I don't have a lathe . . .

That is good,  - as we so often find on here the battle is getting 'the obvious' out of one head into another, and without a pic, and even sometimes with one,  it is easy to run off with the wrong end of the stick - I have lost count of the times I have commented with an answer to not quite right for the question that was actually intended. 

Be aware that mechanical language is a bit regional, so  my words and what folk call the bits may not match at your local motor factors or whatever. 
I should have said - if the motion of the ram end and the steering arm is not co-planar, (and if it isn't then the ram mechanism may jam), then the place to let it rise and fall is  on the pintle in the hole of the rose joint ball . If you do need that then that will need to be lubricated, as it will also tend to turn there as well as at the ball in the frame. Looking at your photos more closely, the hole in the rose joint ball does look like it may be lined - if that is an oiling bronze bush, then it is intended to allow that use, but of course not on a thread, but a smooth hardened surface.

Mike.

That is good,  - as we so often find on here the battle is getting 'the obvious' out of one head into another, and without a pic, and even sometimes with one,  it is easy to run off with the wrong end of the stick - I have lost count of the times I have commented with an answer to not quite right for the question that was actually intended. 

Be aware that mechanical language is a bit regional, so  my words and what folk call the bits may not match at your local motor factors or whatever. 
I should have said - if the motion of the ram end and the steering arm is not co-planar, (and if it isn't then the ram mechanism may jam), then the place to let it rise and fall is  on the pintle in the hole of the rose joint ball . If you do need that then that will need to be lubricated, as it will also tend to turn there as well as at the ball in the frame. Looking at your photos more closely, the hole in the rose joint ball does look like it may be lined - if that is an oiling bronze bush, then it is intended to allow that use, but of course not on a thread, but a smooth hardened surface.

Mike.

Just an update in case you're interested, I bought a set of blacksmith's drills abd successfully drilled out the steering arm to 18mm and fitted the sintered bronze bush.

There's still too much play in the rose bush so what us the technical term for that component?

Thanks for your inputs.

Good. The bush is snug fit in the arm I hope - now sintered bronze is an oil absorbing metal, and assuming you have oiled it, that implies that the shaft or pintle that runs within it is smooth, hard, and expected to slide or rotate... If you are locking it together as I thought you were going to you do not really need an oil bearing bush, but it will do no harm. So where is the play - between bronze and pintle, between pintle and rose hole, or between rose frame and rose ball ?
(pintle is just a short stepped shaft or one with either  a thread section or  changes in diameter.)

Mike

Hi Mike, thank you for your continuing interest. I got a sintered bush as it was readily available at the sizes I needed and I thought it wouldn't do any harm. The bush is a snug fit in the steering arm and the bolt is a snug fit in the bush. The play is between the rose ball and the frame. What is the technical term for the rose ball assembly that ends with an M14 rod that screws into the power steering ram? I reckon I need a new one!

If I understand you correctly, it would normally be a "track-rod end". Or just a "rose joint".

You're right Chris, thanks. I had a quick google and plenty came up although I suspect motor sport standard may be a little over the top for my old banger!

Having been to a garden party this afternoon I'm a little "tired" tonight so I'll get to it on the morrow.

Thanks Mike and Chris, your help is much appreciated.