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ISO Fits question

ISO Fits question

ISO Fits question

(OP)
I'm taking a first stab at using standard fits (from ANSI B4.2) and running into some confusion:

I have a linear motion bearing riding on a shaft; the shaft is press fit into a plate and protruding through the far side. A second component will have a slip fit on the far side of the shaft.

The shaft & bearing I have selected from a catalog. Everything's nominally 6mm dia. The bearing stipulates that the shaft shall be class g6 (ie, 5.988 - 5.996). If understand the system correctly, this then is a hole-basis fit - the hole will have the basic dimension as one limit; the shaft is sized to provide the desired fit with this hole.

How now do I select a fit for this g6 shaft and a press fit hole that holds the shaft? This feels like it should be a shaft-basis fit, but I'm operating with hole-basis components. The shaft I'm stuck with is hole-basis, but the required hole will not will not have a basic preferred dimension as a limit like the bearing hole does.

One thought I had was to look at an H7/p6 locational interference fit for reference. This fit varies from 0 to -0.02mm interference. Applying this interference to a g6 shaft gives me a required hole of 5.984 - 5.988mm (+-.002mm? yikes!) which is nearly a R6 hole. So, if my logic is correct, a R6/g6 fit is a locational interference fit? A hole that tightly toleranced hardly seems appropriate though! And then I need to repeat for a sliding fit with the remaining component mating to this shaft, which will yield yet another really wacky-sized hole.

Obviously I'm pretty muddled with all this. Any guidance?

RE: ISO Fits question

tdculbert = 6g6 = -4,-12 . 5.996 - 5.988
I think I would go with a hole size 6S7 (-15,-27)

RE: ISO Fits question

tdculbert,
long time ago we discussed here the use of ISO fits. Try to search in this fora. You can also look at the calculator in the link below, it'll make your fits calculations simpler.

http://eassistant.nmmn.com/en/AppletFitCalc.html

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