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How to Find a Machine Shop That Works to Japanese Drawing Standards

Choosing a Shop / 24 Aug 2026

The instinct is to look for a shop that speaks Japanese. That is the wrong filter. Plenty of shops with fluent Japanese sales staff quote parts wrong, and plenty of shops with no Japanese at all quote them right.

The real test is whether the shop reads the standards the drawing points at. A JIS drawing is mostly references: a tolerance class in the title block, a geometrical class beside it, finish symbols on the faces, a thread class on the callouts. Those are numbers and letters, not language. A shop that ignores them produces a part that is legal against its own quote and wrong against yours.

The three ways it goes wrong

Quoting against tolerances nobody read. Your title block says JIS B 0405-f. That is the fine class: plus or minus 0.1 mm on a dimension between 6 and 30 mm. A shop that assumes the medium class quotes plus or minus 0.2 mm, prices the part accordingly, and delivers something that fails inspection on dimensions that were never individually toleranced. Nobody lied. The drawing was not read.

Misreading the views. JIS B 0001 specifies third angle projection, the same convention used in the United States. Most European drawings are first angle. A shop that works mainly to European drawings and does not check the projection symbol can place a feature on the opposite side of the part. This survives right up to first article inspection.

Treating legacy finish marks as decoration. Older drawings carry triangle symbols instead of Ra values. One triangle is roughly Ra 25, four is roughly Ra 0.2. That is the difference between an as machined face and a ground or polished one. A shop that does not recognise the symbol quotes as machined and is surprised later.

Six questions to ask before you send a drawing

Ask these by email before the drawing goes anywhere. The answers take a shop about five minutes and tell you most of what you need.

1. “Which general tolerance standard do you work to, and what does the class letter change?”

Want to hear: ISO 2768 or JIS B 0405, four classes f, m, c and v, and the tolerance depends on the dimension band as well as the class. Should worry you: “We hold plus or minus 0.1 on everything.” That is a shop that has never read a title block.

2. “If my drawing has a geometrical general tolerance class, where do you look it up?”

Want to hear: JIS B 0419 or ISO 2768-2, classes H, K and L, covering flatness, perpendicularity, symmetry and run-out. Should worry you: silence, or a request for you to dimension it explicitly.

3. “What does three triangles mean on a face?”

Want to hear: legacy JIS surface finish notation, roughly Ra 1.6, and they would confirm with you before pricing. Should worry you: a guess, or a confident answer with no offer to confirm.

4. “Which stainless grades do you run every week?”

Want to hear: specific grades and specific machines. “SUS303 and SUS304 on the sliding heads daily, 316L on the mills a couple of times a month.” Should worry you: “all of them”.

5. “What tolerance do you hold in production, not on a one off?”

Want to hear: a real number with a caveat. “Plus or minus 0.02 on a turned diameter in production, h7 without grinding up to about 30 mm, tighter needs grinding.” Should worry you: a machine brochure number, or anything quoted without mentioning inspection.

6. “What inspection equipment is on site?”

Want to hear: CMM, surface roughness tester, thread gauges, height gauge, and who is qualified to run them. Should worry you: calipers and a subcontracted CMM. That is fine for general tolerance work and a problem for anything tighter.

Evidence worth asking for

Questions can be answered by a salesperson. These cannot:

A first article report against a JIS drawing, customer details removed. It shows whether the shop knows how to build an inspection sheet from a title block.
A photo of stainless work with the grade named. Not a stock photo. A part they made, and which grade it was.
The inspection equipment list with models. A specific CMM model is checkable. “CMM” is not.
A mill certificate they have issued to a customer, again redacted. It tells you what standard they habitually buy against.

Translation is not the hard part

A common assumption is that the risk lives in the Japanese notes. It mostly does not. The notes usually say things like heat treatment, deburring and packaging requirements, and a competent translator handles them.

The risk lives in what translation cannot fix:

A tolerance class that is read but not applied
A datum scheme that is interpreted differently than intended
A thread callout that gives pitch but no tolerance class, so the shop picks one
A material designation translated to an equivalent, with a certificate that then names the wrong standard

None of those are language problems. They are standards problems, and they survive translation intact.

Prototype before production

Whatever a shop says, one part against the real drawing is the cheapest test available. Order a single piece, inspect it yourself against the drawing including the general tolerances, and look specifically at:

Features that carry no individual tolerance. Are they inside the class letter?
Surface finish on the faces that were symbol marked
Thread fit with a gauge, not by eye
Whether the certificate says what you asked it to say

A shop that passes that on the first piece will usually pass on the hundredth. A shop that fails it will fail more expensively later.

What we do before a drawing goes out

SUS CNC is a trading company: we sell you the finished part and buy the machining from a shop in the network we manage. The checks above are the same ones our engineer runs before your drawing is placed: tolerance class, geometrical class, finish call-outs, thread class, certificate requirement, and whether the shop we have in mind has actually held those things on stainless recently.

If the checklist itself is what you need, the JIS drawing checklist covers it point by point, and the general tolerance guide covers the class letters in detail.

Have a drawing to place now? Get a quote. An engineer reads it and prices it within 24 business hours, and if you order we place it with the right shop, follow it every week, inspect it and ship it on one PO and one invoice.

Questions

Does the shop need to speak Japanese?

No. It needs to read the title block, the general tolerance class and the finish symbols. Those are standards references, not language. A shop that knows what JIS B 0405-m means will quote your part correctly even if a translator handled the notes.

Should I translate the drawing before sending it?

Send the original. A translated drawing loses the title block formatting, and a re-drawn one introduces errors nobody catches. Send a translation of the notes alongside the original if you have one.

What is the single best test of a shop?

Ask what the general tolerance class on your drawing is before you tell them. If they have to look, they have not read it. If they answer and then ask which geometrical class applies, they have read both standards.

Is it worth ordering one prototype first?

Almost always. One part against the real drawing tells you more about a shop than any reference check, and it costs less than a rejected production lot.

Have a drawing for a stainless part?

Send it and an engineer reads the title block, quotes it within 24 business hours, and if you order we place, manage, inspect and ship the parts on one PO and one invoice.

Get a quote