Back-up rings for Chart 50 metric sizes:
When ordering back-up rings to match
our suggested Chart 50 metric shaft and
cylinder sizes, please use:
l Prefix 150 for shaft applications.
l Prefix 250 for cylinder applications.
l Also indicate spiral or single turn and
material.
(The reason is that ‘O’ rings can be
stretched or squeezed slightly — see
General design notes on pages 27-28
— but the back-up ring must be
manufactured exactly to suit the shaft or
cylinder.)
EXAMPLE 1: For 140mm OD shaft, order
JW 150-433 PTFE spiral back-up ring.
EXAMPLE: For 155mm ID cylinder, order
JW 250-433 PTFE spiral back-up ring.
Back-up rings for Aerospace Sizes to BS
ISO 3601-1: Please contact our Technical
Support Team for back-up rings to BS ISO
3601-4.
Back-up rings for Chart 72: When
ordering back-up rings (which cover those
to BS 5106) please state the same JW 72
number as the ‘O’ ring. Also indicate spiral
or single turn, and material.
EXAMPLE: JW 72-1393-57 PTFE spir