Help with HELIX & SWEEP.

[cvriv.charles]

Ok. I'm trying to make some simple threading. I decided to use the SWEEP tool with a HELIX as the path because that makes sense.

 

Anyways,... lets just say that im using an equilateral where all the sides are 1" as the object to SWEEP.

 

Lets say the HELIX has a base and top radius of 5". The turn height being 1" and the number of turns being 15.

 

It doesn't work. So I enlarge the turn height by a little and it ends up working. I switch to conceptual view and noticed that the geometry of the helix isn't lining up. Im guessing this is why I couldnt specify a turn height of 1". I'm not even sure if it would let me have a turn height of 1" even if the geometry did line up. I dont see why not.

 

So my question is,... why isn't the geometry lining up? When I use to make threads like this using SU I did it manually one section at a time until I had a full turn. Then I would just copy and paste upwards until I had the height I wanted. All the geometry lined up.

 

What am I missing here?

 

Thanks.

[ReMark]

The topic of making a threaded screw has been covered numerous times. Try doing a search. As the software changed (new commands) the methods improved. I think there may even be a couple of lisp routines pre-AutoCAD-helix command (2007?).

[JD Mather]

... lets just say that im using an equilateral where all the sides are 1"

radius of 5".

height being 1"

turns being 15.

 

Wouldn't be a lot easier to simply attach the file here rather than ask others to recreate the geometry?

 

You might go through this tutorial first to see if it answers the question in any way http://home.pct.edu/~jmather/content/CAD238/AutoCAD%202007%20Tutorial%204.pdf

[JD Mather]

make threads like this using SU I

 

What am I missing here?

 

I think I suggested that tutorial before

http://www.cadtutor.net/forum/showthread.php?t=32988

 

I would love to see that Sketch Up thread feature can you attach the file here.

[cvriv.charles]

I will check out your tutorial in hopes that it solves my problem.

 

As for the SU manual threads,... I converted it to dwg so you can open it right in AC.

[cvriv.charles]

I have another question,... I googled thread specifications or something like that and found a big list of different threads.

 

My question is,... what if my diameter is not on the list? I have a tube with threaded ends. The tube has an ID of 2.25" which mean the OD of the cap that will screw into in must bit a bit larger. How do I know what threads I can use?

 

I want to try 16 and 18 TPI. But I can't model the threads accurately to try them out because all the specs are geared for a sizes that are not mine. You know what I mean?

[cvriv.charles]

I read through your tutorial and even though it was informative it did not help me. I pretty much did what was done in the tutorial. It does not explain why the geometry doesnt line up and what all these extra lines are. It's like the 3D faces aren't touching the lines or something.

 

Here's an example.

 

Look at the inner of the threads from the side. You will see a very small gap between the turns. You'll also see all the screwed up geometry.

[JD Mather]

As for the SU manual threads,... I converted it to dwg so you can open it right in AC.

 

Those SU threads look much better than I expected, but of course they are of little use in engineering as they are heavily faceted surfaces.

[JD Mather]

...It does not explain why the geometry doesnt line up and what all these extra lines are.

 

Have you ever had a machining class and chased threads on a lathe with a single point tool?

 

It sounds like you have an NPT thread you are trying to reproduce. You might consult the Machinery's Handbook.

 

my diameter is not on the list? I have a tube with threaded ends. The tube has an ID of 2.25" which mean the OD of the cap that will screw into in must bit a bit larger.

 

Keep in mind that pipe thread sizes are nominal (in name only) , for example a 1/8" NPT is much much larger than 1/8" - even the hole in the pipe is much larger than 1/8".

Can you post a digital picture of the pipe end you are trying to model?

[cvriv.charles]

Have you ever had a machining class and chased threads on a lathe with a single point tool?

 

A long time ago in high school I had a machine shop class. I never got around to cut threads. I have an idea on how it works.

 

It sounds like you have an NPT thread you are trying to reproduce. You might consult the Machinery's Handbook.

 

I'm just trying to reproduce a thread with 18 TPI. Thats a pitch of .05556 with a 60 degree angle. Thats all. But seriously,... my question isnt even about threads anymore. I want to know why the geometry is not aligned for the helix/ sweep like the geometry of manual thread is. Why cant I sweep the tread cross section that has a pitch of .05556 along the helix that has a pitch of .05556(turn height)? That should work.

 

I colored the sweep path blue by placing it on another layer and saw the the sweep wasn't fully sweeping across the sweep path. I'm going to make another example to show you. This is driving me nuts. I want to use the helix/ sweep because it's quick but it has unexplainable results.

 

 

Keep in mind that pipe thread sizes are nominal (in name only) , for example a 1/8" NPT is much much larger than 1/8" - even the hole in the pipe is much larger than 1/8".

 

So basically I just choose a TPI for the diameter im working with?

 

Can you post a digital picture of the pipe end you are trying to model?

 

I'm mdeling from my head. Just general stuff.

 

 

And about the heavily faceted US threads,... when you helix and sweep whats making up the thread solid? Arent there facets for that too? Isnt there and way to smooth out the lines for the faceted thread model in AC?