Drawing standards only for Military work 6

[KENAT]

We have a number of Engineers here who seem to think that the ASME drawing standards etc are only for military work and have no place in a commercial organization.

How would you respond?

Also If people want to make this some kind of survey of "We use the standards and are/are not Defense/Defence" that would be great.

KENAT, probably the least qualified checker you'll ever meet...

 

[KENAT]

No mass production here. Howevever mistakes can be expensive and/or cause delays so we have the checking function.

KENAT, probably the least qualified checker you'll ever meet...

 

[drawoh]

MikeHalloran,

I prepare fabrication drawings that call up thread inserts that are to be installed by the fabricator. I do not get to see the intermediate steps. If the inserts work okay, I do not care. Presumably, if the shop follows the manufacturer's instructions, everything works.

Obviously, if I were planning to install the thread inserts, it would be better for me to read the manufacturer's literature and provide complete call-outs.

I cannot recall having problems with PEM inserts. I have had problems with some helicoil inserts. Eventually, I inspected the tapped holes with a thread gauge and I determined that they were oversized. The fabricator's excuse was that they had used an old, dull tap. Calling up the tap drill size on my drawings, another popular trick, would not have saved me.

In a truly mass production environment, would it not be logical for the fabricator to provide additional documentation and tooling for manufacturing and inspection? The usual principle behind engineering drawings is that they describe what we will accept at our loading dock. There is no reason to assume that manufacturer A would do the job the same way as manufacturer B, and we do not care.

JHG

 

[Tunalover]

I forgot to mention a few other reasons why the INSTALL PER THE MANUFACTURER'S RECOMMENDATIONS or INSTALL PER THE ITEM'S GOVERNING SPECIFICATIONS is the right way to go:

A. The drawing is tolerant of changes. Change of a fastener would require only a change to the parts list. The drawing itself would be unaffected.
B. Invoking the fastener manufacturer's recommendations places the latest and greatest quality assurance provisions on the installation; it requires the fabricator to keep an up-to-date version of the fastener mfgr's installation procedure at hand at all times. Otherwise he may get complacent and use an installation procedure from 1979 while the design and installation procedure may have evolved since since then. It's absurd to discuss this in the context of a clinch nut, but this practice becomes more influential as the fasteners becomes more complex, expensive, and expensive to install.

It all boils down to following sound principles and practices. A good drawing promotes consistency and quality by emphasizing the end-item and functional requirements and leaving out rote process data like installation hole sizes.

It looks like MikeHalloran has succumbed to Manufacturing's propaganda. Now that we've started breastfeeding the fabricators why don't we add a note that says "DO NOT DEBUR INSTALLATION HOLE"?

An assy may have threaded holes in it too. Wow, I think we could REALLY handhold the fabricator there. Let's call out the drill size for tapping into AL6061-T6. That way, when we change the material to titanium three years later and we forget to change the drill size (SH7, Zone B6) then we can argue with the fabricator when he complains about using the wrong drill size for 27 pricey titanium parts.

I'm sorry to preach to the choir but we must LET THE FABRICATOR DO WHAT HE DOES (KNOWS) BEST. A good fabricator doesn't need (or want) to be told what drill size to use for tapping a .086-56 UNC-2B hole a quarter inch deep in titanium. If he DOES want the information then he's using inexperienced (cheap) machinists or has poor practices. A good machinist has the information in his head or in a tattered up handout at his workstation. If not then the traveler that goes onto the floor will have the information in the form of instructions from the Production Planner.

Resist the urge to complicate the drawings by adding all that process information to the drawings!

Now multiply these notes by the number of fabrication drawings a big project has and you end up with a set of drawings that would be very expensive to revise!



Tunalover

 

[KENAT]

tunalover, while I tend to agree with you you are maybe a little harsh on Mike.

In the particular instance talked about in detail, i.e. installation information for captive fastener, there isn't a one size fits all answer.

If treating as an inseperable assembly then yeah, per manufacturers instruction. However, not all drawing systems really deal/cope with inseperable assemblies as such, the one I worked to in the UK didn't so we tended to put the hole size etc on the part drawings while the captive fasteners were called up at the assy level.

Even then using the manufacturers instruction assumes that in between the creation and the drawing there is either a manufacturing/production/industrial engineer and/or a skilled machinist that can invoke & apply the manufacturers instructions.

For a small shop creating their own drawings for internal use, there may be justification for puting the detail on the piece part even when treating as an inseperable assy however, I agree this is straying away from classical drawing practices and in most cases is a bad idea.

KENAT, probably the least qualified checker you'll ever meet...