Connecting a screw thread to a flat end cap cleanly?

I’ve been trying to model a thread, which has a flat end cap and a nice smooth finish with subsurf. I’ve modelled both parts with 16 verticies in their circles, but I can’t for the life of me figure out what to do with the 11 verticies in between the two parts I wish to connect to join them up smoothly - they are identical in diameter so I can’t hide any behind a lip etc.

Attached a file of my problem, highlighting the circular shape I’m trying to join up cleanly.

What’s the best way of going about doing this without leaving creases in unrealistic places?


Post the blend file. Something like this is really hard to describe.

well it wont be perfectly smooth at least not 100 %

try to select a sort of a circle at then end of the screw then etxrude it and make it Sharp or if you use subusurf use the other one crease and set weight to 1 so it is sharp

and it shoudl work fine

good luck

First, get rid of supporting loop cuts and make a selection as shown in pic.

Than extrude.

Shift S to align the cursor to selection. Than S to scale on whatever axes to Zero.

still need to close the circle by adding some faces

but should work fine

unless you want to take really close shot of it then may ahve to be more carefull!

Make a loop cut as in pic.

Add faces

You should have something like this

After that, add supporting loop cuts and sub surf.

Thanks for all of your suggestions, I tried them out but ended up reducing the number of verticies and using ‘Shift E’ creasing instead of edge loops to sharpen up my corners of my thread. I joined it together as follows which left almost no noticeable unwanted creasing at all.

Dampening the creasing off so it gradually gets harsher (I did this over 5 edges with 0, 0.25, 0.5, 0.75 and then finally full creasing) helps to smooth it out considerably too.

Think I can call this one solved now, cheers guys.


Ya that looks good. I was thinking about the thread and you trying to use subsurf. Subsurf can give you fine mesh but it seems to do what it wants at times. But is does not work too well in this case. You can get fine mesh if you increase Steps to 32. And rely on standard Smoothing and Edge Split modifier. Here is my test build:

ridix: That is damn impressive that you’ve cleaned that up with only 4 triangles and have it looking so smooth. I tried this sort of method 10 or so times starting at different points of the thread and could never close the loop without getting an unwanted crease in there, so it’s nice to see that is is actually doable!

The reason I had 16 steps was solely because this thread joins on to part of another complex mesh (also via a circle with 16 verticies) that was already smoothed out. I also had to smooth the thread out on the other end of it too (so the same joining method, but in reverse direction) so the less of this sort of modelling I had to mess around with the better.

Creasing seems to have worked pretty well with the mesh I posted above with subsurf level 2 as the only modifyer when rendered, check the following attachment for a rendered version.

The only issue I have now is that if I did want to sharpen up the edges to give them a more metally feel, I couldn’t do it with edge loops without affecting the roundness of the end cap due to how the loop would cut into it, so would have to use something like edge split as you say.


Probably a little late now, but you might find the thread tutorial in the Precision Modelling guide useful. It is using a different profile thread but the technique works well.

The tutorial is for Blender 2.4 series and can be found at