Torque on nuts.

[BufordBoone]

You guys helped with my blade issue. Now, in reading the manual (yeah, I do that), it says to torque the nuts to 644 ft. lbs.

The nut requires a socket that is 1 11/16" so is a large nut.

I have a torque wrench that only goes to 150 ft. lbs.

I found wrenches that go up to 700 ft. lbs. but they are expensive.

I have a DeWalt cordless 1/2" impact wrench that says it has max torque of 700 ft. lbs. However, the manual does not say how one can figure out how much torque one is applying.

I'd assume that any nut designed to handle 644 could also handle 700 so wonder, do I just use the DeWalt till it "seems" like it has applied all it can apply?

I'd really rather not have to spend $400 on a torque wrench. Last resort would be a breaker bar, cheater pipe and "farmer tight" but that may be the end result.

Thanks.

 

[CincyFlyer]

Actually, you can use a pull-scale (little crane scale), or even a bathroom scale, and a cheater of a given length: on a six foot bar, put ~107 lbs. of force and you'll be good.

 

[prichard]

Breaker bar with a pipe. 640lbs is 100 lbs at 6.4' if I did the math right. You can use a fish scale to to verify the 100 lbs.

Of course, I'd just use the Dewalt.

 

[BufordBoone]

Thanks, to both of you.

Prichard, I totally understand the math of the answer you posted. That will serve me well in the future, even if I do "just use the Dewalt".

 

[TimberHole]

Calculate the the length of the wrench so that your full body weight on that arm provides 640ft/lbs. Very simple and very accurate. That's a lot of torque. I don't think there is any chance that a 1/2" electric impact is going to even come close to that figure. To give you a point of reference a 3/4" high strength bolt used in steel structures will require approximately 350 ft/lbs of torque to achieve proper tension. In other words, make sure you are reading your manual correctly.

 

[Gary Fowler]

I did indeed see a Dewalt 20V 1/2" impact that stated max torque of 700 Ft. lbs but I would take that with a grain of salt. For sure it isn't going to hurt your 644# requirement by hammering it to the max.

 

[bcp]

Buy/rent/borrow a torque multiplier.

Here's one:
Klutch Torque Multiplier | Northern Tool + Equipment

Bruce

 

[747driver]

Most auto parts stores will rent you a torque wrench.

 

[prichard]

A 644 lb/ft toque wrench at an auto parts store? Last time I rented a torque wrench at an auto parts store it was broken.

 

[BufordBoone]

The idea of calculating how long to make the arm so that my full body weight would provide the 640 ft. lbs. would certainly make it easy.

But then, turning the bush hog on its side so that I could hang from the wrench might just make things more difficult.

I do like the line of thinking, though.

I'll also look at torque multipliers.

Inasmuch as these bolts also have lock washers, I think that whatever torque my DeWalt actually puts on the nut will probably be fine. I doubt that most farmers apply 640 ft. lbs. even when going "farmer tight".

Thanks, to all, again.

 

[newbury]

Buy/rent/borrow a torque multiplier.

Here's one:
Klutch Torque Multiplier | Northern Tool + Equipment

Bruce

AWESOME!!
This will require some research, there are some on Amazon for around $70.

 

[TimberHole]

Use a fish scale on a long lever arm. I wouldn't count on that electric impact getting anywhere in the ballpark of 640 ft lbs regardless of there claims. I'd be surprised if you can get 250! A bigger problem might be how to keep the shaft from turning. 640 is a lot of torque for us average joes.

 

[prichard]

I'll have do some searching. Now I'm curious about real world toque on impact drivers.

 

[TimberHole]

I'll have do some searching. Now I'm curious about real world toque on impact drivers.

To put the claim of 700 with a 1/2" electric in perspective, when we used 3/4 A325 hex bolts in the steel business we rattled them with a 3/4 drive air impact to get them to roughly 350. We use a Skidmore to establish the relationship between torque and proper tension. If I remember correctly a 3/4 A325 was to be torqued to achieve 27,000 lbs of tension. The torque/tension relationship would be impacted by thread cut, lubricant, etc.. Here, we are talking straight up torque and there is only one way to achieve it.

Weight X arm = moment

If there are electric guns able to achieve those numbers I'd sure be interested in getting one.

 

[4570Man]

My Harbor freight cordless impact is rated at something like 1100 foot pounds. It's a far fetched at best claim. Although the HF gun is pretty stout. It failed at taking the lugs off my Kodiak. A 3/4 air gun with high flow fittings and hose also failed. I finally got my hands on a 1" gun and it did it with about 5 hits.

 

[MHarryE]

I believe the electric impacts can reach their rated torque under specific test conditions, but not my real world experience. My largest disk has 1 1/8 " coarse thread. Torque is supposed to be 550. I can hammer for a minute after its tight, then get out my 2.5 foot 3/4 drive ratchet, step on the end (I'm about 210 in work clothes) and get another 1/4 turn.

 

[TimberHole]

I believe the electric impacts can reach their rated torque under specific test conditions, but not my real world experience. My largest disk has 1 1/8 " coarse thread. Torque is supposed to be 550. I can hammer for a minute after its tight, then get out my 2.5 foot 3/4 drive ratchet, step on the end (I'm about 210 in work clothes) and get another 1/4 turn.

I agree but I'd love to know how they can make those claims. Since torque is a moment it seems to me it will either do it or it won't. I don't think changing the test conditions changes the moment but maybe I'm thinking about it wrong. Changing things like thread cut and lubrication would change the tension in the bolt for any given torque but it doesn't change the moment.

 

[4570Man]

It's probably breakaway torque in ideal conditions. That or just flat made up like shopvac HP.

 

[daugen]

wow, I'm faced with exactly the same problem with my new Kubota F2690 mower, they want 650-700 pounds to tighten the mower bolts.
And I have the 700# rated Earthquake air gun, and wondered if that would cut it.

Most importantly..........do all air guns have more removing torque than tightening? What happens when you let it whang all the way in, and then the gun can't unscrew it???

I have a HD 3/4 inch socket set, guess I'll need a torque multiplier for that.

This somewhat begs the question, why do these nuts need to be put on so tight?

 

[newbury]

My Harbor freight cordless impact is rated at something like 1100 foot pounds. It's a far fetched at best claim. Although the HF gun is pretty stout. It failed at taking the lugs off my Kodiak. A 3/4 air gun with high flow fittings and hose also failed. I finally got my hands on a 1" gun and it did it with about 5 hits.

I had a similar problem, had to get a long breaker bar and my 240lbs. to get some bolts off.

wow, I'm faced with exactly the same problem with my new Kubota F2690 mower, they want 650-700 pounds to tighten the mower bolts.
And I have the 700# rated Earthquake air gun, and wondered if that would cut it.

Most importantly..........do all air guns have more removing torque than tightening? What happens when you let it whang all the way in, and then the gun can't unscrew it???

I have a HD 3/4 inch socket set, guess I'll need a torque multiplier for that.

This somewhat begs the question, why do these nuts need to be put on so tight?

If the gun can't unscrew it then you need to get the nut in a position so you can use a long breaker bar, maybe along with heat. For tightening to 400 lbs I put a 200 lb weight (my son) on a 2' breaker bar AFTER running the bolts on to "snug" with an impact.