Blade bolt comes loose

[amatureleccy]

Hi all, I have a Hayter Harrier 48.  Unfortunately the blade bolt keeps coming loose.  Does anyone know what causes it and when can be done to fix it.   

Thanks,

[Mick]

Hi. what code is your Harrier 48?

I've never seen a blade bolt on one of these coming loose, so if you have the code number or a photo of the machine it would be helpful.

[Changy]

As Mick said, that is not a common fault on Hayter mowers. Have you noticed increased vibration on the mower? I repaired a few other mowers with a loose blade bolt caused by a damaged blade, bent crankshaft, or both. It usually occurs when the mower has hit something hard, like a log or rock, and the vibration causes the bolt to work loose.

I like to add some thread lock and then tighten the bolt.

[Mick]

Thanks Changy. 

The reason I asked amatureleccy which code it was is because obviously there's a difference in blade disk setup between series. Just wanted to make sure he had the blade fitted like in my diagram I posted here, https://thegardenmachineryforum.co.uk/index.php?topic=837.0

I have never felt the need for any thread lock to be honest.  I have had cases where someone has sheared the bolt off and you can imagine with thread lock it's a mare to get out.  There should be a spring washer under the head of the blade bolt, which strangely I forgot to add to my diagram. lol..

[amatureleccy]

Hi. what code is your Harrier 48?

I've never seen a blade bolt on one of these coming loose, so if you have the code number or a photo of the machine it would be helpful.

The code is 496F.

Thanks

[amatureleccy]

Hi Mick,

Thanks for the help.  It looks like I have the newer type friction disc. 

[Mick]

OK, thanks.  So does the disk sit flat on the boss over the two pegs when you offer it up, or does it wobble?

Also, You have the distance piece fitted like in the diagram? And a spring washer on the bolt?  The blade done up tight so it's bending as in the diagram?

[amatureleccy]

OK, thanks.  So does the disk sit flat on the boss over the two pegs when you offer it up, or does it wobble?

Also, You have the distance piece fitted like in the diagram? And a spring washer on the bolt?  The blade done up tight so it's bending as in the diagram?

Yes, it is set up the wahy you have shown in the diagram.  There is a washer, same as in the diagram - is that what you mean by "spring" washer?  The disc does fit snug on the boss with the two pegs used to host the friction plate.

[Mick]

There is a washer, same as in the diagram - is that what you mean by "spring"

Like I mentioned, I forgot the spring washer in my diagram, what you are seeing is what they call the DISTANCE PIECE https://www.gardenhirespares.co.uk/genuine-hayter-distance-piece-cutterbar-hy4014.html

The Spring Washer I'm referring to is part number - 09273 and can be seen here, https://www.gardenhirespares.co.uk/genuine-hayter-washer-3-8-sc-spring-9273.html

Torque setting for bolt is 54Nm

Just curious, when you originally said the bolt keeps coming loose, did you actually mean the bolt? Or just the fact that the blade is slipping on the disk?  If the latter then you have a soft and bent blade, it should be flat until you bolt it to the machine. Or the disk is worn on the edges where the blade has been slipping, or worn distance piece.
 

[amatureleccy]

Thank for that - yes I have that piece in place.  The blade itself is brand new and is flat when I put it on.  I think it is coming lose rather than just slipping.  When I put it on and fix it, it works just fine.  But when I try and start it again after some use, it is lose. 

Next thing I will try is to get hold of one of those torque wrenches that shows the Nm.  Anyone got any recommendations for a torque wrench?

Thanks

[Mick]

Ok, but does the blade bend when you tighten it up?

[amatureleccy]

Yes, it as you tighten the bolt, the blade bends upwards fitting more snuggly into the friction disc. 

[Mick]

OK, so then it doesn't make any sense to me as to why it would come loose, unless you're not tightening it enough.

The blade other than it being driven from the outside edges of the disk via the bending action, it should spin freely on the spacer or distance piece so shouldn't be able to undo the bolt in any scenario.

[Mick]

Just another thought, although this would normally cause it to tighten itself. Do you have the little woodruff key missing that keys the crankshaft to the actual blade hub / boss?

[amatureleccy]

Eureka - with my torgue wrench, I tightened it to the required 54Nm and it works.  I got it working a second time so it didnt come lose.  Stripes on my lawn again - very happy to see them. 

Thanks all.