Aluminum Tube Drawing with Position Control 3

[jimbod20]

I have two fundamental questions:

Is the attached drawing an appropriate way to define the tube assembly?
What does the position tolerance zone at each end of the tube look like? Is the position tolerance zone at each end of the tube a cylinder of diameter and length?

The tube is standard 1/4 inch od 6061 aluminum tube per AMS 4082.
The coordinate data of tube centerline bend points is defined by cartesian x/y/z coordinate intersection points with a toleranced bend radius at points 1-5 along the length of the tube.
The origin of the coordinate system is the geometric center of the tube
at the bracket location.
The bracket/fitting are tack welded in place and then dip brazed.
A mechanical fastener is installed in the bracket hole, therefore, the datum structure is primary (surface A) secondary (fastener hole-B) and tertiary/clocking (radius .205-C).
Drawing interpretation per ASME Y14.5M-1994.

Would you please comment/elaborate on my questions.

 

[jimbod20]

Hello,

I provide an updated attachment with more drawing definition.

 

[powerhound]

My first inclination is to say no, this is not an appropriate way to dimension this part. This is mostly because I don't bend tubes for a living so I don't know if there is a standardized way to do it. I do, however, read prints, make prints, and build parts on CNC mills and lathes from prints for a living and I don't think I could make this part with the information provided. I think you need at least one more view and definitely some angles other than an edge bevel. Any positional tolerances must be linked back to the datum reference frame through basic dimensions and there aren't any of those here.

The positional tolerance zone in both of your callouts are cylinders that are the length of the feature specified. Those lengths are not specified.



Powerhound, GDTP S-0731
Engineering Technician
Inventor 2010
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[pmarc]

jimbod20,
You may want to have a look to this link:

http://tec-ease.com/gdt-tips-view.php?q=128

Although it shows a tube with less complex geometry, the approach for dimensioning can be useful.

 

[SeasonLee]

jimbod20
Here is an excellent thread, a good reference.

http://www.eng-tips.com/viewthread.cfm?qid=237732

SeasonLee

 

[jimbod20]

Thanks Powerhound/Pmarc/SeasonLee,

I appreciate the help and would like to discuss drawing structure in more detail. I have spent ~20+ years in aerospace engineering as an analyst and test engineer (lubricated components and aero-thermo disciplines), however, I have a 'moderate' understand of GD&T and tube fabrication is new to me.

To the point;

I have reattached the tube drawing with drawing detail that was missing from the original post.

Design intent is as follows.
The brazed tube assembly is installed in the end assembly with a mechanical fastener through the hole in the machined bracket. The datum structure A/B/C is in accordance with mount installation. Surface A is primary, the .160 diameter hole is secondary and the .205 radius is tertiary. I provide B/C size as a reference at tube assembly level.

Points 1-2-3-4-5 lie along the centerline of the tube and are defined via x/y/z coordinates in upper left hand drawing coordinate data block. Note 14 provides x/y/z dimension tolerance of +/- .030 at points 2-3-4. Bend radius at points 2-3-4 is .375 +/- .020. Each end of the tube (points 1 and 5) are defined by "Basic" x/y/z coordinates with a position of .030 relative to datums A-B-C.

Note 12 requires inspection to be performed when restrained as installed in the end assembly.

I machine the fitting and bracket. I ship fittings/brackets to a tube supplier who performs tube bend, assemble/fixture tack weld, dip braze, heat treat, pressure test and final inspection. I provide a solid model in addition to the engineering drawing.

Would you please provide additional comment on drawing structure/notes and GD&T application/Interpretation/misuse relative to design intent.