Hole Notes (ASME Y14.5M-1994) 4

[ModulusCT]

So we've had a question about our notes for some time where I work... Simply put, we're not sure how to do it. I have an idea of how it should be, but I'm unsure... Maybe someone here can help me out.

A few examples:

If I've got a tapped hole (#2-56 UNC 2B) with a depth of .18, I would think that the hole note should look like the following:

2X #2-56 UNC 2B <depth symbol>.180

... but what does that mean in regards to the drilling operation done before tapping? Is the drill tip going to be held to the same .18 depth dimension the tap is? If not, what is the proper way to control the depth of the drill? I would assume the following:

2X DRILL <depth symbol>.200
#2-56 UNC 2B <depth symbol>.180

,.. and if I want the hole fully threaded? Is that even possible? What about the drill tip? Is that part of the depth stated on the drawing? Or does it always go beyond the stated depth value by some amount?

Lastly, we use a lot of helicoils on our parts. How would one go about making a hole note for a helicoil insert while simultaneously communicating the parameters below:

10X DRILL <depth>.22
#2-56 UNC 2B
1.5X DIA. HELICOIL (TANGLESS)

Is that correct? Will the drill used for the .22 depth hole be the proper diameter to allow the end of a threaded fastener to pass through? Or will it be a pilot hole drilled for a #2-56 thread? I would obviously want to communicate that the drill diameter is whatever is appropriate for the helicoil insert.

Thanks for the help!

I'm not a vegetarian because I dislike meat... I'm a vegetarian because I HATE plants!!

 

[ewh]

I apologize if I offend... that was not my intent; sometimes we over-analyze the problem when it is really quite simple if seen from a different perspective, such as that of Homer Simpson.

... and KENAT is right; I've killed my share of threads with some misplaced bombs before.

Technically, the glass is always full.

 

[CheckerHater]

Are you guys saying I am to buy another standard?

What is it, ISO?

 

[ewh]

ASME

Technically, the glass is always full.

 

[ewh]

(duh!)

Technically, the glass is always full.

 

[CheckerHater]

C'mon, I was told you only buy 1 ASME standard, as opposed to ISO, where you have to spend several thousand dollars!

 

[ModulusCT]

No harm done... I took your comment to mean that I was asking a dumb question or that I should have known something very simple. Which might be the case actually, hah. Anyway, like I said, sometimes I ask, not because I don't know the best way to do it (although, many times, I don't), but because I've got to explain my methods to a higher-up and you guys nail down many of the angles I don't think about initially.

So anyway, it sounds like the syntax I'm using is correct, and "DO NOT BREAK THRU" is sufficient in most cases. When the remaining thickness is critical, a cross section with a dimension from drill tip vertex to opposite wall is a good idea (something like .XXX MIN).

I understand that it's not a good idea to specify manufacturing processes on the drawing, but that seems counter-intuitive to me when you consider the fact that we put c'sink and c'bore symbols on our drawings regularly, which in some sense, is as much an indication of process as the term DRILL is. I leave out the drill diameter intentionally as I know, DRILL is sufficient to get my point across... which is, that I want the machinist to drill no deeper than the specified amount.

Y14.6... Got it.

I'm not a vegetarian because I dislike meat... I'm a vegetarian because I HATE plants!!

 

[KENAT]

Counterbore and countersink have come to describe both the tools and the features created by the tools (or perhaps vice versa).

For instance, it is possible to create a counterbore feature using a separate drill/mill process from the initial hole.

So on drawings the symbol is specifying the feature created not the tool often used to create that feature.

Checkerhater, you need less standards for ASME, anyone saying only 1 is exagerating though;-) Having worked both systems you can get most of the ISO stds into maybe 4x 4" binders. For ASME you can get them into 1 or (may have been a 5x binder I don't have it on my desk right now).

Posting guidelines faq731-376

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

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

 

[CheckerHater]

Kenat,

In the Brave new world (tm) you can fit most of the stuff on one disk:

http://www.iso.org/iso/pressrelease.htm?refid=Ref1262

And it cost less than Genium manual.

 

[ModulusCT]

Last question... On a hole note, is it permissible to say the following:

<c'bore><dia>.095±.005
<depth>.025±.005

I'm asking because initially I thought that omitting the c'bore symbol would communicate the same thing. But in reality, I'm thinking that he would have no idea that we want to have a flat bottom unless we show, in a cross-section, or with the c'sink symbol, that we want otherwise.

I'm not a vegetarian because I dislike meat... I'm a vegetarian because I HATE plants!!

 

[ModulusCT]

Let me ask that another way... We want a threaded hole with a flat bottom. Is that a threaded c'bore? Or is there a way to designate a flat bottomed hole that I'm not aware of?

