Hi community, newish to SketchUp and would appreciate some help. I have two legitimate solid objects one is a screw thread created using the extensions “Helix Along Curve”, “Extrude Lines” and “Joint Push Pull”. When using the Subtract Solid tool to remove the screw thread object from the cylinder object im getting some odd and at times differing results. skp file attached.
Thanks
Jason
Spool Roller.skp (1.7 MB)
Without looking at your model I’m going to guess it is an issue of size. If you are working quite small then scale up before you do the subtraction.
How are you going to use these threads? Is this a thing for illustration or for 3D printing? Are the threads supposed to be a standard thread?
Thanks all, DaveR - 3D printing and no not a standard thread.
I see. Thanks.
When you model screws like this you might find it useful to run the thread of the end of the part by a turn or so.
When I model screw threads I run them a little long and cut them off with a chamfer. You can see the end of the screw on the left.
Certainly nothing wrong with the method you used although I use a slightly different method that results in the threads without having to cut them.
Thanks Dave great tip. FYI Scaling has resolved the issue.
Thanks Taxsola and Box this resolved my issue really appreciate your help.
Something to keep in mind when modelling for 3d printing, you can model in meters and export the .stl at the appropriate size for your printer software. .stl files are unitless, so it’s only a matter of understanding what your software is working with to know how to export your .stl files.
There is also The Dave Method, which came about long before 3d printing and .stl files were relevant, so it is more useful for modelling small things in large models.
If your slicer will let you specify import units you might try what I do when modeling for 3D printing. I set model units to meters and use millimeters (or inches) as if they are meters. No need to scale up and back down. Just export the .stl with Model Units and import in the appropriate units. Example:
I only exported the hext nut for this.
Cheaper to by a box of 50 hex nuts than to print one nut.
Edit: @Box posted the same thing while I was making screenshots. 
Thanks Box and DaveR appreciate the tips.
Many (all the few I know) slicers will allow you to scale an object after loading an .stl. You can let the slicer do that job too!
Yes, many, but not all, I had one with a previous printer that only allowed scaling by dragging via percentage, very difficult to match or replicate sizes.
