Hose Clamp Torque Chart by Band Width

A hose clamp torque chart is only useful if you know where each number came from and what kind of torque it describes. Most “charts” floating around workshops are a single line copied from somewhere, with no source, no band width and no clue whether the figure is a target or a breaking point. This page takes a different approach. Every figure below was read from a manufacturer or distributor’s own published data, it is labelled with that source, and it is grouped by band width and clamp type, because those two things decide the number far more than hose diameter does.

Treat everything here as indicative. Clamp makers revise their sheets, and a value printed for one maker’s screw and housing does not transfer perfectly to another maker’s clamp. Use the chart to sanity-check a job, then follow the instruction printed by the company that made the clamp in your hand. If you want the hands-on version (how it should feel, how to tell when a joint is tight enough, what over-tightening looks like), read our practical companion, how tight should a hose clamp be.

Three torque figures that get mixed up

Before reading any hose clamp torque chart, know which of three figures you are looking at. Mixing them up is the commonest reason people strip housings or under-tighten joints.

Installation (tightening) torque

This is the target. It is the value the maker recommends you apply to the screw when fitting the clamp over a typical hose on a typical fitting. Some makers print a single figure, some print a range, and some print “up to” a value. NORMA calls it tightening torque; Ideal Tridon calls it recommended installation torque. It is the only number you should be aiming for with a torque driver.

Ultimate, test or failure torque

This is the ceiling. It describes how much torque the clamp can survive before the screw jumps the band slots, the housing opens up or the band tears. Boshart calls it rated ultimate torque and prints it as a minimum the clamp must withstand. NORMA’s datasheet lists a testing torque and, in a distributor version of the same sheet, a minimum break value. The gap between installation torque and ultimate torque is the safety margin. Never use the ultimate figure as a target.

Free-running torque

This is the friction you feel when the clamp is turning freely, before the band has closed down on the hose. It is a quality check, not a target. NORMA lists a maximum free-running torque of roughly 0.7 to 1.2 for its TORRO clamps depending on material, which is small compared with the tightening figure. Why does it matter to you? Because a torque driver set to the installation value will click early if the screw is gritty, corroded or binding. If a clamp takes noticeable effort to turn before it even touches the hose, swap it rather than trusting the click.

Rule of thumb: installation torque is what you set the tool to; ultimate torque is what the clamp is proven to survive; free-running torque is the friction you subtract mentally before you trust the reading.

Torque chart: worm gear clamps by band width

This hose clamp torque chart collects published installation torque for worm gear clamps by band width. Each row names its source; ranges are shown where the maker gives one. N·m values are printed by the maker or converted at 1 in-lb = 0.113 N·m.

Reading the 5/16″ mini rows

Three makers land almost exactly on the same window: about 10 to 15 in-lb, or a little over 1 N·m. Boshart also publishes a rated ultimate torque of at least 15 in-lb for its minis, which tells you how thin the margin is on a small clamp. The installation target and the minimum survival figure are only a few in-lb apart. That is why mini clamps should be tightened by hand with a nut driver, never with a cordless drill. OneTouch lists mini clamps such as the OTE-4SC004M mini clamp for 0.25–0.63 in hoses; follow the narrow-band figures above for that class, not the 1/2″ band figure.

Reading the 1/2 inch band hose clamp torque rows

Boshart’s published installation range for standard (#6 and larger) worm gear clamps is 35 to 45 in-lb, with a rated ultimate torque of at least 60 in-lb. OneTouch’s 1/2″ band clamps, with a 301 stainless band, zinc-plated carbon steel (rather than stainless) screw and 5/16″ hex, carry a stated torque rating of 45 in-lb, about 5.1 N·m. That figure comes from the product page for parts such as the OTE-4SC0016 worm gear clamp (0.81–1.50 in).

Be clear about what that 45 in-lb means. It is the torque rating OneTouch states for the product. It is not a promise that every joint needs 45 in-lb. On a firm rubber coolant hose over a beaded steel spigot, working up toward that rating is reasonable. On a soft hose, a plastic fitting or silicone, you will usually stop well below it because the hose or the fitting becomes the limit before the clamp does. Treat the rating as the top of the window for this clamp, and treat the hose maker’s guidance as a second ceiling that may be lower.

Reading the 9/16 band clamp torque rows

Here is a result that surprises people: Ideal Tridon prints the same 35 in-lb for its 9/16″ Hy-Gear as many makers use for 1/2″ band clamps. A wider band does not automatically mean a higher target. It means the same screw load is spread over more hose, so contact pressure per unit area drops and the joint is gentler on the hose. Where a maker does raise the number on 9/16″, it has usually also changed the housing and screw, as with Ideal’s Flex-Gear at 50 in-lb. So the honest answer to “what is 9/16 band clamp torque?” is: 35 in-lb is a common published figure, and higher values belong to specific reinforced designs.

