AS568: the number tells the section
The first digit of an AS568 dash number sets the cross-section: -0xx is 1.78 mm, -1xx 2.62, -2xx 3.53, -3xx 5.33 and -4xx 6.99 mm, apart from the smallest -001 to -003. Parker’s 2-xxx number is the same size.
Reference tool — not inspection
Identify the O-ring before it goes in an RFQ.
O-ring
A designation or a measurement.
Material and hardness go into the RFQ line. Under the designation, an offered replacement can be checked against it on the inside diameter and the cross-section. The result updates as you type.
Examples:
Replacement check
On the sizes alone: the groove, the material and the hardness decide.
All 130 engineering tools
O-rings are ordered in dozens of sizes, and a request often describes one only as an O-ring, without a size. The parts list usually gives a designation: an AS568 dash number such as 214, a Parker number such as 2-214, or a JIS size such as P25 or G60 on Japanese equipment. Type the designation and the tool gives the inside diameter and cross-section; type a measurement and it lists the standard sizes that fit.
AS568 is an inch series and JIS B 2401 the Japanese one; close sizes in the two can be fractions of a millimetre apart. The tool shows the difference instead of hiding it, and leaves the decision on a substitute to whoever knows the groove.
Size series
The cross-section sets the series.
JIS: a letter and a number
In JIS B 2401 the letter is the series (P for dynamic and static use, G for static use) and the number is close to the inside diameter. The cross-section changes by size group, as in the table below.
Close is not the same
AS568-214 (24.99 × 3.53 mm) and JIS P25 (24.7 × 3.5 mm) almost agree, but do not. When the list shows both series, give the designation from the parts list in the request.
| Series | Designations | Cross-section, mm |
|---|---|---|
| AS568 | -001 | 1.02 |
| AS568 | -002 | 1.27 |
| AS568 | -003 | 1.52 |
| AS568 | -004 – -050 | 1.78 |
| AS568 | -102 – -178 | 2.62 |
| AS568 | -201 – -284 | 3.53 |
| AS568 | -309 – -395 | 5.33 |
| AS568 | -425 – -475 | 6.99 |
| JIS B 2401 P | P3 – P10 | 1.9 |
| JIS B 2401 P | P10A – P22 | 2.4 |
| JIS B 2401 P | P22A – P50 | 3.5 |
| JIS B 2401 P | P48A – P150 | 5.7 |
| JIS B 2401 P | P150A – P400 | 8.4 |
| JIS B 2401 G | G25 – G145 | 3.1 |
| JIS B 2401 G | G150 – G300 | 5.7 |
Sources
AS568 sizes: the Parker Series 2-XXX table of the Parker O-Ring Handbook (ORD 5700, Section IX), checked against Greene Tweed’s AS568 table: 344 of the 345 shared sizes agree; at -391 Greene Tweed prints 21.995 in, which breaks the 1-inch step of -385 to -391, so Parker’s 21.955 is kept. JIS B 2401 P and G series: Table 9-7 of the same handbook, checked against NOK’s ranges on MISUMI (the same 122 P sizes and the same inside diameters); G60 is 59.4 mm per NOK, where Parker prints 50.4. G sizes above G300 are left out.
Before you send the ring
Questions about O-rings in an RFQ
Is AS568-214 the same as JIS P25?
No. AS568-214 is 24.99 × 3.53 mm and P25 is 24.7 × 3.5 mm: close, but 0.29 mm apart on the inside diameter. Whether one can stand in for the other depends on the groove, which the equipment drawing or maker confirms; give the designation from the parts list.
What does the 2- in 2-214 mean?
It is Parker’s size number for its 2-XXX series, which carries the AS568 dash numbers: 2-214 is the AS568-214 size. The compound is a separate code.
What are the JIS P and G series?
JIS B 2401 sizes. P rings are made for dynamic and static use, G rings for static use. The number is close to the inside diameter: P25 is 24.7 mm, G60 is 59.4 mm.
My ring is metric, for example 50 × 3. What do I order?
Order it by inside diameter and cross-section in millimetres, with the material and hardness. Metric series such as ISO 3601-1 are outside this tool, which still shows any AS568 or JIS size close to the figures.
Size found?
Send it with where the ring sits.
A found size is a cross-check on your designation or measurement, not proof. Give the designation from the parts list, the equipment and position, the material and the quantity, and Vessel Core checks them against each other before an offer goes back.
Buyer tools
