Take two hoses with exactly the same 1 in bore. One is a textile-reinforced 300 psi jackhammer air hose that measures about 1.43 in across. The other is a heavier-wall hose that measures 1.75 in. Both slide onto the same 1 in interlocking stem, but they do not take the same clamp. On a typical interlocking hose clamp size chart, the air hose falls in the 4-bolt, 4-finger band for 1 in hose, which runs from about 1.41 to 1.56 in. The thicker hose is outside that band altogether and needs a 4-bolt, 2-finger clamp from the 1.69 to 1.94 in band. Published 1 in steam hoses, at roughly 1.50 to 1.55 in, sit right on the seam between the two families. The bore picks the stem. The wall picks the clamp.
This page is a measuring reference. It covers the three measurements that have to agree, a representative chart rebuilt from published maker data, a field method for stiff steam hose, three worked examples, and a record sheet you can copy. Up front: OneTouch Exim does not make or sell interlocking clamps, stems or ground-joint couplings, and is not affiliated with Dixon, Kuriyama or any other brand named here. Order the clamp from your system’s maker or distributor, and use this page to get there with the right numbers. The parts themselves are explained in our explainer on what an interlocking hose clamp is. Steam duty rules and retirement criteria are in the guide to choosing an interlocking hose clamp.
The three measurements that must agree
A worm gear clamp needs one number. An interlocking clamp needs three, and each answers a different question. If one disagrees with the others, the assembly is wrong, even if the clamp looks fine on the bench.
1. Hose ID decides which stem
The inside diameter is the nominal hose size (1/2, 3/4, 1 in and so on). It selects the stem shank, and through the stem it fixes which row of the clamp chart you may read. Capital Rubber’s bolted clamp sheet warns against pairing a clamp and coupling with mismatched inside diameters. It points out that a clamp whose OD range fits can still fail to seat, because its fingers are sized to the collar on a stem of one particular bore. The ID is normally printed on the hose brand line. If the print has worn off, caliper the bore at a fresh square cut and round to the nearest nominal size. A reading stuck between two sizes usually means metric hose, which you settle with the stem maker before anything else.
2. Hose OD decides which clamp within that ID
Each ID row carries two to five clamps covering OD bands that are often only 1/8 to 1/4 in wide. The OD tells you which one to buy, so the reference condition matters. Dixon’s Boss clamp selection procedure says to measure the free OD before the stem is inserted, and to read the chart against that number. Growth caused by the stem is built into the clamp design. You do not add it yourself.
3. Stem collar identity decides which system
The fingers hook behind a raised collar on the stem, and that collar’s diameter and profile belong to one system. Capital Rubber describes Boss-pattern clamps as working with ground-joint and Chicago-type universal stems that carry the matching ring. Kuriyama says its 2-, 4- and 6-bolt clamps have a lip that engages the collar on its own ground-joint shanks. Similar is not the same as interchangeable. Capital Rubber marks some clamps as unsuitable for certain ground-joint female and male NPT stems, and Dixon’s list flags its 2 in four-finger clamps as not for use with a named set of its own stems. So record the stem’s marking and part number, caliper the collar, and photograph it side-on. A distributor with ID, free OD and stem identity can pick the clamp. One with only the bore is guessing.
ID picks the stem, OD picks the clamp, the collar picks the catalog. If any of the three is a guess, stop and measure.
Interlocking hose clamp size chart (representative)
This chart is re-tabulated from Dixon’s published Boss clamp lists (2-bolt, 4-bolt 2-finger, 4-bolt 4-finger and 6-bolt patterns) and cross-checked against Capital Rubber’s sheet, whose 2-bolt and 4-bolt bands agree to within rounding. Individual clamps are grouped into OD bands for each ID and style. Part numbers are left out on purpose, because they change and some are being phased out. Inch values are the printed 64ths as decimals. Millimeters are inches × 25.4, rounded to 0.1.
