Xantia P bush fitting

[elma]

I've nicked one before now, but managed to file it out completely. It left a slight flat on the jounal, but the bush was still a tight fit.

There's an issue with that though.

You have to be ever so careful grinding it James. You must, on no account, mark the journal surface of the arm by accidentally going too deep with the grinder. Such marks can give rise to a stress-riser and this could lead to catastrophic failure of the arm.

Mine is marked about half an inch above the journal (clumsy) and I'd never refit it. Paranoid? Yes, I worked in a machine shop and I'm paranoid with good reason. What happens on a molecular level when castings are nicked and filed can only be guessed but will change the tension within the structure in a less than positive way.

[CitroJim]

James, in that respect I share your paranoia....

[dnsey]

I understand the principle of stress-raisers, but aways thought that smoothing allowed the stress to 'ride over' the area. After all, things like these suspensioon arms start out as pretty rough castings which are subsequently fettled, and the journals and lands machined. How is that different from filing-out a grinder nick?
I can by no means claim to be an expert in such matters, though, and am very happy to be educated!

[elma]

Machining is done on set programmes in pre defined atmospheres.
Every xth component will be ultra sounded to make sure that everything is ok from batch to batch.
When we made certain car parts and aircraft parts the customers would send their own technicians with scanners to check the materials and the finished parts.

Putting a flat spot on a cylinder upsets the lattice structure and thats not so good.
Metal is alive, it moves like the sea on an atomic level.
Imagine all the electrons which bind the metal together going around a roundabout happily.
Then imagine putting a flat bit in the roundabout. Velocities will change at that spot affecting the rest of the roundabout.
As these electrons essentially glue the structure together changing their behaviour can have unexpected effects when used in a high force application.

Thats way oversimplified and 2d but I don't remember all of this in great detail and that's how I simplify it in my head.

Of course you are probably right that you'll get away with it.
You haven't met me though, I'm the exception to the rule.
If I did that I can guarantee you that my front wheels would leave the car at the worst possible moment then probably take out a Police car and a row of school kids.