Quoting a JIS Drawing: The Nine Checks That Protect Your Margin

For Shops / 25 Sept 2026

A JIS drawing is not harder than any other drawing. It carries its requirements in slightly different places, and shops that do not know where to look price the wrong part.

That mispricing goes both ways. Quote too low and the first article report tells you the general tolerance class was tighter than you assumed. Quote too high because the drawing looks unfamiliar and our engineer places the job with a shop that read it properly. Both are avoidable with nine checks that take about ten minutes. Our order package arrives with the title block already resolved, and these checks are how you confirm it rather than take it on trust.

1. The general tolerance class

Find the note in the title block. It reads something like JIS B 0405-m or ISO 2768-mK.

This is not a single number. Class m gives plus or minus 0.2 mm between 6 and 30 mm, and plus or minus 0.3 mm between 30 and 120 mm. Class f gives 0.1 mm and 0.15 mm for the same bands. Class c gives 0.5 mm and 0.8 mm.

The gap between f and c is a factor of five, and it applies to the majority of dimensions on most drawings, because most dimensions carry no individual tolerance. If you price a class c part and deliver against a class f drawing, the rework is yours.

The full tables are here. Pin them up.

2. The geometrical class

The letter appended to the same note, H, K or L, points at JIS B 0419. It applies whether or not any geometric symbol is drawn on the part.

This is the one that catches shops that already know to read B 0405. The H class circular run-out limit is 0.1 mm. On a shaft with features produced in two operations, holding 0.1 mm without a plan is not automatic. The H class flatness on a 200 mm face is 0.2 mm, which on a machined plate can mean a fixturing change or a second operation.

If the drawing says -fH and the part is a bracket, it is worth asking our engineer whether the buyer meant it. Many drawings carry a company default that nobody revisited, and the cover sheet says whether that question has already been asked.

3. The projection symbol

JIS B 0001 specifies third angle projection, the same convention as ASME. Most European drawings are first angle.

Check the truncated cone symbol in the title block. A shop that reads the views by habit can place a feature on the opposite side of the part, and that survives programming, setup and machining. It fails at inspection, on the finished part.

4. Material designation versus certificate

The drawing says SUS316L. Your stockist sells 1.4404. Those are the same alloy for design purposes and different documents for inspection purposes.

Before you price:

Which standard must the certificate name? JIS G 4303, EN 10088-3, ASTM A276?
Is EN 10204 3.1 required, or will a mill certificate do?
Is heat lot traceability required, and does the part need marking?

A 3.1 requirement narrows which stock can be used, which changes both price and lead time. It is not a formality, it is a line in the quote, and the package says whether you or we are buying the material. The certificate guide has the detail.

5. Surface finish call-outs

Modern JIS drawings give Ra to JIS B 0601. Older ones carry triangle marks.

The usual reading is one triangle around Ra 25, two around 6.3, three around 1.6, four around 0.2. Published tables disagree on the four triangle value, which is exactly why you confirm rather than assume.

The cost structure on stainless:

Ra	Effect on your quote
3.2 and 1.6	None, normal machining leaves this
0.8	Attention and a tooling change schedule
0.4	Usually an additional operation
0.2 and below	Grinding, lapping or electropolishing

A blanket note applying Ra 0.8 to a whole part is the single most common source of an inflated quote. Our engineer asks the buyer whether it applies everywhere or to two faces before the package reaches you, and the answer is on the cover sheet. Buyers usually meant two faces.

6. Thread call-outs

M10 on its own leaves you to pick the pitch and the class. If the part is gauged at our final inspection, that is your risk, not ours.

Before quoting, confirm pitch and tolerance class, for example M10 x 1.25 - 6H, and whether a go and no-go gauge result has to be recorded. Gauging is real time per feature.

Also check thread depth against diameter. Anything beyond about 2D is tapping time you are absorbing for no functional gain, and it is worth raising with our engineer rather than quietly pricing.

7. The heat treat sequence

If the part is SUS630, SUS440C or SUS420J2, the sequence is part of the specification whether the drawing says so or not.

Rough, heat treat, then finish. Quoting the part as machined complete with heat treatment as a final step produces a number that cannot hold the dimensions. If the drawing does not state the sequence, state it in your quote. It protects you and it shows our engineer you have done this before.

8. Outside processes and their queues

Passivation, electropolishing, heat treatment, plating. Each has a minimum lot charge and a lead time you do not control.

On a small batch the minimum charge can exceed your machining. Price it as a line rather than folding it in, and quote the lead time honestly including the queue. A date you miss because the passivation house was full is still a date we missed with the buyer.

9. What the drawing does not say

Three requirements regularly live outside the drawing and arrive after the quote:

Magnetic permeability. Cold work raises it on austenitic grades. If the part goes near a sensor or into a vacuum chamber there may be a limit.
Cosmetic requirement. Ra is roughness, not appearance. If a face has to look a certain way, that is a different operation.
Packaging. Individually bagged and interleaved is a real cost on a stainless part that gets rejected for scratches.

Our engineer asks the buyer about all three on anything that looks like a visible or instrument part, and the answers are on the cover sheet. If they are missing, ask.

The quote structure we ask for

Break the number out:

Material, including certificate level
Machining, by operation
Outside processes
Inspection and documentation
Tooling or fixturing, amortised, stated separately
Lead time, with the outside process queue named

Our engineer can only check a quote against the drawing if it is broken out. A single number invites a price conversation. A broken out quote invites a scope conversation, which is the one you want, because that is where it emerges that the Ra 0.8 applied to two faces rather than twelve, and the price comes down without your margin going with it.

The habit that separates shops

Send the clarification questions before the quote, not with it.

One short message to our engineer the same day: here is what I read in the title block, here are the two things I need confirmed, the quote follows on this date. We remember the shop that read the drawing, and it is the shop that sees the next package first. It costs you ten minutes and it is the cheapest differentiation available.

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Questions shops ask

Do I need to read Japanese to quote a JIS drawing?

No. What you need to read is the title block: the general tolerance class, the geometrical class and the projection symbol. Those are standards references, not language. Get the notes translated if they affect the process.

What is the most commonly missed item?

The general tolerance class. It is one line and it governs most of the dimensions on the page. Shops that assume medium when the drawing says fine quote a looser part than the one they have to deliver.

Should I quote higher because it is a JIS drawing?

No. Quote accurately. Adding a blanket risk margin because the drawing looks unfamiliar is how you lose work you could have done well. Reading the title block removes the risk that the margin was covering.

Is third angle projection really a problem?

It is if your shop works mainly to European first angle drawings. JIS B 0001 uses third angle, the same as ASME. Check the symbol every time rather than reading the views by habit.

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