View Full Version : Just a heads up on Tube Sizes

Paul Kay
07-02-2019, 05:34 PM
Just a heads up for anyone who is looking for thick walled tubing, but with walls less thick than jointing tubing. I was hunting for 0.8 - 1.00mm walled tubing.

Betts have been updating areas of their website and appear to have decided to redefine how tube wall thickness is expressed :D

While the industry standard (probably across most industries, world-wide, since time immemorial, or at least the first industrial produced tubing) would seem to be (OD - ID)/2 (OD = Outside Diameter; ID = Inside Diameter), so tubing with an OD of 4mm and an ID of 3mm has 0.5mm walls. i.e. the actual thickness of the metal! Give or take, since some tubing still seems to be made on imperial measurement machinery and then sold sized to the nearest metric sizing.

Betts have (currently, I have sent them a message) redefined it as simply OD - ID, so their OD 4mm ID 3mm tubing is said to have a 1mm wall thickness. i.e. twice the actual thickness of the metal.

07-02-2019, 08:45 PM
Yes its the sort of typo that creeps into catalogues and websites, especially if the designer doesn't have basic maths.
I expect quite a few of their customers are giving them a bit of stick. Dennis.

I am fortunate that as I only make one-offs, I can devote time to drawing down a piece of tube to thicken the walls as needed, or even insert one tube into another for extra strength. Dennis