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Torque Stick for air impact

DustyBar

Subscriber
Last Subscription Date
01/14/2020
What is your opinion on using a torque stick to limit torque with an impact wrench? In our shop we have been using them a few years but I often wonder how accurate they are which is why we only use them on lug nuts. Ten pounds error or maybe twenty on a lug nut usually isn't that significant. Its hard to actually measure the torque they applied to a bolt, once the nut stops turning its not much good to test it with a torque wrench since it takes so much to break them loose and turning again.
 

jcarter

Registered
A few years ago I was considering buying some of those. I talked to two tire shops in this area and they both said they would never use them. I am a big believer in properly torquing fasteners, especially those holding a rotating mass. I took their advise and didn't buy them.
 

J.B. Castagnos

Registered
Last Subscription Date
01/01/2006
It seems to me that the torque delivered would depend on the torque applied, who knows how much that is. We torque every wheel installed in our shop with a torque wrench, have two by the alignment-tire bays and one in the tool box, a chart with specs hangs on the wall.
 

DustyBar

Subscriber
Last Subscription Date
01/14/2020
They come in different sizes/colors and only limit the torque as you said. I got two for Christmas, the yellow one is marked as 60 ftlbs and the gray one is 100. I've only used the 100 ftlbs one in the shop. These are for my own use.

---------- Post added at 07:51 PM ---------- Previous post was at 07:46 PM ----------

I'm sure they are somewhat affected by the torque input. I've been told the tolerance is about 10% and if you put way too much torque into them they will shatter. We never use them as a regular extension to remove anything because of that. I think my IR is supposed to put out 800 ftlbs in reverse and something less in forward depending on which setting.
 

ehpower2

Registered
Age
29
What i always learned is they are good for wheel studs and nothing else as they are not accurate they just protect you from stripping out the wheel studs by flexing
 

DustyBar

Subscriber
Last Subscription Date
01/14/2020
I found some instructions on the back of the bubble pack the stick came on. It says the stick is calibrated at 250 ftlbs input and 90-100 psig air. Instructions are to verify the torque with a wrench in the tightening direction and to adjust the impact if the torque is not on spec. I'm skeptical of using a torque wrench to check the break-away torque. Grey Pneumatic even says to tighten the nut with one steady push and quit when it stops turning. Of course their catalog, www.gpsocket.com, doesn't contain any of this info.
 

dkamp

eMail NOT Working
The operational principle of the Torque Stick extension, is that it has known properties, therefore, will twist a certain amount based on the amount of force applied.

You can DEMONSTRATE the torque stick by connecting it to something that will not turn (like a socket in a bench vise), then attaching a pointer to the driven end, scribing a line on the workbench, then applying a needle-indicating torque wrench, and turning it until you get an indication of the torque-stick's rating, and observing the needle move off the scribed point.

Now, the torque stick twists a certain amount (known material properties, and known structural dimensions of the rod) just like a torsion bar. If the impact wrench's flying hammers can only swing it say... 10 degrees per impact, and the torque stick twists 11 degrees at that impact level, the torque stick will not be able to transmit more force than indicated.

If the torque wrench could swing it more like... 40 degrees, and the torque-stick requires three times' the rated torque to go that distance, one of two things will happen- it will either transmit more torque, or it will break.

So it depends on input, but more precisely, the NATURE of the input. If you put a standard wrench on it and then pull with your arm, it'll wind up like a rubber band, and either transmit more torque, or it will break...

And it's not a precise instrument. One could rig up a test set to measure applied torque, but the result would certainly vary based on the impact wrench's characteristics and the air pressure/volume, and probably to some level, ambient temperature.

I haven't had a torque-stick result in breaking anything, nor have I broken one, but I don't make a habit of using the impact gun to do anything other than install and remove fasteners quickly. I manually torque fasteners that are torque-sensitive. Impact wrenches are fast, and handy because they work in places when ratchets, breaker bars, and other tools would requre more hand, more body, or better angles, or a long time at all of the above.
 

SteveK

Subscriber
Last Subscription Date
08/26/2019
Maybe I am the exception:uhoh: I have used them for years installing hundreds of wheels with no problems. I set MY impact on 2 for my shop air pressure. Periodically I double check with the torque wrench. This is for cars.

I also have a 375lb torque stick that I run with the 1 inch impact for bus wheels, again hundreds have been installed with nary a ruined or loose nut.

I personally feel it is like most tools if used mindfully with some knowledge of how it works you will have no trouble.

Others have explained correctly exactly how it works.
Steve
 
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