齒輪，2段變速，車床主軸V，金屬車床

The 44-tooth end engages perfectly with my lathe's threading, and the gear teeth mesh smoothly without any wobble. I've been using it for a week now on my bench setup, and it's held up well under metal turning.

Was a little nervous about the 10mm bore fitting perfectly, but it slid right onto the shaft with no play. The 21-tooth to 44-tooth combo gives me exactly the range I needed on the SC4, and the machining is clean with no burrs.

Had to swap out the old carriage shaft gear on my SC4 lathe, and the 21-tooth end meshed perfectly with the existing setup. The 44-tooth side gives me a nice slow speed option for threading, which made a big difference in control.