Plane rule

[John Whitley]

Somewhere in the history of this forum, and here on japan-tool.com I've found mention of a notched rule for checking the sole of kanna.

This raises a question: why this versus a good machinist's straightedge? (E.g. the Starrett rule I've already got in my toolbox.)

[Chris Hall]

The notch on the metal plane straightedge allows the blade to be tapped into the operating position, which means the sole of the plane, especially in the portion trailing the blade, is distended to proper position. The notch allows you to check the sole without chipping the blade.

You could obtain a machinist's straightedge and have a notch ground in it - it would work fine, but I doubt it would be cheaper than the existing product. A Starrett rule is a good tool, but the lack of a bevel ground on the edge means ultimate accuracy is compromised if you want to use it for checking a surface precisely.

[John Whitley]

Ah! Of course, the sole is flexible. Still in a cast-iron plane body mindset.

The bevel makes sense as well. The Starrett is really a fallback for testing flatness for me, mostly used with feeler gauges when needed.

Thanks!