Multiple Hole Pattern Defintion

[ModulusCT]

So, per a previous post of mine, we've discussed that fact that TYP is a nonstandard way of indicating multiple instances of a dimension and a preferred method is to actually state how many times the dimension is applied (e.g. 24X R.125).

So I'm working on a fixture drawing that holds 4 164 pin connectors. I'm wondering if it would then be logical, given the statement above, to indicate the pin spacing of .100 is applicable 644 times.

Have a look at the attached PDF and let me know what you think. Another problem I'm having is in determining exactly how many times the .050 dimension applies (bottom left). It's 4X in one direction but really it's applicable in ~200 places. This is something that's always confused me... Perhaps an old company defined drafting practice is conflicting with Y14.5... In the case of the 8X .079 dimension on the left side of the print, would this dim actually be 32X? Or do I have to indicate 8X .079 in four different locations? I hope my question is clear.

Any references to the standard as it pertains to my question would be appreciated.

p.s. This drawing is not completed obviously... I'm aware that it looks unfinished.

 

[MechEng2005]

Before I start, I would like to point out that where I work we follow only company standards and not Y14.5 or anything of that nature. However, from my gut...

I believe many of you "#X" are incorrect simply because they indicate the same feature on a single line. For example, on the very bottom "4X 6.622", it should just be a dimension locating the centerline, and not have a "#X" preceding it. The 6.622 is locating the centerline (qty 1), not the holes.

Similarily, the 0.100 dimension is used to locate the holes in the 2nd line of each pattern. Therefore, each "instance" of the dimension locates 4 holes. The top and bottom lines in each pattern are then located by the horizontal (0.050) and vertical (0.100) already indicated. So the "0.100" dimension is only required to determine the spaces between holes for a single center row of a single pattern, hence "53X".

I've attached a (poor) markup of how I would interpret the drawing and what the quantities should be.

-- MechEng2005

 

[drawoh]

ModulusCT,

I try to not place quantities on linear dimensions.

If I am showing a dimension to a row of holes, I try to dimension to the hole on the far side, such that my dimension line crosses all the other centre lines. This has the additional advantage that sometimes I notice that the dimension line does not cross all the centre lines exactly.

I will show quantities for two holes separated by some detail that would be cluttered up by my dimension line. Dimensioning each hole separately, might be less messy and complicated.

On your drawing, I would make two detail views, each showing one of the connector configurations.

I do use the quantites on the repeated dimensions. This removes a lot of clutter as well as showing design intent.

JHG

 

[ModulusCT]

Wow - two very different answers... I'll have to give this some thought. The standard doesn't have any particular stance on this subject? I'll look myself, but if anyone knows off hand...

 

[drawoh]

ModulusCT,

I believe we are discussing format and clarity here, not the standard. If I see a plate with five holes apparently in a row with a dimension to the first one, I will assume they line up and that the dimension applies to all of them. If the part is complicated, I may be very confused. Your 5X tag tells me to look for five holes. A line all the way across allows me to see which holes lie exactly on the line. At some point, you have to do a drill table.

GD&T is a language. Often, there are several valid ways to express what you want. It is like writing prose. If you locate the verb a long way from the subject, it is hard for us to figure out what you meant, however correct the grammar is.

JHG

 

[ModulusCT]

Well my main concern is that it is clear... My next concern is adhering to the standard. I didn't mention that in my initial post, but I'm making this drawing in accordance with Y14.5 '94.

If it doesn't match the standard, than it's no good to me. Sorry I didn't mention that before. I should have.

 

[drawoh]

ModulusCT,

Everything we have described, including the drill table, is allowed by ASME Y14.5M-1994. You can put the X[ ]dimension to your hole on sheet[ ]2 of your eleven sheet drawing, the Y[ ]dimension on sheet[ ]6, and the hole diameter on sheet[ ]8, and the results will conform to ASME Y14.5M-1994. It will serve you right if your design checker is authorized to use force.

Section 1.9 shows you all sorts of ways to locate features. What is going to be clear to the people who have to read your drawing?

JHG

 

[ModulusCT]

I'm dissapointed however that there's nothing in the spec (that I've found so far) that states whether or not you can apply a dimension like the 644X .100 in my drawing to holes that are not in line with the dimensions extension lines.

In any case, I've decided to go with the two detail views idea... I've attached a pdf of the updated version. I think it's very clear now. Only thing I don't like is having to indicate "2 ROWS" in detail A. I also don't want to duplicate that dimension. Only other way I can think to indicate that those two rows are the same is to connect centerlines across all 55 columns. Unfortunately, my boss doesn't like using centerlines for that purpose (he's quirky).

Let me know what you think.

Thanks.

 

[drawoh]

ModulusCT,

That is a big improvement. Note how you have uncluttered the main drawing. Also, you provide the fabricator with an explicit statement that the detail features are indentical. He can now find some clever way to take advantage of this and make your part cheaper.

The 8X specs up the left side and the 56X specs up the right hand side are uneccessary at best, and confusing at worst. Your dimensions are locating the patterns.

The 54X on Detail[ ]A is very clear to me, even without the 2[ ]ROWS.

I do not see a problem with 644X one way or the other, except for the fact that it does not make things clear. However legal it may be, it is not good formatting.

JHG

 

[ModulusCT]

"The 8X specs up the left side and the 56X specs up the right hand side are uneccessary at best, and confusing at worst. Your dimensions are locating the patterns."

I did that to be accurate, nothing more... If I didn't include the 8X or 54X I would be worried that someone may not know that all 8 holes are in line with each other. I'm not sure how anyone could find those dimensions confusing.

Because the centerlines touch all the way across the 8X holes, I could see a case being made that the 8X is redundant, but not so on the 54X dimension.

Still disagree?

 

[drawoh]

ModulusCT,

Okay, maybe not confusing, but not necessary. I would do it if there were other features scattered across the panel such that the fabricator had to search for the five features. There is no interpretation of your drawing other than that the holes line up.

JHG

 

[ModulusCT]

I suppose I agree with you...

Thanks for the help!