[Nikhilb2008]

Thanks to a post on t-bhp by Dieselfan, my dad and me want to use Torque wrenches in our shops.

The problem is, manually using a torque wrench instead of a penumatic gun is very cumbersome and time consuming. Most people dont give a damn and it is only t-bhpians who will actually appreciate the effort.

So, what we thought was to calibrate the different settings on the pneumatic gun using a torque wrench.

There are 6 different settings on the gun. 0,1,2,3,4,5.

Now, my idea was to tighten a nut using, say setting no.3, and then use the torque wrench at any setting, say 80Nm.

Now, if the wrench clicks (implying that the required torque has been reached), I would increase the setting and keep trying until the nut got tightened a bit more.

This way, I could arrive at a rought estimate of each setting.

The problem is this.

Using the above method, I concluded that setting 3 was set to 135Nm. And setting 5 was beyond that. And setting2 was 75Nm. First of all, I dont think this is right.

Anyway, after arriving at these figures, I used the torque wrench to tighten a bolt to 100Nm. then I used the pneumatic gun. According to my calculations, at setting 3,4 and 5, the nut should tighten further.

But it didnt. The nut didnt get tightened further.

What am I supposed to do ? any other suggestions ?

Or is there anyway of using the Torque Wrench to check each nut after fitment has been done ?

[WasavaTyres]

Hi Nikhil,I'd also read the same and had pondered over it.Though I haven't practically tried it as yet.But I did speak to my IR supplier assuming he'd have some idea about the torque on various settings on a impact wrench,but it came to a naught. As far as I see it,the procedure you have followed is the only way to get a rough estimate of the various settings to use on the torque wrench.I'm also working on this and will keep you posted on the same. Do you use IR or CP tool ??

[anupmathur]

There are pneumatic and electric torque wrenches available. Accuracy of +or- 5% is possible.

[1100D]

Originally Posted by nikhilb2008

I used the torque wrench to tighten a bolt to 100Nm. then I used the pneumatic gun. According to my calculations, at setting 3,4 and 5, the nut should tighten further.

When you were trying the different settings on the Pneumatic gun, were you changing the torque settings on the wrench as well?

[Rehaan]

Very interesting topic nikhilb2008,

Your experiment has been done in a fairly scientific method, but there are two things you need to consider to gain more insight into your finding -

Originally Posted by nikhilb2008

Using the above method, I concluded that setting 3 was set to 135Nm. And setting 5 was beyond that. And setting2 was 75Nm.

1. Repeatability / consistency : Im guessing you did this only once. Do it several times and average the readings.

2. Starting torque : You say you are using a pneaumatic gun. (With no concrete evidence) i choose to assume that there is no way it generates as much starting torque (on its first few revolutions, or lack of) than it does once it has spooled up to operating speed.

So in conclusion, the first part of your experiment was right (and can be fine tuned by averaging a bunch of runs), since chances are that you will almost always be tightening a nut with a bit of a "run up" and therefore the pneaumatic gun should be putting out its specified torque on that setting once it has spooled up. You can neglect the part about trying the gun on a already torque-wrenched nut.

Hope that makes sense.

cya
R

ps - also try looking up the manual for your gun, it might have some torque ranges per setting.
ps2 - also i would "re-calibrate" your mental settings from time to time, since you never know what effect wear and tear on the limiting / clutch or whatever mechanism in the pneau gun may have.

[Nikhilb2008]

Originally Posted by anupmathur

There are pneumatic and electric torque wrenches available. Accuracy of +or- 5% is possible.

Mine is mechanical. Not pneumatic. The only pneumatic tool I am using is the pneumatic gun.

Originally Posted by 1100D

When you were trying the different settings on the Pneumatic gun, were you changing the torque settings on the wrench as well?

I was changing settings on thge pneumatic gun also !! I thought thta was obvious from my post .

Originally Posted by Rehaan

Very interesting topic nikhilb2008,

Your experiment has been done in a fairly scientific method, but there are two things you need to consider to gain more insight into your finding -



1. Repeatability / consistency : Im guessing you did this only once. Do it several times and average the readings.

2. Starting torque : You say you are using a pneaumatic gun. (With no concrete evidence) i choose to assume that there is no way it generates as much starting torque (on its first few revolutions, or lack of) than it does once it has spooled up to operating speed.

So in conclusion, the first part of your experiment was right (and can be fine tuned by averaging a bunch of runs), since chances are that you will almost always be tightening a nut with a bit of a "run up" and therefore the pneaumatic gun should be putting out its specified torque on that setting once it has spooled up. You can neglect the part about trying the gun on a already torque-wrenched nut.

Hope that makes sense.

cya
R

ps - also try looking up the manual for your gun, it might have some torque ranges per setting.
ps2 - also i would "re-calibrate" your mental settings from time to time, since you never know what effect wear and tear on the limiting / clutch or whatever mechanism in the pneau gun may have.

Repeatability --- Rehaan, that is the problem.... the first time, I got 70Nm for Setting 2 on the gun. Another time, I got 100Nm.

Now, after this, I didnt try a third time. I shifted tracks to trying to tighten the nut with the wrench and then used the gun to see if the nut got tightened further.

Hi Nikhil,I'd also read the same and had pondered over it.Though I haven't practically tried it as yet.But I did speak to my IR supplier assuming he'd have some idea about the torque on various settings on a impact wrench,but it came to a naught. As far as I see it,the procedure you have followed is the only way to get a rough estimate of the various settings to use on the torque wrench.I'm also working on this and will keep you posted on the same. Do you use IR or CP tool ??
__________________

What is IR and CP ?

