Hex hole sizing plate
by ToddF, published
1/2" hex shaft is very common in FRC robot drive trains and transmissions. Team 2363 uses our Replicator to make parts for our West Coast Style drive train. If you print parts with .500" hexes, the printed parts do not fit onto 1/2" hex shafting. I created this plate to allow the proper sizing of the hex holes in a solid model.
Print the plate with the fill ratio you want to use in your finished parts.
Label the holes as shown in the photo. Smallest hole is .500", and the holes go to .535" in increments of .005".
Test fit your hex shaft in the holes starting with the largest size hole and working down.
Select the nominal hole size to give the fit you want between the shaft and the part, and use that size in your part.
Be aware that the top and bottom layers may be smaller than the interior layers of the part. Filing or trimming the top and bottom layers back with a file or Xacto knife may give a slightly different fit of the shft to the hole.
If you modify your print speeds, accelerations, layer thicknesses, or fill ratios, any of these may affect the fit of the hex holes to the shaft. Reprint another plate with the new parameters to use for test fitting.
You can also use the outside dimensions of the plate to check how well your machine is holding tolerances. The plate nominal dimensions are 3.4375 x 1.75 x .250. The plate shown in the picture measured 3.423 x 1.752 x .235/.242