Building and civil
Fits (JIS B 0401-1:2016 = ISO 286-1:2010, 30 mm diameter example)
The same 30mm turns into a running fit or a permanent one depending on two letters: H7/g6 leaves 7 to 41 microns of clearance, H7/p6 always bites by at least 1 micron
This drawing comes from one YAML file. No shape was moved by hand.
Notes in the source (in Japanese)
同じ φ30 でも、記号で役目が変わる。 H7/g6 はすべり動き、H7/p6 はプレスで入れて止める。
大文字が穴、小文字が軸。 文字が「基準の線からどちら側へどれだけ離すか」、数字（IT 等級）が「公差の幅」を決める。H は下の許容差が 0。
数は引き算で出る —— 最大すきま ＝ 穴の上 − 軸の下、最大しまり ＝ 軸の上 − 穴の下。φ30 の H7/p6 なら しまり 1〜35μm で、いちばん都合が良くても必ず食い込む。
穴を基準にするのは、穴のほうが作りにくいから。穴は工具（ドリル・リーマ）の寸法に引きずられるが、軸は旋盤で削り分けられる。
数値は「18 を超え 30 以下」の欄（単位 μm）。
JIS B 0401-1:2016 は ISO 286-1:2010（＋追補 1:2013）と一致（IDT）。使い分けの言い方は ANSI B4.2-1978 の優先はめあいの説明に照らした（H7/g6 sliding・H7/h6 locational clearance・H7/p6 locational interference）。2026-09-29 確認。（規格の本文は kikakurui.com の JIS B 0401-1:2016 で確かめた。）
Source (YAML)
examples/gallery/243-はめあい.zumen.yaml
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