Mine is one made by "Macmaster India".

[im_srini]

Hi Nikhil, I think what Wasava meant was Ingersoll Rand (IR), & Chicago Pneumatic (CP), both popular manufacturers of pneumatic wrenches... I was turned on to pneumatic wrenches when one was used to tighten the lug-nuts in my car when I upgraded my tires, & when I tried to loosen them on getting home, I actually broke a socket wrench !

Could the anomaly you're experiencing be because of the way impact wrenches work ? I mean the hammer spinning, & then made to impact the anvil, & all that ? A mechanical torque wrench on the other hand would pretty much experience a very consistent load. You seem to have followed a very logical procedure to calibrate your impact wrench, I would like to hear a technically satisfying reply to your query from the experts.

[anupmathur]

Originally Posted by nikhilb2008

Or is there anyway of using the Torque Wrench to check each nut after fitment has been done?

Very interesting problem, Nikhil. Till some satisfactory method can be found, I would suggest the following:
Use the pneumatic gun to quickly tighten each nut to a value WELL BELOW the required torque. Then do the last bit of torquing with the Torque Wrench.
And you are aware that torquing is highly dependent on the lubricant being used, otherwise the 'bolt elongation' is simply not correct.

[Nikhilb2008]

thank you for replies....

But I am still stuck.

I dont know how to use the torque Wrench quickly.

@anup Mathur --- That is one way...but it is a bit complicated.

And how do I know which is a value well below the required torque ?? I am not able to find any proper value for the settings on the pneumatic gun.

Setting 2 first came up to 70Nm and then it came up to 100 or so.

[anupmathur]

For correct and repeatable 'torquing' EACH nut must move EQUALLY freely on the threads of its bolt. Finally, the 'landing' face must be EQUALLY smooth in each case (in terms of the coefficient of friction). The FINAL contact is the mating faces of the nut and the base - these are generally larger values than the friction being offered by the threads during the last stages of tensioning.
If any of these conditions are not met, (and in real life they will most often NOT be met), you will be sitting with each bolt tensioned to a different value. Which is why in critical applications only hydraulic tensioning is used.
Sorry, cannot think of any further practical tips at the moment.

[Nikhilb2008]

Anyway, I have come to the conclusion that I dont have any choice but to use the Torque Wrench like this....

Tighten the nuts with the pneumatic gun set at very low setting (1 or 2). then, use the Torque Wrench to tighten it to the required torque (which will vary from car to car and I have already started making a list of cars and the torque at which they should be tightened).

The problem is, we cant do this for every car, so, we plan to put up a board saying something like "If you want us to check the torque, please request".

This will be done only on a request basis.

Any other suggestions ??

[anupmathur]

Nikhil, since you are in the trade, you would know: How many cars have their wheel nuts (& bolts) in good enough condition to allow accurate torque tightening?
I mean this in the sense of good threads and undamaged mating faces. And how many makers specify the torque to which wheel nuts should be tightened? And with which lubricant?
For example, the torque requirement with oil as lubricant would be nearly DOUBLE of torque required if a molybdenum disulphide grease is used, for the same degree of tightening as measured by bolt elongation. (Most 'black' greases are molybdenum disulphide based).

I'm asking because I feel that this is not a critical area. Makers seem to have left enough margins for these nuts to be tightened over a very wide range. (Is that correct?).
I am full of admiration for your sincerity! I'd love to see more garages become as conscientious.

[Nikhilb2008]

Originally Posted by anupmathur

Nikhil, since you are in the trade, you would know: How many cars have their wheel nuts (& bolts) in good enough condition to allow accurate torque tightening?
I mean this in the sense of good threads and undamaged mating faces. And how many makers specify the torque to which wheel nuts should be tightened? And with which lubricant?
For example, the torque requirement with oil as lubricant would be nearly DOUBLE of torque required if a molybdenum disulphide grease is used, for the same degree of tightening as measured by bolt elongation. (Most 'black' greases are molybdenum disulphide based).

I'm asking because I feel that this is not a critical area. Makers seem to have left enough margins for these nuts to be tightened over a very wide range. (Is that correct?).
I am full of admiration for your sincerity! I'd love to see more garages become as conscientious.

Thanks for the kind words

I am not in the business yet. We dont have a garage but a tyre showroom.

It is Dad's shops. I am just helping out when I have time. Plan to join once I am done studying.

And abt the manufacturer specifying the settings, my dad is also in the garage equipment business and so, he has a book where all the relevant info is given. But that booklet consists of mainly imported cars and the numbers given there are useful for cars like the Corolla, Skoda, etc....

For the others, I am still trying to find out what the recommended settings are (Maruti, Hyundai, etc... )

And I have no idea abt how many nuts are actually in a good condition.

And, while tightening wheel nuts, we dont use lubrication.

[Rehaan]

Also, you probably know this, but its reccomended that alloy wheels are retorqued once again 100km after fitting the wheel back on.

cya
R

[Nikhilb2008]

Originally Posted by Rehaan

Also, you probably know this, but its reccomended that alloy wheels are retorqued once again 100km after fitting the wheel back on.

cya
R

Nope... I didnt know that ! My dad might have known abt it before though

And what do you mean retorqued ? Just removing the nut and fitting it back again? Why only for alloy wheels ?