A heavy duty hose clamp size chart turns one number, the hose outside diameter measured on its fitting, into a part that will actually close on it. Find your measured OD in the left column of the map below, read across the four OneTouch heavy duty families, and pick a size that puts your reading near the middle of its range, not at either end.
This chart is a coverage map: hose OD bands from 1 in to 9 in, in half-inch steps with millimetres, down the side, and the four OneTouch heavy duty families across the top. Each cell names the parts reaching into that band, or says “gap”. Ranges come from the OneTouch category pages as listed in October 2026. After the map: reading overlaps and gaps, measuring large stiff hose, family by application, worked cases and common errors. The general method lives in our hose clamp measuring guide and the all-family size hub in millimetres and inches.
The four heavy duty families on the map
Here “heavy duty” means four specific builds. For background, see what a heavy duty hose clamp is; selection logic is in choosing a heavy duty hose clamp.
- Hi-torque 4SCH: worm drive, 5/8 in wide 301 stainless band, 410 stainless screw with a 5/16 in hex, rated 150 in-lb. The 20 sizes in the high torque clamp category run from 1 in to 9.13 in.
- Plain T-bolt 4TB: a solid band pulled closed by a bolt through a trunnion. The pages list a 3/4 in band in 301 stainless, a zinc-plated carbon steel bolt, 7/16 in nut and 150 in-lb rating. 33 sizes, 1.25 in to 8.81 in.
- Spring-loaded HD T-bolt 4ST…H: the same bolt principle with a built-in spring and a 1/2 in nut. 50 sizes, 2.06 in to 8.63 in. Both T-bolt families sit in the T-bolt clamp category, which also holds 20 standard spring-loaded 4ST…B parts that are not on the map.
- HD constant torque 4CT…L/S: 5/8 in band, Belleville washer stack, 3/8 in hex, 92 in-lb rating. The L suffix means a zinc-plated steel screw; S means 410 stainless. 15 sizes in each version, 1 in to 8.63 in.
Heavy duty hose clamp size chart: coverage map from 1 in to 9 in
A part appears in a row if any of its range falls inside that band, even if it only touches the edge, so check the exact range before ordering. “4CT” cells apply to both the L and S versions.
| Hose OD band | Hi-torque 4SCH | Plain T-bolt 4TB | Spring HD T-bolt 4ST…H | HD constant torque 4CT…L/S |
|---|---|---|---|---|
| 1 to 1-1/2 in (25.4 to 38.1 mm) | 4SCH175, 4SCH212, 4SCH919 | 4TB0125, 4TB0138; gap below 1.25 in | Gap (series starts at 2.06 in) | 4CT175, 4CT200 |
| 1-1/2 to 2 in (38.1 to 50.8 mm) | 4SCH175, 4SCH212, 4SCH919, 4SCH262 | 4TB0138, 4TB0150, 4TB0163, 4TB0175, 4TB0188 | Gap | 4CT175, 4CT200, 4CT250 |
| 2 to 2-1/2 in (50.8 to 63.5 mm) | 4SCH212, 4SCH919, 4SCH262, 4SCH914, 4SCH312 | 4TB0188 to 4TB0238 (5 sizes) | 4ST206H to 4ST244H (7 sizes); gap 2.00 to 2.06 in | 4CT200, 4CT250, 4CT300 |
