Do I need a torque multiplier to get these nuts off?

[RickB]

There's no substitute for heat on those blade bolts/nuts. reinstall with Never-Seize on threads and keyed portion of the shank.

 

[Baby Grand]

Hopefully, not a hijack.

I have the 286 Bushhog and when it comes time for me to change the blades out, I have a question about the above picture. What keeps the blade assembly from turning as you are torquing on the bolt head? Are you clamping the gear box or the PTO shaft or what?

I always understood it that changing out a bushhog blade was a two man job, one on the bolt, one to hold the blade assembly from turning.

Thanks,

Not a hi-jack ... just a related tangent:
A properly placed 4x4, located between the beam that the blades are bolted to and the frame/housing of the 'hog will stop all rotation.

Back on point:
I used a 6' pipe on the breaker bar from my HF 3/4" drive socket set, after soaking the nut with PB Blaster and walking away from it for an hour.
Still had to put my back into it.

 

[pclausen]

Success at last! A little heat on the bottom threads of the bolts, and then resting the stump jumper directly on the cinder block was key along with going back to the 10 lbs sledge and not be afraid to give it 3 full swings!

Those definitely were some shot blades compared to the new ones.

Cut for about 3 hours afterwards. Much more balanced and the cut was so much nicer!

The cutting edge is already nice and "polished" from the cutting. I plan to raise the hog up all the way and hit the edge with a grinder to get it nice and sharp. I'm trying to get a large field that hasn't been cut yet this year to look as nice as possible before switching over to my Woods RM990 finish mower. Grass is about 5 feet tall and the RM990 would just bog down and slip the belts. Will probably take another 2 cuttings with 3209 before I can hit it with the Woods.

 

[SPYDERLK]

Ok, so after working on these 4 nuts on and off for the last 2.5 years, I FINALLY GOT THEM OFF!!! Just kidding, well sort off. I did actually get them off summer before last using a little heat. Problem was, that was only half the battle. The challenge I had then, and now, is trying to drive the bolts out to free the blades so that I can replace them.

I have lowered the stump jumper into a cinder block with a pair of 4x4 blocks on either side of the bolt pancake head, and then rested a 2" diameter piece of steel on top of the bolt thread and have whacked it like 50 times with a 10lbs sledge to no avail. Next I progressed to a tamping bar, standing immediately above the bolt and dropping the tamping bar directly down on the 2" piece of steel. And other than a lot of ringing in the tamping bar, noting. This is after soaking on the bolt in PB Blaster for days.

I guess my next step will be to heat up the bolt, then let it cool and try again...

Too much cushion. ... Increase reaction mass and its rigidity, and go back to the hammer. A 12-15 sledge would be better. The 2inch dia "punch" should be minimum length.

I have gotten a 27 ton impulse from a moderate blow with a 12lb sledge in a rigid setup.

 

[Egon]

They taught you correctly. When the bolts are torqued the threads stretch and will not go back to the original size when loosened. At work we actually confirm bolt torque by measuring the initial and finial length of some critical bolts on assemblies to validate the torque drivers. Now for a lot of things it isn't necessary to scrap the bolt but something like a brush hog I would spend the money. I wouldn't want to be anywhere near one of those blades of the bolt fails.

If that is the case hasen't the bolt/threads been torqued to failure. Hysteresis may account for a very little deformation but measuring for it would be beyond the required equipment most of us have.

 

[SPYDERLK]

According to the Torque class I went through at work, any nuts or bolts that have been torqued once, and removed, they should not be used again in an application that requires a torque setting. In other words, nuts or bolts should only be torqued once, and then tossed.

They taught you correctly. When the bolts are torqued the threads stretch and will not go back to the original size when loosened. At work we actually confirm bolt torque by measuring the initial and finial length of some critical bolts on assemblies to validate the torque drivers. Now for a lot of things it isn't necessary to scrap the bolt but something like a brush hog I would spend the money. I wouldn't want to be anywhere near one of those blades of the bolt fails.

This is certainly true of hi performance applications where bolts may be torqued to their yield point. The bolts in the instant case however, are torqued to waaay less than 50% of their yield stress. -- Not an issue here unless the bolt will not accept the nut with just a few ftlb interference.
,,,larry

 

[DuckSlayer1017]

Agree I was just trying to explain that there are reasons for only using bolts one time. I doubt I did the topic justice but didn't want to draw any stress strain diagrams on here either.

 

[RickB]

Agree I was just trying to explain that there are reasons for only using bolts one time. I doubt I did the topic justice but didn't want to draw any stress strain diagrams on here either.

Fair enough. Also a good comment by Larry about the ineffectiveness of an impact wrench due to rebound/bounce.

 

[Egon]

Agree I was just trying to explain that there are reasons for only using bolts one time. I doubt I did the topic justice but didn't want to draw any stress strain diagrams on here either.

On the initial torquing of a bolt it may return to a slightly elongated state due to the atoms and grains getting aligned by the the force's applied. If it does not return to this length after retorquing and release it has been strain hardened.

Bolts torqued to their yield point are no longer usable.

 

[WranglerX]

Guys.... NOT RATCHETS... NO... NO.... No..no.....

Use breaker bars... Have broken more ratchets and been hurt many times when ratchets self destructs.... When getting up there past 300 ft-lbs or more you need 3/4 or 1 inch BREAKER BAR and not HF piece of crap.....

Wonder how you get hurt?.... It's probably using tools not rated for work at hand...

Dale