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ISO 8434-1 · DIN 2353 · ISO 6149
Metric 24° Fitting Dimensions (DIN 2353)
LL, L and S series of DIN 2353 / ISO 8434-1 24° cone fittings with cutting rings: tube OD, nut thread, pitch, ISO working pressure and the matching ISO 6149 stud end thread.
Quick answer
Metric 24° cone fittings (DIN 2353 / ISO 8434-1) are specified by tube OD and series: 12L is the light series for 12 mm tube, with an M18×1.5 nut thread; 12S is the heavy series for the same tube and uses M20×1.5. For carbon steel bodies, ISO 8434-1 gives a working pressure of 250 bar for L series sizes 6–15 mm and 630 bar for S series sizes 6–12 mm. Because the same nut thread can be used in two series (M14×1.5 = 8L and 6S), the tube diameter must also be checked.
ISO 8434-1 · DIN 2353 · ISO 6149
Size chart
Metric 24° cone fitting dimensions, DIN 2353 / ISO 8434-1 (LL, L, S series)
| Designation | Series | Tube / pipe ODmm | Nut / body thread | Pitchmm | Nominal ODmm | Female basic minor diameter (calculated)mm | Max. working pressure, ISO 8434-1 (standard value)bar | ISO 6149 stud end thread |
|---|---|---|---|---|---|---|---|---|
| LL series (extra light) | ||||||||
| 4LL | LL | 4 | M8×1 | 1 | 8 | 6.92 | 100 | no value |
| 5LL | LL | 5 | M10×1 | 1 | 10 | 8.92 | 100 | no value |
| 6LL | LL | 6 | M10×1 | 1 | 10 | 8.92 | 100 | no value |
| 8LL | LL | 8 | M12×1 | 1 | 12 | 10.92 | 100 | no value |
| L series (light) | ||||||||
| 6L | L | 6 | M12×1.5 | 1.5 | 12 | 10.38 | 250 | M10×1 |
| 8L | L | 8 | M14×1.5 | 1.5 | 14 | 12.38 | 250 | M12×1.5 |
| 10L | L | 10 | M16×1.5 | 1.5 | 16 | 14.38 | 250 | M14×1.5 |
| 12L | L | 12 | M18×1.5 | 1.5 | 18 | 16.38 | 250 | M16×1.5 |
| 15L | L | 15 | M22×1.5 | 1.5 | 22 | 20.38 | 250 | M18×1.5 |
| 18L | L | 18 | M26×1.5 | 1.5 | 26 | 24.38 | 160 | M22×1.5 |
| 22L | L | 22 | M30×2 | 2 | 30 | 27.83 | 160 | M27×2 |
| 28L | L | 28 | M36×2 | 2 | 36 | 33.83 | 100 | M33×2 |
| 35L | L | 35 | M45×2 | 2 | 45 | 42.83 | 100 | M42×2 |
| 42L | L | 42 | M52×2 | 2 | 52 | 49.83 | 100 | M48×2 |
| S series (heavy) | ||||||||
| 6S | S | 6 | M14×1.5 | 1.5 | 14 | 12.38 | 630 | M12×1.5 |
| 8S | S | 8 | M16×1.5 | 1.5 | 16 | 14.38 | 630 | M14×1.5 |
| 10S | S | 10 | M18×1.5 | 1.5 | 18 | 16.38 | 630 | M16×1.5 |
| 12S | S | 12 | M20×1.5 | 1.5 | 20 | 18.38 | 630 | M18×1.5 |
| 14S | S | 14 | M22×1.5 | 1.5 | 22 | 20.38 | no value | no value |
| 16S | S | 16 | M24×1.5 | 1.5 | 24 | 22.38 | 400 | M22×1.5 |
| 20S | S | 20 | M30×2 | 2 | 30 | 27.83 | 400 | M27×2 |
| 25S | S | 25 | M36×2 | 2 | 36 | 33.83 | 400 | M33×2 |
| 30S | S | 30 | M42×2 | 2 | 42 | 39.83 | 250 | M42×2 |
| 38S | S | 38 | M52×2 | 2 | 52 | 49.83 | 250 | M48×2 |
Chart notes
- LL = extra light, L = light, S = heavy series. The same nut thread is used on two different tube sizes and series (e.g. M14×1.5 = 8L and 6S; M30×2 = 22L and 20S); the thread alone is not enough, so check the tube OD and the cone bore.
- Pressures are ISO 8434-1 Table 1 values (carbon steel, 4:1 design factor, −40…+120 °C) and are standard values; for a product's rating, the manufacturer's test and catalog value applies.
- Under ISO 8434-1, pressure and temperature ratings for stainless steel bodies are set by the manufacturer.
- Use a stainless steel cutting ring and stainless steel tube with a stainless steel body.
- The cone angle is 24°; do not confuse it with JIC (37°) or SAE 45°.
