#5 mower pitman arm problems

[chas036]

The carriage bolts that attach the wood pitman arm to crank wheel on my #5 mower keep coming loose and sometimes fall out causing the arm to detach from the crank wheel. I tighten the nuts down with new lock washers and I tighten them as I much as I can, but still they come loose after a few hours of mowing. Already this year I have damaged two pitman arms that came loose. Is there some secret that i am missing here on how to tighten the nuts on those carriage bolts?

 

[David from Kansas]

Looked at an old pitman end with the bearing and the bolts that hold the stick on just go through the nut a couple of threads and then the the threads were peened on the nut which would keep it from loosening.

 

[Roger in Iowa]

Can you double nut the bolts?
What shape are the cutting components? Sections sharp, ledgers sharp, holddowns keeping cutting parts in close tolerance?

 

[Scott 730]

Nylock nuts.

 

[rustred]

You could use stover lock nuts. They have a lot tighter grip than the nylock nuts.

 

[Willow Lane]

Loctite, blue should be adequate.

 

[ET]

I use lock nuts or double nuts on them as well as red lock tite. I check them regularly.

 

[chas036]

Today I am going for a new pitman arm because the old one got split when it came loose yesterday. Also I am going to buy some new carriage bolts that are longer than required so I can double nut them . I will also buy some lock tight and try that too. I hope this works.

 

[Willow Lane]

Two more thoughts: Is the outer end of the pitman where it attaches to the scythe tight? if it's loose you may be getting vibration from there that is affecting the bolts. Also, I believe you need bolts that are only partially threaded so that the shank of the bolt is full size where it passes thru the plate that is in the center of the pitman, and you may need to search for full size bolts, not ones with undersize shanks and rolled threads.

 

[wore out]

Is the knife ''in register''?

As the other poster said, if the cutting components aren't in good shape and/or the knife isn't in proper register there will be a LOT more strain on the pitman which will tend to wiggle the bolts loose.