Q:

Metal-metal seal, tolerances

What tolerances should be used for a hole and a shaft at least so that the seal is sufficiently airtight (for example, the valve stem and the valve bore)? Is H7/h7 sufficient?

Mods/Machinists

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marc,
stem seal without oring
clearance stem to body

H7/h6 would be alright maybe a bit on the tight side.

The important part is that the seat and seatingface are lapped together/like a car engine valve. And all parts that are inline are machined without taking the part out of your chuck. Valvestem bore should be bored using a boring bit and not a reamer(it is able to wander).

If you make the stem thin enough as to let it flex a bit then you should be able to make it seal.

But why not going with delrin. If you have the machining capability to machine a metal to metal valve the Delrin won’t be to difficult! If you make a flat toilet plunger valve design on a flat face than opening forces should be minimal!

Regards,

Marc

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