Reading the metric 9 mm and 12 mm rows

Metric worm drive clamps built to the DIN 3017 pattern usually come with 9 mm or 12 mm bands, and their makers publish torque in N·m. NORMA’s TORRO datasheet lists roughly 2 to 3 (+0.5) for the 9 mm band, with the smallest 8–12 mm size at the lower figure, and 5 (+0.5) for the 12 mm band. The datasheet table does not print the unit beside each value, but the numbers match the N·m figures Ideal Tridon publishes for its own non-perforated 9 mm and 12 mm clamps (2.0, 3.0 and 5.0 N·m by size), so read them as N·m and confirm against NORMA’s current sheet. Our guide to the DIN 3017 hose clamp standard explains the band classes and why non-perforated bands behave differently from slotted ones.

Notice how much more conservative these metric figures look than the 1/2″ inch-pattern figures. A 9 mm clamp at 3 N·m is about 27 in-lb. A 12 mm clamp at 5 N·m is about 44 in-lb. The 12 mm band and the 1/2″ band are almost the same width, and the published targets end up close together too.

T-bolt, hi-torque and constant torque clamps

Once you move away from the standard worm gear design, torque values climb because the band, housing and fastener are all heavier. T-bolt clamp torque in particular is set by a proper bolt and nut rather than a worm screw in a pressed housing. The table below lists only what could be verified from published maker data. Where no figure could be verified, the cell says so.

What the T-bolt row tells you

At 75 in-lb (8.5 N·m), Ideal Tridon’s published T-bolt figure is well above a standard worm clamp, yet still modest in bolting terms. People who treat a T-bolt like a wheel nut ruin silicone boost hoses and sometimes crack aluminium pipe ends. OneTouch’s T-bolt clamp range covers diameters from about 1.25 in to 8.81 in, plus spring-loaded versions such as the OTE-4ST306B spring-loaded T-bolt (3.06–3.38 in). For those parts, ask for the torque that applies to your exact part number rather than copying another maker’s value.

Hi-torque: capability is not a target

Breeze describes its 5/8″ hi-torque liner clamp as able to take over 150 in-lb. Read that carefully. It is what the drive can withstand, not what you should apply. Ideal Tridon’s installation figures for comparable 5/8″ designs sit at 75 to 90 in-lb. The extra strength exists so the clamp can pull large, stiff hoses and ducts round without the housing deforming. OneTouch’s hi-torque clamps are aimed at that same large-hose and duct work.

Constant torque: tighten to the spring, not past it

Constant torque clamps use Belleville spring washers that keep load on the joint as the hose cools and shrinks. Their installation figures are “up to” values for a reason: once the washer stack is flat, the spring has stopped working and you have turned it back into an ordinary worm clamp. Many workshops tighten until the washers are just compressed, then stop. See OneTouch constant torque clamps for sizes, and our constant tension vs standard hose clamp comparison for when the extra cost pays off.

Why band width changes the number

Look down both tables and the pattern is obvious. Hose clamp torque by band width rises from about 1 N·m on a 5/16″ mini to roughly 4–5 N·m on a 1/2″ or 12 mm band, then to 8.5 N·m and above on 5/8″ and 3/4″ heavy designs. Band width on its own does not create that increase. It comes with three other changes.

1. A wider band spreads the same load over more hose

Screw torque becomes band tension, and band tension becomes radial pressure on the hose. For a given tension, the pressure on the hose surface is roughly inversely proportional to the contact width. Double the width and you roughly halve the pressure per unit area. That is good for the hose: less cutting, less extrusion through slots, less cold flow over time. It also means a wider band can carry more total tension before it damages the hose, which is why makers can raise the target as width goes up.

2. Bigger bands come with bigger screws

Mini clamps typically use a 1/4″ hex screw (Ideal Tridon lists a 1/4″ hex for its Micro-Gear). Standard 1/2″ band clamps, including OneTouch’s, use a 5/16″ hex. Some 9/16″ clamps step up to 3/8″ hex, as Ideal does on one of its 9/16″ series. T-bolts move to a real threaded bolt and nut. A larger screw thread can carry more load before the threads or the band slots give way, so the ceiling rises.

3. Housing strength sets the real ceiling

On a worm gear clamp the weak point is usually the housing, the folded steel bridge that holds the screw against the band. Under too much torque it opens up, the screw lifts and the thread skips over the slots. Heavier housings, riveted or welded bridges and thicker band stock are what let hi-torque designs accept 75–90 in-lb where a light standard clamp tops out much lower. If you see two clamps with the same band width but very different published numbers, the housing is almost always the difference.

Converting in-lb, ft-lb and N·m

US clamp makers publish hose clamp torque in in-lbs; European and DIN-pattern makers publish in N·m. Many torque screwdrivers carry both scales, but plenty of mechanics end up converting on the fly. The conversions are simple:

• 1 in-lb = 0.113 N·m
• 1 N·m = 8.85 in-lb
• 1 ft-lb = 12 in-lb = 1.356 N·m

The table below was calculated, not copied, using 1 in-lb = 0.112985 N·m and rounded to two decimals. Rows cover the values that actually appear in clamp data.

