I have "screw" geometry problem with my bolt

hello, everyone. I’m making a bolt, and have some problems with end and start of geometry. After subsurf my geometry has unnatural bulges, as you can see

  1. Bulge itself

  2. Bulge geometry (After subsurf)

  3. Original bulge geometry (No subsurf)

How do i resolve this issue, and make my bolt endings clean and properly round, with no bulges? I’m making it for 3D printing. So, I would like clean and correct form.

Thank you

Quite easy to fix,post the .blend file so we can take a look.

here it is
screw-problem-geo.blend (531 KB)

You have a pole (vertex with 5 or more edges) at the bottom edge where one surface abruptly transitions to another. May be able to fix that by having a slight extrusion of the bottom faces and moving some of the side geometry up, that way you’ll have a row of quads before the surface transition with the bottom.

Thank you. Can you, please, give me some example? I’m not that good in understanding English.

I think the main goal to avoid the deformation at the base is to get rid as soon as possible of the spiral going down.
Maybe a possible way would be there :

But would the subsurf rounding there be acceptable then ?

one problem I see is that your bottom thread are not parallel to the top threads

which is not normal ?

try to correct that first and it should work much better

here corrected !

a real thread would not be that sharp
more bevel a little
and same idea with the bottom of you object
add a bevel may be!

but even with that it does correct all the defect

why do you keep the thread on the bottom part ?
why not try to remove it and keep it only under the base !

happy bl

Thank you for advice. I need that lower part, so i can’t delete it.
I’m afraid that deformation at the end of spiral is not an option, either, because i need clean spiral with no deformations.

The only solution i’ve found yet, is to simply push the bulge inside, just by moving vertex. It looks not so good, but since bulge is inside of main form, it will not interfere with other surfaces when user will screw this bolt.

There is an add-on called “Bolt factory” enable it - add a bolt and look how the bottom part (beginning) is modeled. Your close but you need to “taper it out” more.

Message was too short.

thank you, for your help, guys.
2 eppo Can you show geometry without subsurf? Or attach a *.blend file?

There is nothing different than in your file concerning screw mesh. If you are going to print the screw you do not care much about how many tris or quads you have: more - better, up to the point where printer’s resolution does allow to go.
What is different - “glass” shaped cylindrical object created from your initial mesh’s one loop and also quite subdivided: this acts as a form for Shrinkwrap mod which is smoothing out bulge you had. Bulge is still present but higher you set Subsurf, less visible it is.
As you see there is no sense to show image without subsurf or post back the same blend file.