Help with Torque Please

I'd set it at the maximum safe rating of the tank and compresser.

Set the regulator to the maximum rating of the air tool.

The air tool should have a toruqe setting. Or you could compare some readings between the air tool and a hand torque wrench ans set the controls to that.

You want magimum possible air flow with air tools, that's what the big surge tank is for. You DO have a surge tank, right????

That's the only way to do it unless you're changing tires for Jeff Gordon.

I insist on it at the tire shop. I have had shops overtighten them and use a torque wrench after that. Problem is, the torque wrench they used was a clicker type. Once it clicked the tech let off. That click didn't tell him if the nut was overtorqued by 30 foot pounds.

Does that make sense?

There's no way to do this reliably, all impact wrenches are different....and the hose setup makes a difference...best way is to check with a torque wrench to ballpark it....work with the same impact tool until you get a feel for it...test with a torque wrench occasionally...

OK,

I gotta ask.

Is your compresser over 5HP and do you have a surge tank? What's their specs?

Kramarat is correct. A torque wrench should always be used for the final torquing. Garages use pneumatic wrenches, so they don't know what the torque is. results in broken studs or loose nuts.

The most fun is when a garage does it, like with a tire rotation, they overtorque the lugs to the point that no human could loosen them, and then you get a flat in the middle of nowhere.

There are torque limiting devices for use with pneumatic wrenches, but I've never seen any garage using them.

Either use a torque wrench or buy a torque stick (also known as a Torque Extension Bar) to use with your impact wrench. http://www.google.com/search?q=torque+sticks

After a quick search on torque sticks I found no convincing explanation as to how they work, all they say is basically: "after applying certain torque, they apply no more because they flex" so I ellucubrated an explanation myself:

The impact wrench used at the shops is basically a pneumatic hamer pushing a ratchet mechanism to produce rotative movement.

The stroke of the hamer is always the same, and it moves past the edge of every tooth of the rush in order to get hooked on it and push it for the total stroke lenght.

When the torque stick is attached to the tool, due to its spring-like construction, it twists when reaches certain torque, not allowing the full stroke of the hamer to be transmited to the ratchet, so the next tooth won't catch and the hook will be running within the same tooth over and over; all of wich results in no more rotation of the socket.

How about that ?

P.S. To the O.P. I say: I'd buy one of those things, besides it is in our gender nature to always want more tools.

Only impact wrench supplier/manufacturer can tell some rough estimate. With pneumatic impact wrenches even estimates have higher value of variations. For good results use torque wrench only.

No, because of the fact -which nobody mentioned- that the torque obtained depends on the assembly stiffness. If you bolt is short the torque will go higher and lower if the bolt is long. Those tools do not generate "torque" , they "inject" energy impulses" in the assembly this is the reason for the difficulty to control.

There are devices called simulators which can give an information but most of them have not variable stiffness so that one can only compare tools for same conditions but not calibrate them for the specific assembly.

The only correct method is to make a series of torquing of SAME assembly as you will have to work on and control with a calibrated torque wrench which torque level has been obtained at different supply pressures.

Unfortunately such procedures are not used in workshops around the corner.

The problems with the mechanical impact tools lead to the development of the hydraulic impact tools which allow a torque setting for a given assembly.

Hi Poops,

We sell several different 1/2" torque wrenches that deliver from 230 to 590 ft.lbs.

It depends on the internals.

You can limit the torque with the air pressure but the main problem is, the longer you hammer, the more the torque, so you really do need to do the final tightening with a torque wrench.

Also don't let the tool impact too long (2 or 3 seconds will do) or you will wreck it.

Best regards,

John

I am sorry to contradict you but what you write is wrong. Every impact injects an energy amount into the assembly. The assembly is as a spring when energy goes into it it will deform (thus allowing to the nut/bolt a rotation) and the preload will increase. But there is a but: the increase in preload per impact will decrease and after a number of impacts which depnds on the pulse energy and the assembly compliance the torque does not increase anymore.

This is the way the torque sticks work they increase compliance and thus capacity to absorb energy so that less energy goes into the assembly, direct follow up is a limitation of torque.

The problem with impact or impulse tools is that you shall not any more thik "torque" as with all other torquing tools but "energy". This is usually NOT clear and never well explained so that many errors are made and many assemblies destroyed by over tightening.

Thanks so much everyone. Think I will just use a normal torque wrench

I calibrate these. They work very well and will do what you want.

http://www.radtorque.com/products_pneumatic.php

Great ! with one of these I'd even be willing to do the tire rotation to my cars.

Anybody ever used one of these digital socket torque adapters? Looks pretty slick.

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It goes on your existing socket wrench. Harbor Freight has them for $30.00USD. (Not an endorsement)