Thread Note
Thread Note
(OP)
Once upon a time, back in the days of board drafting, we old folks were taught this is how to read a thread note:
1/4-20 UNC
1/4 = Major Diameter in inches
20 = Threads per inch
Everybody in agreement so far?
How about this one:
1-8 UNC
1 = Major Diameter in inches
8 = Threads per inch
Still all on the same page, are we?
Well, how about this one:
4-40 UNC
Hmmm..., we have a situation here. Does the "4" mean "Major Diameter in inches" or does it mean "#4", which translates to a .112 Major Diameter in inches?
Without the "pound sign" (#), wouldn't the 4 mean a "4-inch diameter bolt"?
But perhaps the "UNC" defines the "4" as meaning "#4". After all, UNC is a standard unto itself.
Thoughts?
It has been my habit to include the pound sign (#) for good measure, but I do not find that requirement in the ASME drafting standards.
Can anybody find the requirement to use the "pound sign" (#) in a standard? If so, please post.
1/4-20 UNC
1/4 = Major Diameter in inches
20 = Threads per inch
Everybody in agreement so far?
How about this one:
1-8 UNC
1 = Major Diameter in inches
8 = Threads per inch
Still all on the same page, are we?
Well, how about this one:
4-40 UNC
Hmmm..., we have a situation here. Does the "4" mean "Major Diameter in inches" or does it mean "#4", which translates to a .112 Major Diameter in inches?
Without the "pound sign" (#), wouldn't the 4 mean a "4-inch diameter bolt"?
But perhaps the "UNC" defines the "4" as meaning "#4". After all, UNC is a standard unto itself.
Thoughts?
It has been my habit to include the pound sign (#) for good measure, but I do not find that requirement in the ASME drafting standards.
Can anybody find the requirement to use the "pound sign" (#) in a standard? If so, please post.





RE: Thread Note
4-40 UNC is ID'd by the number of threads. Standard 4" threads do not have 40 threads per inch, nor would that be UNC...it would be UNS.
Nowadays, it is recommended that we use the decimal equivilent to the old numbers, but many of us still use the traditional numbering system.
Matt Lorono
CAD Engineer/ECN Analyst
Silicon Valley, CA
Lorono's SolidWorks Resources
Co-moderator of Solidworks Yahoo! Group
and Mechnical.Engineering Yahoo! Group
RE: Thread Note
KENAT,
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RE: Thread Note
What I was going to say was that sadly ASME B1.1-2003 doesn't quite agree with 14.6.
If you look in table 2 or 3 it lists and if you look at section 6, Screw Thread Designation it essentially says you can use just the screw number and has examples showing this.
If memory serves yet another inconsistent method is shown in one of the specs I mentioned but I can't find it now.
As you suggest in your case it is effectively governed by the fact that there are only certain specific sizes that are UNC and 4.000-40 isn't one of them.
I don't see the '#' sign used for screw size anywhere in either standard. That said we do use it on our standard thread callouts such as "#10 (.190)-32 UNF-2A" - a real belt & braces approach.
KENAT,
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RE: Thread Note
http://www.draftingzone.com/standards/standard5/
http://www.inserta.com/PDF/AI-STR-THD-PORT-DIM.pdf
Look in the Machinery Handbook for more info.
Chris
SolidWorks 08, CATIA V5
ctopher's home (updated Aug 5, 2008)
ctopher's blog
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RE: Thread Note
It seems that usage of the options in Y14.6 depends on the company or industry. Government jobs pretty much use the decimal callout exclusively, and ignore the letter callouts for the small machine screw threads. i.e.
.190-32 UNF-3B.
RE: Thread Note
Suspenders are a garter belt.
Well off topic though.
KENAT,
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RE: Thread Note
Chris
SolidWorks 08, CATIA V5
ctopher's home (updated Aug 5, 2008)
ctopher's blog
SolidWorks Legion
RE: Thread Note
Solid Edge V20
RE: Thread Note
Matt Lorono
CAD Engineer/ECN Analyst
Silicon Valley, CA
Lorono's SolidWorks Resources
Co-moderator of Solidworks Yahoo! Group
and Mechnical.Engineering Yahoo! Group
RE: Thread Note
Chris
SolidWorks 08, CATIA V5
ctopher's home (updated Aug 5, 2008)
ctopher's blog
SolidWorks Legion
RE: Thread Note
Solid Edge V20
RE: Thread Note
Matt Lorono
CAD Engineer/ECN Analyst
Silicon Valley, CA
Lorono's SolidWorks Resources
Co-moderator of Solidworks Yahoo! Group
and Mechnical.Engineering Yahoo! Group
RE: Thread Note
You can normally copy the old holes.txt file over to the location required for the new version of SE, I think V19 was an exception because they added a new parameter but generally it's not a problem as far as I know.
If you want to delete the # then just open the holes.txt in word or similar and just do find replace, it wont take that long. However, we have the # and I can't get excited about it.
KENAT,
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RE: Thread Note
We have been copying the Hole.txt file over for except V19.
For the # sign, it's one those things that actually at time works to our benefit. So least at this time, until i have to redo hole.txt cause they change something and they removed the # sign, were going to stay on the same course.