| Hose ID | Typical clamp style | OD bands (in) | OD bands (mm) |
|---|---|---|---|
| 1/4 in | 2-bolt, 2-finger | 0.562–0.656 | 14.3–16.7 |
| 3/8 in | 2-bolt, 2-finger | 0.688–0.875 | 17.5–22.2 |
| 1/2 in | 2-bolt, 2-finger (3 sizes) | 0.812–0.938 / 0.938–1.062 / 1.062–1.188 | 20.6–23.8 / 23.8–27.0 / 27.0–30.2 |
| 1/2 in | 4-bolt, 4-finger | 0.906–1.031 | 23.0–26.2 |
| 3/4 in | 2-bolt, 2-finger (3 sizes) | 1.156–1.312 / 1.312–1.500 / 1.500–1.688 | 29.4–33.3 / 33.3–38.1 / 38.1–42.9 |
| 1 in | 4-bolt, 4-finger | 1.406–1.562 | 35.7–39.7 |
| 1 in | 4-bolt, 2-finger (3 sizes) | 1.531–1.719 / 1.688–1.938 / 1.938–2.125 | 38.9–43.7 / 42.9–49.2 / 49.2–54.0 |
| 1-1/4 in | 4-bolt, 2-finger (3 sizes) | 1.500–1.781 / 1.781–2.094 / 2.125–2.375 | 38.1–45.2 / 45.2–53.2 / 54.0–60.3 |
| 1-1/4 in | 4-bolt, 4-finger (2 sizes) | 1.688–1.875 / 1.875–2.062 | 42.9–47.6 / 47.6–52.4 |
| 1-1/2 in | 4-bolt, 2-finger (5 sizes) | 1.812 up to 2.750 | 46.0 up to 69.8 |
| 1-1/2 in | 4-bolt, 4-finger (2 sizes) | 2.000–2.125 / 2.062–2.250 | 50.8–54.0 / 52.4–57.1 |
| 2 in | 4-bolt, 2-finger (4 sizes) | 2.344–2.531 / 2.500–2.781 / 2.750–3.062 / 3.094–3.438 | 59.5–64.3 / 63.5–70.6 / 69.8–77.8 / 78.6–87.3 |
| 2 in | 4-bolt, 4-finger (3 sizes) | 2.250–2.500 / 2.500–2.750 / 2.750–3.062 | 57.1–63.5 / 63.5–69.8 / 69.8–77.8 |
| 2-1/2 in | 4-bolt, 2-finger (2 sizes) | 3.094–3.438 / 3.500–3.938 | 78.6–87.3 / 88.9–100.0 |
| 2-1/2 in | 4-bolt, 4-finger | 3.062–3.500 | 77.8–88.9 |
| 3 in | 4-bolt, 2-finger (3 sizes) | 3.500–3.938 / 3.812–4.062 / 4.062–4.438 | 88.9–100.0 / 96.8–103.2 / 103.2–112.7 |
| 3 in | 4-bolt, 4-finger (4 sizes) | 3.500 up to 4.500 | 88.9 up to 114.3 |
| 3 in | 6-bolt, 3-finger | 4.250–4.812 | 107.9–122.2 |
| 4 in | 6-bolt, 3-finger (4 sizes) | 4.625 up to 5.938, overlapping | 117.5 up to 150.8 |
| 6 in | 6-bolt, 6-finger (2 sizes) | 6.875–7.375 / 7.500–8.000 | 174.6–187.3 / 190.5–203.2 |
Reading the interlocking hose clamp size chart without tripping
- Stay in your ID row. A 1-1/4 in hose at 1.60 in OD also falls inside a 1 in band (1.531–1.719 in), but that clamp’s fingers suit a 1 in collar.
- Bands touch and overlap. Neighbors often share an end value or overlap by 1/32 to 1/16 in. The tie-break rules below decide those cases.
- 2 bolt vs 4 bolt interlocking clamp is set by size. In Dixon’s list, 2-bolt clamps stop at 3/4 in hose, although Capital Rubber also shows 2-bolt patterns for 1 in. Four bolts cover about 1 to 3 in, plus a single 4-finger clamp at 1/2 in, and six bolts appear from 3 in up.
- Brands do not share breakpoints. Kuriyama lists its 3/4 in 2-bolt clamp at 1-5/32 to 1-9/32 in (1.156–1.281 in), while the comparable Dixon band runs to 1.312 in.
Choosing between two clamps that both fit
Dixon’s selection procedure gives three tie-break rules. They run against the instinct most fitters bring over from worm gear clamps.
- Steam hose: pick the clamp whose upper “To” value is closest to your measured OD. That leaves the most travel for re-tightening as heated rubber cold-flows away from the bolts.
- Hard-wall hose with wire: if the OD is at or near a clamp’s maximum, you may need the next size up. A wired wall hardly compresses, so a clamp at the top of its range may not close enough to seat.
- Soft-wall hose without wire: if the OD is at or near a clamp’s minimum, you may need the next size down, because a soft wall squeezes so far that the clamp can run out of travel.