| 2-1/2 to 3 in (63.5 to 76.2 mm) | 4SCH919, 4SCH262, 4SCH914, 4SCH312, 4SCH362 | 4TB0225 to 4TB0288 (6 sizes) | 4ST225H to 4ST281H (10 sizes) | 4CT250, 4CT300, 4CT350 |
| 3 to 3-1/2 in (76.2 to 88.9 mm) | 4SCH914, 4SCH312, 4SCH362, 4SCH412 | 4TB0275 to 4TB0325 (5 sizes) | 4ST275H to 4ST344H (10 sizes) | 4CT300, 4CT350, 4CT400 |
| 3-1/2 to 4 in (88.9 to 101.6 mm) | 4SCH914, 4SCH362, 4SCH412, 4SCH462 | 4TB0325, 4TB0350, 4TB0375 | 4ST325H to 4ST388H (11 sizes) | 4CT350, 4CT400, 4CT450 |
| 4 to 4-1/2 in (101.6 to 114.3 mm) | 4SCH914, 4SCH412, 4SCH462, 4SCH918, 4SCH512 | 4TB0375, 4TB0400, 4TB0425 | 4ST375H to 4ST438H (9 sizes) | 4CT400, 4CT450, 4CT500 |
| 4-1/2 to 5 in (114.3 to 127.0 mm) | 4SCH462, 4SCH918, 4SCH512, 4SCH562 | 4TB0425, 4TB0450, 4TB0475 | 4ST425H to 4ST488H (6 sizes) | 4CT450, 4CT500, 4CT550 |
| 5 to 5-1/2 in (127.0 to 139.7 mm) | 4SCH918, 4SCH512, 4SCH562, 4SCH612 | 4TB0475, 4TB0500, 4TB0525 | 4ST488H to 4ST538H (5 sizes) | 4CT500, 4CT550, 4CT600 |
| 5-1/2 to 6 in (139.7 to 152.4 mm) | 4SCH918, 4SCH562, 4SCH612, 4SCH662 | 4TB0525, 4TB0550, 4TB0575 | 4ST525H, 4ST531H, 4ST538H, 4ST581H; gap 5.69 to 5.81 in | 4CT550, 4CT600, 4CT650 |
| 6 to 6-1/2 in (152.4 to 165.1 mm) | 4SCH918, 4SCH612, 4SCH662, 4SCH916, 4SCH712 | 4TB0575, 4TB0600, 4TB0625 | 4ST581H to 4ST638H (5 sizes) | 4CT600, 4CT650, 4CT700 |
| 6-1/2 to 7 in (165.1 to 177.8 mm) | 4SCH662, 4SCH916, 4SCH712, 4SCH762 | 4TB0625, 4TB0650; gap 6.81 to 7.00 in | 4ST625H, 4ST631H, 4ST638H; gap 6.69 to 7.00 in | 4CT650, 4CT700, 4CT750 |
| 7 to 7-1/2 in (177.8 to 190.5 mm) | 4SCH916, 4SCH712, 4SCH762, 4SCH812 | 4TB0700; gap 7.31 to 7.50 in | 4ST725H, 4ST731H; gap 7.00 to 7.25 in | 4CT700, 4CT750, 4CT800 |
| 7-1/2 to 8 in (190.5 to 203.2 mm) | 4SCH916, 4SCH762, 4SCH812, 4SCH862 | Gap | 4ST725H, 4ST731H, 4ST750H; gap 7.81 to 8.00 in | 4CT750, 4CT800, 4CT850 |
| 8 to 8-1/2 in (203.2 to 215.9 mm) | 4SCH916, 4SCH812, 4SCH862, 4SCH912 | 4TB0800; gap 8.31 to 8.50 in | 4ST831H; gap 8.00 to 8.31 in | 4CT800, 4CT850 |
| 8-1/2 to 9 in (215.9 to 228.6 mm) | 4SCH916, 4SCH862, 4SCH912 | 4TB0850; gap above 8.81 in | 4ST831H; gap above 8.63 in | 4CT850; gap above 8.63 in |
| 9 to 9-1/8 in (228.6 to 231.8 mm) | 4SCH912, 4SCH916 | Gap | Gap | Gap |
How to read the map: overlaps, gaps and range width
Overlaps are a choice, not a duplicate
Almost every row offers two to five parts per family. The staggering is deliberate. When two sizes cover your number, work out where it lands in each: subtract the minimum of the range from your OD and divide by the range width. A result of 0 percent is the closed end, 100 percent is fully open. As a working rule we aim for roughly 30 to 75 percent. On soft silicone, which compresses as you tighten, favour the upper half of that window so the clamp still has travel left once the hose squashes. On firm rubber or thick reinforced hose, which barely moves, a reading a little lower in the range is fine.
