Seems a rather strange requirement. Metals work-harden by being distorted, so your hammering needs to locally alter the shape of the crystal structure over the whole bulk of the rod, this presumably means a lot of hammering. In practice I'd suspect the result would be rather uneven, with most effect being near the outer skin. Are you sure that this is needed? Bushes don't usually need to be particularly hard.

Following ancient instructions maybe? Not sure hardening the whole rod was how it was done in the good old days, I think you cut a blank rather bigger than the bush and bash that before machining. One of my old books mentions the method – I'll see if I can find it.

These days more usual to use Phosphor Bronze, Oilite or a roller bearing I guess.

Dave

I was always under the impression that cast brass was preferred to CZ121 bar for bushes as the structure had the ability to hold more lubricant. I have been using my casting risers for sometime now for bushes and haven't hade any problems (perhaps I shouldn't have said that) so far.

If you are making bushings, the work hardening needs to be in the hole where the pivot goes to be of any use. So I think you will struggle to do that by hammering, even of a blank.

The normal way of work hardening the bearing surfaces of a clock bush is to finish off with a smoothing broach which burnishes the inner bearing surface.

Found my book with a sections on Bearing Brasses but it's all about fitting, not making them. Amusing to discover things dismissed as "old-fashioned" in a 90 year old book, but it would have been nice if it had answered the question!

Hammering to harden cast-brass for use in a bearing sounds likely to me, but I think it's 19th Century technology. Brass was one of the first bearing metals, but it's not ideal. Fairly quickly given a white-metal coat.

However, before white-metal, hammering Brass would improve the hardness, and the metal would last longer in a plain bearing. I imagine the hammering was done to a lump before the bearing was machined, much as spanner blanks are drop-forged today.

Judging by what the fitters had to do with them, brass bearings weren't precision made. Lots of filing off high spots found with red-lead, before super-careful scraping. Apparently common to scrape slightly too much off, causing the bearing to fail prematurely. White-metal is described as a huge improvement, not least because it can be melted off and done again.

Also described disparagingly are early octagonal brass bearing holders. They made life difficult because the brass had to be carefully fitted into them as well as to the shaft. Time consuming and easy to get wrong!

David hasn't explained how big the bush is, or what it's for. Fitting as described above is of large bearings in textile mills etc. I use small brass bushes (up to 15mm) quite a lot, and simply make them from brass rod, which is already hardened. Not heavily loaded, but do David's need to be.

Dave