Hello my name's Austin Jarrett from Allett Mowers. Today I want to talk to you about back-lapping of
cylinder mowers. The Allett homeowner range of mowers have interchangeable cartridges so that
is the Classic, the Sandringham and the Kensington range all have cartridges like this which can be
removed from the mower and that's really useful from a maintenance point of view. Now a cylinder
mower cuts grass by cutting between two metal surfaces; we have the bottom blade and then
we have the blades on the cylinder and sometimes due to damage or through to wear the grass plant
eroding the metal away over time you'll find that the mower doesn't cut quite as sharply as you
would like and one way of doing this in season when you haven't got time to get the cylinder
ground properly by one of our service dealers you can use a technique called back lapping. This is
a cylinder out of a 17 inch mower and when I do the paper test I've just got folded double paper
here and when I go to cut this I'm cutting quite cleanly in the middle but I think no matter how
I just this mower I can't quite get it to cut the paper cleanly on this side and here I am getting
some sort of cut but it's not as good as it is in the middle so what I want to do is as the cylinder
turns in this direction I need to put a sharp edge on both the leading edge of the cylinder and also
the top edge of the bottom blade. The things I'm going to need to do the back lapping are;
an electric drill with a reverse drive, a short extension (half inch) and a 24 millimetre socket.
This 24 millimetre socket fits very neatly onto the sprocket at the end just here. I'll need a
screwdriver because I will need to adjust the cylinder as I'm applying the grinding paste.
I'll need a longest handle brush that I can get this is an inch and a half brush which
is just absolutely ideal and I'm going to use this to apply the grinding paste. I need the
grinding paste and this is quite a large tub you don't need to have anything quite as big
as this we're not going to use anywhere near this amount of material I'm just going to use
this on my brush and I'm going to apply this to the cylinder. I'm going to be turning the
cylinder in reverse and that way the trailing edge of the blade combined with the grinding
paste will put a sharper edge onto the onto the edges that I need so that I'm going to cut my
grass cleanly. You also need a hose pipe because before this grinding paste dries it's like a gel
almost at the moment before it dries I'll need to have a hose pipe just to wash that grinding paste
off. If I don't do that then when I'm using the mower it will continue to grind the blades and I
don't want it to do that. So make sure you've got your electric drill in reverse drive so I
want to turn the cylinder so that it turns in this direction so the blades are coming away
from the bottom blade. So I'll just double-check that and that's the direction. I need to turn
it slowly and of course you do need to be really really careful this is not something you want to
do with kids around. I'm going to take the back lapping paste just put a small amount onto the
brush and then what I'm gonna do is I'm just going to brush this on apply this and you'll
hear the change in the sound as the grinding paste starts to work between the two surfaces
So I feel like the grinding paste now is starting to shine up the surfaces and I can see where it's
having an effect right on the very edges. I now need to start adjusting my cylinder down
to my bottom blade so that's where I need to have the screwdriver and all I'm going to do is just
apply a click at a time to tighten the cylinder down to the bottom blade and so it will start to
apply more pressure between the grinding paste and the two surfaces and then I'll carry on again. So
this is about the last turn, I've done about three turns on this three notches on the adjustment for
the cylinder to the bottom blade and so this is my final one now I can feel I'll take that off I can
feel my edge here is now getting sharper squarer it doesn't become sharp like a knife remember
it's a guillotine type cut and this final one I'm going to do I'm just going to paste the material
on until I start off quite noisy as it's grinding more material off and then it gets quieter and
quieter and then once I've done that I'm going to wash off all the grinding paste with the hose and
then we'll give it the paper test again so here we go with the last step the last adjustments.
So now I'm happy that those surfaces are nice and square and ground and fresh so
now I need to wash off all the grinding paste so I've got my hose here and I'm
gonna hose that off as best as I can I'm probably going to just spin that
cylinder as well just to make sure all the materials off all the way around.
So now I've washed off all the material I need to just double-check the edges are all looking
beautiful and sharp here. I don't want to take off too much material remember because all I'm doing
is just wearing my blades out but I just need to take off enough and just put an edge back on. So
I now need to double check if you remember it was cutting beautifully in the centre which it still
is and then it's cutting at that side now much more cleanly that it was and then if you remember
this side it wasn't cutting at all but he's now cutting really nicely .So I haven't got a lot of
contact on that cylinder so it's going to be nice and quiet again and something that you tend to do
is the blades get more blunt as you tend to adjust the cylinder to the bottom blade that causes a lot
more noise more strain on either the engine or the battery system that's driving it so it's really
good to keep these cylinders blades nice and sharp cutting the grass nice and cleanly and the
grass won't bleed as much so it will be much more healthy as well. So there I am I can put this back
in the back in the cylinder mower again and and get mowing so you can put a nice sharp edge back
on with back lapping you probably won't be able to correct a stone damage in the machine but you know
sometimes it's worth giving it a try but if it is really serious you will need to take this to your
Allett mower dealer who will need to do a much more serious regrind and maybe even replace the
bottom blade for you and that that's something you would do after probably several seasons depending
on how much grass you're cutting you need to go and have a proper regrind and put the the cylinder
and the bottom blade cutting surfaces right. So I hope that's been helpful I'm going to go
and get mowing the lawn now with my nice sharp cylinder and I hope that's been helpful you can
always find more information on our website at www.allett.co.uk. Thanks for watching.