Gaps tell you to switch family, not to stretch a size
Only two columns are gap-free inside their own limits: hi-torque runs unbroken from 1 in to 9.13 in, and HD constant torque runs unbroken from 1 in to 8.63 in. The T-bolt columns have holes. The plain 4TB series stops at 6.81 in and restarts at 7.00 in, has nothing between 7.31 in and 8.00 in, and skips 8.31 to 8.50 in. The spring-loaded HD series has a small hole between 5.69 in and 5.81 in and larger ones from 6.69 to 7.25 in and from 7.81 to 8.31 in. Neither T-bolt family goes below 1.25 in (plain) or 2.06 in (spring HD).
If your OD falls in a gap, read sideways. A 7.6 in reading has no plain T-bolt, but the spring HD 4ST750H (7.50 to 7.81 in) covers it, as do 4SCH812 and 4CT800. The small 5.69 to 5.81 in hole in the spring HD column is mostly covered by the standard spring-loaded 4ST575B (5.75 to 6.06 in), which is not on the map but sits in the same T-bolt category; below 5.75 in, use plain 4TB0550 or a 5/8 in band clamp.
Why T-bolt ranges are about 1/4 in and hi-torque ranges about 7/8 in
The difference comes from how each clamp takes up slack. A T-bolt band is a fixed length with a trunnion at one end and a bridge at the other. The only adjustment is how far the nut draws the ends together. A 0.31 in diameter change needs about 1 in of circumference (0.31 × 3.14) to disappear, roughly the travel a compact T-bolt gives. So most 4TB and every 4ST…H range spans 0.31 in (5/16 in), and the smallest plain sizes are narrower still: 4TB0150 covers only 1.50 to 1.63 in.
A hi-torque or constant torque clamp uses a worm screw running along the band itself, so the band slides through the housing for as long as there is band. Most 4SCH and HD 4CT sizes span 0.88 in (7/8 in); the smallest span 0.75 in. Four hi-torque parts go much further: 4SCH919 (1.25 to 2.63 in), 4SCH914 (2.13 to 4.13 in), 4SCH918 (4.00 to 6.13 in) and 4SCH916 (6.13 to 9.13 in), each spanning 1.38 to 3 in.
| Family | Sizes listed | Smallest to largest | Typical range width | Measuring tolerance this allows |
|---|---|---|---|---|
| Hi-torque 4SCH | 20 (16 standard, 4 wide-range) | 1.00 to 9.13 in (25 to 232 mm) | 0.75 to 0.88 in; wide-range parts 1.38 to 3.00 in | Forgiving: a 1/8 in reading error rarely changes the part |
| Plain T-bolt 4TB | 33 | 1.25 to 8.81 in (32 to 224 mm) | 0.13 to 0.31 in | Tight: read to the nearest 1/32 in or 1 mm |
| Spring HD T-bolt 4ST…H | 50 | 2.06 to 8.63 in (52 to 219 mm) | 0.31 to 0.32 in | Tight: read to the nearest 1/32 in or 1 mm |
| HD constant torque 4CT…L/S | 15 per screw version | 1.00 to 8.63 in (25 to 219 mm) | 0.75 to 0.88 in | Forgiving on fit, but aim mid-range so the washers can work |
So for T-bolts, measurement quality decides fit: a 1/8 in error is 40 percent of the range, against about 14 percent on a hi-torque clamp. Our separate guide covers choosing a T-bolt hose clamp in detail; here we only care about getting the number right for it.
How to measure big, stiff hoses for a heavy duty clamp
The general rules are in the measuring guide. These points apply specifically to large, reinforced and pressurised hose.
Push the hose fully home before you read anything
Hose ID is always a little smaller than the pipe or shank it goes on, so the hose stretches when fitted and its OD grows. A loose length of hose on the bench reads smaller than it will on the joint, and catalogue OD figures describe free hose. Kuriyama, for example, lists its Tigerflex WST suction and discharge hose with a 7.17 in OD for the 6 in size; on a hose shank that number can climb by a meaningful fraction of an inch. For a hi-torque clamp the difference rarely matters. For a T-bolt with a 0.31 in range, it can push you into the next size or into a gap. Fit the hose, then measure where the clamp band will sit. Gates’ hose installation guidance puts the clamp on the hose over the fitting, clear of the hose end, which is also where your measurement belongs.
