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Discussion Starter · #1 ·
I have a Kuhn 700 disc cutter that is getting pretty old but it is still cutting very well. I have one concern, however: the knives. When I install new knives, I torque the nuts to 88 foot lb as specified in the manual. I noticed that even when I use new bolts for the knives (after evert five knife replacements), some of the knives do not rotate with respect to the bolt. If I were to use a smaller torque, then all knives can rotate.

Once I use the cutter for a couple of hours, I noticed all the knives are now stuck and cannot rotate with respect to the bolt.

Is it not supposed that these knives rotate?

I certainly do not wait until a significant fraction of the knife (25% or so) is missing. Is there a better rule for when to change the knives?

Thank you,

Paul
 

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The knives not rotating is a non-issue. The centrifugal force from them spinning will hold them straight out anyway. The reason they quit spinning after you run the machine is crop material gets jammed in between the blade and the disc. The reason they rotate is so that when you hit something it doesn't damage the disc turtles. I would recommend you continue torquing them to the spec in the manual.
 

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Often, a little rust and scale builds up on the flat surface on the underside of the turtle - especially if the cutter has been sitting for a couple of weeks when you change the blades. You could probably take a wire brush or a large flat file to it - just enough to knock the scale off.
 

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My Zweegers drum mower has spring-loaded pins that are pressed down and the blade is slipped over it. These rapidly pack up with cut grass and dirt from anthills and such that are in the blade path. They get "stuck" in place and won't move either... the centrifugal force of a blade spinning and 2650 RPMs or so is enormous... they won't swing back until and unless they hit something substantially solid, like a rock, post, pipe, etc. When they do, a little grass and dirt isn't going to stop them from swinging back...

Usually I have to take the handle that you lift the blade pins with to remove the blades, and hammer the blade around at least a half turn if not the whole turn so the blade can knock the packed in dirt and grass and crud out of the area of the blade pin so that the pin can be pushed down and the blade pulled up off it.

So, in short, don't worry about it...

Later! OL JR :)
 
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