# Tolerance for ID on Acrylic Tube **URL:** \ **Category:** Watertight Enclosures\ **Created:** [May 30, 2022, 7:45am UTC](https://discuss.bluerobotics.com/t/tolerance-for-id-on-acrylic-tube/12220 "2022-05-30T07:45:54Z")\ **Posts on this page:** 4\ **Page:** 1
**Author:** ![psupine](https://sea1.discourse-cdn.com/flex019/user_avatar/discuss.bluerobotics.com/psupine/32/16137_2.png) [@psupine](https://discuss.bluerobotics.com/u/psupine)\ **Post date:** [May 30, 2022, 7:45am UTC](https://discuss.bluerobotics.com/t/tolerance-for-id-on-acrylic-tube/12220/1 "2022-05-30T07:45:54Z")
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? ---
**Author:** ![EliotBR](https://sea1.discourse-cdn.com/flex019/user_avatar/discuss.bluerobotics.com/eliotbr/32/6937_2.png) [@EliotBR](https://discuss.bluerobotics.com/u/EliotBR)\ **Post date:** [May 30, 2022, 8:40am UTC](https://discuss.bluerobotics.com/t/tolerance-for-id-on-acrylic-tube/12220/2 "2022-05-30T08:40:41Z")
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). ---
**Author:** ![EliotBR](https://sea1.discourse-cdn.com/flex019/user_avatar/discuss.bluerobotics.com/eliotbr/32/6937_2.png) [@EliotBR](https://discuss.bluerobotics.com/u/EliotBR)\ **Post date:** [May 30, 2022, 1:55pm UTC](https://discuss.bluerobotics.com/t/tolerance-for-id-on-acrylic-tube/12220/3 "2022-05-30T13:55:44Z")
> [@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. ---
**Author:** ![psupine](https://sea1.discourse-cdn.com/flex019/user_avatar/discuss.bluerobotics.com/psupine/32/16137_2.png) [@psupine](https://discuss.bluerobotics.com/u/psupine)\ **Post date:** [May 30, 2022, 10:11pm UTC](https://discuss.bluerobotics.com/t/tolerance-for-id-on-acrylic-tube/12220/4 "2022-05-30T22:11:42Z")
Thanks