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

 

[BufordBoone]

I've been very pleased with my DeWalt 20 V 1/2" impact wrench. It had no difficulty removing the blade bolts from my Bush Hog mower. I don't know how long they had been on there but it is well over 5 years.

It also helped me remove bolts that were rusted in place in the slip clutch. Well, 7 of the 8 anyway. It broke the 8th one in half.

Very pleased with this purchase.

I think this is the one I have: DEWALT DCF899P2 2V MAX XR Brushless High Torque 1/2" Impact Wrench Kit with Detent Anvil - - Amazon.com

 

[RalphVa]

I got a Bush Hog 3209 cutter, and I'm trying to get the 1 5/16" bolts off that holds the blades on as I'm replacing them.

The 4 nuts have been soaking in PB blaster for a week, but neither my 3/4" impact wrench (being feed from a 1/2" hose @ 150 psi), nor my 3/4" ratchet with an extension will break any of them free.

I spoke to my dealer about it and they use a torque multiplier in the shop for getting bolts like that loose. Here's a link to one that takes a 3/4" input:

Central Tool 6387 4:1 Torque Multiplier : Amazon.com : Automotive

Does anyone have any experience with these devices? For that price, I wonder if I would be better off getting a monster 1" impact wrench? On the other hand, it would be nice to be able to accurately torque large bolts.

Any other thought on how to break these nuts free? I'm have reservations about using heat given that the bolt are hard to get to and I don't want to cause damage to anything else.

I use a 6 ft long piece of pipe where you have that puny 2 or 3 ft one. 6 ft multiplies out to 480 ft lb if you apply 80 # at the end of the pipe. That's about what it'll take to remove the nuts. I use a plain driver, not my ratchet one. Not sure the ratchet ones are good for that kind of torque. I use the ratchet once they're loose and again when tightening until I get them tight enough to use the plain driver and 6 ft pipe.

Ralph

 

[johnems]

I feel your pain and was their the first time I changed my blades as well. for me I went with one of the Milwaukee Fuel ratchets. If you check the revers toque speciation of this gun Is 1400 FtP.

The 2863™ M18™ FUEL™ w/ ONE-KEY™ High Torque 1/2” Impact Wrench with Friction Ring provides the Most Powerful, Most Compact, and the Most Repeatable Impact Wrench in the industry! The POWERSTATE™ Brushless motor delivers up to 1,000ft-lbs of fastening torque and 1400ft-lbs of nut-busting torque, providing users a cordless solution that will eliminate the need for corded Impact Wrenches.

Yes the torque multiplier is higher output. But I think the impact wrench would have much more vestal. Also some rental place catering to construction companies have torque multipliers for rent.

 

[Tractorable]

I've been very pleased with my DeWalt 20 V 1/2" impact wrench. It had no difficulty removing the blade bolts from my Bush Hog mower. I don't know how long they had been on there but it is well over 5 years.

It also helped me remove bolts that were rusted in place in the slip clutch. Well, 7 of the 8 anyway. It broke the 8th one in half.

Very pleased with this purchase.

I think this is the one I have: DEWALT DCF899P2 2V MAX XR Brushless High Torque 1/2" Impact Wrench Kit with Detent Anvil - - Amazon.com

I have one of these too. It's a total beast monster for removing tough nuts/bolts. It laughs at crankshaft pulley bolts and has never failed to remove any tight bolt I've come across.

As for heat, remember what you're doing with it. Heat expands metal, so applying heat to the blade surrounding the bolt will open up the bolt hole enough to allow the bolt to come free. Or heat the nut on the bolt to expand it.

Propane torches usually don't provide enough heat. As others have said, use an oxy/acetylene torch to heat the metal to a dull red color. Another method is to use heat followed by shock cooling with a wet rag. This can break the bonds of the rust holding the bolt/nut together.