Hayter Lawnmower Disc Blade Carrier - how to remove?


D

Davy

I am servicing a Hayter Hayterette mower and need to remove the large metal
disc that the bladelets are attached to so that I can replace them. I
assume I undo the nut in the centre. But how to stop the disc/shaft
turning?
And does anyone know which way the disc rotates in use - I suspect that the
bladelets are on the wrong way round!

cheers

Davy
 
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T

The Natural Philosopher

Davy said:
I am servicing a Hayter Hayterette mower and need to remove the large metal
disc that the bladelets are attached to so that I can replace them. I
assume I undo the nut in the centre. But how to stop the disc/shaft
turning?
And does anyone know which way the disc rotates in use - I suspect that the
bladelets are on the wrong way round!

cheers

Davy
The blades are actually bidirectional

work out which way it rotates by pulling the starter cord
These are total buggers to remove..not sure the central nut is not
reverse threaded? check.

They have a woodruff key and IIRC a tapered crank as well.

Heat may be needed and a scrap bolt in the crankshaft with a large mallet.

I generally grind off the bolts that hold the blades. and leave the disk
in place till its totally buggered, and then cut that off as well.
 
J

John Rumm

Davy said:
I am servicing a Hayter Hayterette mower and need to remove the large metal
disc that the bladelets are attached to so that I can replace them. I
assume I undo the nut in the centre. But how to stop the disc/shaft
turning?
And does anyone know which way the disc rotates in use - I suspect that the
bladelets are on the wrong way round!
You may find the bolt has an anticlockwise thread.
 
B

Bill

I am servicing a Hayter Hayterette mower and need to remove the large metal
disc that the bladelets are attached to so that I can replace them. I
assume I undo the nut in the centre. But how to stop the disc/shaft
turning?
And does anyone know which way the disc rotates in use - I suspect that the
bladelets are on the wrong way round!

cheers

Davy
Any nut securing a blade on a rotating shaft,
that is a saw,a grinder, a lawnmower blade
holder, is designed to tighten up under rotation.
Otherwise they'd be flying off everywhere.
So, think about it, when the blade is rotating
the nut is tightening in the opposite
direction.

So mark the rotation with a chalk arrow on the
blade holder. Lock the blade holder somehow,
clamp it to something.
Turn your spanner in the direction of the arrow
to undo the nut.

They are bastards to undo. My mate who is a
lawnmower mechanic uses an air rattle gun.
Give it a blast of penetrating oil.
Get a good fitting solid spanner.
Try a lever on your spanner, or belt the spanner
with a lump hammer.
Failing that belt the nut round with a lump
hammer and cold chisel.
On grind a section off the nut and while it is still
hot, belt it with the lump hammer and chisel

Depending how solid you have it, it could be
a piece of piss. Then again you could bend
your shaft, but that's part of the fun of DIY
innit?
Regards
Bill
 
T

The Natural Philosopher

Bill said:
Any nut securing a blade on a rotating shaft,
that is a saw,a grinder, a lawnmower blade
holder, is designed to tighten up under rotation.
Otherwise they'd be flying off everywhere.
So, think about it, when the blade is rotating
the nut is tightening in the opposite
direction.

So mark the rotation with a chalk arrow on the
blade holder. Lock the blade holder somehow,
clamp it to something.
Turn your spanner in the direction of the arrow
to undo the nut.

They are bastards to undo. My mate who is a
lawnmower mechanic uses an air rattle gun.
Give it a blast of penetrating oil.
Get a good fitting solid spanner.
Try a lever on your spanner, or belt the spanner
with a lump hammer.
Failing that belt the nut round with a lump
hammer and cold chisel.
On grind a section off the nut and while it is still
hot, belt it with the lump hammer and chisel

Depending how solid you have it, it could be
a piece of piss. Then again you could bend
your shaft, but that's part of the fun of DIY
innit?
Regards
Bill
I've never failed to get the nut off OK. Mole grips on the disc and a
2ft bar on the socket set.

