The Nature of a Hole

[Will M]

Let's chat.

"Perfection is achieved, not when there is nothing more to add, but when there is nothing left to take away."

A drilled hole is one of the simplest machining operations.
My question for this discussion would be:
When you are designing a component do you see a drilled hole as REMOVING material or ADDING a feature?

No wrong answers, both are accurate, but what do you think?

I am a process engineer so I say adding a feature.

-William

[AxelRipper]

Well it depends on the nature of the hole. If it is simply there to decrease the mass of a part, then it is removing material. Same goes if you are drilling the hole as a pilot hole or starting another machining operation. However, if it is the mounting point for another feature or the part that you are making, then I would say you are adding a feature.

Now the question could be brought up what do the tolerances of the hole need to be? If it is simply there to reduce weight, does it need to be perfectly round? If something is mounted there, does it actually NEED to be a reamed hole? Is there a limit on how far off the hole can be and still accomplish its given function? If it is covered up and not moving, does the hole still need to be within a .100" tolerance if the part is still doing its job?

[Markus]

Naturally FSAErs don't get that much hole (racecars >> girls).
And a-holes are by nature usually, well, just that. But where goes the line between complete a-holes and regular a-holes? http://fsae.com/groupee_common/emoticons/icon_confused.gif

[MCoach]

Depends on your perspective.

To quality control, a hole is an added stress riser.
To the vehicle dynamics group, it's less weight.
To the machinist, it's an added operation.
To the interior designer, it's being modern. http://fsae.com/groupee_common/emoticons/icon_razz.gif

[onemaniac]

Originally posted by MCoach:
Depends on your perspective.

To quality control, a hole is an added stress riser.
To the vehicle dynamics group, it's less weight.
To the machinist, it's an added operation.
To the interior designer, it's being modern. http://fsae.com/groupee_common/emoticons/icon_razz.gif

Gold!

[BeunMan]

As an engineer I would say: Both are correct.

But it is stated by a philosopher and thus can be viewed as striving towards perfection by adding an operation (if it is a part or a hole or a calculation or anything) which gets you closer towards your goal.

And what Markus said.

[Z]

From "Tao Te Ching" (Verse 11):

"Thirty spokes converge at a hub, but it is the hole in the hub that makes it useful.
Mix clay to make a bowl. It is the empty space in the bowl that makes it useful.
Cut out doors and windows to make a room. It is these empty spaces that make the room useful.
Therefore, that which is there is an advantage, but it is emptiness that is useful."

Lao Tzu, ~400 BC.
~o0o~

(Wonder what sort of car "Old Man" would build? http://fsae.com/groupee_common/emoticons/icon_smile.gif)

Z

[Will M]

@AxleRipper
I like your point about reaming the hole.
In doing so you remove negligible material but add significant complexity to the feature.
If you are surpassing what is needed functionally for the machine how does that differ from decoration?

@Markus
“I’ll take ‘anal bum cover’ for $500, Trebek”

@MCoach
Hit it right on the nose.

****

A drill hole is a simple example but it scales as well.
i.e.
‘this part can be made in one piece but its saves X hours and Y dollars to make two items and bolt them together’
’I can make a custom part or buy it off the shelf’
‘I can spend a week doing FEA on this part and save one Kg or move to next piece and save that Kg in one day’

The simplest car may not be the lightest or have the fewest parts.
Removing weight can add complexity.

-William

[Owen Thomas]

Obviously from a manufacturing perspective, adding a hole will always be an extra operation. But, I like to look at it from an optimistic designers perspective and say that it can definitely be both. You can be removing material and adding a feature at the same time (from a functionality perspective), like designing a cooling channel. The same can be said for adding material. Adding a mounting bracket? Why not use it to stiffen your structure so weight can be lost elsewhere. Considering how features can be used for multiple purposes without compromising the primary functionality is one of the things I would attribute to elegant design.

I feel like this quote has less to do with manufacturing, and more with the paradox that designing a simple part is not a such a simple thing to do.