Mary wanted a rigid cap for a Clover seam ripper that came with a small plastic sheath, so I called one from the vasty digital deep:

Clover Seam Ripper – new cap

The solid model looks about like you’d expect, with a brim around the bottom to paste it on the platform:

Clover Seam Ripper Cap – Slic3r preview

I added a slightly tapered entry to work around the usual tolerance problems:

Clover Seam Ripper Cap – bottom view

The taper comes from a hull wrapped around eight small spheres:

Clover Seam Ripper Cap – Entry Pyramid

That’s surprisingly easy to accomplish, at least after you get used to this sort of thing:

hull() {																		// entry taper
	for (i=[-1,1] , j=[-1,1])
		translate([i*(HandleEntry[0]/2 - StemRadius),j*(HandleEntry[1]/2 - StemRadius),0])
			sphere(r=StemRadius,$fn=4*4);
	for (i=[-1,1] , j=[-1,1])
		translate([i*(HandleStem[0]/2 - StemRadius),j*(HandleStem[1]/2 - StemRadius),HandleEntry[2] - StemRadius])
			sphere(r=StemRadius,$fn=4*4);	
}

The side walls are two threads thick and, at least in PETG, entirely too rigid to slide on easily. I think a single-thread wall with a narrow ridge would provide more spring; if this one gets too annoying, I’ll try that.

The OpenSCAD source code as a GitHub gist: