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NH 451 mower

K

kenbob

Well-known Member
I have broken the bolt that attaches the sickle bar to the rotating mechanism twice. Not sure what bolt was in there first, but 2nd was a grade 5 as per specs. It shear
ed it off right at the bolt head. We were in some tough cutting. Just wondering if I am doing something wrong. The bracket is not the reenforced bracket as it is an
early model. Thanks, all.
 
There were two types if my memory serves me.. one has a taper like a lug nut and the other one didnt. If you have smooth side plates , it takes the one without a taper. Tighten it tight and make sure your bearing are not loose causing excess vibration. Make sure rock guards are not bent putting strain on the knife bar. Check the wear plates behind the knife bar.
 
I have the smooth side plates. I am not sure what bearing you are referring to unless you are talking about the bushing in the bar. I have a parts book and I don't show anything except bolt and nut. When I put it together, How tight do you make it? There is daylight between the bar head and those plates. Am I supposed to tighten it up till there is no gap? That would bend the plates. Thanks for previous answer.
 
I don't think ''daylight'' is good in your situation. Everything has to be tight or it will destroy itself. I have the newer model and the torque on that bolt is 90 ft lbs.
 

The bushing in the bar should have a steel tube in the center for the side plates to mate up against, if it's not there the head bushing is bad and needs replaced
The side plates should draw up tight against the head bushing when the bolt is torqued to spec
If the steel tube is in the head bushing but the side plates are have a wide gap either the side plates are bent out or the wobble assembly has been assembled wrong
 
Thanks, that would explain my problem. I will draw it up tight next time. I was afraid to bend those sides too much.
 
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