DIN 3017 Hose Clamp Standard Explained

If you have ever ordered hose clamps from a European supplier, or pulled one off a German-built engine, you have probably seen a line like “DIN 3017 W4 9 mm 20–32” on the box. DIN 3017 is the German standard for hose clamps, and those few characters tell you more about the clamp than most US catalogue listings do: what metal every part is made of, how wide the band is, and the exact diameter range it is built to close on. The catch is that nobody explains the code. This guide decodes it one piece at a time, compares it with the American SAE J1508 approach, and gives you a conversion table for moving between metric DIN ranges and inch-sized clamps.

One note first. DIN standards are paid documents, so we have not reproduced clause numbers, tolerances or test values here. What follows draws on the publisher’s listings, manufacturer datasheets and an older edition. For a purchase specification, buy the current edition and check it directly.

What DIN 3017 actually covers

It is not a single document but a series published by DIN, the German Institute for Standardization, and sold through its publishing arm DIN Media (the business formerly known as Beuth Verlag). The series title is simply “Hose clamps”, and each part deals with a different clamp design.

The part almost everyone means when they say “DIN 3017” is Part 1. According to the DIN Media listing for DIN 3017-1, the current edition is dated September 2021, replaced the 1998 edition, and is titled “Hose clamps – Part 1: Clamps with worm gear drive, shapes A and B”. In other words, it is the screw-tightened band clamp that every mechanic recognises, defined the European way.

The other parts that turn up in catalogues are:

• DIN 3017-2: clamps with fastening lugs, shapes B1 and B2. The current edition of Part 2 is dated July 2023. These use a bolt pulling two jaws together rather than a worm screw.
• DIN 3017-3: bolt clamps, sometimes listed as clamps with a round bolt. DIN Media shows the 2002 edition as withdrawn and replaced by a July 2023 edition. This is roughly the European counterpart of the heavy T-bolt clamp.

So when a supplier writes the standard number with no suffix, assume Part 1, the worm drive clamp. A bolt or lug style should carry “-2” or “-3”.

What the clamp looks like in your hand

The everyday DIN 3017 hose clamp has three parts: a band, a housing (the box riveted or folded onto one end of the band) and a screw. The detail that sets it apart from most American clamps is the band itself. Instead of a row of slots punched through the steel, the thread profile that the screw engages is pressed or embossed into the band surface. The band stays solid, with no holes going all the way through. That is why you see these described as “non perforated hose clamp”, “German style hose clamp” or “embossed band clamp” in trade listings.

To be precise, the older edition we read did not ban perforated bands outright; it required slotted designs to protect the hose under the housing. In practice, the clamps the big European makers sell to this standard are overwhelmingly the embossed type, and that is what buyers expect.

What the standard sets, in general terms

Without quoting the paid text, Part 1 sets out what a buyer needs agreed:

• clamping ranges in millimetres, so a 20–32 from one maker replaces a 20–32 from another;
• band widths and the matching screw head sizes;
• material classes, the “W” codes, so the buyer knows exactly which parts are stainless;
• tightening and test torque requirements, which differ by band width and material class;
• design rules that protect the hose, such as rounded band edges;
• a designation format, so a clamp can be ordered with one line of text.

We won’t guess at those torque values. If your job depends on one, take it from the maker’s datasheet for the exact size and W class.

Decoding the W numbers: DIN 3017 W1, W2, W4 and the rest

The W code is the most useful part of any German clamp description, and also the most misunderstood. “W” comes from the German Werkstoff, meaning material. Each class tells you what the band, the housing and the screw are made from. The important point is that the three parts are not always the same metal.

The table combines the older edition’s material list with how major manufacturers describe W1 to W5 on current datasheets. EN material numbers are given with AISI equivalents.

The W2 trap: “stainless” is not the same as 304

Many buyers order W2 assuming they are getting 304 stainless. They aren’t. W2 bands and housings are usually 1.4016, a ferritic chromium steel with no nickel. It resists rust far better than plain steel, but nowhere near as well as 304 in wet or salty service, and it is magnetic, which surprises people who use a magnet as a quick stainless test. If you want to understand why, our explainer on magnetic versus non-magnetic stainless steel covers the metallurgy.

The second half of the trap is the screw: plated carbon steel. In road spray it corrodes first, and a rusted head may not back off cleanly. W2 is a good, economical clamp; just don’t specify it for a boat.

W4 versus W5

W4 is all 304-type stainless and is the sensible default whenever the clamp will see water. W5 moves every part to 316-type steel with molybdenum, which handles chlorides much better: seawater, de-icing salt, pool chemicals, some cleaning agents. The older edition described W5 material as seawater-suitable and hard to magnetise, and one major maker publishes salt-spray minimums that climb steeply from W2 to W5. For the full grade comparison, see our guide to 304 vs 316 stainless steel.

