I don't have a lathe . . .

how badly oval ? Is there any merit in a taper ream to take a more readily available ball-joint from another machine ? (harder to get a taper wrong than a parallel ream as well ) Why is it oval - has it been running for a while half undone ? I have been known to 'fix' that sort of thing in the field with a quick tack weld that can be cut off later when mission is over and things return to base.  (and to fill in gaps with a coating of braze metal and then recreate the original diameter, but not for an in-situ repair.)

As you note the correct final solution is to drill out larger (but it may be quite hard to get perfectly square in situ) and to fit a suitable reducer bush.

Mike.

Grumpy said:

My first thoughts were to try and drill out and then ream the oval to 18mm and insert a new 12mm id bush but I was wondering if the collective brains on here had a better solution.

I think that the fairly obvious question here is that if you drill out to 18 mm and bush, will there be enough meat left in the steering arm?

and I suppose if not,  is there enough 'arm' exposed to cut short and thread it to support a new eye?  And why 18mm -  is it so worn that 16mm or 15mm would not fit ;-)
maybe like Zooms hydraulic pipes question a photo or a sketch may be helpful.
M

Thanks for your responses.

Yes there is plenty of meat left to enable an 18mm hole.

I chose 18mm as I roughly measured the oval at 17mm and I have sourced a suitable bush.

I'll take some pics and better measurements tomorrow and I would really appreciate your further comments.

Many thanks.

G

Is what is wanted similar to one of these  

https://www.autozone.com/fittings-and-hose-line-connectors/power-steering-adapter-fitting/p/duralast-18mm-flare-straight-fitting/83904_0_0Flare fitting 

I am sure they are available over here

Edit, got confused should have posted to Zooms pipes. I blame old age.

Right, I've taken pics, hopefully I'll be able to attach them!

I'm not convinced that this hssn't been bodged in the past as, surely, a taper would be more usual. The arm is 18mm thick and the oval is 15mm x 17.5mm.

I briefly used a conical drill to clean up the top of the hole and the metal is quite soft so I would have no difficulty drilling out to 18mm for a bush. And as you can see there is plenty of meat left around the hole.

But do you think this approach will work ie a straight bolt or should I be looking to replace the existing ball joint with a tapered type? If so, how do I match the taper when drilling the arm out. Finally, it'll be a pretty big old taper if it's got to be 18mm at the bottom. As you can tell, this is not my area of expertise so all comments welcome!

Darn, there was one more . . .

I'd put a straight bolt through that rose joint - it would never have had a tapered fitting.

When you drill a new hole, how will you ensure that it is true and round, and perpendicular?

• The truth is I can't. I'll just have to do the best I can. I'm hoping the "round" will be catered for by an interference fit bush and that the  rose joint will have enough tolerance if I'm a bit off perpendicular. What do you think Chris?

I don't think that the rose joint will mind.