Threads 1

[shyrgyl]

is there any relationship between pitch, major and minor diameters of a thread. let me know if this one is true(major dia. - minor dia. = pitch).a new problem arises when u increase the value of the pitch.let say first I restrict the value of pitch to 1 and then to 5.according to me there must have been a difference in visualisation of views(front,left,top)when I switch over from part design wrkbnch to drawing wrkbnch.but I hardly see any difference.please elaborate.

 

[weavedreamer]

The machinist handbook has the tables used for deriving the pitch diameters.

For metric threads, the max pitch dia is = basic major dia - 0.649519 * pitch - es (based on fastener grade). The min pitch dia = max pitch dia - value from a table based on pitch and grade.

 

[shyrgyl]

thanx for sharing. but what about the difference in visualisation of different views on changing values of pitch from 1 to 5 or something else after switching over to drawing wrkbnch from part design in catia. i hardly see any change.

make a solid cylindrical rod .click on thread/tap tool in dress up features in part design.adjust the values.now switch over to drwing wkbcnh.
if the threads are not visible in the drawing named file, right click on the views in the specification tree and check the centreline, hidden line, axis, thread. u wont see any difference if u change value of pitch in the part design file and then coming over again to drawing workbench .

 

[jackk]

CATIA follows standard drafting conventions for representing standard threads on engineering drawings: CATIA shows symbols for the profile and end views of threaded features (both internal threads and external threads). These symbols are typically not to scale; they may show the major and minor thread diameters, but they do not show the pitch. The drawing should include a thread callout that describes the exact thread type and size. (My guess is most CAD systems do the same).

If you have a special, non-standard thread, you might want to model the threads in 3D with the exact thread shape and pitch. Then the associated drawing will show the thread exactly as you modeled it in 3D.

For more information about representing threads on drawings please refer to the ASME, ANSI, ISO, JIS, DIN or whatever drafting standard you are using.

There is an excellent forum here on Eng-Tips specifically for DRAFTING STANDARDS, GD&T, AND TOLERANCE ANALYSIS that contains a wealth of information about general drafting topics.

 

[shyrgyl]

i appreciate ur response. well,there is one more thing i would like to ask u.suppose there is a hollow cylindrical solid tube.i am able to use metric thick pitch option in thread/tap definition in dress up features when i select the inner cylindrical surface.but when i select the outer surface(cyl.)the metric thick option changes to no standard option. any explanation for the same.