Band width, embossed threads and why non-perforated bands matter

The next number on the label is band width. In current German catalogues two widths dominate: 9 mm and 12 mm. Some makers add a 7.5 mm mini band, and older editions listed other widths, so the odd 13 mm or 5 mm listing turns up in old stock.

9mm vs 12mm band hose clamp: which one?

It is mostly about load and space.

• 9 mm suits smaller hoses, light-duty lines and short landing areas behind a hose bead. On small diameters it gives plenty of grip.
• 12 mm spreads the load over more hose, which matters on larger diameters, thicker-walled hose and higher tightening torque. Some suppliers only make their smallest ranges in 9 mm and switch to 12 mm from about 12–20 mm or 16–25 mm upwards.

For reference, a typical US worm clamp band of 1/2 inch is 12.7 mm, so it sits just above the 12 mm DIN band. A 9 mm band is a little over 11/32 inch. If you are replacing a 12 mm DIN clamp with an inch-sized one, the half-inch band gives you equal or slightly better coverage; going from 12 mm down to a 9 mm band on the same hose is a step down in contact area.

Datasheets also state whether the band’s inner face is smooth or stamped. A smooth face leaves nothing to dig into the hose cover.

Perforated versus non-perforated: the practical difference

On a perforated band, the screw engages slots punched right through the steel. It is a strong, proven design, and most North American worm clamps use it, including ours. Its weakness is that soft hose can squeeze into the slots as you tighten. On firm rubber that rarely matters; on silicone or thin-wall PVC the cover can get chewed.

A non perforated hose clamp avoids that because there is nothing for the hose to extrude into. You get a more even ring of pressure and less surface damage, usually at a slightly higher band cost.

There is another way to get the same hose protection with an inch-sized clamp: a lined clamp. A smooth stainless liner sits between the slotted band and the hose and bridges the perforations. OneTouch carries these in both the worm clamp family and a dedicated range of lined hose clamps, and they are what we usually suggest for silicone. Our guide to choosing clamps for silicone hose goes into that in more detail.

Screw head size

European worm clamps usually have a 7 mm hex; American ones use 5/16 inch, about 7.94 mm. A 5/16 socket slips on a 7 mm head, and a 7 mm socket won’t fit a 5/16 head. Mixed fleets need both.

Reading a DIN 3017 part description, element by element

Catalogue descriptions vary in order, but they carry the same pieces of information. Take this typical line:

Hose clamp DIN 3017-1 A W4 9 mm 20–32 mm

Here is how to read it:

The older edition used a formal order: standard number, shape, range “×” band width, then W class, sometimes with extra codes. You may meet both styles; the content is what matters.

How the metric size ranges are laid out

A DIN 3017 size chart is easy to recognise because the ranges overlap. Across European catalogues the steps run 8–12, 10–16, 12–20 or 12–22, 16–25 or 16–27, 20–32, 25–40, 32–50, 40–60, 50–70, 60–80, 70–90 and so on, with clamps commonly available up to around 140–160 mm and larger ranges made to order. Each range is roughly 10 to 20 mm wide, and the next range starts well before the previous one ends.

The overlap is deliberate: most hose ODs fall in two ranges, so you can pick the one that places your diameter near the middle, leaving thread to take up settling.

The range is not the hose bore. It is the hose outside diameter where the clamp sits, on the fitting, and the same 25 mm bore can measure very differently outside depending on wall construction. Measure it with calipers or a tape wrapped around and divided by pi; do not guess from the bore.

DIN 3017 vs SAE J1508

If the German standard is the European reference for worm drive clamps, the closest North American reference is SAE J1508, Hose Clamp Specifications. SAE first issued it in 1987 under the title “Worm Gear Hose Clamps”, and the current revision is dated January 2023. Its scope has grown well beyond worm clamps: SAE’s own summary says it covers 32 clamp types used in original equipment coolant, fuel, oil, vacuum and emission systems.

The differences show up on the shelf:

Size numbers versus ranges. An SAE-style clamp is ordered by a size number, and the range that number represents is published by each manufacturer. On OneTouch parts the SAE number is the last digits of the part number, so the OTE-4SC0012 worm clamp is an SAE 12 that covers 0.69 to 1.25 inch. A DIN clamp prints the range itself.

Materials. The W system fixes all three components in one code; SAE-style catalogues use words, so read carefully. Our standard worm clamps, for example, pair a 301 stainless band and housing with a zinc-plated carbon steel screw, which is closest in spirit to a DIN W2, though the band is an austenitic grade rather than the ferritic 1.4016 a W2 normally uses. Our all-stainless 4SS series, such as the all-stainless OTE-4SS0016, moves the screw to stainless too, closer to a W4 in intent. These are rough equivalents for choosing a replacement, not claims of DIN conformity.

