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Is Heater Fan Shaft Diameter .234" or 15/64" or 6m

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I am doing the trick of replacing my heater fan with the equivalent Porsche part and using a McMaster-Carr 5" fan. There are numerous threads about this, saying that the hole in the fan is too small so you need to drill it out to fit the shaft on the motor, but I can't see anyone specifying the proper drill size.

I've measured the shaft with calipers and I'm reading 0.234, which is very close to 15/64". It's also very close to .236, which is 6mm.

Does anyone know which one it is? I want to use the correct size drill bit.


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Rob, I'm no expert on your question, but, if the fan is held on with a set screw, or something similiar, I'd think you'd need a hole just a very small bit larger than the shaft in order to get the shaft through the hole.

2/1000ths of an inch isn't a whole lot bigger. Or, drill it with the 15/64" and see if the shaft will fit. If not, you can then go with the 6mm bit.

Bob Napier

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I measure the shaft at exactly 6mm...

...of the stock motor, that is.

If it's a press fit like the original, the 'machinist' answer is that you

drill it .020 undersize, then ream with a '6mm interference' reamer

(which will be 5.96mm or so)

and then press it together.

The far easier way is to drill it to 6.05mm , drill and tap it for a setscrew,

and that guarantees it never needs to be taken apart.


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