MTD (Murray) 30" Rear Engine - Stubborn Blade Nut

1saxman

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Hey y'all, a newbie to this forum but not mowers. I was cleaning up/lubing my mower after its second season (light use) and planned on taking off the blade and sharpening/balancing like I do with my smaller mowers. I got out my breaker bar and a heavy-duty 15/16" socket, braced the blade and pulled - no go. Okay, did it again, but got myself in a better position and really yanked - no go. So, just wondering if these are maybe LH thread? That doesn't sound right because blade bolts are always threaded so they would tend to tighten with blade rotation rather than loosen, and I was pulling to loosen in the direction of blade rotation. Is there anything funny about these bolts before I put the jack handle on the breaker bar? I'm working on it on its wheels so I can't get my weight on it.
 

ILENGINE

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From your description this sounds like the MTD made Murray. The normal torque on the nut is 80-100 lb/ft, and with grass and other debris I have times that a 600 lb-ft impact won't remove it. And it is the normal right hand thread. I have a 4 foot long 3/4 drive breaker bar that I keep handle for those stubborn nuts.

Need to find a solid stop for the blade, and break out the cheater pipe.
 

StarTech

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Or just get a very good impact a hold of it. Here I am using an Aircat 1150 with 1300 ft-lbs of reverse torque. BTW I also got a 1/2 breaker that I put a 5 ft cheater pipe and row boat off the bolts but I haven't used it since I got the Aircat.
 

bertsmobile1

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Not uncommon to be forced to cut the blade nut / bolt off because I can not remove it .
Like the other techs, I have a 1480 ft.lb 1/2" drive impact and the landlord has 2200 ft.lb 1" job ans still the angle grinder has to come out a 1/2 dozen time a year.
Nut are fine cause I can cook them red hot & remove while still hot but you can't do that with a bolt .
You might have to remove the blade every season to prevent this happening in future .
 

1saxman

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Thanks, gentlemen, I appreciate your input. I have a lift for it that I haven't assembled yet which will get the mower to an angle where I think I can brace the blade and get a foot on the bar. First, I'll soak it a few times in 'Sili-Kroil'.
 
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PTmowerMech

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When I can't get the nuts off, I'll take the pulley off and the blade and spindle will drop out the bottom.
You may not have that option.
But with the blade and spindle out, and have more options.
Like taking it to a shop that has accessto heat, 1" impacts or other tools.
 

1saxman

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  • / MTD (Murray) 30" Rear Engine - Stubborn Blade Nut

1saxman

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At least I found out it is a nut, which simplifies the problem. I'll hit it with Kroil and wait a day or so, then heat it with propane and do the Kroil again. Finally I'll heat it again when I'm set up to loosen it. Not red hot, and I think the blade will be enough of a heat sink to protect the bearings in the spindle. The purpose of the heat is to wick the Kroil all the way into the threads and maybe with a little expansion the nut will break loose enough for me to get that elusive first movement.
 

1saxman

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Got it this morning. Grass is growing like crazy with downpours lately so I had to do something. Had applied Kroil several days ago, wiped off the residue today and put the air-service 15/16 socket on the breaker bar. I had to raise the deck all the way (I run it only one notch down from the top) and still had to push it up to get that long socket on the nut. Solidly blocked the blade with a 2x4 in the discharge port, and put the heavy-duty jack handle upper half over the bar. Laying on the floor now, head to the front with a foot on the bar, and holding the front wheel to stop the mower, I laid some torque into it. I was sort of leery of breaking the tool and nothing was happening. Finally I said 'Break it' so I really gave it a maximum effort - POP! I thought I had cracked the socket but I had broken it loose! Went ahead and removed the blade and sharpened it. I don't normally use the bench grinder on a blade in good condition so I clamped it in the vise and used my favorite file - an 8" flat/round file from my Grandad's tools, probably 100 years old and still cuts the best I have seen. The rounded side is great for those curved cutting edges found on this and other blades.
Put it back on and used all the torque I could muster with just the breaker bar. I'm sure that will be good enough. I'd say I got about 95-100 lbs on it, comparing it to lug nuts with that same bar. I think it must have been on with at least 175.
Interestingly, the oil residue from the Kroil was on the flat flange of the nut as well as on the threads. That stuff really is 'The Oil That Creeps'. I don't know if I would have been able to break it loose without it.
 
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