On account of the woodruff key they don't tighten up that much.


But the disk has usually stuck to the point where I decoded to attach
blades in situ...

The key is the key IYSWIM, rusted in place.
 
D

Davy

The Natural Philosopher said:
Bill wrote:
I've never failed to get the nut off OK. Mole grips on the disc and a
2ft bar on the socket set.

On account of the woodruff key they don't tighten up that much.


But the disk has usually stuck to the point where I decoded to attach
blades in situ...

The key is the key IYSWIM, rusted in place.
Dear Phil',
So a mole grip on the edge of the disc and then manually hold the mole grip?
The nut is supposed to be tightened to 40ft lb so might need 80ft lb to get
it off?? Not sure I could hold a mole grip against 80 ft lb?

Even then, you have found that the disc is usually rusted on. I am now
wondering about taking it to the local dealer and getting them to remove the
nut and disc???

Go on then, I know you are dying to be asked; what does 'the key is the key'
and IYSWIM mean?

cheers, Davy
 
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T

The Natural Philosopher

soup said:
IYSWIM = If You See What I Mean
I think he is saying something about the Woodruff key (the key) is the
pivotal thing (the key) but no doubt the Natural philosopher will be
along shortly to clarify
in a nutshell.

The bloody key rusts into the keyway.

Blowlamp and WD40 time and big mallets
 
T

The Natural Philosopher

Ian said:
9) When the retaining bolt is out, the thread in the crank is actually
smaller than the hole in the disc through which the retaining bolt
passes. Furthermore this hole is threaded to take a bolt to draw the
disc off the crank. I'm not very up on bolt threads but I THINK it was
described as 1/4" when I got it. It is about 7/16ths diameter and
pitch is about 19 per inch. The head has three radii on it which I am
sure indicates something! Over to someone else on this one.
I cannot conceive how screwing a bolt back into the crank after you have
removed on from it will 'draw the disk off.'

The normal method is to put a scrap bolt in the crank and hit it very
hard with a mallet to break the seal between the crank and the disk.

Allegedly. I chickened out.

Apologies about the reverse threaded thing..I was thinking of a ride on
I stripped last year where one or both of the blades had a reverse
thread on ..
 
T

The Natural Philosopher

Ian said:
Hi NP
The bolt concerned is NOT the retaining bolt and does not go back into
the crank but into the disc....
Ah. Got it.

Now that may just make me do the disk removal thing and an oil change
this week.

Integral hub puller. Never knew they had one of those..

Shame you don't know the exact thread..
 
D

Davy

Ian said:
On Sat, 19 May 2007 19:00:28 +0100, "Davy"
9) . Furthermore this hole is threaded to take a bolt to draw the
disc off the crank. I'm not very up on bolt threads but I THINK it was
described as 1/4" when I got it. It is about 7/16ths diameter and
pitch is about 19 per inch. The head has three radii on it which I am
sure indicates something! Over to someone else on this one.

thanks for that Ian, I don't think many of us realised that the blade disc
has a built in facility for its removal.

Regarding which is the correct bolt to draw the disc off the crank; garden
tools and mowers tended to have British Std Whitworth (BSW) threads. A 1/4"
BSW has 20 threads per inch and a obviously screw diameter of 1/4"; but you
say it has a diameter of 7/16ths - or maybe you meant across the flats? A
7/16th dia BSW is 14tpi so it can't be that. However a 7/16th dia BSF
thread is 18 tpi - maybe?
Not sure what you mean by it having three radii on it; but UNC/F bolts have
three circles in a row - I wonder if this is what you meant?. A 1/4" UNC
bolts has is 20tpi and 7/16ths across the flats - if you did mean 'across
flats' then this is a good match to what you have. But a UNC thread is
wrong for a British lawnmower. So my guess is that the Hayter Hayterette
requires a 1/4" BSW bolt; but that someone gave you a 1/4" UNC bolt which
will screw in to a 1/4" BSW thread; but a UNC thread is cut at 60 deg whilst
BSW is cut at 55 deg; so the mismatch will give a weak interaction because
the stresses are not transmitted through the flanks of the thread.