Converting between metric DIN ranges and SAE inch sizes

Because the ranges are drawn on different grids, there is rarely a perfect match between a metric range and an inch-sized clamp. The table below converts the common DIN ranges to inches (1 inch = 25.4 mm) and suggests the nearest OneTouch perforated worm clamp. Where a DIN range falls between two inch sizes, we list both; your measured hose OD decides which one to use.

How to use this table properly:

1. Measure first. The DIN range on the old clamp only tells you what the previous buyer chose. Measure the hose OD on the fitting and work from that number.
2. Convert the measurement, not the range. Divide your measured millimetres by 25.4. A 29 mm OD is 1.14 inch.
3. Pick the inch clamp that puts that number near the middle. 1.14 inch sits comfortably in 0.81–1.50 (SAE 16) and toward the top of 0.69–1.25 (SAE 12). The SAE 16 is the safer choice there.
4. Check band width and material. Replacing a 12 mm W4 clamp? Use a half-inch band in all stainless, not a plated-screw clamp.

If you want worked examples in a specific size, our 1 inch hose clamp size guide walks through the same reasoning for the most common automotive diameter.

Is a German style clamp right for your job?

A well-made worm clamp of either pattern seals most hoses if sized and tightened correctly. The choice comes down to a few factors.

Choose the German style when

• the hose is soft, thin-walled or silicone, and you want the smooth inner face without adding a liner;
• you are maintaining European-built equipment and want like-for-like replacement, metric tooling and metric ranges;
• a customer drawing or tender explicitly calls for the standard with a named W class;
• space is tight and a 9 mm band fits where a half-inch band will not.

Choose an SAE-style perforated clamp when

• the equipment is North American and the service literature lists SAE sizes or OEM part numbers;
• the hose is firm rubber, as on most coolant, air intake and fuel lines on trucks and diesels;
• you want the widest inch-size selection and easy matching against existing stock;
• you need a lined version for silicone but would rather keep one tooling standard in the shop.

Consider something other than a worm clamp when

Neither standard pattern is ideal for every joint. Hoses that run hot and cold cycles shrink and relax, a form of cold flow, and a plain worm clamp does nothing to follow that movement. That is where a spring-backed design helps; our constant torque clamps use stacked spring washers to keep load on the hose as it settles, and our article on constant tension vs standard hose clamps covers when that matters. For large boost hoses and high-pressure joints, a solid-band T-bolt clamp gives a more even 360-degree grip than any worm drive, and is the closest thing in our range to the bolt clamps in DIN 3017-3.

For small, permanent, tamper-resistant joints, single-ear or stepless crimp clamps are another good option. We don’t make those, so look to a specialist supplier if that is the right fit.

Material choice matters more than band style

More clamps fail from corrosion than from band style. Decide the environment first, the material class second and the band style third. On boats and coastal kit, the guidance in our marine hose clamp guide applies whichever standard you buy to.

Where OneTouch fits: inch sizes, SAE style, and honest cross-referencing

To be clear about what we sell: the OneTouch Exim clamp catalogue is built around inch sizes. Our core perforated worm gear hose clamps are SAE-style, with a half-inch 301 stainless band, a 5/16 inch hex screw and size numbers that follow the familiar SAE pattern, plus all-stainless versions. Alongside them we carry lined clamps, constant torque clamps, hi-torque clamps and T-bolt clamps, 347 sizes in total. We do not list W-class metric clamps or 9 mm embossed bands as catalogue items, and we will not claim DIN conformity for parts that are not made to it.

What we can do is help you find the right inch-sized equivalent. If you have a metric W-class designation, a European OEM part number or a mixed list of SAE and metric clamps, send it through our hose clamp cross-reference page. Tell us the measured hose OD, the environment and, if you know it, the W class you are replacing. We will come back with the closest OneTouch part and say plainly where the match is not exact, for instance where a 9 mm band would be replaced with a half-inch band.

Manufacturer names and part numbers mentioned on our site are used for reference and interchange only. We are not affiliated with any of them.

Questions we get asked about the standard

Matching a metric part to an inch clamp? Send us the list

Whether you are replacing one metric clamp on a European tractor or converting a whole fleet bill of materials from DIN ranges to SAE sizes, OneTouch Exim can quote inch-sized worm, lined, constant torque, hi-torque and T-bolt clamps by the piece or by the export carton, shipped worldwide. Send your DIN designations, measured hose diameters or OEM numbers and we will match them to the closest parts, flag anything that is not a like-for-like swap, and price it. You can also reach us on WhatsApp at +91-7838759114.