3-Disc Plunger Heads

Guide by KaneTheMediocre
Design origin unknown, multiple authors

The 3-disc plunger head was originally developed to mount the McMaster #9562K46 "Stretch-Fit Rotary-Shaft Ring Seal", or as they are more commonly known in the DIY Nerf community, skirt seals. That skirt seal is extraordinarily robust and seals well inside 1 1/4" PVC or any tube with a 1 3/8" inner diameter.

There are a few ways to make this sort of plunger head, mostly depending on the type of plunger rod to which it will be attached.  I have suggested dimensions for a couple.

End-wise on a plunger rod with female #6-32 thread:

#6-32 Screw:
1.125" x 0.150"
0.875" x 0.150"
1.250" x 0.150"

Around a threaded 1/4"-20  shaft:
1/4-20 Nut
1.125" x 0.250"
0.875" x 0.250"
1.250" x 0.250"
1/4-20 Nut
It's not hard to see how these dimensions could be changed to fit a variety of other mounting situations.  Just make sure that the skirt is squeezed between two discs, and that the front disc is small enough to press on the inner lip of the skirt without compressing the lip of the skirt.