定位環，滑座軸

It’s a small part but critical for alignment—machined precisely enough that I could slip it on without any binding. The ID and groove dimensions match the SC4 diagram exactly, so no extra filing was needed. Saved me making one from scratch.

Finally got my SC4 lathe back together after losing one of these positioning rings during a move. The replacement fit perfectly into the carriage shaft and the machining is precise enough that the whole assembly turns smoothly now. Exactly the part I needed without having to buy a whole new assembly

Fit perfectly on my SC4 lathe’s carriage shaft — the inner diameter is exactly right, so there was no slop or need to file anything. Only gave 4 stars because I wish they included a set screw with each ring instead of having to source my own.