Mower blade bolt torque

[ghmerrill]

So here I am again about changes my blades in my old Howse mower. It's been a few years.

What do people tend to do in terms of the torque specs for bolts like these. The spec is 600 lb.-ft. I know that I can get to/above 600 lb.-ft. with my nice new Aircat 1150 (great tool!), but I can't MEASURE it. My torque wrench (automotive goes up only to 150). Even at the lowest setting on the 1150, it's above that.

What I've done previously is to put the nuts on at what seemed like "tight enough" with an impact wrench and not worried about. But this time I was wondering if I could at least approximate the "correct" torque.

What do other people do? Any thoughts? My guess is that pretty much everyone just wings it, but I'd like to know of any alternatives.

 

[RalphVa]

I use a 6 ft pipe that slips over a 3/4" socket handle. Just push on it until you cannot push any more, and it'll probably be close to 600 ft lb.

Mine's only 450 ft lb, but I tend to do the same thing.

Don't think it's rocket science on these big nuts.

Ralph

 

[TractorGuy]

For stuff like that I put a 6' pipe on a pull handle and lean on it with about half my weight. Okay maybe ALL my weight but that is only 165 lbs.

 

[TractorGuy]

Funny that two people were posting at the same time that use a 6' pipe. :laughing:

 

[WranglerX]

My favorite tool for high torque is "torgue multiplier"... Mine is 4:1 so my 150 ft-lb torque wrench will take torque up to 600 ft-lbs... Though torque multiplier is rated to go to 1000ft-lbs...

Input side is 1/2 inch drive, out put is 3/4 inch drive...

Dale

 

[TimberHole]

If you can get it vertical divide 600 by your body weight and that will give you the length of the wrench. Example: 600 ft/lbs / 200 lb body weight = a 3 wrench. Hang all your weight on a 3 horizontal wrench and you have 600 ft/lbs

 

[LD1]

Good half inch impact, hammer it til it quits.....good enough

 

[Maxify55]

I use the 1,2,3 ugga dugga measurement.
You can get a 400# gorilla to use his 4 ft pipe wrench OR
Whatever the impact driver delivers is close enough for me.

 

[5030]

I use a 6 ft pipe that slips over a 3/4" socket handle. Just push on it until you cannot push any more, and it'll probably be close to 600 ft lb.

Mine's only 450 ft lb, but I tend to do the same thing.

Don't think it's rocket science on these big nuts.

Ralph

Some 'big' nuts on this forum as well or should I say 'loose' nuts....:laughing:

 

[ghmerrill]

Thanks for the responses. They at least made me feel a bit better about not overlooking anything obvious.

I used to use the length of pipe and 3/4" breaker bar. But I was much younger then, and there are several problems with that. First, I have no way of actually measuring the result. So given that, I may as well use what I think seems like a reasonable application of an impact wrench.

Following up on that, I don't think there's any way to get confidence on how much torque you're applying with the pipe method. Yes, if you apply 100 lbs of force at the END of a 6' pipe, you get 600 lb.-ft. of torque. But you have to apply it at the END, and you have to know it's 100 lbs. You can't do that by any method of "leaning" into it. In part this is because the force needs to be in the same plane as the nut, and if your bar is horizontal (which it is unless you stand up the mower on its side) and unless you can somehow set it up so you are pulling straight, a lot of the force isn't going into that horizontal plane.

Setting up to apply that force in the horizontal plane is VERY tricky and requires fully stabilizing the mower so it doesn't, for example, swing on the hitch and doesn't move on whatever supports you're using. That's practically impossible. Again, given that, I'm at least as happy using an impact wrench that I've guestimated in terms of the torque it's producing. Also, given that I now have lumbar back problems (and successful surgery for that a year ago, but I don't want to invite more problems), I'm leery of having to pull with 100 lbs. or so of force.

What I decided to do in this case is to use the impact wrench at its lowest setting and see how that works. I expected that to produce a decent-looking result and then I might move up to the middle setting (maybe with reduced psi). But when I used the lowest setting, the nuts tightened to make the washers substantially, but not fully, compressed -- and so they're still exerting a locking effect. I'm thinking this is also at least an informal indication that the nut isn't overly tightened. So this is what I'm going with at this point, but will inspect things from time to time until I'm comfortable that there aren't any obvious problems.