When tighten blade spindle will not spin, are bearings the cause?

You will need to find a way to level the spindle if the shafts isn't bent, remove belt and release spindle brake then spin blade and check for wobble. If you have shafts wobble replace spindle. If no wobble find a block of wood that fits snugly between good blade and concrete floor or drive. Check all blades for height from floor if center is the only one that has a different height then you will need to loosen spindle ,place some type of metal shim under low side , re-tighten and re-check. If other blades show difference on one side , you may have a bent blade or spindle or spindle mounting on them. The deck is sheet metal and can be bent when a foreign object is struck. There are also deck levelers on the supports. If the front of mower is up or down it will cause a high or low center blade path of cutting. All blades should be as close to the same height from a level surface as possible. This is time consuming but the only way other than new deck and/or spindles and blades.

Would check blade spindle bearings, loosen belt to deck and try to spin blades they should turn freely if not probably bad bearing in spindle.

There is a positioning "washer" that needs to be in place. If you don't line up the blade and position the washer it will not tighten. The blade will just spin around. Some even have a washer in front and in back. Be sure you have correct diameter of arbor that matches your blade too.

Sounds like your'e missing a spacer.

Remove deck belt from blade pulleys and Tri to spin blades by hand. If they don't spin freely, you probably need new spindle bearings but if you do need a new spindle I would replace the whole spindle housing... Just make sure the one (s) you buy has housing, spindle, bearings, nut and washer.

The job is much easier and safer with compressed air and an impact. I would try really hard to find someone with air to borrow but if no air is available then wedge a piece of 4x4 between the blade and deck to keep the blade from spinning. BEWARE, the board can pop out and the spinning blade can be dangerous. Remove the deck from the unit. Remove the pulley first, hold the blade with your hand ( only if you have air/ impact) to prevent the spindle from spinning. Note the washer under the pulley. Then remove the blade, then the spindle bolts. Most AYP replacement spindles now come pretapped but if not place spindle in a vice and use one of the old spindle bolts ( they are self tapping) to make threads in the mounting holes. Then mount the new spindle in reverse order being sure to instal the washer between the spindle housing and the pulley. Again hold the blade with one hand and securely tighten the pulley nut with an impact. Also the unit probably has a blade brake arm and the spring holder is mounted by one of the spindle mounting bolts. Pay attention to its positioning before removal. If you have a heavy duty replacement spindle the notch on the bracket may not fit the new spindle. with a file or grinding wheel enlarge the notch on the bracket to fit.

I dont believe there is a shear pin on your blade spindles, what I have found on these machines is the the spindle nuts on the balde spindles sometimes loosen or wear and no longer squeeze the pulley on the blade spindle. To make this process easy on your self you need to tighten these with a impact wrench. However if you dont have access to a impact wrench you can use hand tools and block the blades you are trying to tighten with a wooden block. Just make sure you block the blade you are trying to tighten

Hello:

This is Usually Caused by Worn Blades or a Bad Mandral/Blade Spindle Bearing.
Remove the Deck from Under the Mower.
Remove the Deck Belt.
Check the Mandrals/Blade Spindles for Bad Bearings. Do the Sound Rough when you Spin the Pulleys by Hand? Can you Move the Mandralls/Blade Spindles from Side to Side? If Yes, then the Bearing s Require Replacing.
Look At the Tips of the Cutting Edge of the Blades. You will Se the Tips are Rounded and Not Square. This Condition will cause the Strip in the Center of the Deck.
I have Just Joined this Site. If you Send me the Model Numbers Off the Unit, I can Assist you Better.
Please, Do Not Hesitate, If you Hit a Snag or this Does Not Correct the Problem, I am Here if You Require More Assistance.
Hope this Helps. Let me Know What Happens, Please. May the All Mighty Bless You and Yours. Be Safe and Be Happy. Thanks.

Good Luck

Respectfully

John

If the deck drive belt tightens but the blades don't spin it is because the spindle bearings have frozen. This usually happens with age and is made far worse from storing the machine outside.

If you have the technical ability, remove the cover over the belts on the deck, and see if you can spin each pulley. They should spin rather easily. If they don't, replace the top and bottom bearings in each offending spindle. If you don't have the know-how, bring the machine in for repair.