Sanding Length of Composite Pivot Tubes to +/- .0005" with a Beltsander

Sanding the sides flat to a length tolerance was harder. Good fixture design was key.
3D printing the sanding fixture

Fixture straddles the belt sander bed holding itself perpendicular to the platform. The threaded knob allowed me to hold the pivot tube at a fixed distance from the belt to carefully bring it into dimension without sanding too much material. Sand, measure, adjust if necessary. The large V-block tray allowed me to hold the axle securely while sanding/rotating.
Printed belt sanding fixture

Parts of sanding fixture

Assembly of belt sander fixture


Here is how it is used. Rubbing graphite powder on my thumb reduced friction.
Setup of belt sander fixture

Belt sander operation

Composite pivot tubes sanded to length within one thousandth of an inch with a Chinese belt sander and a 3D printed jig.
Measuring composite pivot tubes sanded to length
  • 10mm Pivot Length held to 1.929"-1.930"
    • 1.929
    • 1.930
    • 1.930
    • 1.929
  • 14mm Pivot Length held to 1.810"-1.811"
    • 1.811
    • 1.810
    • 1.811
    • 1.811

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