But none of this is making sense to me because I think I understand you to
be saying that your withdrawal bolt screws into a thread in the centre hole
of the disc? - and that "When the retaining bolt is out, the thread in the
crank is actually smaller than the hole in the disc through which the
retaining bolt passes" The retaining bolt which goes into the crank has a
diameter of about 5/16ths - larger not smaller than 1/4".

I think my knickers are now sufficiently twisted to hand the subject back to
you!

cheers

Davy
 
T

The Natural Philosopher

Davy said:
thanks for that Ian, I don't think many of us realised that the blade disc
has a built in facility for its removal.

Regarding which is the correct bolt to draw the disc off the crank; garden
tools and mowers tended to have British Std Whitworth (BSW) threads. A 1/4"
BSW has 20 threads per inch and a obviously screw diameter of 1/4"; but you
say it has a diameter of 7/16ths - or maybe you meant across the flats? A
7/16th dia BSW is 14tpi so it can't be that. However a 7/16th dia BSF
thread is 18 tpi - maybe?
Not sure what you mean by it having three radii on it; but UNC/F bolts have
three circles in a row - I wonder if this is what you meant?. A 1/4" UNC
bolts has is 20tpi and 7/16ths across the flats - if you did mean 'across
flats' then this is a good match to what you have. But a UNC thread is
wrong for a British lawnmower. So my guess is that the Hayter Hayterette
requires a 1/4" BSW bolt; but that someone gave you a 1/4" UNC bolt which
will screw in to a 1/4" BSW thread; but a UNC thread is cut at 60 deg whilst
BSW is cut at 55 deg; so the mismatch will give a weak interaction because
the stresses are not transmitted through the flanks of the thread.

But none of this is making sense to me because I think I understand you to
be saying that your withdrawal bolt screws into a thread in the centre hole
of the disc? - and that "When the retaining bolt is out, the thread in the
crank is actually smaller than the hole in the disc through which the
retaining bolt passes" The retaining bolt which goes into the crank has a
diameter of about 5/16ths - larger not smaller than 1/4".

I think my knickers are now sufficiently twisted to hand the subject back to
you!

cheers

Davy
As I understand it finally, the way it all hangs together is this.

The crank is untapered and fitted with a woodruff key in a slot. The
boss of the disk is slotted for this key and by an large fits over te
crankshaft.

The crankshaft is end drilled for a retaining bolt, but this is an
enormously loose fit in the disc, as this is fully located by the boss
and the key, and the bolt merely stops it falling off. Removal of the
bolt reveals that the end part of the disk is threaded and a bolt can be
screwed into the disk, to bear on the crank end and push the disc off.

So I might tale the disc bolt out and see what is there.

Now I am fairly sure that around 1990 or so, Hayterettes did NOT have
this arrangement..mine is 1995 but I never took the disc of myself yet.
It got serviced once about 6 years ago at the service shop. It had never
had even an oil change up till then. We USED to change the blades by
angle grinding the heads off the bolts that hold them in, that part of
the head that hadn't already been ground off by mowing lumps of bricks
and discarded spanners and the like.

Sine the bolts can't generally be removed any other way, there is no
need to remove the disc as well. Just grind off the heads, and fit new
blades and bolts. Flat side down and bevelled side up.


Only if the disk is damaged need it be removed. Or if you really feel
like draining the oil. Though I THOUGHT mine had a plug in the sump side
where it could all be tipped out of.
 
