JIS B 0405 and JIS B 0419: The General Tolerances Everyone Skips
Drawings / 7 Sept 2026
Look at the title block of a JIS drawing and you will usually find a line like JIS B 0405-m or JIS B 0405-mK. It is small, it is easy to skip, and it silently sets the tolerance on most of the dimensions on the page.
A shop that misses it quotes a looser part than you asked for. A shop that reads it and quotes accordingly sometimes looks expensive next to one that did not. The only way to compare quotes fairly is to make sure everybody read the same line.
What the two standards cover
JIS B 0405 handles linear and angular dimensions that carry no individual tolerance. Four classes: f fine, m medium, c coarse, v very coarse. It corresponds to ISO 2768-1.
JIS B 0419 handles geometrical characteristics that carry no individual tolerance: straightness, flatness, perpendicularity, symmetry, run-out. Three classes: H, K, L. It corresponds to ISO 2768-2.
A drawing marked JIS B 0405-mK is carrying medium linear and K geometrical. Both apply.
Linear dimensions, JIS B 0405
Permissible deviations in millimetres:
| Nominal size | f (fine) | m (medium) | c (coarse) | v (very coarse) |
|---|---|---|---|---|
| 0.5 to 3 | ±0.05 | ±0.1 | ±0.2 | - |
| over 3 to 6 | ±0.05 | ±0.1 | ±0.3 | ±0.5 |
| over 6 to 30 | ±0.1 | ±0.2 | ±0.5 | ±1 |
| over 30 to 120 | ±0.15 | ±0.3 | ±0.8 | ±1.5 |
| over 120 to 400 | ±0.2 | ±0.5 | ±1.2 | ±2.5 |
| over 400 to 1000 | ±0.3 | ±0.8 | ±2 | ±4 |
| over 1000 to 2000 | ±0.5 | ±1.2 | ±3 | ±6 |
| over 2000 to 4000 | - | ±2 | ±4 | ±8 |
Dimensions below 0.5 mm must be toleranced individually. The standard does not cover them.
Two things fall out of this table immediately. First, the class letter is not a tolerance, it is a column. The same letter gives you ±0.1 mm on a small feature and ±0.5 mm on a large one. Second, the gap between f and c is a factor of five. That is not a detail.
Chamfers and external radii
Handled separately, because a general linear tolerance on a 1 mm chamfer would be meaningless:
| Nominal size | f and m | c and v |
|---|---|---|
| 0.5 to 3 | ±0.2 | ±0.4 |
| over 3 to 6 | ±0.5 | ±1 |
| over 6 | ±1 | ±2 |
Angular dimensions
The tolerance depends on the length of the shorter side of the angle, not on the angle itself:
| Shorter side, mm | f and m | c | v |
|---|---|---|---|
| up to 10 | ±1° | ±1°30’ | ±3° |
| over 10 to 50 | ±0°30’ | ±1° | ±2° |
| over 50 to 120 | ±0°20’ | ±0°30’ | ±1° |
| over 120 to 400 | ±0°10’ | ±0°15’ | ±0°30’ |
| over 400 | ±0°5’ | ±0°10’ | ±0°20’ |
Geometrical tolerances, JIS B 0419
This is the part that surprises people, because it applies whether or not any geometrical tolerance is drawn on the part.
Straightness and flatness, by nominal length in mm:
| Nominal length | H | K | L |
|---|---|---|---|
| up to 10 | 0.02 | 0.05 | 0.1 |
| over 10 to 30 | 0.05 | 0.1 | 0.2 |
| over 30 to 100 | 0.1 | 0.2 | 0.4 |
| over 100 to 300 | 0.2 | 0.4 | 0.8 |
| over 300 to 1000 | 0.3 | 0.6 | 1.2 |
| over 1000 to 3000 | 0.4 | 0.8 | 1.6 |
Perpendicularity, by the length of the shorter side:
| Shorter side | H | K | L |
|---|---|---|---|
| up to 100 | 0.2 | 0.4 | 0.6 |
| over 100 to 300 | 0.3 | 0.6 | 1 |
| over 300 to 1000 | 0.4 | 0.8 | 1.5 |
| over 1000 to 3000 | 0.5 | 1 | 2 |
Symmetry, by nominal length:
| Nominal length | H | K | L |
|---|---|---|---|
| up to 100 | 0.5 | 0.6 | 0.6 |
| over 100 to 300 | 0.5 | 0.6 | 1 |
| over 300 to 1000 | 0.5 | 0.8 | 1.5 |
| over 1000 to 3000 | 0.5 | 1 | 2 |
Circular run-out, independent of size:
| H | K | L |
|---|---|---|
| 0.1 | 0.2 | 0.5 |
Three more rules complete the picture:
- Roundness takes the numerical value of the diameter tolerance, but never more than the circular run-out value for the class
- Parallelism takes the larger of the dimensional tolerance or the flatness and straightness tolerance
- Cylindricity and coaxiality are not covered by the general tolerance and must be drawn if they matter
Why the class letter changes the price
Take a 40 mm turned diameter with no individual tolerance.
