# Archimedes screw?

I'd like to make an archimedes screw in blender.

I can't use a pre-built STL file, because I'd like to render it as a book/story illustration, so to avoid copyright kerfuffles, I need to do it my own self.

Only problem: doing archimedes screws in something like a CAD program is difficult, I imagine doing it in something like Blender will be ooober difficult.

That is my only option, however, so... ...alas, please tell me how to do it.

PS: remember, and archimedes screw is an auger, so; it exists inside of a bore, and I can do: the bore (a cylinder with an object modifier in the shape of an other cylinder cut out of the middle of it, then, another optional openning to open up one of its sides as though it were cut in half, by using another object modifier, this time: a cuboid, stretched and then placed halfway into and subtracted from it), then, the central drive shaft is obv just a cylinder, but then, the spiral which passes through that driveshaft at a near exact 60 degrees? That's the part that's got me stumped. I've done curved tubes in blender before, but, this challenge... ...thinking about it has me scratching my head, no offense.

So, I really just need help making a spiralling screw-cut surface endowed with the exact properties of an archimedes screw. I know there is a "screw" plugin, but I haven't played with it too much, so I don't know if that'll come into play, if it is a viable solution though: I'm all ears, thanks in advanced

Working looking down Z, X across, pivot: 3D Cursor at origin.

• In Edit mode, GX it to the left, so its left side is at the desired radius of the screw in X, leaving the object's pivot at the origin.
• X > Delete its right edge (also deleting the face), scale to the thickness of the screw blade in Y, and move the inner vertices to the desired radius of the shaft, in X.
• E extrude the inner vertices, dragging and right-clicking to leave the extrusion in place. SY the extrusion up and down a little way in Y.
• If you need to adjust the angle between the blade and the shaft from the 90 degrees shown, you can do it at this stage.
• CtrlShiftB the corner vertices to tighten the profile.
• Assign a Screw modifier, axis Y. To obtain an exact screw angle, set the 'Screw' field to tan([angle])*2*pi*[r], where [angle] is the screw angle expressed in radians, and r is the outer radius of your profile. My angle is 30 degrees, and radius 3, so I typed tan(pi/6)*6*pi into the 'Screw' field. You may have to check 'Calc Order' to turn the solid the right-way-out.
• Check 'Merge' in the modifier, and then scale the previously extruded vertices in Y until the spiral gap in the shaft is just closed, and the 'Merge' catches.

You are free to edit the profile at any time, to adjust the result, before applying the modifier.

You're basically done. Trimming the ends for good topology varies from case to case, but if this is for illustration, (presumably you can retouch the image) you should probably get away with a Boolean to a cube.

The bore is a cap-less cylinder of radius (r + tiny), with a Solidify modifier directed to the outside.

This example has kept the vertex count as low as possible, and assigned a Subdivision Surface modifier at the end to smooth the result.

• I have not gotten this technical before, so I'm a bit nervous, but I'm going to set a day aside to try this, and then once it works: I'll consider my question formally answered. This seems vert helpful thank you. Once it was very helpful [in the future] I will hit the checkmark, I obviously need to apply it before I can absolutely know for sure – user179283 Feb 7 '19 at 8:22
• @user179283 No problem at all.. I wouldn't want approval of an answer that didn't work for you.. come back with a comment if you get stuck. I guess the most important thing to understand to start with is the difference between an object and its mesh. Leave the object's pivot point at the world origin at all times, moving its vertices in Edit mode, and you're on your way. – Robin Betts Feb 7 '19 at 9:04
• Just checking in. I have not died. Just very slow, sorry (I can literally watch the sun rise and set like Snake in that one Metal Gear game trailer, so when I say "slow", I just mean "unnaturally slothic". Not lazy, but it is a struggle. It's like every moment is a race against time, it's tiring sometimes) – user179283 Feb 23 '19 at 4:23
• @user179283 ..strangely reminiscent...:) – Robin Betts Feb 23 '19 at 5:11

Not shure if i understand the problem correctly...