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D

Davy

..
Now I am fairly sure that around 1990 or so, Hayterettes did NOT have
this arrangement..mine is 1995 but I never took the disc of myself yet.
Dear Phil'

If your Hayterette was made about 1990 then it may well be metric. My
hayterette and B&S engine was made in 1968 so might be different still. In
my rambling discussion about bolt size, because all of the dimensions that
Ian gave were imperial, I had not considered that Ian's machine might be
recent and hence metric.

Let me know what happens if you have a go at getting the disk off. I am
losing the courage to take off the blade disc retaining bolt since if the
head shears off leaving the bolt thread in the end of the crank then my old
machine would probably be scrap!

best wishes, Davy
 
T

The Natural Philosopher

Davy said:
.
Dear Phil'

If your Hayterette was made about 1990 then it may well be metric. My
hayterette and B&S engine was made in 1968 so might be different still. In
my rambling discussion about bolt size, because all of the dimensions that
Ian gave were imperial, I had not considered that Ian's machine might be
recent and hence metric.

Let me know what happens if you have a go at getting the disk off. I am
losing the courage to take off the blade disc retaining bolt since if the
head shears off leaving the bolt thread in the end of the crank then my old
machine would probably be scrap!
That does NOT happen. That bolt is really high tensile steel.

But if all you want to do is replace the blades, just grind the bolts
off and leave the disc where it is.
 
D

Davy

Ian said:
Looking end on at the head with a flat horizontal there are three
lines one pointing to the top flat (12 o'clock), and the other 2 at
120 degree intervals (i.e pointing to about 4 and 8 o'clock). Does
this help identify it
yes, this is a 'unified screw' bolt; the bolts have three equally-spaced
radial markings, the nuts would have three circles. The bolts should also
have a figure at the 6 o'clock position which denotes the grade of steel and
hence the maximum tightening torque; if this is missing then the bolt is
low-grade steel. In which case the maximum torque that should be applied to
the bolt is below 65 ft/lb - more than this and you risk damaging the thread
or shearing off the head.
The closest match to your description is a 7/16 UNF bolt which has 20 tpi.
It will not fit a 7/16th BSW thread so my supposition about BSW being used
was wrong. But you state that your machine is metric so we would expect a
metric thread; a 7/16th diameter bolt equates to 11mm. The nearest common
metric sizes are M10 (17tpi) or M12 (14.5 tpi) - so no metric equivalent of
this size. Perhapsy Hayter changed the fastenings to metric by 89/90 but
not the components?

I look forward to hearing whether your old machine has the same arrangement
since it is much closer in age to my 1968 machine.

Many thanks, Davy
 
D

Davy

I now know how to do this.

Cutter disk is held by a 3/8 UNF bolt (9/16AF or 14mm socket - either fit
just as well) and a woodruff key to prevent rotation. Bolt can be very rusty
and tends to be worn smooth by contact with hard objects; would be better to
replace but is unusual so would need to order.
Recommended to jam cutter disc with a mole grip which will jam against a
piece of wood against the mower skirt. Retaining bolts needs a lot of torque
to get off; is said to be high tensile so head will not shear off. Recommend
a six-sided (not usual 12) socket. If this fails then weld a long bar to the
nut.

The centre of disc is threaded so a 7/16 UNF bolt can be screwed in against
the crankshaft end and will force disc off. Need to put a spacer in to
prevent threads in crankshaft being damaged. If disk has not been off for a
long time then woodruff key is likely to be rusted into the keyway and disk
will be difficult to remove. Disk is thin so has only a few threads and
these are likely to strip. Some resort to WD40, blow gun and big mallets.
Some cut the disk off. If done by a dealer then expect an hour at £30.

Examine disk for cracks - if it disintegrated at speed then not funny. If
blade bolt holes are elongated then needs a new disk.

Whilst disc is off, allows access to oil drain plug so oil can be changed.

hope this helps,

Davy
 
T

The Natural Philosopher

Davy said:
I now know how to do this.

