all depends if the spring eyes are open or shut……

I would guess they are the open sort…..I would say .25 -.5 of a mill would be enough..per inch of diam…..

subject to wall thickness…..

if the wall is thin it will alter the size of the hole……

most spring bushes of modern decent were made so that once pressed in they ended up the correct ID size…..

In the old days they were roughed out and reamed once fitted….

also be careful that the eye is prop round…..if the tail of the spring is not prop formed it can distort the bush….

look at the old bushing for extra marks where the spring eye ends….often a big gouge mark….

Most are happy with the terms press fit, force fit etc and Loctite.

However fits and tolerances are clearly defined and charted:

The above takes quite some working out but should be useful once it is understood.

Try to make the hole first. The reamer, if not home made should have the size marked on it. Just as important is the limit and fit, usually H7.

An example: You want a bush with a sliding fit on a 25,00mm shaft. You ream the bore using an H7 reamer. This should give you a bore between 25,00mm and 25,02mm. The required limit and fit on the shaft would be g6. This gives a shaft diameter between 24,98mm and 24,99mm. The number 6 suggest that you should be able to achieve this by turning or grinding. You need good measuring instruments for this and experience.

Back to the Loctite!

JA

14mm Martyn? – Lord Austin would turn in his grave if he heard you saying that !

I think you will find that the spring eyes are not truly round and that you should ream the bushes after pressing into place.

Ps How did the radiator cap go ?

Bob

If they are to be fitted to the end of a leaf spring, you are not fitting inside a tube, but in a open ended spring which can stretch. That means that the interference can be much greater, but the bush would need a chamfer. At least 0.080" or 2mm would probably work. Rubber bushes are used in more up to date vehicles.