How do I replace rotary cutter blades?

[jduke]

I have a 72" Mohawk cutter on a 55HP tractor. I was mowing with it, and found a root ball that didn't give....One of the blades broke off at the bolt holes and then proceeded to violently shake the shredder for a couple of seconds before I could get it shut down.

Anyway, once I order a new set of blades, what's the procedure for replacing them? Is this something I do through the hole in the deck? Can I do it with hand tools or do I need an impact wrench? Guessing no other damage was done but who knows.

 

[whistlepig]

You should be able to get to the nut through the hole in the deck. These are big nuts. 1 3/4" nuts if I remember correctly. May differ on your cutter. I use an impact wrench cause I have one it's easier. A big ratchet or breaker bar with a cheater bar would work also. These nuts are tight.

 

[moship]

Not certain about this model of cutters, but many require a new lock nut be used. Shims are also used to get the correct clearance between the bolt head and blade.

 

[jduke]

Yeah, ill order new nuts/bolts. Thats what the manual says. How do you keep the bolt from spinning? Or will it?

 

[whistlepig]

On all the cutters I have changed the blades the shank of the bolt is keyed into the stump jumper. If yours is the same the bolt shouldn't spin. You may have to take a big hammer and punch to drive the bolt out of the stump jumper through the hole in the top of the cutter. This is usually a press fit.

 

[jduke]

Cool. Sucks. JUST had these things sharpened a couple months ago when the tractor was in the shop for a grapple install. :/ Its got a slip clutch too, not sure why it broke.

 

[cheoah]

The bolt is keyed on mine, but still a good two person job. I use a 3/4" drive, 4' long breaker bar to change ours, but you can use a pipe for leverage too. Get everything nice and clean for re-install, and consider some loctite on the new bolts.

 

[whistlepig]

It's not easy but I have changed many blades by myself. It's easier if the one end of the rotary is lifted with a loader.

 

[cheoah]

I hook the chain hoist to the rear of the mower to secure it. The 5/8" thick blades on our mower are unwieldy but the keyed bolt usually does provide enough friction to hold the blade as it hangs there.

 

[skipmarcy]

I just changed blades & bolts on my older Howse 6' (about 20+ years old) cutter this past season. Our local farmer's co-op keeps bolts in stock and the ones for mine fit quite a few other brands as well. The nuts took a 1 11/16" socket - not quite in everyone's toolbox. The bolts on mine have a shoulder for a 1/2" thick blade and the keyed shoulder that fits into the stump jumper is ever so slightly tapered. The last time I had changed blades & bolts was about 15 years ago but the nuts came loose with my Snap-On 1/2" drive impact after soaking overnite with Thrust penetrating fluid. My deck has the typical hole behind the gearbox for accessing the nuts.