Thanks (duh).

I'm not a vegetarian because I dislike meat... I'm a vegetarian because I HATE plants!!

 

[KENAT]

So, you want to specify a threaded hole where the tap drill is flat bottomed not 'V', but you don't necessarily care what depth the untapped portion is?

Nothing springs to mind in 14.5M-1994 (or 14.6) that addresses the 'flat bottom' issue.

I'd suggest a note saying 'flat bottom', and probably at least one section illustrating/clarifying that the flat bottom applies to the tap drill hole not the threaded portion.

(Note there can be a cost penalty to flat bottom holes, and certainly if you want the tapped portion itself to be flat you'll face issues.)

Posting guidelines faq731-376

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

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

 

[MintJulep]

The depth can't logically include the tip, as the dimension is not met there. Duh.

Just thinking like the bad machine operator that I am, and noting that drawings are not supposed to dictate process.

To drill a hole to a depth:

Bring the bit to touch the surface.

Set your zero or plunge stop.

Make hole.

No math involved if the depth is dimensioned to the pointy bit.

 

[ewh]

Yes, but the conical surface of the pointy tip doesn't meet dimensional requirements, does it?

As to flat bottom, I don't recall the specs addressing it. I have always added a reference pilot diameter then the note "FLAT BOTTOM" after (not reference), to be followed by the rest of the thread callout. The pilot diameter is a reference dimension (more to note which feature of the hole needs the flat bottom) so as not to unnecessarily limit the machinist, as noted earlier.

Technically, the glass is always full.

 

[KENAT]

If it wasn't for the explicit mention of Y14.5M-1994 you'd have a very good point MintJulep.

However, as that reference is made, and that reference has a very clear explanation in 1.8.9 & figure 1-34 about it being the depth of the full diameter I'm afraid ewh's point stands.

Posting guidelines faq731-376

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

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

 

[CheckerHater]

MintJulep,

Two points:

1. After machinist makes the hole without thinking (pardon, using the math), somebody will have to check the depth; and checking "pointy" hole requires special equipment.

2. To avoid your drill dancing erratically before going into the material, you want to hit the spot with center drill first.

I do not insist my way is the only way; just a thought.

 

[ModulusCT]

"So, you want to specify a threaded hole where the tap drill is flat bottomed not 'V', but you don't necessarily care what depth the untapped portion is?"

Not exactly, Kenat. I want to specify a fully threaded hole with a flat bottom. I'm OK with there being 2 incomplete threads at the bottom and perhaps a small amount of unthreaded hole due to tooling limitations.

I'm not a vegetarian because I dislike meat... I'm a vegetarian because I HATE plants!!

 

[KENAT]

You want a fully threaded hole but you don't really?

2 incomplete threads mean it isn't a fully threaded hole by definition.

So, you basically do want what I said except that you want the depth of tap drill overrun minimized?

Posting guidelines faq731-376

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

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

 

[fcsuper]

For $2000 worth of ASME standards, you'll have to spend nearly $6000 for the equiv ISO standards. It's also much easier to find information in ASME standards since there are fewer books to thumb through. What do you get for the extra $4000 in ISO? Many more title/author/contributor/copyright notice pages, many more under utilized pages (often where half the page is left blank in the middle of a section because of poor placement of images). However, the extra large images are nice. Also, there are presumed standard methods from the style established within the images, but sometimes without any support of the wording of the document itself.

For the life of me, I still cannot find where display of quanity is explicitly stated to be "4 x", which is often presumed to the standard because of examples given in the images. However, they've chosen such a non-descript font, it doesn't appear to be the same in all examples throughout the standard.

That's not to ASME doesn't have it's own problems, maybe I'm just used to them.

Matt Lorono, CSWP
Product Definition Specialist, DS SolidWorks Corp
Personal sites:
Lorono's SolidWorks Resources & SolidWorks Legion

 

[ewh]

I think a bottoming (or plug) tap?.


Technically, the glass is always full.

 

[ModulusCT]

"So, you basically do want what I said except that you want the depth of tap drill overrun minimized?"

Not just minimized, but clearly defined. So what I did was a normal callout:

<dia>.095 +.005/-.000
<depth>.25 +.000/-.005

And I added a section view with a clear view of the hole in question so that the flat bottom is clearly visible. I then added a reference MAX wall thickness dimension from the bottom of the hole to the cavity on the opposite side of the wall just to make it clear that no feature, drill tip or otherwise, should extend beyond the .025 dimension.

I think I'm all set now... I found a copy of Y14.6 as well, although, it's from 1978 unfortunately. It'll have to suffice until I can get my greedy lunch hooks on the 2003 standard.

I'm not a vegetarian because I dislike meat... I'm a vegetarian because I HATE plants!!