I (from Southern England, never been to the US) certainly recognise 'hewing to' in this sense. It's not particularly common but I don't have any sense of it being American. Also, to me it sounds strange in any form other than 'hewing to'. "'They hewed to' or 'They have hewn to' the party line" sounds very odd.

OK, one vote against Americanism. I'll note, though, that 'have hewn to' gets 22,400 google hits and 'has hewn to' gets 20,100. 'Hewing to' gets 44,000. So, I don't think that in general 'hewing to' is a frozen form.

I grew up in Boston (MA) and have the same gut feeling about "hewing to" as RWMG. Seamus Heaney spent a lot of time across the river in Cambridge in the eighties, and seemed quite taken with the American language at the time, so it's an open question whether his usage hints at an Irish pedigree. By the way, I was delighted to see an ad for a Chinese tool company with an illustration of large axe at the bottom of the page.

I've added a P.S. with a corpus search to the original post--it's looking fairly American.

Oh, and 'have hewed to' gets over 30,000 google hits--so that's probably why 'have hewn to' sounds odd to some. It might be that this figurative (and prepositional) sense of the verb has regulari{s/z}ed because it's not perceived as being the same verb as the ax(e)-related 'hew'.

For the record, this entirely unofficial transcript of the speech doesn't include any instance of hew.

The OED says that hewed as the participle has been around since the 14th century, but hewn has always been more common. However, that's unmodified OED1 text, and some things have happened to the English language since the 19th century. (The past tense has been firmly hewed since 1500.)

I have to say that, while I knew what the headline meant, I (AmE - midwest/Illinois) would not use "hew" in that situation. Stick with, maybe, but not hew.

Unless it referred to chopping wood, I think I'd be unlikely to use the word hew at all.

AmE speaker here.

I have always thought of hew in the same way as "bear" when speaking in terms of travel. To me, to "hew left", and to "bear left" are identical, or nearly so.

I did hear this usage, especially from older folk, both in the Northeast and Deep South of the U.S.

I didn't understand the headline, and have never come across the AmE sense of conform. I have come across the other sense of cutting or shaping with an axe, as in a well-hewn piece of wood, but it is rather literary. My Oxford English reference dictionary gives the former meaning as the third meaning (after variants of the meaning that I know) and identifies it as "N. Amer".

I was interested to see Heaney use the word "cleave" in close proximity, because I think of that word as meaning splitting (eg a piece of wood with an axe), but of course it can also mean cling to, so both words seem to have similar duality of meaning.

As Mark said above, I've heard 'cleave' in both senses but never 'hew'. I've only ever heard 'hew' in the context of hewn stone or similar.

As Seamus Heaney came from Northern Ireland and has spent a most of his career between the US and RoI, perhaps his English is a bit mixed...

Ha, my first parse of the headline led me to believe that there was an Irish minister named Hewing who was not in favor of the mentioned peace plan as it stood.

Could 'hew' have acquired its double meaning on analogy with its better-known cousin 'cleave'?

It doesn't strike me as an Americanism, but I'm not the best person to ask on this sort of thing as lots of things I assume are common in British English turn out to be picked up from my parents or American blogs. It's possible that it's journalese more than anything.

If it is an Americanism - and I think it is - the rest of us should steal it: such a fine archaic ring. Although Mrs Clinton didn't use the word, it seems to carry over from its other meaning such a sense of concentrated effort that it fits perfectly the message she was giving.

As a youngish (and rapidly increasingly less so) EnE speaker 'Hew' and derivatives therof do sound pointedly archaic to me and I'd agree I've only heard them in reference to stone and suchlike things.

This IrE speaker was able to infer the meaning of the headline, but that may well be because Clinton was unlikely to be urging taking an axe to the Peace Process.

I don't recollect ever hearing the expression, but a websearch of the Irish Times archives reveals numerous matches, not all from Americans. Webster's New World College Dictionary definition of "hew" has a ☆ marking the relevant sense, whatever that's supposed to indicate.

Note that, whereas cleave "split" and cleave "cling" are two etymologically different words, it would seem that hew "split" and hew "adhere" are two senses of one and the same word.

I had thought the literal meaning of "hew" was well-known, but the dictionary link above corrected my misunderstanding. In building, hewing is to square timbers, generally with a broadaxe or an adze. You would mark a line, then hew to that line for a perfectly straight timber before cutting the interlocking joints. It's a rather precise operation. Most homes built before 1900 or so were made this way.
It's only a short jump from the line marked on the log to a "party line" or other precise instruction.

As an young(ish) American, I would have thought that hewing was an Olde-Countryism! It sounds very old fashioned to me.

On a tangent (sorry), was Picky's use of "what means she" ironic, mistyped, or normal usage? That phrasing is definitely quite odd to my ears.

Julie's explanation sounds plausible. Since timber-frame houses are very rare in cisatlantea, it would also account for its tranatlanticity.

Matt: It was a piece of ghastly twee facetiousness of a kind very much better avoided.

Julie's description of 'hewing to the line' gives a great feeling of the effort involved in staying close to the 'line' - whether the 'party line' or 'the line to take', or indeed 'the straight and narrow'.
Another phrase - to 'toe the line' could be an admonishment to someone who has gone astray: one who 'ploughs/plows a lone furrow'. In all of these the image is of a line drawn to guide the construction or the pathway, not 'lines' to learn when speaking. But here too, the poet would no doubt deliberately get extra value by confusing the two uses of the word.

Toe the line is a metaphor from foot racing, now widely eggcorned as tow the line.

Speculation on American origin: many beams in wood-framed houses in 18th and early 19th Centuries were hand-hewn. Lacking milling infrastructure, our forebears used adzes and other tools to shape members to fit. The hew of the member was the degree to which it conformed to spec. Seems like an obvious possibility. -tig

It seems plausable that the origin of the American usage is from what Julie and Tig offered -- and that "to hew to the line" orginally meant "to cut to" but grew (as a misunderstood assumption of the definition) to mean "to keep close to."

"Hew(hewing)(hewn) to the line" is the preferred form, used in toto. "Hew to the Party line" is a clever 20th C. reworking. It basically conjures up the image of one's axe blows staying along a particular marking and not straying far from it.