Hand lathe for PTFE bearing / bushing turn down

thingiverse

Motivation I set out to experiment with solid PTFE bushings (D15mm, d8mm, L10mm) because they provide similar static and dynamic coefficients of friction. This prevents the stick-slip effect which is very pronounced with PLA on hardened steel. However, I was unable to find precisely manufactured PTFE tubes (or hollow poles) on ebay (www.ebay.de/itm//261909054576). Tolerances are quite poor: A D15mm, d8mm tube turned out to be D16.2mm, d7.8mm. So reaming and lathing is necessary. This handheld lathe uses a box cutter blade for milling, an 8mm rod as an axis and a cordless screwdriver as a motor. Radius adjustment is done by means of a 16mm M3 screw. This lathe is not precise. Iterative corrections are required to get the proper outer diameter. The photos show an older version, which did not work well. The blade has to be close to perpendicular to the cylindric surface and not close to tangential. Usage Insert the rod through the long hole, place the cut PTFE tube on the rod and finally insert the rod through the short hole. Position the PTFE tube close to the short hole. Adjust the desired cutting radius. I recommend not to turn down more than 0.5mm per run. Pull the rod in direction of the long hole to start milling. Maintain a low rotation speed and slowly pull the rod. Try which rotation direction (clockwise or counterclockwise) offers the best result. You need to develop experience or a feel for the process to obtain a perfectly smooth outer surface. Yes, a perfectly machined outer surface is possible. Use a reamer or a rough sanded 8mm rod to get the proper inner diameter until no friction occurs. Print Settings Notes: Please select a proper printing orientation by hand.