Thread Note

[TXspace]

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.

 

[cadman1964]

hopefully this will clear it up

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

 

[fcsuper]

cadman1964,

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

 

[ctopher]

Bucking the system and doing it all your way will cause you troubles later.
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

 

[powerhound]

I agree with the rest. You're going to cause yourself problems in this case. The example of the shop that sent you the part with the bad threads is an example of a bona fide screw-up. No amount of notes would have prevented something that incredibly messed up.

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

Powerhound, GDTP T-0419
Production Manager
Inventor 2009
Mastercam X3
Smartcam 11.1
SSG, U.S. Army
Taji, Iraq OIF II

 

[drawoh]

powerhound,

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

JHG

 

[cadman1964]

Yea then I would of said, why didn't you ask if you could change the drill size since the dumb butt engineer (I am a design ENG by the way) doesn't know what he's doing....

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