# Creating a thread



## katellwood (8 Feb 2008)

Is there anyone out there who can assist in drawing screw threads and spirals in sketchup

Thanks


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## SketchUp Guru (8 Feb 2008)

I can. What kind of threads do you want? And out of curiosity, what are you drawing.


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## katellwood (9 Feb 2008)

Hi DaveR 

Something along these lines







but with an internal and external thread I want to draw an adapter for a lathe to change the nose thread


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## SketchUp Guru (9 Feb 2008)

Diameters? Pitch? Inside and outside on the same part?


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## katellwood (9 Feb 2008)

Dave R 

What I was hoping for is some sort of tutorial to assist in myself drawing the thread, I wish to produce a drawing to give to an engineer friend of mine to assist in making the item, 

I have a big old Dominion Wood lathe with an extremely large nose thread approx 2" in dia unfortunately I have no face plates or anything that can be placed on this thread, there is a morse taper on the nose unfortunately the headstock is not through bored therefore a morse fitting with the external thread attached is likely to come loose 

I also possess a Poolewood 28 - 40 wood lathe with a nose thread of 11/2" dia 6tpi nose thread for which I have chucks etc that will fit.

The adapter is to allow the chucks to be used on both machines 

Through your posts and tutorials on this forum I have I feel become quite competent in the use of Sketchup, unfortunately this has beaten me 

If you are interested I can show some sketchup drawings I have created then photo's of the completed item, I would value your input and constructive criticism on my work to unable me to improve 

I think it is accepted that you are the guru on sketchup and I would value your input and assistance

Regards


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## SketchUp Guru (9 Feb 2008)

OK, I'll work up a generic tutorial on drawing threads.


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## SketchUp Guru (9 Feb 2008)

Here we go. Hopefully this will make sense.

Although drawing threads could be done without it, I start by drawing a helix with a plugin which you can get here.. The helix is used as a sort of path for the following steps and is later deleted. For this example I decided on a 1" diameter 8TPI thread. I scaled everything up by a factor of 100 to make it easier to work.

The helix drawn by the plugin is centered on the origin by default and is made into a group. You enter the radius (actually two radii because the script will make a tapered helix if you want.), the pitch and the number of turns. For this model I set the radii at 50", the pitch at 12.5" (100/8) and turns to 1. I kept the default 24 segments for the helix.






Now, from left to right in the image above,

With the helix drawn, I started off the bottom end of it and drew a triangle vertically so its apex is at the end of the helix and the face is vertical. This is the profile of the threads. Because I'm showing my work, I also drew some cross hairs at the origin which got copied down the line for the various steps. If you are doing this, just work at the origin and you can skip that part.

Select the profile and rotate/copy (Ctrl+Rotate) it 15° (360/24).

Move the new copy of the profile up so its apex is at on the helix at the intersection of the first two segments.

Draw lines between the profiles to fill the faces. You'll need a couple of diagonals to fill the faces on the outside of the thread. Delete the inside face. You'll also find a triangular face inside that needs to be deleted. Smooth (Ctrl+Eraser) the diagonals so they aren't visible. After that, make this little bit of the thread into a component.






Select the component and rotate/copy it 15°. Hit Enter. Move the copy up so the apex is aligned with the apex on the first.

Select both copies and rotate/copy them 30°. Hit Enter. Move them up as you did on the first.

Select all four copies and rotate them 60°. Hit Enter. Move them up.

Now here's a tricky one. Select the eight and rotate copy them 120°. Hit Enter and then *2, Enter. Move each new set of eight up.

A single turn of the threads is complete. Select one of the components and hide (Shift+Eraser) the end edges.

Select all of the thread components, make a component of them and copy them up. the distance to move the copies is, in this case 12.5". I then typed *7 to make a total of 8 turns of threads. Then draw a cylinder inisde the threads. Drawing it this way makes it a simple matter to adjust the length. Push/Pull for the length of the shaft and copy the threads up. 

I didn't do anything to treat the ends of the threads. If they would be visible, you'd need to make the end component or two unique and edit them as needed.

If you want the SKP file, send me your e-mail address in a PM and I shoot it off to you.


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## Shultzy (9 Feb 2008)

katellwood, although this is a great exercise in sketchup (congrats Dave, another brilliant demo) normally full threads are not drawn on a machine drawing just dimensioned (tpi etc.) as even full size it would be labourious and serve no purpose.


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