machined into the
>motor shaft that a wrench can secure.

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

>The picture of the armature does appear to have left hand threads.

I asked about getting the blade off when I was buying the part, and
the counter girl asked the guy in the back and sh said nothing about
that. And the manual, which is online, would also have mentioned it.

And it is right-handed.

Posted by on July 7, 2009, 1:52 am

According to the manual wedge a piece of 2x4 by placing one end in the
shoot opening in the deck. Then it is easy - I've done it.

Posted by mm on July 10, 2009, 12:12 am

On Tue, 07 Jul 2009 01:52:45 -0400, NoSpam@aol.com wrote:

>According to the manual wedge a piece of 2x4 by placing one end in the
>shoot opening in the deck. Then it is easy - I've done it.

I already tried that. It didn't work. You may have done it but not
all mowers are the same.

You came in late and didn't read the whole thread.

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