Sears Humidifier Bottle Cap Reinforcement

In the midst of the humidification season, I spotted this while refilling one of the ancient Sears Humidifier bottles:

Humidifier bottle cap reinforcement – crack

While it’s possible to buy replacement caps, this seemed more appropriate:

Humidifier bottle cap reinforcement – installed

It’s PETG-CF, of course:

Bottle cap reinforcement – solid model

The shape is a ring with a simplified model of the cap removed from the middle:

Bottle cap reinforcement – lid solid model

It fits snugly over the cap atop a thin layer of JB PlasticBonder that should hold it in place forevermore:

Humidifier bottle cap reinforcement – bottom view

The other side shows the crack over on the right:

Humidifier bottle cap reinforcement – top view

Close inspection showed a few smaller cracks, so that cap was likely an original.

I made another ring for the other cap, only to find it was slightly larger with a black washer inside: apparently a previous owner had replaced one of the caps. The OpenSCAD program has measurements for both, not that you have either.

The OpenSCAD source code as a GitHub Gist:

	// Humidifier bottle cap reinforcement
	// Ed Nisley – KE4ZNU
	// 2025-11-29

	include <BOSL2/std.scad>

	Layout = "Show"; // [Show,Build,Cap]

	/* [Hidden] */

	Protrusion = 0.1;

	//—–
	// Bottle cap/valve
	// Collects all the magic numbers in one place

	Left = false; // the caps are different, of course
	CapODs = Left ? [43.0,42.1] : [43.1,42.9]; // [0] = base of cap

	CapHeight = 10.0;

	Notch = [0.6,2.0,8.5 + Protrusion]; // Z + hack for slight angle
	NumRibs = 24;
	RibAngle = 90 – atan(CapHeight/((CapODs[0]-CapODs[1])/2));
	echo(RibAngle=RibAngle);

	$fn=2*NumRibs;

	module Cap() {

	difference() {
	cyl(CapHeight,d1=CapODs[1],d2=CapODs[0],anchor=BOTTOM);
	for (a=[0:NumRibs-1])
	zrot(a*360/NumRibs)
	right(CapODs[1]/2) down(Protrusion)
	yrot(RibAngle)
	cuboid(Notch,anchor=RIGHT+BOTTOM);
	}

	}

	//—–
	// Reinforcing ring

	RingThick = 3.0;

	module Ring() {

	render()
	difference() {
	tube(CapHeight,od=CapODs[0] + 2RingThick,id=CapODs[1] – 2Notch.x,anchor=BOTTOM);
	Cap();
	}

	}

	// Build things

	if (Layout == "Cap")
	Cap();


	if (Layout == "Build" \|\| Layout == "Show")
	Ring();

view raw Bottle cap reinforcement.scad hosted with ❤ by GitHub

Sears Humidifier Bottle Cap Reinforcement

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