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Interferance fit


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Hello, I'm hoping the machinists out there might be able to give ema crash course in interferance fits.

Its a long story so i'm trying not to over whelm this thread with detail, but i'm planning on making up some links that use standard panhard rod bushes.

I need to get the sleaves they will press into machined up by a local engineering firm, but have no idea on diameter undersize required to get a good interferance fit.

The bushes measure in at exactly 30mm, and the sleave will have a length of 38mm.

Can any one give me a guideline, or even tell me what landrovers size is for the panhard rod bush hole?

Thanks in advance


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You say the bush is 30mm exactly but that would rarely be the case. There would be a manufacturing tolorance of a +- something.

Maybe an easier way is to measure the hole in the Panhard rod, or a number of Panhard rods, to get a range of acceptable tolerance and then get the engineering company to machine to that.

The other thing is that if you have a sleeve machined and then, say, weld the sleeve to a construction the hole will change anyway due to the shrinkage of the weld.

If you need accuracy you may need to have a reamer to get the 'fit' of the holes after the welding has been done.

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What happens with interference fits changes when you are dealing with relatively thin wall cylinders, compared to more common cases with interference between relatively rigid shafts and housings.

A particular amount of interference between substantially rigid parts will result in higher pressure at the mating surface than the same interference between thin wall cylinders. It is this resulting pressure and friction that retains the parts.

The pressure also results in stress in the material which increases with a thin wall cylinder.

Night Train's suggestion to measure the bore in some panhard rods is a good one.

Edit: It is possible to calculate the the pressure that would result, how much force that would be required to press the parts together, the resulting stress in the cylinders, etc. - these are standard mechanical engineering procedures that I won't go into here.

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