Torque callouts
Torque callouts
(OP)
Is there a particular standard that gives the requirements for calling out torque values on the drawing? When I worked for a military contractor, we used a table with Roman numerals and their corresponding torque values. Where I am now just calls the torques out next to the fastener callout. Please help.





RE: Torque callouts
Chris
Systems Analyst, I.S.
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ctopher's home site (updated 06-21-05)
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RE: Torque callouts
Best Regards,
Heckler
Sr. Mechanical Engineer
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RE: Torque callouts
Thanks for all of the input.
RE: Torque callouts
Don't forget to provide reasonable tolerances on the torque values!
Tunalover
RE: Torque callouts
RE: Torque callouts
A target torque should be identified. This is what an operator would use.
A torque range can be specified for quality control purposes. Another person in QC would use this range to inspect the process.
The relationship between target and inspection limits should be developed with actual data from actual parts.
Regards,
Cory
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
RE: Torque callouts
Chris
Systems Analyst, I.S.
SolidWorks/PDMWorks 05
AutoCAD 06
ctopher's home site (updated 06-21-05)
FAQ559-1100
FAQ559-716
RE: Torque callouts
Pete
RE: Torque callouts
The concept of a QC torque check on an already tightend fastener is rediculous.
So, the only possible use for a torque range on an assembly drawing is to QC check the calibration of the torque wrench.
RE: Torque callouts
Chris
Systems Analyst, I.S.
SolidWorks/PDMWorks 05
AutoCAD 06
ctopher's home site (updated 06-21-05)
FAQ559-1100
FAQ559-716
RE: Torque callouts
RE: Torque callouts
Chris
Systems Analyst, I.S.
SolidWorks/PDMWorks 05
AutoCAD 06
ctopher's home site (updated 06-21-05)
FAQ559-1100
FAQ559-716
RE: Torque callouts
However, we need to differentiate between design and process and process control.
The process for the guy pulling the wrench should define what to set the wrench to. In my opinion this should be a single number.
The process controls need to define how much devation between the wrench setting and the actual torque applied is allowed before the wrench goes for recalibration. The manufacturing engineer needs to know both the joint design and the calibration information to properly define the right number for the guy pulling the wrench.
RE: Torque callouts
Chris
Systems Analyst, I.S.
SolidWorks/PDMWorks 05
AutoCAD 06
ctopher's home site (updated 06-21-05)
FAQ559-1100
FAQ559-716
RE: Torque callouts
This is standard practice in the automobile industry.
The concept is that you are checking the process (operator, power tool, air pressure, etc.) and the parts (torque variation might be due to stripped threads, burrs, relaxation due to insufficient strength, etc.)
I think it has limited value, but the auto industry "found religion" with QC, and so QC has a huge inertia (large department workforce, representation on committees, management oversight, etc.).
Taking the QC check to the next level, here is what one company proposes as a QC check to determine torque-tension relationship:
http://www.hexagon.de/tasignat.htm
Regards,
Cory
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
RE: Torque callouts
RE: Torque callouts
Do those auto stds indicate what to call out on the dwgs for torque?
Chris
Systems Analyst, I.S.
SolidWorks/PDMWorks 05
AutoCAD 06
ctopher's home site (updated 06-21-05)
FAQ559-1100
FAQ559-716
RE: Torque callouts
Starchief
Sr. Project Engineer
SolidWorks 2006/Cosmos 2006
RE: Torque callouts
Chris
Systems Analyst, I.S.
SolidWorks/PDMWorks 05
AutoCAD 06
ctopher's home site (updated 06-21-05)
FAQ559-1100
FAQ559-716
RE: Torque callouts
ok, I'll buy that-
Number of active coils on a spring, plus/minus?
Pitch diameter of a gear, plus/minus?
4340 steel, plus/minus?
The first two were actually demanded by an inspection department. But you know what its like arguing with an inspector, ha ha.
RE: Torque callouts
Everything specified on a drawing should have some type of tolerance associated with it. 4340 steel is toleranced by it's composition and manufacturing process. It is not the same as 4130 or 4140.
A 1/4-20 UNC-2B thread has tolerances determined by "UNC-2B". If the number of active coils on a spring is critical to the function of the design, then yes, it is specified. The same goes for the pitch diameter of a gear, even if it is only a partial diameter and only consists of a few gear teeth.
Fortunately, most of the tolerancing in the above examples is defined in their related specifications, or engineering drawings would be that much more complex.
You can argue with inspectors all you want, but if you don't have solid evidence to back yourself up, no inspector worth his salt is going to let you win.
RE: Torque callouts
thank you.
EngJW, you should have a copy of Machinery Handbook if you don't have one ... and ASME/ANSI standards.
Chris
Systems Analyst, I.S.
SolidWorks/PDMWorks 05
AutoCAD 06
ctopher's home site (updated 06-21-05)
FAQ559-1100
FAQ559-716
RE: Torque callouts
The assembly documents will have an assembly torque specification and an inspection torque specification. Some companies use ranges for both. For example, if you use an electric power tool, it can be automated to shut off after a certain torque or torque plus angle or angle only. There will be some variation in these values, so the tool controller is pre-programmed with a lower torque limit, upper torque limit, lower angle limit, and upper torque limit. Then, each joint on each vehicle can be monitored for quality.
Regards,
Cory
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
RE: Torque callouts
Chris
Systems Analyst, I.S.
SolidWorks/PDMWorks 05
AutoCAD 06
ctopher's home site (updated 06-21-05)
FAQ559-1100
FAQ559-716
RE: Torque callouts
Also, I would put the tolerance in my tolerance block. That way you only have to spec the tolerance once. And besides, whoever is assembling the parts should aim for the torque number spec'd and let QA deal with the tolerances. That is why you have tolerances, so that you can have imperfect people building to a perfect spec and when it comes out wrong, QA decides if it passes or not based on the tolerances.
RE: Torque callouts
Starchief
Sr. Project Engineer
SolidWorks 2006/Cosmos 2006
RE: Torque callouts
Chris
Systems Analyst, I.S.
SolidWorks/PDMWorks 05
AutoCAD 06
ctopher's home site (updated 06-21-05)
FAQ559-1100
FAQ559-716