Steam hose is usually wire-braided, so rules 1 and 2 can pull in opposite directions inside an overlap. When they do, send the exact free OD, hose construction and stem part number to the system maker and let them decide. Example 2 shows this with real numbers.
How to measure hose OD for an interlocking clamp on stiff steam hose
Steam hose is thick, often slightly oval from the reel, and its wrapped cover may carry a faint spiral ridge. With bands only 1/8 to 1/4 in wide, a 1/32 in error can mean the wrong clamp. Use at least two of the methods below and compare them. General technique is covered in our guide to measuring hose clamp size, and this is the interlocking version.
- Cut square first. A crushed or flared end does not represent the hose.
- Measure 2 to 3 in back from the end. Dixon’s diameter tape procedure puts the tape there, which is roughly where the clamp body sits.
- Both ends, twice each. Dixon advises this because tolerance and spec changes between production runs move the OD.
- Fresh hose at room temperature. A section that has been clamped before has cold-flowed and will read small.
Method A: diameter (pi) tape
A pi tape is graduated so that one wrap reads diameter directly. Dixon’s version reads in 64ths, which matches the way its clamp lists are printed. Wrap it square to the hose axis, scale up, buckle low, pull it snug without stretching the cover, and read at the reference line. The tape averages the hose, giving the diameter of a circle with the same perimeter as an oval section. It also hides ovality, so pair it with Method B.
Method B: calipers at 90 degrees
Close the jaws until they just touch the cover, read, rotate the calipers 90 degrees about the hose axis at the same spot, and read again. Squeezing is the classic error on soft covers and can take off a 64th or more. The two readings give you both mean and out-of-round.
Method C: string wrap, with the maths
Wrap a thin, non-stretch cord once around the hose, mark the overlap, lay it flat and measure the length C. Divide by π, then subtract the cord thickness. The cord’s centerline sits half a thickness outside the surface all the way round, which adds one full thickness to the calculated diameter.
OD = (C ÷ 3.1416) − cord thickness
Example: a 1 mm (0.039 in) cord around a 1 in steam hose wraps 5.00 in. 5.00 ÷ 3.1416 = 1.592 in. Subtract 0.039 to get 1.553 in, which is 39.4 mm. Skip the correction and you read 1.59 in, a different band on the chart above.
Loose hose versus over the stem: why the loose number rules
A stem shank is slightly larger than the bore, so pushing it in stretches the wall and grows the OD. How much it grows depends on wall stiffness, so a soft air hose and a braided steam hose grow differently over the same stem. Read an over-stem number against a free-OD chart and you tend to pick a clamp one band too large. On steam, that clamp runs out of re-torque travel early. That is why the makers fix the reference as free OD.
The over-stem check still earns its place as a dry fit. Before torquing, slide the clamp on and confirm the fingers clear the collar and the bolt lugs still have a visible gap to close. If the halves touch at hand pressure, the clamp is too small. If they stand well apart at full bolt engagement, it is too large. Either way, recheck the free OD first. The tightening sequence is in our step-by-step guide to installing an interlocking hose clamp.
Ovality and tolerance
Ovality from the two caliper readings is (max − min) ÷ mean × 100. A steam hose reading 1.57 and 1.53 in has a mean of 1.55 in and 2.6 percent ovality. That is normal for reeled hose, and the clamp halves round it up as they close. What matters more is the distance to a band edge. If the mean sits within about 1/32 in (0.8 mm) of an edge, ovality and measuring error together exceed your margin, and you are in tie-break territory. Re-measure, apply the three rules, and refer close calls to the maker.
When you check a reading against an interlocking hose clamp size chart, hose spec sheets make a good sanity check, and they show how far ODs spread on one nominal size. Aeroquip lists its H9568 1 in 250 psi steam hose at 1.55 in (39.37 mm) on Danfoss’s product page. Other 1 in hoses we checked range from 1.43 in (a textile jackhammer air hose) to 1.50 and 1.52 in (two 250 psi steam hoses). That is a 0.12 in spread that straddles the 4-finger and 2-finger 1 in bands of a typical interlocking hose clamp size chart. If your tape says 1.45 in on a hose sold as 1.55 in, question the hose or the measurement before you order.
Three worked examples
Example 1: 3/4 in ID, OD 1.30 in
A wash-down line runs 3/4 in steam-rated hose on interlocking stems. The pi tape reads 1-19/64 in (1.297 in) at both ends. Calipers give 1.31 and 1.29 in, a mean of 1.30 in (33.0 mm) with about 1.5 percent ovality.
- Row: 3/4 in, which means 2-bolt, 2-finger clamps.