- Class f: ±0.15 mm. Comfortable on a well set up lathe, still requires attention
- Class m: ±0.3 mm. Routine
- Class c: ±0.8 mm. Almost free
Now take a 200 mm flat face with no flatness call-out.
- Class H: 0.2 mm flat. On a machined plate that may mean a second operation or a fixturing change
- Class K: 0.4 mm. Usually achievable in one operation
- Class L: 0.8 mm. Effectively no constraint
The H class run-out limit of 0.1 mm deserves separate mention. On a turned shaft with features produced in two operations, holding 0.1 mm run-out without a specific plan is not automatic. Many drawings marked -fH are asking for more than the person who drew them realised.
How this goes wrong in practice
The class is never read. The most common failure. The shop assumes medium, quotes medium, delivers medium, and the drawing said fine.
The geometrical class is ignored. Even shops that read B 0405 often skip B 0419, because the letter is appended to the same note and looks like part of the same class.
The class is too tight for the part. A drawing marked -fH because that is the company template, on a bracket where nothing needs it. This costs money on every part forever.
No note at all. Then there is no agreement, and the argument at inspection has no reference to appeal to.
What to do about it
If you are buying: know which class your drawing carries and say it in the enquiry. One line in the email, general tolerances JIS B 0405-m, geometrical JIS B 0419-K, removes the ambiguity before anybody prices anything.
If you are drawing: choose the class for the part rather than taking the company default. If three features genuinely need precision, tolerance those three individually and set the general class to medium or coarse. That is cheaper than lifting the general class for the whole drawing.
If you are comparing quotes: ask each shop what general tolerance class they quoted against. If the answers differ, you are not comparing the same part.
For the rest of the title block, see the JIS drawing checklist. For what surface finish symbols add on top of dimensional tolerance, see JIS surface finish symbols.
Have a drawing where the class matters? Get a quote. An engineer reads the title block before the drawing is placed with a shop, and the priced quote comes within 24 business hours.
Questions
What does JIS B 0405-m mean on a drawing?
Every dimension without its own tolerance carries the medium class general tolerance. That is not one number. It is plus or minus 0.1 mm up to 6 mm, plus or minus 0.2 mm from 6 to 30 mm, plus or minus 0.3 mm from 30 to 120 mm, and so on up the size bands.
Is JIS B 0405 the same as ISO 2768?
Yes, in substance. JIS B 0405 corresponds to ISO 2768-1 for linear and angular dimensions, and JIS B 0419 corresponds to ISO 2768-2 for geometrical tolerances. The class letters and the values match.
What happens if my drawing has no general tolerance note at all?
Every shop assumes something different, usually the loosest thing it can defend. That is the most expensive omission you can make on a drawing, because it is invisible until inspection.
Do general tolerances apply to dimensions that already have a tolerance?
No. An individually toleranced dimension governs itself. The general tolerance covers everything else, which on most drawings is the large majority of dimensions.
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 quoteRelated guides
SUS303Se and SUS303Cu Compared with SUS303: Which Free Cutting Grade to Use
SUS303Se and SUS303Cu against standard SUS303: what selenium and copper change for finish, cold forming and corrosion, and what a drawing should state.
SUS Spacers and Collars to JIS Drawings: What Drives the Price of Small Lots
How stainless spacers and collars are made from JIS drawings in small lots: length and parallelism, bore and set screw details, stack-up and price breaks.