Dimensioning Multiple Unique Holes 1

[chez311]

I have a quick question that I can't seem to find an answer to by searching around in the usual spots - however to be fair I haven't poured over ASME Y14.5 or similar GDnT documentation/standards.

I do quite a bit of fixture plate design for use in a CNC mill and they are often filled with quite a few holes of varying size/depth. More times than not, several of these holes are very close in size, sometimes within a few thousandths so they aren't necessarily easily visually discernible as different if I were to put 3x "X" dimension/depth and 2x "Y" dimension/depth and so on. I have my own ideas about what I could do to group these together short of dimensioning every single hole individually, however I am wondering if anyone out there might have a suggestion, maybe from their own best practices or a drawing standard. I do not necessarily need to conform to a strict standard, I really just need something that is visually neat/organized.

I have attached a sample (blank) plate which I will have to create a drawing for.

 

[DraftingMan]

chez311,

A hole chart might be the cleanest way.


John H. Dunten, CD
Certified Drafter

 

[drawoh]

chez311,

I have actually been banned from using hole tables. This is unfortunate, since the machine shops like them, and DraftingMan is correct.

I am on SolidWorks here. If I have two sets of similar holes, I sometimes open the Insert, Annotations, and I place the dowel pin symbol on one set of holes. On 3D[ ]CAD, you can show multiple instances of the same view, and use each one for one set of holes, only. This is bad practice on a drafting board, but hopefully, you are not on a drafting board.

If you are on a board or on dumb[ ]2D[ ]CAD, you can methodically draw one set of holes out of scale. The ASME AY14.5 standard requires you to underline not-to-scale dimensions. It would be helpful to leave a prominent note warning that you did this. In 3D[ ]CAD, the model is accessed separate from the drawing, so that practice is unacceptable.



--
JHG

 

[dgallup]

This is exactly what hole charts were invented to do.

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The Help for this program was created in Windows Help format, which depends on a feature that isn't included in this version of Windows.

 

[KENAT]

With our current version of CAD they 'forgot' to add the ability to properly add GD&T FCF's to the table so I don't use hole tables much.

We will sometimes end up with holes of the same size but different depths (e.g. in some areas they are .XX min full thread while in others they are just 'thru') or just holes of different sizes etc. that aren't obviously different.

In these cases I'll leave one set blank, and then annotate the others with a letter e.g. X and then for the call out put "HOLES INDICATED X".

Posting guidelines faq731-376

http://eng-tips.com/market.cfm?

(probably not aimed specifically at you)
What is Engineering anyway: faq1088-1484​

 

[AndrewTT]

See figure 1-16 in the attached pdf. This is a method to minimize leaders on a drawing.

 

[KENAT]

Cheers Andrew, Fig. 1-16 is exactly what I was suggesting.

Posting guidelines faq731-376

http://eng-tips.com/market.cfm?

(probably not aimed specifically at you)
What is Engineering anyway: faq1088-1484​

 

[chez311]

Thanks guys for the replies.

KENAT/AndrewTT - thats along the lines of what I was thinking, I just didn't know if there was more universally accepted way of doing it. I like the "INDICATED X" notation.

This should suffice if I don't have an exorbitant amount of holes - otherwise I might resort to a hole chart similar to what was mentioned.

drawoh - whats the reason you were banned from using hole charts? is there some disadvantage to their use or standards to which they do not conform?

 

[drawoh]

chez311,

They want consistency.

--
JHG

 

[3DDave]

drawoh - consistency is <sarcasm> always the best </sarcasm> answer.

Years ago the checkers wouldn't let reference trimetrics to be used on drawings. First, on the claim that it was redundant with the rest of the drawing and second, that if the CAD generated drawing needed to be updated by hand, it might be difficult to do.

IOW - consistency.

 

[drawoh]

3DDave,

How many years ago? I have actually been handed plots that were done in eraseable ink. This allowed me to update the prints on a drafting board. I have no problems with reference dimensions now.

--
JHG

 

[3DDave]

drawoh,

It's been a while. The plots were ink on mylar - the checkers were thinking the drafters couldn't do the trimetric geometry updates or get a new version to trace. The sick part was that it took less time to replot the drawings than to get the drawing from the vault, et al.**

It's funny all the rules that -had- to be followed about drawing scale and such; now people print E-size drawings on B-Size paper and that's OK, but when CAD started out, people would freak at a 2/3 scale.

**Best ink/plastic lead-on-mylar story: There was a project that was in production and going along and a non-CAD drawing needed an update. So drafting sends for the original from the vault. It comes up and is a repro. Some program manager on another project wanted a derivative product so they ran repros of the originals, and put the repros back because the originals were easier to alter - they scrubbed the signatures and revision history and drawing numbers from the originals. The repros were the ones you need to use erasing fluid to alter. And no, the other program manager didn't mention his plan in advance.

I've had CAD monkeys do the same to CAD models; go into the PDM system and rename them to keep the relationships and save-out a copy under the original name.

 

[drawoh]

3DDave,

Putting the copy back in the file and renumbering and renaming the original makes a lot of sense to me, much of the time. Presumably, the new drawing is the latest version, and you plan to keep updating it. It ought to be easier to modify.

I was in charge of our original CAD network. People copying out to make changes worried me. I made it clear that files were to be edited in place, unless they were doing something new. When they screwed up the existing files, I was polite and friendly as I recovered them from the backup.

--
JHG

 

[3DDave]

In this case it was done without consulting the documentation management group. In your case, I guess it would be like users setting up their own CAD network and changing drawings without your control. Don't worry, if you had deleted them, they would restore them from the floppies they used for back ups.