Blades keep coming loose

[Budro2o21]

I have a Craftsman LT 2000 46" deck mower I bought new several years back and the blades would always loosen while cutting thick high grass and eventually wore both star shaped spindle ends which had to be replaced. After that I still had to check the blade nuts, every time I used it. Then my son bought a Cub Cadet and gave me his Craftsman LT 1500 42" deck mower. After a couple years now one of the blades gets loose every time I use it. I've checked the spindle, balanced the blade, tightened it to a breaking point but one blade still gets loose. Both mowers run great but the cutting deck is always the issue. Is this a Craftsman thing due to that star shape on the spindle? Never had this problem with any other brand I've ever run. Any ideas on a permanent fix?

 

[ILENGINE]

Are your getting the blade on the star properly. Only takes one time of missing the star when installing the blade to damage it to were the blade doesn't properly fit. Other than that the blade nut on the MTD versions are supposed to be torqued to 80-100 lb/ft.

 

[StarTech]

Caution here as the LT 2000 can either AYP or MTD and MTD blade nut torque is way too much for the AYP blade bolt. But it looks like the 46" was only made by MTD.
But assuming we are dealing with MTD since the OP say blade nut it should be torque to 95 ft/lbs. Use a toque wrench to do this as the 5/8 nut and spindle can handle it; unless either is worn out. No oil or grease applied. I have yet to see one come loose when properly torqued.

Note I cut knee high to waist high with my Yard Machines 42" and never had a loose blade. And I have bent several blades hitting tree roots and never one to slip even with these impacts.

 

[Budro2o21]

I'll go back and check the spindle end and blade but I'm aware of how it all fits together and I know its getting over torqued if anything.

 

[bertsmobile1]

GO back to what Illengine said in the first reply
The star is soft and the blade hole is hard so it is very easy to damage the star.
Pull your spindles out and carefully check the star end.
Once the blades have come loose a single time it is damaged and will need to either be dressed using an end mill or replaced.
They are a lot easier to damage than most think .
And the nuts themselves have a limited life.
But I am sure if you get a good magnyfier and look closely you will see little fretted steps in the star .

 

[Joed756]

Replace your spindles and use Loctite on the threads.

 

[Budro2o21]

GO back to what Illengine said in the first reply
The star is soft and the blade hole is hard so it is very easy to damage the star.
Pull your spindles out and carefully check the star end.
Once the blades have come loose a single time it is damaged and will need to either be dressed using an end mill or replaced.
They are a lot easier to damage than most think .
And the nuts themselves have a limited life.
But I am sure if you get a good magnyfier and look closely you will see little fretted steps in the star .

Thanks, I'll do that. Makes since because only one on this deck has come loose on that one spindle, even though it tightens up pretty good is is probably worn more than I realized. So can you replace just the spindle shaft itself or do you have to replace the whole assembly. I'll check that blade too. That one blade may have some issues. I figured if it tightened up good on the star it was ok. Thanks again.

 

[ILENGINE]

You can replace the shaft by itself in most cases. I have replaced those blades and put the nut on by hand but didn't realized the blade had slipped off of the star and tightened with a ratchet wrench and mushroomed the star on the shaft. If you make that mistake with an impact about have to replace the shaft. Have dremeled more than one star to make it work. Just did a set on a 54 inch White brand MTD ZT the other day, and had to use my big high torque Dewalt impact to remove the nuts because my 600 lb/ft air impact wouldn't even try to remove them. That 1200 lb/ft battery impact sure comes in handy sometimes.

 

[Cusser]

For my LT1000 lawn tractor, a replacement mandrel is about the same price as an entire new spindle.

I purchase such parts online, from Ebay retailers.

 

[Budro2o21]

Thanks to all, I'll check everything suggested, I did get that high area cut so I won't need it again until the weather cools off then I'll need it.