Wire-reinforced and thick-wall hose
Embedded wire or a rigid helix makes hose stiff, so it hardly compresses under a clamp. That is good news for accuracy: the diameter you measure is close to the diameter the clamp will finish at. It also means there is no “squash allowance” to hide a wrong size. If the hose has an external helix, read across the crests where the band will bear and check that the band will not land on a single crest edge. Thick-wall rubber (common on heavy truck radiator and charge air hose) behaves the same way: measure on the joint, expect little give, and choose a size where your reading sits near the middle rather than near the closed end.
Beaded charge-air pipes: the clamp goes behind the bead
Charge air cooler (CAC) tubes and turbo outlets usually have a rolled bead near the pipe end. The hose slides over the bead and the clamp sits on the pipe side of it, so boost pressure pushes the hose against the bead rather than off the pipe. Measure the hose OD in that exact spot, behind the bead, not over the bulge. The reading over the bead is still worth taking for one reason: if you plan to slide a closed clamp over the bead, its maximum diameter must clear that number. With a T-bolt range of 0.31 in, a bead can easily be bigger than the clamp’s open size, in which case you either fit the clamp onto the hose before pushing it on or open the clamp fully at the nut.
Pi tape or string on 5 to 9 in hose
Calipers big enough for a 7 in hose are rare in a workshop, and long jaws flex. Above about 5 in, wrap the hose instead. A diameter (pi) tape is printed so that wrapping it around the circumference reads the diameter directly. Without one, wrap a strip of paper or a non-stretch cord, mark where it overlaps, lay it flat, measure the length and divide by 3.1416. A 22.0 in circumference gives 7.00 in; a 22.5 in circumference gives 7.16 in. Pull the wrap snug but not tight on soft hose, keep it square to the hose axis, and repeat twice. If the two readings differ by more than 1/16 in of diameter (about 3/16 in of circumference), wrap again.
Ovality on old hoses
Hose clamped for years, or sagging under its own weight, takes a set and goes oval, so two caliper readings at 90 degrees can differ noticeably. Use neither alone. A clamp band follows circumference, so the tape reading (or the average of the two caliper readings) is the one that matches what the clamp will see. If ovality is severe, replace the hose: a new heavy duty clamp on an old, permanently flattened hose end will not seal reliably whatever size you choose.
Which family fits this measurement, by application
The job decides which column to read first.
Charge air cooler boots and turbo hoses
Read the spring HD T-bolt column first. The 4ST…H pages list charge air cooler, turbo and intake hoses as the application, and say the spring keeps tension on the hose as it expands and contracts with heat and pressure. Truck CAC tubes commonly fall between 2.5 and 4.5 in, the densest part of the 4ST…H series, where sizes mostly step every 1/16 in. Measure behind the bead to 1/32 in. NORMA pitches its Breeze HD Constant-Torque as a smaller, lighter substitute for spring T-bolts on many boost joints, so the 4CT column is a second option at moderate pressure; confirm with us before switching on a high-boost joint.
Air intake ducts
Intake ducts between the air cleaner and turbo run at or below atmospheric pressure, often at 4 to 7 in. Hold-down force matters more than pressure sealing, and ducts get removed at every filter change. Read the hi-torque and HD constant torque columns first: wide ranges forgive a so-so measurement, and the worm screw makes service quick. Use plain T-bolts where a thick moulded elbow needs more band load.
Radiator and coolant hose on heavy trucks
Read the HD constant torque column. OneTouch’s 4CT…L/S product pages name coolant and heater duty, and the washer stack follows the hose as it heats and cools. Truck radiator hose often measures 2 to 3.5 in OD, where 4CT250, 4CT300 and 4CT350 overlap. Choose S (stainless screw) where the radiator area is pressure-washed. A full reverse lookup for this one column already exists in our constant tension sizing chart.
Dredge, suction and discharge hose
Suction hose is stiff and helix-reinforced, usually 3 to 8 in, and often clamped with two clamps per joint. Read the plain T-bolt and hi-torque columns. A plain T-bolt gives the highest even band load on a stiff hose, but its narrow range means you must measure on the shank. Hi-torque is the fallback wherever the T-bolt column shows a gap or lands your reading near an end.
