thread depth callout
thread depth callout
(OP)
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
DIA.10 THRU
M3X0.5-6H .24 DEEP
Would you interupt the thread depth to mean full thread?
thanks
lear





RE: thread depth callout
David
RE: thread depth callout
I don't understand why the thickness of the part matters. If the part was less than .24 thick then you would be tapping all the way through the part. You would only need to specify a depth when not tapping all the way through.
RE: thread depth callout
Another reason you may have a depth that is larger than the material thickness is if your hole ends at another hole or similar cylindrical feature. You want the hole thru the material but you may not want it to go thru the other side of the hole. In this case you can either say thru to bore (there is a whole series of threads about the validity of this note) or you can give a depth that is larger than the material thickness and this ensures that the machinist drills deep enough to get through the material but stops short of cutting into the other side.
David
RE: thread depth callout
RE: thread depth callout
What if you don't care what the tap is? You have specified a tap drill size thru and you have specified a tap with a depth, what else do you need? Anything else would be telling the machinist how to do their job.
David
RE: thread depth callout
".24 DEEP" is a full thread requirement. If it were not full thread, it would not meet "M3X0.5-6H" at the bottom of the depth callout.
RE: thread depth callout
David
RE: thread depth callout
I think you are misinterpreting the "full thread depth" to refer to the length of thread down the hole instead of "full-thread depth" across the hole for a depth of .24".
RE: thread depth callout
e.g. if the tolerance for 2 decimal places is +-.01 then the full thread depth could be anywhere from .23 to .25.
RE: thread depth callout
Chris
SolidWorks 06 5.1/PDMWorks 06
AutoCAD 06
ctopher's home (updated 02-10-07)
RE: thread depth callout
To me if you specify the length of thread then the length specificed (with its tolerance) is full thread form (allowing for lead in etc).
RE: thread depth callout
Chris
SolidWorks 06 5.1/PDMWorks 06
AutoCAD 06
ctopher's home (updated 02-10-07)
RE: thread depth callout
If you let the machine shop determine the length of full-thread engagement, then why bother specifying a depth? The whole point of specifying a depth is to ensure the correct amount of thread is available for a mating screw.
RE: thread depth callout
We use 'min full thread depth' when we need a minimum length of thread to accomodate a fastener but don't mind if the thread goes a bit deeper.
That is not what the callout in the OP says. It just says .24 Deep.
Hence to me you are saying you need .24 (+- whatever drawing tol) of full thread form.
RE: thread depth callout
Chris
SolidWorks 06 5.1/PDMWorks 06
AutoCAD 06
ctopher's home (updated 02-10-07)
RE: thread depth callout
RE: thread depth callout
RE: thread depth callout
Otherwise you are calling for less than 1/2 a thread.
But yes, the depth call-out specifies the distance down from the surface that the specified thread form must be maintained, subject to drawing tolerances.
RE: thread depth callout
I'm never against ASME/ANSI standards.
Also, If a dim for thd depth is needed, show the dim (w/tol)instead of a callout. If there is a Cbore or some other feature above the thd, having a callout would confuse a machinst where to start.
Chris
SolidWorks 06 5.1/PDMWorks 06
AutoCAD 06
ctopher's home (updated 02-10-07)
RE: thread depth callout
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...
RE: thread depth callout
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
RE: thread depth callout
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.
RE: thread depth callout
Chris
SolidWorks 06 5.1/PDMWorks 06
AutoCAD 06
ctopher's home (updated 02-10-07)
RE: thread depth callout
RE: thread depth callout
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
RE: thread depth callout
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
RE: thread depth callout
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
RE: thread depth 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!
RE: thread depth callout
RE: thread depth callout
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
RE: thread depth callout
RE: thread depth callout
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)
RE: thread depth callout