thread depth callout 3

[learman3]

I have a drawing with the following callout:

DIA.10 THRU
M3X0.5-6H .24 DEEP

Would you interupt the thread depth to mean full thread?

thanks
lear

 

[KENAT]

I agree with what you just put Ctopher, if in doubt put a section and dimension it there.

However, I still stand by my interpretation of the OP and while I'd probably use the depth symbol rather than say 'deep' I would use pretty much the same callout if I needed to better control the length of thread than just saying 'min full thread'.

Perhaps I need more sections...

 

[Tunalover]

At risk of "kicking a dead horse here", a few remarks:

A. I agree with the majority and yield to ASME Y14.5M-1994 which makes it clear that the full thread depth is .24. What happens below that depends on the tap and the machinist's preferences. That's why it's preferred to provide a section view of a blind hole.

B. In most cases when you specify a through-hole the note "THRU" is not required. Only in cases where the hole could produce multiple penetrations is this needed (and even then only when the dwg lacks a far side view).

C. Metric thread standards (invoked with ASME Y14.100) permit a drawing to state only "M3" to call out the coarse M3 metric thread (M3X0.5-6H or 6g). That is "M3" is shorthand for M3X0.5-6H as long as it's clear its internal.

D. When using the shorthand callout "M3" it may be necessary to provide the thread gender (if it's not clear on the drawing) by amending the thread callout with "EXT THD" or "INT THD" or the spelled-out equivalents.

E. Of course "DIA" and "DEEP" have been replaced with internationally standard symbols that we all know about.


Tunalover

 

[KENAT]

tunalover

B. I'm a fan of thru. Mainly 'cause I'm the idiot that takes minutes trying to work out if it's a thru hole when it doesn't say thru. I know you don't need to say it if other views make it clear but it's something I like.

C I'd double check this. We went through this a few months ago and looking at the actual ASME thread specs and it appeared that in the US you still have to say the thread pitch on metric threads even though in the rest of the world you can just say M3 and get the standard course pitch. We did research this and looked closely at the standard, I don't have the standard to hand but I think you're wrong.

 

[ctopher]

If a section view shows the thd or any hole going THRU, there is not a need to indicate "THRU".

Chris
SolidWorks 06 5.1/PDMWorks 06
AutoCAD 06
ctopher's home (updated 02-10-07)

 

[KENAT]

Like I said, I like it due to my own failings.

 

[prohammy]

Chris,

Just a quick note.

From dealing with many different machine shops , the clarification on holes which are THRU' is always appreciated (even though it is unnecessary if obvious). As most will know, machinists are a funny bunch, anything you do to hinder them is a disaster, but anything you do to help them can turn you into a God.

From my own point of view, when it comes to checking drawings, the THRU command is great


Kevin Hammond

Mechanical Design Engineer
Derbyshire, UK

 

[Tunalover]

prohammy-
There are many factors that try to influence the drawing and one of the biggest are machinists and other tradesmen. The drawing is an engineering document emphasizing the end-item and its functionality and, as such, we should resist "dumbing it down" to suit those who may end up reading it (there are other documents like work instructions is for doing this).

I've found that the assemblers, manufacturing engineers, and machinists always want to turn the drawing into a manufacturing document with all the "hot to's" spelled out in gut-wrenching detail using piles of notes and exploded views. Tailoring a drawing set to the whims of ONE manufacturer only stifles OTHER manufacturers' creativity and know-how by telling them precisely what to do to get to the end-item.

The safest approach is to emphasize the the end-item and its functionality while keeping the drawing as simple and straightforward as possible. Machinists are trained and paid to read drawings so don't let them make changes that clutter the drawing and defeat its purposes.

It takes a lot more money for the engineer or designer to draft (and check, and redraft, and recheck...) a manufacturing-friendly drawing than it takes for the machines to read and understand the drawing.

Maybe I'm a bit too sensitive on this subject but let's concentrate on OUR jobs and avoid doing OTHERS jobs for them!





Tunalover

 

[prohammy]

Tunalover,

I beg to differ. The point of an Engineering Drawing (99% of the time) is to get a part made to suit a design that I as an engineer has produced. It is about dissemination of information. I can produce many and glorified drawings that detail the end-item, but if I am not clear in my specification (which you so politely call 'dumbing-it-down'), then I have failed the basic functionality of an engineering drawing. Adding 'THRU' to a dimension clarifies and distinctly specified (beyond doubt) what I require from the specific feature. The fact that it makes someone else's job easier is my goal, NOT pandering to the whims of others outside an engineering departmant.

One other point of view worth considering is the financial implications of unclear drawings. Many organisations now count the cost of clarity on a drawing (minimisation of rework, greater repeatability etc) towards the overall performance of an Engineering Dept.


Kevin Hammond

Mechanical Design Engineer
Derbyshire, UK

 

[KENAT]

In principle I agree with tunalover but sometimes you can be slightly pragmatic without selling your soul and on the issue of Thru I don't think it's really turning it into a work instruction, it's just clarifying/condensing all the information you need into a single callout.

Drawing defines the finished part, at least this is my understanding of common practice and the standards I've looked at. It is effectively the 'requirement' of the part.

Most of the time, how that requirement is met doesn't matter. Trying to detail how to meet it on the drawing can lead to problems in is certainly agains ASME standards in most cases.

If I have a section showing the hole I probably wont add THRU. If I don't then even if I have views showing both sides of the hole, and hence arguably making it clear that it's thru, I'll typically add THRU for clarity.

Tuna you are perhaps being over sensitive but having worked in my current place for over a year I can understand why so wouldn't beat yourself up over it. You let little things slide and then it's an avalanche!

 

[CheckerRon]

Regarding manufacturing friendly drawings vs. end product drawings, I go with tunalover and concur most of his points, and feel that maybe Prohammy has been brainwashed by manufacturing like the engineers and designers at my present job. Here, I have been battling to turn a bunch of miserable work instruction drawings, full of clutter, dumb, obvious notes and bad exploded views, with often no picture of the end product except maybe a pasted in photograph into a respectable engineering drawing package IAW ASME Y14.100, et al. I too use "THRU" a lot, admittedly by force of habit, but not on sheet metal parts where it's obvious. The worst is "THRU NEXT, or THRU ALL", which CAD jockeys took from their hole generating menus.

 

[fcsuper]

I concur with tunalover as well. There is no place for processes on the drawing. If there is a need to detail an extremely rare process which is not covered by standard practices, then the place for the description of that process in on a work instructions document. In fact, there's even rules against addressing processes on drawings. One does not say "MACHINED JUNCTION BOX" in the title. One simply says "JUNCTION BOX".

That said, the original discussion regarding "THRU" or not doesn't really matter that much because the drafter should simply use it where clarity is necessary. It's not a description of the process, but a requirement of the end-item.

Bottom line, engineering drawings should not address processes because drawings are not work instructions.



Matt
CAD Engineer/ECN Analyst
Silicon Valley, CA

http://sw.fcsuper.com/index.php

 

[CheckerRon]

AMEN! I love to quote ASME Y14.5 ¶1.4(c)and(e) to engineers at my place, whenever I get step by step assembly notes on drawings, or drill, ream, tap drill, or the like.

 

[ctopher]

I also concur with tunalover.
If the machine shop or anyone else needs to understand the dwg, take classes.

Chris
SolidWorks 06 5.1/PDMWorks 06
AutoCAD 06
ctopher's home (updated 02-10-07)

 

[ewh]

I also agree with tunalover. The pupose of a drawing is to define the part as concisely as possible, NOT how to achieve the finished product (with the exception of special engineer required methods, which should be kept to a minimum).