--- Hi, the total length of the cap has been shortened. What you see in the photo is still the long one. Excuse me.---

This is the end cap of the pipe. It can handle various pipe diameters.
Customization is done by changing the parameters of fusion360 file (.f3d).
Even if you're not using fusion360 right now, it's easy to install fusion360 and change its parameters, so give it a try.

I designed some pipe caps.
-Customizable pipe cap https://www.thingiverse.com/thing:4795549 ...this thing
-Customizable Pipe Cap "Cover type" https://www.thingiverse.com/thing:5150957
-Customizable Rectangle Pipe Cap https://www.thingiverse.com/thing:4875215
-Customizable Rectangle Pipe Cap "Cover type" https://www.thingiverse.com/thing:5153134

[Features]
-Customizable
-Fixed firmly
-Hard to break even if squeezed strongly with a wrench
-Easy to remove from the pipe
-Easy to print(no support)

[Design point]
Designed so that when the bolt is tightened, the bolt is parallel to the pipe. This enabled stable tightening.

[Bolt/Nut type to use]
type: CAP bolt and Nut M3 - M6
bolt length: The needed screw length is approximately equal to or greater than the pipe diameter.

[Customizable parameters]
-Inner diameter of pipe (min:10mm at M4, max: no limit)
-Flange diameter (min: inner diameter of pipe, max: no limit)
-Flange thickness (min:0.1mm, max: no limit)
-Flange chamfer
-screw size (M3, M4 ,M5, M6 ) screws larger than M6 are also possible by manually setting the screw related parameters.

[caution]
-The hole for the nut is designed tight. Completely remove any residue remaining in the holes. I think the fastest way to insert a nut into a hole is to use pliers.

-Since the input value of the parameter is not verified in the fusion360, an error may occur. For example if you use a too large bolt for a small inner diameter pipe, it may break. ex. M4 to 9mm pipe.
If an error occurs, click the OK button in the parameter change window, and then click the undo button to return.

[revision]
2021/05/28(v6)
Fixed a bug that the hole for the bolt head became abnormal when the screw size was changed to M3.

2021/04/04(v5)
The parameters flange_t and flange_c can be set to zero without error.

2021/04/03(v4)
In the case of a thin flange with a large bolt, it may break, and this has been fixed.

2021/03/27(V3)
The total length of the cap has been shortened. First, I made the cut angle to be set freely, tested several angles, and found that it worked even at 30 degrees.
The cut angle can be made smaller (for example, 20 degrees) and the overall length can be made shorter, so if you need shorter, give it a try.

2021/03/23 (v2)
Until now, screw parameter settings had to be changed in five parameters, but now only one is required. The remaining parameters of the screw are set automatically.