- DIN 3852 / ISO 9974 stud ends use the same thread as ISO 6149 stud ends except for 22L: for 22L the DIN 3852 stud is M26×1.5 and the ISO 6149 stud is M27×2.
- 14S is not listed in the ISO 8434-1 pressure table (some sources describe it as a non-standard size), so no pressure rating is given.
Reference standards
- ISO 8434-1
- 24° cone fittings (cutting ring type)
- DIN 2353
- Cutting ring fittings (former DIN name still used in the trade)
- ISO 6149
- Metric ports and stud ends (O-ring sealed)
Values are nominal; for critical applications, verify against the current standard and the manufacturer's catalog.
Description
Description
DIN 2353 / ISO 8434-1 24° cone fittings are used to join metric OD tube without welding; they are also known as bite-type or cutting ring fittings. The seal is made by a cutting ring (ferrule) or an O-ring cone end seating in the 24° internal cone of the body; the thread only provides the clamping force. The chart gives the tube OD, nut thread, pitch, ISO working pressure and matching ISO 6149 stud end thread for the LL, L and S series.
Series and designation
A fitting size is written as the tube OD followed by the series letter: 12L is the light series for 12 mm tube, and 12S is the heavy series for the same tube. In this chart the LL extra light series is listed for 4–8 mm tube, the L light series for 6–42 mm and the S heavy series for 6–38 mm. Tube OD is in millimeters; this chart does not apply to inch tube.
Same thread, two series
Some nut threads are used in both the L and S series: M14×1.5 = 8L and 6S; M16×1.5 = 10L and 8S; M18×1.5 = 12L and 10S; M22×1.5 = 15L and 14S; M30×2 = 22L and 20S; M36×2 = 28L and 25S; M52×2 = 42L and 38S. So the thread alone does not determine the series; measure the tube OD as well.
Telling L and S series apart
Measure the tube OD first, then the nut thread. For 6–12 mm tube, the S series nut thread is 2 mm larger than the L series: 10L uses M16×1.5, 10S uses M18×1.5. ISO 8434-1 working pressures also vary by series: 100 bar for the LL series; for the L series, 250 bar at 6–15 mm, 160 bar at 18–22 mm and 100 bar at 28–42 mm; for the S series, 630 bar at 6–12 mm, 400 bar at 16–25 mm and 250 bar at 30–38 mm. These values are for carbon steel bodies in the −40…+120 °C range.
Sizes to watch
- 14S: Appears in DIN 2353 and some catalog tables; it is not listed in the ISO 8434-1 table (some sources treat it as non-standard). No pressure value is given in the chart.
- 22L stud end: The thread is M27×2 on an ISO 6149 stud and M26×1.5 on a DIN 3852 / ISO 9974 stud. Don't order without confirming the port type.
- Cone angle: The 24° cone does not mate with JIC 37° or SAE 45° cones.
On stainless steel 24° fittings
ISO 8434-1 leaves the pressure and temperature ratings of stainless steel bodies to the manufacturer; for the usable pressure of an AISI 316/316L fitting, go by the value given in the quotation and product information. A stainless steel body should be used with a stainless steel cutting ring and stainless steel tube. During assembly, cut the tube square, deburr it inside and out, check the orientation of the cutting ring and tighten the nut by the number of turns in the manufacturer's instructions.
FAQ
Frequently asked questions
If your question isn't answered here, message us on WhatsApp with dimensions or a photo, and our technical team will answer directly.
How do I tell L and S series apart?
Measure the tube OD and the nut thread together. For 6–12 mm tube, the S series nut thread is 2 mm larger than the L series: 12L uses M18×1.5, 12S uses M20×1.5. Some threads are shared by both series (M14×1.5 = 8L and 6S); in that case the tube diameter determines the series.
Can L and S series fittings be connected?
They should not be. In some sizes the nut thread is the same, so the nut may screw on, but because the tube diameter and internal cone dimensions differ, the joint won't seat correctly. Body, cutting ring, nut and tube must all be of the same series and tube size.
What does 12L mean?
12L means an L (light) series 24° cone fitting for 12 mm OD tube. The nut thread is M18×1.5; under ISO 8434-1, the working pressure with a carbon steel body is 250 bar. The heavy series for the same tube is 12S, which uses an M20×1.5 nut thread.
Are DIN 2353 and ISO 8434-1 the same?
DIN 2353 has been withdrawn and replaced by ISO 8434-1; the old name is still widely used in the market. The series, tube diameter and nut thread assignments are the same. Some sizes, such as 14S, appear in DIN 2353 tables and some catalogues but are not listed in the ISO 8434-1 table.
Which pressure rating applies to stainless steel 24° fittings?
The pressures in ISO 8434-1 are for carbon steel bodies; the standard leaves the pressure and temperature ratings of stainless steel bodies to the manufacturer. For AISI 316/316L fittings, go by the value given in the quotation and product information. A stainless steel body should be used with a stainless steel cutting ring and stainless steel tube.
From chart to quote
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