We have two 30-year-old poolside chairs. They might be 40 years old. They are excellent metal chairs with adjustable backs. The problem was that the plastic sliders on the bottom of the legs had long ago disintegrated, leaving nothing but bare metal. So, when my wife or kids dragged the chairs across the concrete, the legs would make a brain-curdling screeching sound. I had been thinking about making wooden plugs to stick into the hollow legs like corks, but then I realized I could easily make custom sliders with my 3D printer.
I measured the dimensions of a chair leg hole using the $(removed) digital calipers that John Edgar Park recommended on a recent episode of the Cool Tools Show podcast. (I use these things all the time, and I can't believe I've lived this long without them.) The square hole was 21mm on a side.
I used TinkerCad to make a 3D model of a slider. (I uploaded it to Thingiverse if you happen to have the same nameless 30-year-old poolside chairs and want to make your own.)
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I saved the 3D model as an STL file. (STL stands for STereoLithography / Standard Triangle Language / Standard Tessellation Language – take your pick). I opened the STL file in an application called Repetier-Host. This program "slices" the 3D model into layers and generates a printing plan based on the kind of 3D printer you have. Roughly speaking, TinkerCad is the CAD (computer-aided design) program and Repetier-Host is the CAM (computer-aided machining) program.
I have a Printrbot Jr. It cost $(removed) My daughter and I have made simple toys and name tags with it, but nothing really useful. (The Jr. is no longer in production. The PrintrBot Simple ($(removed)) looks like the improved successor.)
Each chair has 6 legs, so I gang printed six sliders at a time.
I tapped the sliders into the hole with a hammer. It was a very tight fit, but that's what I wanted.
No more horrible squeaking. I am inordinately happy with my obnoxious green chair leg sliders.