- Candidates: 1.156–1.312 in and 1.312–1.500 in. A reading of 1.30 in is inside the first band, 0.012 in below its top.
- Steam rule: the first band’s top is 0.012 in away and the second’s is 0.200 in away, so the smaller clamp wins.
- Hard-wall check: braided hose near the top of a range calls for a dry fit. A visible lug gap before torque confirms it.
If the hose had measured 1.34 in, as one published 3/4 in braided steam hose does, the smaller clamp would be ruled out. The 1.312–1.500 in clamp would be the only candidate.
Example 2: 1 in ID with two possible OD bands
A heavy-wall 1 in braided hose for steam service measures 1.70 in free OD (43.2 mm). Two 4-bolt, 2-finger bands contain it, 1.531–1.719 in and 1.688–1.938 in, and 1.70 in sits in their overlap.
- The steam rule favors the smaller clamp, whose top is 0.019 in above the OD.
- The hard-wall rule warns that wire braid 0.019 in under a maximum may need the next size up.
- Re-measure the other end. At 1.68 in, the smaller clamp is comfortable. At 1.72 in, it is out of range and only the larger clamp fits.
If both ends really read 1.70 in, send the readings, hose spec and stem part number to the maker and ask which clamp they approve. Never over-torque the smaller clamp to force it closed. The bolts are designed for a single bend. For contrast, the 1.43 in jackhammer hose from the opening fits the same stem bore but belongs in the 4-finger 1.406–1.562 in band. That clamp may carry its own stem restrictions, which is why measurement 3 is not optional.
Example 3: 2 in ID, choosing the 4-bolt pattern
A 2 in, 250 psi 3-wire braid steam hose measures 2.72 in free OD (69.1 mm), the same figure Aeroquip publishes for its 2 in H0084 hose. At 2 in there is no 2-bolt option, so the choice is between the two 4-bolt families.
- 4-bolt, 2-finger: 2.500–2.781 in, with its top 0.061 in above the OD.
- 4-bolt, 4-finger: 2.500–2.750 in, with its top 0.030 in above the OD. On the steam rule alone, this one edges it.
- Stem check: Dixon’s list marks its 2 in four-finger clamps as not for use with certain stems. The stem you own decides which column you may read.
- Torque: the published 2 in clamps call for 40 to 60 ft-lb on dry bolts, so have a wrench that reads that range.
At 2.76 in, the hose would miss the 2.500–2.750 in four-finger band by 0.01 in and land at the very bottom of the next one, 2.750–3.062 in. That is the wrong end of a band for steam, so repeat any reading that tight.
Measurement record template
Fill this in for each assembly before you open any interlocking hose clamp size chart, and send it with any order. It answers a distributor’s questions before they ask.
| Field | How to get it | Example |
|---|---|---|
| Hose brand and type | Brand line | 250 psi steam, braided |
| Nominal ID | Print, or caliper at square cut | 1 in |
| Free OD, end A (2 reads) | Pi tape, 2–3 in from cut | 1.547 / 1.547 in |
| Free OD, end B (2 reads) | Same | 1.562 / 1.547 in |
| Caliper max / min at 90° | Light touch, same spot | 1.57 / 1.53 in |
| Mean OD, ovality, mm | (max − min) ÷ mean; × 25.4 | 1.55 in, 2.6%, 39.4 mm |
| Wall type | Wire / no wire | Wire braid |
| Service | Medium, pressure, temperature | Saturated steam, 150 psi |
| Stem brand and part number | Stem marking or invoice | (as marked) |
| Collar OD and photo | Caliper; side-on photo | (measured) |
| Candidate clamp(s) | Maker’s current sheet | Two bands, ask maker |
| Dry-fit check | Lug gap; fingers clear collar | Gap visible, fingers seat |
Mistakes that put the wrong clamp on the hose
- Ordering by bore only. “1 in Boss clamp” covers at least four interlocking clamp sizes on the chart above.
- Reading an over-stem OD against a free-OD chart. You end up a band too large and lose re-torque travel.
- Measuring where the old clamp sat. Cold-flowed rubber reads small.
- Squeezing the calipers, or skipping the cord correction. Either can move you across a band edge.
- Mixing units mid-job. 1/64 in is 0.397 mm, so 1-35/64 in is 1.547 in or 39.3 mm. Convert once and write both.
- Using one maker’s chart for another’s clamp, or leaving out the stem part number.
- Fitting a band clamp to steam hose because the right part is back-ordered. Wait for the right part.
