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rharr (Mechanical) (OP)
4 Jun 08 9:27
I've been working with ISO tolerances for a while and have been puzzled by this. Are the classes used for splines the same as for general holes and shafts even though the nomenclature is reversed?

A typical call out for a shaft could be 150f8. However the tolerance on a spline shaft would be 8f. Is this the same system? Or is there a separate system for splines. Metric threads reverse the letter/number arrangement also. Can anyone tell me why?
gearguru (Automotive)
4 Jun 08 10:05
The spline tolerances do not apply to the outside diameter of the spline, rather they define the "fit" between the external and internal splines. Splines with tolerances 9H/8f will have small backlash ("clearance between the teeth").
The concept of using letters/numbers is similar as in ISO fits for shafts, but here they apply to different features, mostly tooth thickness/space.
The DIN5480 (October 1991) standard explains the concept in details and includes charts with precalculated values for splines. I highly recommend to buy it. There is also the English version.
Check also the newest ISO4156 (October 2006) standard.  
rharr (Mechanical) (OP)
4 Jun 08 11:03
I was afraid you'd tell me that.

I knew the tolerance applied to the tooth thickness or space width. I was hoping I could make some sense out of it and use the tools I already have. That doesn't appear to be the case. I get to buy more reference material.

Thank you.
dimjim (Mechanical)
5 Jun 08 3:17
I am surprised that there would not be a relationship to the general ISO tolerances based on the tooth thickness
or space width.  Our buddies across the pond do seem to be very standard oriented.
Helpful Member!  spigor (Mechanical)
5 Jun 08 4:08
Also, this standard has as many as over 14 sections and you can buy them separately. Those sections contain different moduls. Section 14 talks about tolerances and fits.

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