Ergo handle for Sentro knitting machine

I'm told adult-size hands can cramp up using the ball crank on Sentro machines; these handles are more comfortable than the ball.  My initial design was all PLA, but we found the axle part can snap--it might be better in PETG. I uploaded those Sentro48 and Sentro22 prints if you're stuck.  (The handle "axles" are different lengths.)

SewHandle2 is a more durable design, but it requires $5 of additional parts that you can get at a hardware store:
#10-24 Zinc Rod Coupling Nuts, $1.67/3 @ HD
#10-24 x 1-1/4 in. Combo Round Head Zinc Plated Machine Screw. $1.78/5 @ HD
7/32" X 12" Round Aluminum Tube, Mfr K&S #8105, $1.29 @ Ace

Note 3 perimeters and 25% fill for strength.  After the handle is printed, use a hammer to tap the coupler nut into the hex recess. Use a hacksaw or Dremel w/ cutoff wheel to cut the aluminum tube to length: 16mm for Sentro48, 17mm for Sentro22.  Insert the machine screw in the back of the crank, place the aluminum sleeve over the screw threads, and screw on the hex coupler/handle assembly. If the handle is too loose, you can file the aluminum tube a little shorter.  You don't want it too tight, or the handle will bind on the crank.

Settings:
Filament PLA
Nozzle 0.6
Layer 0.30mm
Supports No
Fill 25% gyroid
Perimeters 3
Temp 215C