Technical Japanese #15 — Mechanical Vocabulary: Materials, Machining, Welding and Surface Treatment
When a Japanese drawing or machining instruction lands on your desk, four clusters do most of the work: 材料 the material, 加工 the machining, 溶接 the welding and 表面処理 the surface treatment. Misread any one of them and the lot is remade. This post gathers the shop-floor vocabulary for all four into a lookup table, with the phrases you need to ask again and confirm with the Japanese engineer.
Core mechanical vocabulary
| Japanese | Reading | Meaning | On the floor | Note |
|---|
| 材料 | ざいりょう zairyō | material | 材料は何ですか | Asking what a part is made of |
| 鋼 / 鉄 | こう / てつ kō / tetsu | steel / iron | 鉄板を切る | 鉄 is iron generally, 鋼 is steel |
| ステンレス | sutenresu | stainless steel | SUS304を使う | Written in katakana, often as SUS |
| アルミ | arumi | aluminium | アルミの部品 | Short for アルミニウム |
| 真鍮 | しんちゅう shinchū | brass | 真鍮のブッシュ | Bushings, fittings |
| 樹脂 | じゅし jushi | resin, plastic | 樹脂成形 | 樹脂 on drawings, プラ in speech |
| 加工 | かこう kakō | machining | この加工は難しい | Covers every machining step |
| 旋盤加工 | せんばんかこう senban kakō | turning | 旋盤で削る | 旋盤 is the lathe |
| フライス加工 | furaisu kakō | milling | フライスで平面を出す | Katakana from "mill" |
| 穴あけ | あなあけ ana-ake | drilling | 穴をあける | 穴 is the hole |
| 切断 | せつだん setsudan | cutting off | 材料を切断する | Cutting stock to length |
| 研磨 | けんま kenma | grinding, polishing | 表面を研磨する | Finishing and polishing |
| 溶接 | ようせつ yōsetsu | welding | 溶接してください | The core of fabrication work |
| 溶接部 | ようせつぶ yōsetsubu | weld, welded area | 溶接部を検査 | The zone that gets inspected |
| ティグ溶接 | tigu yōsetsu | TIG welding | ステンはTIGで | For stainless and aluminium |
| 表面処理 | ひょうめんしょり hyōmen shori | surface treatment | 表面処理を指定 | Plating, painting, coating |
| めっき | mekki | plating | 亜鉛めっき | 亜鉛 is zinc, for corrosion resistance |
| 塗装 | とそう tosō | painting | 塗装色を確認 | Check the colour code |
| 熱処理 | ねつしょり netsu shori | heat treatment | 焼入れをする | 焼入れ is quench hardening |
| 硬度 | こうど kōdo | hardness | 硬度を上げる | Checked after heat treatment |
Phrases by situation
Asking about and confirming the material
- この部品の材料は何ですか。 — What is this part made of?
- SUS304で合っていますか。 — SUS304 is correct, isn't it?
- 材料の指定を教えてください。 — Please tell me the specified material.
Confirming how it is machined
- この加工方法で問題ないですか。 — Is this machining method acceptable?
- 公差はどのくらいですか。 — What is the tolerance?
Welds and surfaces
- 溶接の指示はどこにありますか。 — Where is the welding instruction given?
- 表面処理は必要ですか。 — Is surface treatment required?
Material codes you will meet on Japanese drawings
- SS400 — general structural rolled steel (一般構造用圧延鋼材).
- S45C — carbon steel for machine structures: shafts and loaded parts (機械構造用炭素鋼).
- SUS304 / SUS316 — stainless (ステンレス); 316 has the better corrosion resistance.
- A5052 / A6061 — aluminium alloys.
- FC / FCD — grey cast iron and ductile iron (鋳鉄).
When the drawing simply says "SUS304", the material is fixed. Do not substitute an "equivalent" grade on your own judgement. A change goes through 設計.
Mistakes to avoid
| Mistake | Why it hurts |
|---|
| Treating 鉄 (iron, steel in general) as 鋼 (steel) | On a drawing, follow the material code — never infer the grade |
| Reading 加工 as only turning and milling | It covers cutting, drilling, grinding and welding as well |
| Skipping 表面処理 | A part that is dimensionally perfect but missing its 亜鉛めっき is still a reject, because it will rust |
Hear it, then act — quick self-check
A Japanese engineer says: 「この部品、S45Cで、焼入れしてから研磨してください。」 What do you do?
<details><summary>Answer</summary>The part is S45C. Harden it (焼入れ) first, and grind it (研磨) afterwards. The order matters: heat treatment comes first, and finish grinding brings it to final size.</details>
And: 「溶接部を検査して、問題なければ塗装に回して。」
<details><summary>Answer</summary>Inspect the weld zone (溶接部); if there is no problem, pass it on to painting (塗装).</details>
How MINATA helps
Do you have a Japanese drawing or 仕様書 whose material, machining and surface treatment have to be read correctly before you quote or place the job with a shop? MINATA reads the drawing, breaks the requirements down to Japanese practice, then designs and coordinates the machining in Vietnam. See how we work on our Japan–Vietnam projects, or talk to us through engineering and production services.
For the underlying mechanical subject matter, see MINATA's Mechanical section.
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