Sharpened blades on mower deck

[KEYBEAR]

Rented a torque wrench to do a big diesel overhaul It was 4 feet long took two men to torque things to 450 and then 650 lb .

 

[zzvyb6]

just look at the free-body diagram for a blade on a spindle. Blade bolts are self tightening. Hit something and they really get snug.

 

[Pepsiboy]

I've read elsewhere in OTT that the WSM for Kubota decks seem to recommend 450lbs/ft for most of the MMM decks. My 1/2" Dewalt pneumatic impact will do 650ft/lbs. I haven't found a 3/8" that will go above 350. If possible, I think I'll be blocking my blades with 2x4 and leaving mine on to sharpen. Just seems nearly impossible to get the torque right otherwise.

JK22,

PLEASE recheck those torque specs ! ! ! My SM for the 54" MMM has a spec of 72.3 to 86.8 ft lbs. I tighten mine to 75 ft lbs. Have had no problems with it in nearly 500 hrs of use.

Dave

 

[JK22]

JK22,

PLEASE recheck those torque specs ! ! ! My SM for the 54" MMM has a spec of 72.3 to 86.8 ft lbs. I tighten mine to 75 ft lbs. Have had no problems with it in nearly 500 hrs of use.

Dave

Please note I previously stated my prior post was incorrect. I can't edit my post--- but I did do a new post above. I regurgitated bad information.

 

[JerryK]

Anyone with the initials J/K can't be all bad.... we forgive you your transgressions ....

 

[JK22]

Anyone with the initials J/K can't be all bad.... we forgive you your transgressions ....

Haha. Likewise.

 

[hawkeye08]

I purchased a Harbor Freight fancy 1000lb/ft impact to try and get my blades off my finish mower. I will certainly be putting some anti seize on the bolts when putting back on.. and torquing to proper value with hand torque wrench.

I remember as a kid we had a gear reducing truck lug tool. It had a 5' handle and a big head with gears. It was easy to move the lever, but was slow going.

 

[JK22]

I purchased a Harbor Freight fancy 1000lb/ft impact to try and get my blades off my finish mower. I will certainly be putting some anti seize on the bolts when putting back on.. and torquing to proper value with hand torque wrench.

I remember as a kid we had a gear reducing truck lug tool. It had a 5' handle and a big head with gears. It was easy to move the lever, but was slow going.

First time I've seen the words "fancy" and "harbor freight" in the same sentence.

 

[ning]

[ TL;DR - if you wet threads before torquing, don't torque as hard ]

Just a quick FYI, if you oil/grease/anti-seize threads before torquing:

With less friction (wet threads), the bolt will stretch more before a
torque wench will click. Because friction is such a big factor in bolt torque, it is important to know the
difference between applying torque to a dry bolt and a wet bolt. Using oil, anti-seize or other types of
thread lubricant is a common practice, but an understanding that wet threads require less torque than dry
threads because of friction is very important.​

(From this link, which was the first thing that popped up from a google search for "wet torque vs dry torque".)

 

[Toyboy]

I'm a firm believer in a torque wrench. I torque mine to 80 ft/lb

 

[Pepsiboy]

JK22,

Sorry, I was just trying to prevent you from stripping the threads on those mounting bolts. I didn't see the other post, as my computer has been acting up the last few days. Glad you found the specs in the manual.

Dave

 

[JK22]

JK22,

Sorry, I was just trying to prevent you from stripping the threads on those mounting bolts. I didn't see the other post, as my computer has been acting up the last few days. Glad you found the specs in the manual.

Dave

No worries at all. Always good to correct bad information.

 

[stlbill]

Hello everyone,

I set the blades on my Deere 62C to the manual spec of 50 ft/lbs and lost one blade this week! Fortunately, I can find no damage except a bald spot in the yard. I am going to tighten a little more than the spec and look into some thread seal.

Tips from my experience:

1. Perhaps check the bolts to see what their grade is. I *think* it might be alright to tighten mower blades a little more than the factory specification. Especially if your torque wrench is not calibrated like mine. I use a mid-priced wrench from Northern Tool.
2. Occasionally, remove any ear protection or headphones just before you disengage mower blades. My Wife later told me she heard a strange sound when I had disengaged the blades on at least one occasion before the blade came off. In her defense she did not know I could not hear it. I could not hear it due to the combination of noise protection and music headphones.
3. Try to disengage blades over grass as opposed to a hard surface like asphalt or concrete. I think if I had "dropped" a blade on asphalt it would have traveled much further from the tractor potentially injuring someone or something. The grass took most of the energy as evidence from a scalp trail.

Unsure if MythBusters is still doing new episodes. In a large empty parking lot, I would like to see someone rig up a way to quickly loose a mower blade bolt on asphalt or concrete and see what happens. I bet it would not be good.

 

[hawkeye08]

My overtightened blade bolts were not factory, but me replacing blades a couple years ago. I have two sets and swapped the blades. I did not think I over tightened them, but they were sure a bugger trying to get off.. my new impact did the job, sharp blades are a joy to mow with.

 

[arto98607]

Blade bolts on my John Deere 413 brush hog are supposed to be torqued to 433 ft-lbs by design and torque multiplier wrench is recommended!

I ended up buying one just to be able to remove the bolts, which were not rusted.

 

[JerryK]

I have a 3' long aluminum 3/4" drive ratchet... It is what I go to when I have to put the old 'farmer' torque on big bolts.... [ like FEL attachment bolts ] 400# is one umpf or so... 450#, two umpfs or so .... etc.....

 

[4570Man]

Hello everyone,

I set the blades on my Deere 62C to the manual spec of 50 ft/lbs and lost one blade this week! Fortunately, I can find no damage except a bald spot in the yard. I am going to tighten a little more than the spec and look into some thread seal.

Tips from my experience:

1. Perhaps check the bolts to see what their grade is. I *think* it might be alright to tighten mower blades a little more than the factory specification. Especially if your torque wrench is not calibrated like mine. I use a mid-priced wrench from Northern Tool.
2. Occasionally, remove any ear protection or headphones just before you disengage mower blades. My Wife later told me she heard a strange sound when I had disengaged the blades on at least one occasion before the blade came off. In her defense she did not know I could not hear it. I could not hear it due to the combination of noise protection and music headphones.
3. Try to disengage blades over grass as opposed to a hard surface like asphalt or concrete. I think if I had "dropped" a blade on asphalt it would have traveled much further from the tractor potentially injuring someone or something. The grass took most of the energy as evidence from a scalp trail.

Unsure if MythBusters is still doing new episodes. In a large empty parking lot, I would like to see someone rig up a way to quickly loose a mower blade bolt on asphalt or concrete and see what happens. I bet it would not be good.

I think it would drop off and just skip around a bit because it's pretty close to balanced. A bush hog blade in the other hand would be far worse.