Mining ventilation and dust ducts
Large flexible ducts at 6 to 9 in on rigid spigots are where the map thins out. Only hi-torque reaches past 8.81 in, and the wide-range 4SCH916 (6.13 to 9.13 in) can cover a whole fleet of mixed duct sizes with one part number. NORMA lists heavy-duty sealing among the uses of its Hi-Torque clamp design. For 8 in specifically, our 8 inch hose clamp size range guide compares the options.
Five worked examples: from tape reading to part number
Each example runs one reading through the heavy duty hose clamp size chart above. Fitted ODs are illustrative; percentages show position in each candidate range.
Example 1: CAC silicone boot on a 4 in beaded tube
A Class 8 truck has a four-ply silicone boot on a 4 in CAC outlet. Pi tape behind the bead reads 4.53 in (115.1 mm). Map row: 4-1/2 to 5 in. The spring HD column offers 4ST425H at 90 percent, 4ST431H at 69 percent, 4ST438H (4.38 to 4.69 in) at 48 percent and 4ST450H at 10 percent. Plain 4TB0425 and 4TB0450 land at 90 and 10 percent, both poor. Silicone compresses, so 4ST438H, sitting mid-range, is the pick. See the 4 inch hose clamp size range guide for other families at this size.
Example 2: 6 in air intake elbow
A rubber intake elbow on an air cleaner outlet tapes at 6.30 in (160.0 mm). Map row: 6 to 6-1/2 in. Both T-bolt columns put this reading at the extremes: 4TB0600 and 4ST600H at 97 percent, 4TB0625 and 4ST625H at 16 percent. Hi-torque 4SCH662 (5.75 to 6.63 in) puts it at 63 percent, and so does HD 4CT650. On a low-pressure duct that is opened for filter service, 4SCH662 is the clean answer.
Example 3: truck radiator outlet, 2-1/2 in neck
A thick reinforced hose on a 2-1/2 in radiator outlet measures 3.06 in (77.7 mm) on the neck with calipers. Map row: 3 to 3-1/2 in. HD 4CT300 would sit at 92 percent, nearly fully open, while 4CT350 (2.75 to 3.63 in) sits at 35 percent. Firm hose barely compresses, so 35 percent is acceptable, and the stainless-screw 4CT350S suits a washed engine bay.
Example 4: 6 in dredge suction hose on a shank
The catalogue OD of a 6 in PVC suction hose is 7.17 in, which would put plain 4TB0700 (7.00 to 7.31 in) at a tidy 55 percent. Fitted on the shank, the tape reads 7.34 in (186.4 mm). Map row: 7 to 7-1/2 in. Now 4TB0700 is too small, and the plain series has a gap from 7.31 to 7.50 in. Spring HD 4ST725H reaches it at 29 percent, but the spring adds nothing on a water suction line. Hi-torque 4SCH762 (6.75 to 7.63 in) sits at 67 percent; order two per joint. Ordering from the catalogue OD would have delivered clamps that could not close.
Example 5: 8-1/2 in mine ventilation duct
A flexible duct on a fan spigot wraps at 27.08 in circumference, which is 8.62 in (218.9 mm). Map row: 8-1/2 to 9 in. 4SCH862, 4ST831H and 4CT850 all land at 97 to 99 percent, effectively at their limits. The usable choices are hi-torque 4SCH912 (8.25 to 9.13 in) at 42 percent and plain T-bolt 4TB0850 (8.50 to 8.81 in) at 39 percent.
