Clocked angular dimensions 2

[looslib]

We have a drawing that has a bolt circle with 4 holes on it. The holes are basic angles as is the bolt circle diameter.
The wholes are at the 45 position, so we have 1 dimension of 45 to the first hole off the axis of the part in the drawing.
My questions is, what dimensioning do we use for the other 3 holes with a basic angle: 3X 90 or 4X 90?
I looked in ASME Y14.5-2018, but only shows angular dimensions that are on an axis.


"Wildfires are dangerous, hard to control, and economically catastrophic."

Ben Loosli

 

[Burunduk]

You show just the 45° if this is the dimension that defines the pattern orientation. Basic 90° angles are implied and not shown. It is more important to make sure that there is a clear basic orientation relationship between the pattern and the clocking datum feature that sets its orientation. Is the 45° basic related to it? "45° off the axis of the part in the drawing" alone doesn't mean that much.

 

[axym]

looslib,

Figure 4-52 in 2018 shows angular dimensioning for an 8-hole bolt circle. One 22.5 degree angle is dimensioned, and then 8X 45 deg. So I think in your example it would be 4X 90 deg.

Evan Janeshewski

Axymetrix Quality Engineering Inc.

http://www.axymetrix.ca

 

[3DDave]

Isn't 8X 45 overdimensioned?

 

[pmarc]

Fig. 7-21 in 2018 should help.

 

[axym]

3DDave,

Are you thinking that if the angles are directly toleranced, then the tolerance on the 8th angle will be a stackup of the other 7? Then yes, I think you're right. If the dimensions are basic dimensions for a Position tolerance, then there is no issue.

pmarc,

Fig. 7-26 in 2018 should then muddy the waters. It's the same thing as 7-21, but different. ;^)

Evan Janeshewski

Axymetrix Quality Engineering Inc.

http://www.axymetrix.ca

 

[pmarc]

Evan,

Yes, fig. 7-26 muddies the waters. Interestingly enough, the situation is opposite in 2009. Fig. 4-15 has [4X 45 deg], while fig. 4-18 has [45 deg] only.

But allow me to muddy the waters even more - this time regarding your reply to 3DDave. Fig. 7-45 in 2018 has [4X 72 deg] instead of [5X 72 deg]. So should or should not the sum of angles give 360 degrees?

 

[greenimi]

Fig. 7-45 in 2018 has [4X 72 deg] instead of [5X 72 deg]. So should or should not the sum of angles give 360 degrees?

Sorry, I am not understanding your question: I think it should and 4X (instead of 5X) is just a mistake.
Why do you think otherwise (if you do)?


I think 7-21 and 7-26 are just a mess (gross inconsistency) about those basic angles dimensions

 

[pmarc]

greenimi,

I am not saying it should be [4X 72 deg]. But if this is a mistake, then either [4X 45 deg] or [45 deg] can be a mistake too.

It is really a mess.

 

[3DDave]

I recall that there is a requirement never to double dimension - basic or not - "No more dimensions than those necessary for
complete definition shall be given."

Figures 1-19 and 1-56 in the '2009 version, for example, making no particular differentiation between basic and directly toleranced.

 

[pmarc]

The standard is full of examples where the sum of angles is 360. In 2009, these would, for example, be: 3-29, 4-4, 7-1a, 7-16, 7-24 thru 7-26, and so on and so forth.

 

[Burunduk]

The standard is full of examples where the sum of angles is 360. In 2009, these would, for example, be: 3-29, 4-4, 7-1a, 7-16, 7-24 thru 7-26, and so on and so forth.

There is one even right on the front cover.

 

[3DDave]

Yeah. It's not like the standards group likes consistency.

 

[Burunduk]

8X 45° is just more straightforward. For an eight holes pattern every angular space between any two holes is basic 45° and that's everything that there is to know. Communicated briefly on the drawing, and no need to do any math.

 

[3DDave]

EQ. SPACE => less math than that an gives the exact answer no matter how many holes there are.

But let's try this. On a rotary table, how many times will the 45 degree adjustment be made after the first hole is drilled?

 

[Burunduk]

Agree about EQ. SPACE, that's my preferred way.

7 rotary table adjustments to drill a full crown pattern of eight holes still results in 8 spaces between holes and that's what the drawing reflects.

 

[3DDave]

So - 7 measurements. That's the number to put on the drawing.

 

[greenimi]

Yes, but EQ. SPACE is not a term defined in Y14.5. It is the same as TYP (typical) and is to be avoided.

So, still "counting" features (gaps), basic dimensions is probably the the best from Y14.5 point of view

 

[Burunduk]

What 7 measurements?
There are 8 true position axes locating 8 tolerance zones on a basic pitch circle with 8 basic angular spaces between them.

 

[3DDave]

Since they are basic then it's OK to put the dimensions between each pairs of holes, right? It's cyclical and therefore infinite. so ∞X 45 degrees.