Cutter disk is held by a 3/8 UNF bolt (9/16AF or 14mm socket - either fit
just as well) and a woodruff key to prevent rotation. Bolt can be very rusty
and tends to be worn smooth by contact with hard objects; would be better to
replace but is unusual so would need to order.
Recommended to jam cutter disc with a mole grip which will jam against a
piece of wood against the mower skirt. Retaining bolts needs a lot of torque
to get off; is said to be high tensile so head will not shear off. Recommend
a six-sided (not usual 12) socket. If this fails then weld a long bar to the
nut.

The centre of disc is threaded so a 7/16 UNF bolt can be screwed in against
the crankshaft end and will force disc off. Need to put a spacer in to
prevent threads in crankshaft being damaged. If disk has not been off for a
long time then woodruff key is likely to be rusted into the keyway and disk
will be difficult to remove. Disk is thin so has only a few threads and
these are likely to strip. Some resort to WD40, blow gun and big mallets.
Some cut the disk off. If done by a dealer then expect an hour at £30.

Examine disk for cracks - if it disintegrated at speed then not funny. If
blade bolt holes are elongated then needs a new disk.

Whilst disc is off, allows access to oil drain plug so oil can be changed.

hope this helps,
certainly does mate.

Thanks.
 
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D

Davy

The conclusion of this discussion seems to be:

Cutter disk is held by a 3/8 UNF bolt (9/16AF) and a woodruff key to prevent
rotation. Bolt can very rusty and tends to be worn smooth by contact with
hard objects; would be better to replace but is unusual so would need to
order. Recommended to jam cutter disc with a mole grip which will jam
against a piece of wood against the mower skirt. Retaining bolts needs a lot
of torque to get off; is said to be high tensile so head will not shear off.
Recommend a six-sided (not usual 12) socket. If this fails then weld a bar
to the nut.
The hole in the centre of the disc is threaded so a 7/16 UNF bolt can be
screwed in against the crankshaft end and will force disc off. Need to put a
spacer in to prevent threads in crankshaft being damaged and because the
bolt is unlikely to be long enough to fully draw off the disk. If disk has
not been off for a long time then woodruff key is likely to be rusted into
the keyway and disk will be difficult to remove. Disk is thin so has only a
few threads and these are likely to strip. Some resort to WD40, blow gun and
big mallets. Some cut the disk off. Expect an hour of dealers time at £30.

When you get the disk off examine for cracks - if it disintegrated at speed
then not funny. If blade bolt holes are elongated then needs a new disk.
 
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The disc that holds the cutter blades is connected to the engine drive shaft by a cylindrical hub. There is a small nut in the centre which is easy to undo. It exposes a slightly larger threaded hole which is designed to take a slightly bigger nut which when tightened, in theory, will force off the disc. In practice the disc will be well rusted
and seized onto the drive shaft. It is worth trying this step first with WD 40 sprayed into the hole and a bit of heating from a blow torch. Be careful not to damage the threads in the hole in the drive shaft when tightening the larger bolt.
If this does not work then an angle grinder is required to cut the disc off leaving the hub attached to the drive shaft. I cut a square shape about 2 inches from the centre of the disc. This makes it easier to get to the top of the seized hub and after another dose of WD 40 and the blow lamp I tried a crowbar to get the hub off. Still seized.
If this does not work you will need to use the angle grinder to cut a groove parallel to the drive shaft in the hub and then grind away until you have cut through nearly all the metal of the hub nearly to the drive shaft itself. You can use your eyes to judge but I ground away until I saw the metal of the hub change colour to a darker bluey silver. Do not grind through to the drive shaft. A crowbar in the initial groove cut parallel to the drive shaft will crack the thin metal on the inside of the hub next to the drive shaft. Then a crowbar to lever the rest of the hub off. As you do this you will see a groove in the drive shaft with a "woodruff" key which you need for the new hub. Fitting the new hub was very easy after using wire wool to clean the drive shaft. I use a lot of copperslip on the drive shaft in the hope that next time the disc will come off much more readily.
 

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