Going the other way, from metric sheets:

Notice how small these numbers are in ft-lb. A typical worm gear clamp target is about 3 ft-lb, while most click-type ratchet torque wrenches start at 10 ft-lb or more. They simply cannot measure it.

Tools: torque screwdrivers and nut drivers

The right tool for worm gear clamp torque is a torque screwdriver or a small-range torque driver reading in in-lb or N·m, fitted with a hex bit or socket. A preset or adjustable “cam-over” style driver is ideal for production work because it slips at the set value rather than relying on you to read a scale.

Match the hex size

Use a hex socket or nut driver, not the screwdriver slot. Slotted screwdrivers cam out under load, chew the screw head and, worse, slip and stab the hose. A snug hex socket transfers torque cleanly and keeps the reading honest.

T-handle nut drivers

For day-to-day work without a torque tool, a T-handle nut driver is the next best thing. The short T bar limits how much leverage you can apply, so it is hard to wildly over-torque a clamp with one. It is also quick to spin a clamp down through its free-running travel.

Why power drivers overtighten

Cordless drills and impact drivers strip more clamps than anything else, for three reasons:

1. Clutch settings are not calibrated. A drill clutch marked “5” has no defined in-lb value, and it changes with battery charge and wear.
2. Speed adds energy. A spinning chuck and bit store momentum. When the band suddenly bottoms out on the hose, that energy goes into the screw, often well past the clutch setting.
3. Impact drivers hammer. Each blow can momentarily exceed the ultimate torque of a light clamp. Minis in particular can be stripped in a fraction of a second.

A sensible workflow is to run the clamp down by power or a T-handle until the band just touches the hose, then finish with a torque screwdriver set to the maker’s value.

Using a chart safely

A hose clamp torque chart tells you what the clamp is designed for. It does not know your hose, your fitting or your operating temperature. Before you set the tool, run through these checks.

The hose maker may set a lower limit

Some hose manufacturers publish their own clamp recommendations, and those can be lower than the clamp’s figure. If they disagree, the lower number wins. A clamp torqued to its rating can still cut through a thin-walled hose or crack a plastic spigot.

Silicone wants less

Silicone hose is soft and creeps under load. Slotted bands can extrude it through the perforations. Use a smooth-faced or lined clamp, such as the OneTouch liner clamps, and expect to stop below the clamp’s published maximum.

Re-torque after the first heat cycle

Rubber and silicone relax after the first time they are heated and cooled. On coolant and charge-air joints, a clamp that was right on day one can feel loose after the first run. Check and re-torque standard worm and T-bolt clamps once the engine has cooled fully after its first heat cycle. Constant torque clamps are designed to absorb much of that relaxation on their own, which is one reason fleets specify them on coolant systems.

Never exceed the maximum

If a joint still leaks at the installation torque, adding more torque is rarely the fix. Look at the real cause instead:

• Is the clamp the right size? The hose OD should sit near the middle of the clamp’s range. Measure the hose as fitted on the spigot; OD varies by construction.
• Is the clamp behind the bead, fully on the fitting, and square to the hose?
• Is the hose hardened, cracked or swollen with age?
• Does the job need a wider band, a T-bolt or two clamps rather than one clamp forced harder?

A worm clamp that has been taken past its ultimate torque may look fine yet have a distorted housing or damaged slots. Replace it. Clamps are cheap compared with a lost coolant charge.

Keep records for fleets

Fleets should treat this hose clamp torque chart as a starting point and write the clamp part number and its own torque value into the service sheet for each joint. A replacement from a different source needs its own published figure. If you are matching an OEM number, our clamp cross-reference tool helps identify the equivalent OTE part, and the hose clamp size chart in mm and inches helps confirm the range.

Sources used for this chart

Every external figure in this hose clamp torque chart came from these published maker documents, checked in October 2026. Open the original for size-by-size detail.

• Ideal Tridon product catalog (PDF): installation torque for Micro-Gear, Hy-Gear, Flex-Gear, Pow’r-Gear, SmartSeal, non-perforated metric and T-bolt series.
• Boshart worm gear clamp installation guide: installation and rated ultimate torque for mini and standard clamps.
• NORMA TORRO datasheet (PDF): tightening, free-running and testing torque for 9 mm and 12 mm bands.
• Breeze clamp catalog (PDF, distributor copy): miniature, Constant-Torque and Hi-Torque figures.

Manufacturer names are used for reference only. OneTouch Exim has no affiliation with these companies.

Hose clamp torque specs: FAQ

Built your own hose clamp torque chart for the workshop and need clamps with a published rating to match? OneTouch Exim supplies 1/2″ band worm gear clamps rated at 45 in-lb, plus T-bolt, spring-loaded T-bolt, hi-torque, lined and constant torque clamps in 347 sizes, shipped worldwide in single units or export cartons. Send us your part numbers or hose diameters and we’ll confirm the matching OTE parts and the torque data for each.