When the hose is not on interlocking stems
Many large hoses that look like Boss jobs actually run on plain barbed tails: suction, water transfer, low-pressure air. There is no collar for fingers to grip, so an interlocking clamp has nothing to lock to. For non-steam hose on a plain tail, the usual answer is a heavy band clamp sized to the same carefully measured free OD.
That is where OneTouch Exim fits. Our T-bolt clamps use a 3/4 in band and our hi-torque worm drive clamps a 5/8 in band, both rated to 150 in-lb, for plain-tail hose from about 2 in OD up. Typical duties are covered in our notes on suction and discharge hose clamps and clamps for air compressor lines, and band ranges are listed in our general size chart in mm and inches. A T-bolt size spans only about 0.31 in, so it gets the same OD discipline. For band clamp torque, see how to tighten without over-torquing. Boat plumbing is covered separately in our marine hose clamp size chart. None of these band clamps belongs on steam hose or interlocking stems. For material choices within an interlocking system, see 304 vs 316 interlocking clamps, then buy from the system maker.
Interlocking hose clamp size chart FAQs
How do I measure hose OD for an interlocking clamp?
Cut the end square and measure the free hose 2 to 3 in from the cut, before any stem goes in. A diameter tape reading in 64ths is the best single tool. Add calipers at two positions 90 degrees apart to catch ovality. Read both ends of the length twice each, and use the mean to pick the interlocking clamp OD range from the maker’s chart.
What is the difference between a 2-bolt and 4-bolt interlocking clamp?
Mainly hose size and clamping load. In published Boss-style lists, 2-bolt clamps mostly cover 1/4 to 3/4 in ID, 4-bolt clamps roughly 1 to 3 in, and 6-bolt clamps appear from 3 in upward. More bolts spread the load around a larger circumference. You do not choose the bolt count on its own. Your ID and OD point to a row, and the row gives the pattern.
Is a Boss clamp size chart the same across brands?
The layout is similar, with ID rows and narrow OD bands, but the breakpoints are not. One maker’s 3/4 in 2-bolt clamp might stop at 1.281 in OD while another’s runs to 1.312 in, and collar profiles can differ too. Read the chart from the maker of your stems, and never move numbers from one brand’s sheet onto another brand’s parts.
Should I measure the hose before or after inserting the stem?
Before. Clamp bands are written against free OD, and Dixon’s procedure says to measure before insertion. The shank stretches the hose by an amount that depends on wall stiffness, so an over-stem reading pushes you toward a clamp that is too big. Over the stem, do only a dry fit to confirm the lugs still have a gap to close and the fingers clear the collar.
My hose OD falls in two clamp ranges. Which do I pick?
For steam, choose the clamp whose top value is closest to your OD, which keeps travel in reserve for re-torquing. Wire-reinforced hose near a maximum may need the next size up, and soft hose near a minimum may need the next size down. If those rules conflict, send both end readings, the hose construction and the stem part number to the maker for a decision.
What steam hose clamp size fits a 1 inch steam hose?
That depends on OD, not the 1 in bore. Published 1 in steam hoses we checked run about 1.50 to 1.55 in OD. That sits near the boundary between the 4-finger band (about 1.406–1.562 in) and the first 2-finger band (about 1.531–1.719 in) on a typical chart. Measure your hose, note the stem part number, and confirm with the maker.
How do I convert the 64ths on a Boss clamp chart to mm?
Divide the 64ths by 64, add the whole inches, and multiply by 25.4. For example, 1-20/64 in is 1.3125 in, which is 33.3 mm. One 64th is just under 0.4 mm, so one decimal place is enough. If your readings are metric, convert them to decimal inches before comparing against an inch chart, and keep both on the record sheet.
Does OneTouch Exim sell interlocking or Boss clamps?
No. OneTouch Exim does not make or stock interlocking clamps, stems or ground-joint couplings, and is not affiliated with any brand that does. Buy those from your system’s maker or distributor. We supply band clamps, including T-bolt, hi-torque, constant torque, lined, worm gear and V-band, for non-steam hose on plain tails.
Send us the numbers, even if the answer is “not us”
Have a plain-tail line that needs a band clamp? Send OneTouch Exim the free OD readings from your record sheet, the hose type, the medium, the temperature and pressure, and any part number from the clamp you are replacing. Our clamp cross-reference converts many OEM codes. We will propose T-bolt or hi-torque sizes and quote from a few pieces to export cartons through the quote request page, or on WhatsApp at +91-7838759114. If your sheet shows steam on Boss stems, we will tell you so and send you back to the system maker.