A T-bolt clamp is a heavy-duty hose clamp with a solid band, a single bolt running through a trunnion, and a 360° sealing surface. It holds far more than a worm-drive band — but only if it was sized to the hose it is sitting on. Each T-bolt size closes over a narrow range of diameters, so a clamp ordered off the hose bore, or off a catalogue nominal, often bottoms out before it grips or will not close at all.
This guide covers how to measure for a T-bolt clamp, how to read the series and size code, and the tightening figures that go with each size.
The four decisions, in order
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Measure the hose outside diameter — with the tail inserted
T-bolt clamps are sized by the outside diameter (OD) of the hose, not the bore. The hose swells over the barb of the tail, so measure over the cover at the point where the clamp will actually sit, with the tail already pushed home.
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Pick the band material
Plated carbon steel for dry, indoor and cost-driven work; SS304 band with SS305 screw and nut for general outdoor and wet duty; 316 for salt spray and chlorides.
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Pick the mandrel — hollow or solid
The mandrel (the trunnion the bolt passes through) is what separates the series. Hollow spreads load and suits softer hose; solid takes higher and repeated torque.
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Check that a T-bolt is the right clamp for the duty
Steam, spiral-wire hose and very large bores each have a better answer. See the last section before you order.
Step 1 in detail: how to measure hose OD for a clamp
Use a pi tape or a vernier across two directions and take the larger reading — hose is rarely perfectly round once a tail is inside it. If you only have a tape measure, measure the circumference and divide by 3.14.
“Clamp for 2 inch hose” is not a size. A 2″ bore suction hose and a 2″ bore air hose can differ considerably on the outside, and a T-bolt that fits one will be useless on the other. Send us the OD in millimetres, measured over the tail, and we will match the part number.
Step 2 and 3 in detail: T-bolt clamp series
The series letter tells you the band material, the mandrel and the number of bolts. The three digits after it are the size code, which tracks the hose OD in millimetres.
| Series | Band material | Mandrel | Bolts |
|---|---|---|---|
| EDA | Carbon steel, colour plated | Hollow | 1 |
| EDB | SS304 or SS305 | Hollow | 1 |
| EDC | Carbon steel, colour plated | Solid | 1 |
| EDD | SS304 or SS305 | Solid | 1 |
| EDF / EDG | Plated carbon steel, or SS304 / SS305 | Solid | 2 |
So EDB067 is a single-bolt stainless T-bolt clamp with a hollow mandrel for hose of around 67 mm OD, and EDD067 is the same clamp with a solid mandrel. The stainless series run from size 019 to 252, covering hose OD from 17 mm to 252 mm. Grade 316 is available on request in every series.
Choose solid where the joint will be re-torqued repeatedly or sees heavy vibration; choose hollow on softer or thinner-wall hose, and on large sizes where weight matters.
T-bolt clamp size chart: band and torque by size range
Band width and thickness step up with the size range, and so does the torque the bolt can take.
| Size code | Band width × thickness | Recommended tightening |
|---|---|---|
| 017 – 028 | 18 × 0.8 mm | 8 N·m |
| 031 – 043 | 20 × 1.0 mm | 10 N·m |
| 047 – 067 | 22 × 1.2 mm | 10 N·m |
| 073 – 130 | 24 × 1.2 mm | 20 N·m |
| 139 – 252 | 26 × 1.6 mm | 20 N·m |
Each individual part number closes over a range of a few millimetres within its size code. Tell us the measured OD and we will confirm the exact part, or send the drawing for that part number.
How tight should a T-bolt clamp be?
To the recommended figure for its size, with a torque wrench — not by feel, and not until it stops turning. Going well past it does not add grip; it puts the bolt and band at risk. Ask us for the maximum figure for a specific part number.
- Under-torqued, the joint weeps under pressure surges and the hose can creep off the tail.
- Over-torqued, the bolt yields or the band bites into the cover, and the clamp should not be refitted.
- Re-check after the first heat cycle. Rubber takes a compression set. On a new assembly, and after the first run on anything that gets warm, re-torque rather than assuming the first setting held.
Thin-wall and soft-cover hose may need less than the recommended figure. If you are unsure, tell us the hose construction.
When a T-bolt is not the right clamp
| Duty | Use instead | Why |
|---|---|---|
| Steam and hot water hose | DIN 2817 / EN 14423 safety clamp | An internal rim locks behind the shank collar, so the coupling cannot be pushed out of a hose softened by heat. |
| Spiral-wire (helix) hose | Helix spiral wire clamp | Follows the wire so the load sits on the reinforcement. It must match the hand of the helix. |
| Large-bore suction and delivery | Double bolt clamp | The highest clamping force over a wide band. |
| Light water, air and coolant lines | Worm-drive band | Cheaper, wider adjustment range, and adequate for the load. |
The stainless trap
“Stainless clamp” often describes only the band. On many clamps on the market the bolt, nut or trunnion is plated carbon steel, and that is where the rust starts — the band still looks perfect while the bolt seizes. When you compare quotations, ask what each part is made of. Our EDB and EDD series use an SS304 band with SS305 screw and nut.
Before you send an enquiry
- Hose OD in mm, measured over the tail where the clamp will sit
- Band material — plated steel, 304, or 316
- Hollow or solid mandrel, or the duty if you would like us to recommend one
- Quantity per size, and packing or private-label requirements
Get T-bolt clamps from the factory
We manufacture T-bolt clamps in our own plant in Taiwan under ISO 9001, and have done since 1976. Send the hose OD, material and volume and we will come back with part numbers and a quotation within 24 hours. OEM and private label welcome.
Request a quotation