Tolerance for ID on Acrylic Tube

[psupine]

I know that the ID for the acrylic tubes is now precision bored to match the flanges, but it wasn’t like that on the old tubes.

The new 4" tubes have a stated ID of 101.6 +/- 2.1 mm. Is the tolerance really that bad?

[EliotBR (Eliot)]

Hi @psupine,

@psupine

I know that the ID for the acrylic tubes is now precision bored to match the flanges

The ends are precision machined (not the entire inner diameter) to interface properly with the new locking end caps.

@psupine

The new 4" tubes have a stated ID of 101.6 +/- 2.1 mm. Is the tolerance really that bad?

Hmm, that does seem potentially too large when compared to the outer diameter tolerance and the 2" tube tolerance - I’ve asked internally and will get back to you (I’m thinking the divide by two may have been missed for the 3" and 4" plastic tube inner diameters when converting from a value range to a tolerance about an average).

[EliotBR (Eliot)]

@EliotBR

I’ve asked internally and will get back to you

Following up on this, the tolerances as stated are in fact correct - the castings are indeed that variable.

For some context,

@emillerstead

The 2" is metric acrylic and the 3" and 4" are Imperial. The 3" and 4" tolerances are from the acrylic manufacturer. It’s so large because they control OD and wall thickness, so the tolerance stacks up large for the ID. We haven’t observed such large swings in ID from the parts we have on hand, but it’s theoretically possible.

@rjehangir

… this is one of the biggest reasons why it was important to machine the ends on the tubes. We used to have to deal with that tolerance range in the flange/O-rings and that was much more difficult.

[psupine]

Thanks