Click Type Torque

[Mechotron]

Hi All,

I have a question regarding click type torque wrench. Our assembly shop utilises a click type torque wrench Which has a removal head. Beacuse of a design constraint we had to design a head. The head was longer than the standard heads. Does it affect the torque applied. We are supposed to apply a torque of 70 lbf-ft. Being slightly longer, i would expect the torque applied to be higher as well. Am i right in saying that or because it a click type torque wrench, will be torque still be 70 lbf-ft though the head is higher?

 

[MikeHalloran]

Changing the length of the head changes the torque... so it's not calibrated anymore.



Mike Halloran
Pembroke Pines, FL, USA

 

[tlee123]

If you haven't changed the adjustment (locked by a setscrew maybe?) then I would think that the torque at which the wrench will "click" will not change.

In other words, it's still calibrated.

Any way you can do a quick check which of course is not the same as a calibration?

 

[iainuts]

If you were to put a crow's foot on a torque wrench, the torque will not be correct because of the additional length. So if you've similarly extended the head somehow, chances are the torque is also affected.

 

[unclesyd]

Torque wrenches are calibrated on center distances. If you want to verify check the modified wrench with a sstandard on a double nut setup.

The following calculator will get you within horse show range.

http://www.cncexpo.com/TorqueAdapter.aspx

 

[tlee123]

If you using a toque wrench like the one shown in unclesyd's post, then yes, the torque will change with a different "head" length.

In my earlier response I was thinking of this type, a torque limiting screwdriver:

http://www.bluetools.com/p207/Utica...wdriver,-6-30-in.lb.,-TS-30/product_info.html

 

[waross]

In a click type torque wrench, I believe that the factor is the distance from the bolt center to the center of the pivot pin near the wrench head. Yes an extension will change the torque calibration and much more dramatically than would be indicated by the calculations in the link.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[lumenharold]

Are the heads interchangeable or do you have a calibration standard? You could install a bolt in a plate at your specified tourque and then check the break-away torque with both wrenches. They should be the same as each other and very close but just slightly higher than the installation torque.

Harold
SW2009 SP4.0 OPW2009 SP2 Win XP Pro 2002 SP3
Dell 690, Xeon 5160 @3.00GHz, 3.25GB RAM
nVidia Quadro FX4600

http://www.lumenflow.com

 

[TheTick]

All these engineers, and no one doing the math...

New torque = torque setting * new length / old length

For "analog" wrenches, getting the length is easy, measure from center of socket to the pivot in the handle.

For click-type, I'm not sure how to find that point, as it is concealed inside the handle. You might just need to set up a test apparatus.

 

[waross]

Hi TheTick;
In the few click type wrenches that I have owned, the "Click" pivot is an easily visible pin where the handle joins the head.

http://www.craftsman.com/shc/s/p_10...uipment&cName=Hand+Tools&sName=Mechanic+Tools

In the posted link, you can see the pivot pin very close to the head. I believe that this is the point from which to measure the new distance to the center of the bolt when recalibrating for an adapter that changes the working radius.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[unclesyd]

In a click type wrench the length is from the center of square drive to the middle of the handle, usually marked.

Do not use breakaway torque to calibrate anything as it can be many times the applied torque.

 

[lumenharold]

unclesyd,

True, breakaway can be many times the applied torque. I made some assumptions about the screw head type based on my own experiences. If you have confidence in the calibration or reference standard, would that matter? If the goal is to verify the modified wrench it would seem that a correlation could still be made. A screw in a plate is a pretty cheap test apparatus (although it might not be what the Tick had in mind).

Harold
SW2009 SP4.0 OPW2009 SP2 Win XP Pro 2002 SP3
Dell 690, Xeon 5160 @3.00GHz, 3.25GB RAM
nVidia Quadro FX4600

http://www.lumenflow.com

 

[waross]

I have checked the calibration of click wrenches with bending beam wrenches. I am sure that there are more than one type of clickwrench, unclesyd, my wrenches had the pivot very near the head and it did not matter where on the handle the force was applied. I could clamp the wrench handle in a vise and use a bending beam type wrench to find the "Click" torque. It made no difference where on the handle I gripped it in the vise as long as I didn't interfere with the pivot pin.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[unclesyd]

We used a deadweight tester made by Skidmore Wilhelm, no longer available, if possible. We would use the double nut for a quick and dirty comparison.
If your need results to be very accurate I would get one to a claibration machine and look at the results.
Another way is to buy a torque wrench with interchangeable head tools.

waross,
Did you ever calibrate the beam type torque wrench?