| Name: | SMC D Locking |
| Sub Item: | (full-thread) |
| Category: | screw lock |
| Locking Type: | manual |
| Locks: | screw |
| Unlock Style: | other stopped |
| Sleeve Rotation: | 1710/180° (unlocked) | 6525° (maximum) |
| Shape: | D |
| Material: | aluminum |
| Profile: | round |
| Nose: | notch & pin |
| Nose Guard: | none |
| Rivets: | pin: recessed |
| Gate Shield: | none |
| Weight: | 65 g |
| Dimensions: | Length: 105 mm Width: 52 mm Gate Opening: 17 mm |
| Other Markings: | Stamped: (SMC oval logo) |
| Collection Criteria: | ★ Mechanically Interesting |
| Summary: | bi-directional locking due to full length thread |
| Description & Commentary: | Clearly designed for the sleeve to block the gate from opening at the nose. The sleeve stops on the gate on the thread terminus, and requires a massive 4.75 rotations to unlock. Due to the design/construction/assembly choices, the threading (pitch: 1.26 mm / 20 tpi) extends down through the hinge area - which will also let the sleeve block the opening if jammed against the hinge. This configuration would be extremely weak against gate face loads, and likely be more of an annoyance when accidentally engaged. The long threading does make it easy to distinguish between the nose and hinge end of the carabiner by feel and at a glance. Curiously, the nose pin of one example does not overlap the center of the gate at all - many carabiner use offset pins, but the pin diameter still overlaps with the centerline of the gate. I imagine this would seriously reduce the minor-axis strength if loaded while the sleeve is not locked over the nose. Round stock is a little over 11mm, perhaps 7/16 inch if SMC used the US customary measurements |