Press fit clearance?

[dobbslc]

I have a turning job for a mate that involves a press fit of a sleeve onto a suspension ball joint with nurling on it. Is there any kind of dimension to work to per millimetre of diameter for a good tight fit?
Here's a picture of the parts.

It's going to be made into a wishbone for a car.

 

[daleyd]

Zeuss tables have a chart for differing fits. If you haven’t got a copy I’ll get a pic next time I’m in garage - there is a pdf online.

 

[mtt.tr]

+ a thou is no heat pressfit, 0.0254

 

[Matchless]

they are not easy to press in on E30 BMW's I would try to get someone to measure the internal on a factory wishbone if possible,

 

[addjunkie]

I would also suggest putting the joint in the freezer and ring in the oven before pressing together. So you can pick a tightish fit.

Right hand side of the chart
https://en.m.wikipedia.org/wiki/IT_Grade

 

[mtt.tr]

This might be of interest https://simplybearings.co.uk/shop/Info-Pages-ISO-Limits/c4746_4779.php/index.html?page=1

 

[Brad93]

Thou per inch

 

[dobbslc]

Thou per pinch sounds good Brad.
Those charts are a bit over my head......

 

[addjunkie]

Easy enough to follow your looking for something like an H7n6. The H shaded section on the diagram is the hole
The n the shaft diameter

The numbers in the middle corresponding is how much extra to make your interference.

I prefer the imperial version in the old zeus books

 

[Agroshield]

Everybody is repeating the thou' per inch parrot fashion as if it is a mantra or something.

Do any of you actually look at the photo he has posted and consider if this is the standard situation covered by the books?

Has anyone ever installed wheel nut studs? Do the two things not have some small degree of commonality?

The item to be pressed in is serrated, so consideration of the minor diameter is probably of some importance. A quick file test of the item might tell you if it has any hardness to it, and hence will be designed to deform the item it is pressed into.

Second, the tube into which it is to be pressed is relatively thin wall, so it will deform.

Patrick Gill's advice is correct: find a factory part and copy what they have done.

 

[8ob]

Also worth considering is the bore of the sleeve will distort when its welded in which may tighten things up a bit, I have pressed a few of these things in/out over the years and they either fall out or they are a pig, OEM tin wishbones are probably not the best thing to try and obtain an accurate bore size from.

Bob

 

[Other Daniel]

Thou per pinch sounds good Brad.
Those charts are a bit over my head......

Me too
I wonder if there is a simpler chart for those of us not building electron microscope beds.
Will now get sidetracked into Google searching ...
ATB,
Daniel

 

[dobbslc]

I don't have an original one but my mate does have the hand built one that we're copying, He's dropping it off along with more steel for the inboard sleeves at some point. I don't think it needs to be very tight as the serrations are only about 6mm high.

 

[dobbslc]

Here's a picture of it.

It's off an Alfa GTV / 75 race car.
@Dcal I think it was you that asked what it's for.

 

[rory1]

Personally I’d make it a little bigger than the minor diameter of the knurl. (Without knowing the depth of the knurl or the diameter I can’t say what “a little bigger” is

 

[pressbrake1]

+ a thou is no heat pressfit, 0.0254

That’s diameter and thickness and material dependant. On a bit of good stuff a thou oversize could mean a 50ton press!

 

[Dcal]

Here's a picture of it.
View attachment 228846
It's off an Alfa GTV / 75 race car.
@Dcal I think it was you that asked what it's for.

Thanks @dobbslc thought it looked familiar.
Is he doing away with the torsion bars?

 

[Matchless]

Also worth considering is the bore of the sleeve will distort when its welded in which may tighten things up a bit, I have pressed a few of these things in/out over the years and they either fall out or they are a pig, OEM tin wishbones are probably not the best thing to try and obtain an accurate bore size from.

Bob

the BMW arms are malleable steel forgings I assume, they do bent if stopping very quickly i.e. a tree.

 

[dobbslc]

Thanks @dobbslc thought it looked familiar.
Is he doing away with the torsion bars?

Coil springs all round I think! Same as the 75 he has.

 

[8ob]

the BMW arms are malleable steel forgings I assume, they do bent if stopping very quickly i.e. a tree.

Luxury Patrick, The only vehicles I have had the misfortune of working on with these splined joints have had pressed tin wishbones on yanks and Vauxhalls, normally been in since god was a boy and dont like coming out.

Bob