Solid Edge V20
RE: Thread Note
Forgot to mention, we do not specify Tap drill sizes on drawings unless we want to make sure there going to use the correct tap specified in the mach. handbook. normal thread call out would be something like 5/16-18 UNC .750 THD DP
Solid Edge V20
RE: Thread Note
I agree on the #, technically it should probably be "No." per 14.6-2001 or blank but while normally a stickler for the rules I can't get excited by it.
KENAT,
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RE: Thread Note
Tap drills are specified systematically by SolidWorks, and by designers who do not know better. I do not know abou the other CAD packages.
Machinists know what size tap drill to use. When they see your instruction, they probably will shrug their shoulders and select the drill they think appropriate. Tap drills are uninspectable. All your inspector can do is test the hole with a thread gauge.
If the drilled hole mattered to me, I would make a section view, and explictly apply diameters and depths, with the appropriate tolerances.
RE: Thread Note
If it's a critical hole than a section view is created and hole is spec out with proper tolerance. Tap drill's are more used for none critical item that go to in a tap hole.
"Machinists know what size tap drill to use. When they see your instruction, they probably will shrug their shoulders and select the drill they think appropriate."
Well we just had a die plate where a machinists most of not been properly trained, or didn't remember his drill sizes. they used to big a tap drill so now when we threaded a bolt in, it pulled right out. We ended up sending this back for them to fix.
Solid Edge V20
RE: Thread Note
If the 'tap hole' is truely that, just the start hole for the tap to follow and no part of the tap hole is left/relevant to function after machining then it shouldn't normally be detailed on the drawing per ASME Y14.5M-1994 1.4.
However, if the 'tap hole' is desired to be longer than the thread length to serve some purpose such as in a manifilold, or to hold a pin or similar then this portion of the hole should be properly specified, preferably with a lose enough dia tol to allow the machinist some lee-way in picking his preffered tap dril. I typically dimension this as a counterdrilled hole similar to figure 1-38 & section 1.8.12.
The inability of a machinist or vendor to meet the requirements of the drawing isn't inherently a drawing issue.
KENAT,
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RE: Thread Note
Few reason why we changed the HOLE.txt. Main reason is less steps in modeling of the part. So, if i want to put a e-pin down in the part (see attached pic) i just extend the tap drill to correct depth and then call it out.
Our thinking, correct or not, they should be using the correct tap drill for the specified tap, then why not use it to go all the way down rather than specifying a different drill size.
Hopefully this clears it up a little. everything is detailed out so there's no assumptions.
This is what i want, I'm the designer, detailer and checker...LOL LOL
Solid Edge V20
RE: Thread Note
The flaw in the reasoning you are using is simple. There ARE more than one way to form tapped holes. The information you provide can be a reduntant reference, but it can also be flat out wrong! It depends on how the tap is formed.
Matt Lorono
CAD Engineer/ECN Analyst
Silicon Valley, CA
Lorono's SolidWorks Resources
Co-moderator of Solidworks Yahoo! Group
and Mechnical.Engineering Yahoo! Group
RE: Thread Note
I suggest reading the Machinery Handbook and read up on ASME specs. Listen to the experienced machinists.
Chris
SolidWorks 08, CATIA V5
ctopher's home (updated Aug 5, 2008)
ctopher's blog
SolidWorks Legion
RE: Thread Note
Matt mentioned more than one way to form tapped holes. He's absolutely right. I've been a machinist for 20 years and I can tell you I'm drilling a .201 hole for a 1/4-20 thread if I'm using a cutting tap. If I'm using a roll-form tap it will be more like a .228 if it's in aluminum. If you want me to tap a 0-80 hole in Inconel I can guarantee that your recommendation will snap the tap. You're not going to get 75% of that thread from me. I'm drilling the hole size that I know will work, not the size that the designer, detailer, or checker thinks will work. Of course if you insist, then I could always send you the part with the snapped off taps still in it along with a bill for the taps...LOL LOL
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RE: Thread Note
I figure I have tapped some twenty holes in my lifetime. If the machinist needs me to tell him what size tapping drill to use, I need a new machinst.
JHG
RE: Thread Note
Gentlemen (I'm assuming your all gentlemen who responded...:) )
This thread went way off in the weeds all due to me saying something about replacing the default minor dia in my HOLE.txt file.
Trust me pep's, the line of communication, least for me, is very open. Our outside tool suppliers and in house people know my door always open. (Wait I don't have a door)
As I stated before, due to how the cad system is setup, by UGS or who ever owns them this year or next, we had to decide on a size to use for the minor dia (tap drill). The minor dia set forth by SE didn't suite our needs; it caused many problems when creating models. We just happen to pick the sizes recommend (commercial drill sizes Page #1822) by Mach. Handbook25.
O for a rebuttal for someone saying read the machinery hand book and ASME spec's. All the sizes I determined are in the Machinery hand book. I meant not know the ASME spec backwards and forwards, but I do believe I know them fairly well and what I don't know I look up. This is one reason I like ENG Tips so much.
Please remember you machinist, if you don't like what you see on a print, please ask the Engineer for clarification. Some of us engineers like it when you ask questions
So pep's, let go on with life...:)
Solid Edge V20