Torque callouts

[Starchief]

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.

 

[EngJW]

"Everything on a dwg requires some type of tol."

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.

 

[ewh]

Hey, I can be axxl too.
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.

 

[ctopher]

ewh,
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

 

[CoryPad]

Most auto companies use assembly documents instead of drawings for 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.

 

[ctopher]

The only thing to call out on any dwg is the torque range, nothing else. The rest is up to the mechanic or technician.

Chris
Systems Analyst, I.S.
SolidWorks/PDMWorks 05
AutoCAD 06
ctopher's home site (updated 06-21-05)
FAQ559-1100
FAQ559-716

 

[aardvarkdw]

I would put the torque spec in a table if you have a lot of them and designate which fasteners are which with some sort of letter designation. Otherwise just put the torque spec in a flag note.
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.

 

[Starchief]

OK, so back on topic: Are there any recognized standards that stipulate how torques (regardless of tol.) should be called out on the face of an assy dwg?

Starchief
Sr. Project Engineer
SolidWorks 2006/Cosmos 2006

 

[ctopher]

As you mentioned above, start with the ASME stds as guides. The same stds apply as if it were a dimension.

Chris
Systems Analyst, I.S.
SolidWorks/PDMWorks 05
AutoCAD 06
ctopher's home site (updated 06-21-05)
FAQ559-1100
FAQ559-716