| Example | Measured OD | Map row | Rejected (position) | Chosen part (position) |
|---|---|---|---|---|
| 1. CAC boot | 4.53 in (115.1 mm) | 4-1/2 to 5 in | 4ST425H (90%), 4TB0450 (10%) | 4ST438H (48%) |
| 2. Intake elbow | 6.30 in (160.0 mm) | 6 to 6-1/2 in | 4TB0600 (97%), 4ST625H (16%) | 4SCH662 (63%) |
| 3. Radiator hose | 3.06 in (77.7 mm) | 3 to 3-1/2 in | 4CT300 (92%) | 4CT350S (35%) |
| 4. Suction hose | 7.34 in (186.4 mm) | 7 to 7-1/2 in | 4TB0700 (out of range) | 4SCH762 (67%), two per joint |
| 5. Ventilation duct | 8.62 in (218.9 mm) | 8-1/2 to 9 in | 4SCH862 (99%), 4ST831H (97%) | 4SCH912 (42%) |
Sizing mistakes specific to heavy duty clamps
- Ordering by hose ID. “A 4 inch T-bolt” for a 4 in ID hose is the classic error. The 4TB0400 page itself tells buyers to match the hose outside diameter, not the inside. A 4 in ID hose with a 1/4 in wall needs a 4.5 in clamp, which is a different row on the map.
- Trusting a catalogue OD for a T-bolt. Example 4 shows a shank pushing a reading out of a 0.31 in range.
- Measuring over the bead. The number over a CAC bead is larger than the clamp seat, often by more than a whole T-bolt range. Order from it and the T-bolt will bottom out before it grips.
- Assuming every column is continuous. Both T-bolt families have gaps above 5.5 in. If your reading lands in one, switch columns rather than picking the nearest size.
- Confusing 4ST…H with 4ST…B. Both are spring-loaded T-bolts and share some range labels (4ST250H and 4ST250B both cover 2.50 to 2.81 in). The H parts are the heavy duty build with a 1/2 in nut. Copy the full part number, suffix included.
- Using a wide-range part where a standard one fits better. 4SCH916 covers 6.13 to 9.13 in, but on a 6.5 in hose most of its band ends up as tail. Use wide-range parts for mixed fleets and emergency kits; use the 7/8 in sizes for planned maintenance.
- Tightening past the rating to make a size work. The pages list 150 in-lb for 4SCH and the T-bolts and 92 in-lb for HD 4CT. If you need more than that to seal, the size is wrong or the hose end is worn.
For a side-by-side of when heavy duty is worth it at all, see heavy duty vs standard hose clamps. Worked part pages worth opening: the wide-range hi-torque 4SCH918 (4 to 6.13 in) and the largest spring HD T-bolt, 4ST831H (8.31 to 8.63 in).
Questions fleet and plant buyers send us about heavy duty sizes
What is the biggest diameter OneTouch heavy duty clamps reach?
Hi-torque 4SCH912 and 4SCH916 both reach 9.13 in (232 mm). The largest T-bolt is plain 4TB0850 at 8.81 in, and the largest spring HD T-bolt and HD constant torque clamps stop at 8.63 in. Above 9.13 in, ask us about larger options.
Why does my heavy duty hose clamp size chart show several parts for one OD?
Ranges overlap so you can choose the size that puts your reading near the middle of its travel. Work out the position in each candidate range and pick the one closest to roughly 40 to 60 percent.
How accurate does my measurement need to be for a T-bolt clamp?
Read to about 1/32 in or 1 mm. Most T-bolt ranges are only 5/16 in wide, so a 1/8 in error uses up 40 percent of the range. Measure on the fitting, behind any bead, and repeat the reading.
Can one hi-torque clamp cover a fleet with mixed duct sizes?
Within limits, yes. The wide-range 4SCH914, 4SCH918 and 4SCH916 span 2 to 3 in each. They suit mixed fleets and spares kits, but a standard 7/8 in range size usually sits better on a known diameter and leaves less loose tail.
My OD falls in a T-bolt gap. What should I do?
Read across the same row on the map. Hi-torque and HD constant torque have no gaps between 1 in and 8.63 in, and the other T-bolt family often covers the hole. Between 5.75 and 5.81 in, the standard spring-loaded 4ST575B is also an option.
Send your reading and we will match the map cell
Send a measured OD, the hose type and the job (boost, coolant, suction or duct), and we will tell you which cell on this heavy duty hose clamp size chart fits and whether another family sits better. Already running another brand? Look up its number in the clamp cross-reference to find the matching OneTouch part, or send the readings and quantities through our contact page for sizing help and a quote.