SEIKO S-282 Kojiake – Case Opener for Snap-On Case Backs, Wide Blade 8 mm | Original SEIKO Japan

Original SEIKO watchmaker's tool, imported directly from Japan – rarely available outside Japan.

The Kojiake (こじ開け, "case opener") is the classic Japanese tool for opening snap-on and press-fit case backs. The S-282 model from SEIKO's professional tool range features the series' wide blade with an 8 mm tip width, making it designed for large cases with wide opening notches – typically men's watches, sports models, and larger vintage cases. The wide blade distributes the leverage over a larger contact surface: the case back snaps off in a controlled manner, without the blade digging into the notch or jamming the case.

A special feature of the SEIKO Kojiake: the blade is deliberately designed so that it can be re-sharpened by the watchmaker and adapted to the respective case – as is common practice in Japanese workshops. The tool thus grows with its tasks and, with good care, lasts a watchmaker's lifetime.

The series includes three blade widths: S-282 (8 mm, this offer), S-283 (5 mm), and S-284 (4 mm).

What distinguishes this tool from European counterparts:

European case knives usually work with a short, knife-like edge that applies pressure at a single point. The SEIKO Kojiake, on the other hand, engages the opening notch with its full blade width – the design used to open snap-on case backs of Japanese watches (SEIKO, Citizen, Orient) ex-works. Especially with tightly fitting case backs of large cases, the 8 mm blade significantly reduces the risk of slipping and scratching compared to narrow universal knives. Additionally, the re-sharpenable blade: cheap openers with soft blades bend at the tip and must be replaced; the SEIKO Kojiake is re-sharpened instead. The original SEIKO tool range is not regularly distributed in Europe.

Dimensions:
Tip width 8 mm
Reference: SEIKO S-282 (SE-S-282)

Condition:
New product, original packaging

Note
Improper use of tools can damage watches. Use is at your own risk.