The footnote was not permission: JSA answers a reader who read it that way

Why the limit is there

The answer explains the restriction rather than just asserting it. Table 9 limits grade C to 4.6 and 4.8 because grade C has poorer dimensional accuracy — larger dimensional tolerances — than grades A and B, and so only the low strengths can be applied to it.

The same answer covers Table 5, for product grades A and B, where 3 mm ≤ d ≤ 39 mm specifies 5.6, 8.8 and 10.9. Same verdict, same reasoning in reverse: the higher strengths can be applied to grades A and B because their dimensional accuracy is good.

⭐ So in this product standard the product grade and the property class are not independent choices. That is worth setting beside what a product grade is: product grade A is a tolerance class, not a quality class, and ISO 4759-1 does not cover strength at all. Both are true. The grade does not describe strength, and the product standard still decides which combinations of grade and class are standardised.

And what the footnote was actually doing

This is the part worth carrying to every other standard you read.

The footnote was telling you where those classes are written down. It was not admitting them into that cell of that table. A cross-reference is not an extension of scope — and the reader's mistake was a careful one, which is why it is worth knowing it is a mistake.

The other half of the answer: JSA reports a gap in its own table

Having disposed of the question, the same answer volunteers something the asker had not raised.

A standards body publishing that one of its own tables is short a row against the international standard it was built from, in the course of answering an unrelated question. Two things follow for anyone working from these tables.

• The set of classes in a JIS table is not guaranteed to match the ISO table it came from, even where the intent was to translate without technical change
• Errata exist and are not in the copy you downloaded. If a class you expect is absent, that is a question to ask rather than a conclusion to draw

⚠️ What this page read, precisely

I have not read Table 5 or Table 9. The free preview of JIS B 1180 stops at the beginning of clause 2, as recorded in the piece on its normative annex.

What I read is JSA's own description of those tables, and its ruling, in a Q&A document JSA publishes. That is a primary source — the standards body writing about its own standard — but it is not the tables.

So this page gives no dimensions, does not reproduce either table, and does not generalise to the other tables in the standard. The asker noted that other tables carry similar cases; JSA answered about these two and did not rule on the rest, so neither does this page.

What to do with it

• Do not read a "see standard X" footnote as widening the scope of the cell it sits under. It usually says where something is documented, which is a different claim
• When a product standard pairs a grade with a class, check that your combination is one the standard actually lists — "both exist" is not the same as "this pairing is standardised"
• If a class you expect is missing from a table, ask before concluding. JSA's own answer shows a missing row can be an error awaiting an erratum

References, and how far the reading goes

• Japanese Standards Association, published enquiry-and-answer document (the pdf/jsa/ path on webdesk.jsa.or.jp), tabulated by date, standard, subject, enquiry and answer. The entry used here is dated 2014-12-03, against JIS B 1180:2014, subject: property classes in the product specifications for each product grade of hexagon head bolts.
• ⚠️⚠️ Tables 5 and 9 of JIS B 1180 were not read. This page reports JSA's description of them and its ruling on them.
• ⚠️ ISO 4014:2011 was not read for this page. The comparison to it is the one JSA states in its answer.
• ⚠️ The erratum's status was not verified, for the reason given above.

This is not one of the six steps. It shows up across them, or after assembly. Where the decisions that lead here were made is in specifying a screw, which sets out the order and why doing it out of order is rework.

Common questions

Can a grade C hex bolt be property class 8.8 under JIS B 1180?

JSA answered that question directly and the answer is that it does not become a JIS product. Table 9 limits product grade C to 4.6 and 4.8 for d ≤ 39 mm, and JSA explains the reason: grade C has poorer dimensional accuracy than grades A and B, so only the low strengths can be applied to it. The bolt can of course exist; it is not a product of that standard.

But the footnote says other classes are per JIS B 1051. Does that not include them?

No, and JSA addressed exactly that reading. It states that the meaning of note a) is that classes other than 4.6 and 4.8 — 5.6, 5.8, 6.8, 8.8, 9.8, 10.9 and 12.9 — are described in JIS B 1051, shown for reference. The footnote tells you where those classes are written down; it does not admit them into that cell of that table. A cross-reference is not an extension of scope.

Does the same restriction apply to grades A and B?

The same answer covers Table 5, where 3 mm ≤ d ≤ 39 mm specifies 5.6, 8.8 and 10.9, with the same verdict. The reasoning runs the other way: the higher strengths can be applied to grades A and B because their dimensional accuracy is good. ⚠️ The asker noted that other tables contain similar cases; JSA ruled on these two and not on the rest, so no wider generalisation is made here.

Is this the same thing as product grade meaning quality?

No, and both statements hold at once. A product grade is a tolerance class — ISO 4759-1 does not cover strength, material or coating. What JSA is describing is different: the product standard decides which pairings of product grade and property class it standardises. The grade still does not describe strength; it does constrain which classes that standard offers with it.

What was the erratum about?

In the same answer, JSA notes that in the steel property classes of Table 5 of JIS B 1180, 9.8 is missing compared with the corresponding international standard ISO 4014:2011, and that an erratum would be issued to add it. ⚠️ That entry is dated 3 December 2014 and the wording is future. This page has not confirmed whether the erratum was issued or whether a current copy of Table 5 contains 9.8 — treat it as a reason to check.