How to show threads in autoCAD drawings

[mkmech]

How do I show internal and external threads in 2D orthographic projections of a component? I am using an old version of AutoCAD. Also, how do I determine what size of the hole to drill so that after tapping, it will accomodate a given UNC screw/bolt (e.g 1/4-20 UNC)

Thanks to all the readers.

 

[diamondjim]

As to the tap drill, it is normally
7/8 times the bolt diameter for an
nc thread.

 

[steve1]

I have seen this question posted a number of times in this forum. This is what my drafting book has to say on the subject:

"Most thread are difficult to represent graphically in their true form. The three conventional methods for drawing thread forms are detailed, schematic, and simplified. The detailed thread representation is the most realistic but it is more difficult and time-consuming to draw and is rarely used on technical drawings. It is normally limited to illustrations. The schematic and simplified representations are easier to draw and are more widely used in technical drawings, with the simplified representation being the most common."

"Technical Graphic Communications" 3rd Ed
Bertoline & Wiebe
McGraw Hill, 2003
ISBN 0-07-365598-8
page 777

So why not use the simpified representation ?

 

[diamondjim]

We always used the simplified method
but some people may use the 2d profile
to generate the 3d profile? We never
drew in 3d as 2d drawings were all that
was needed by the shop.

 

[borgunit]

This gives an example how AutoCAD Mechanical defaults for taps viewing...

http://geocities.com/borgunit2003/images/MechTaps.jpg

"Everybody is ignorant, only on different subjects." — Will Rogers

 

[borgunit]

Here is a bit of info on English size taps but I am sure there are numerous sites for this..

http://www.bob-carnaghi-online.net/1433/drill-tap.php

"Everybody is ignorant, only on different subjects." — Will Rogers