BIZOMAT MAKEOS · Fabrication
Brazed Sleeve Joint Plan (Overlap, Joint and Tube Capacity, Clearance, Filler)
For a tube brazed or soldered into a sleeve, how much overlap do I need, does the joint carry my load, is the clearance right and how much filler does it take?
Plan of a brazed or soldered sleeve (socket) joint on a tube: the overlap that makes the joint as strong as the tube wall with a safety factor (as the lap joint length tool, with the joint width taken as the tube circumference), the joint and tube capacities against your load, the diametral clearance against the filler’s range, and the volume and mass of filler to fill the gap.
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How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Tube outside diameter | mm | Outside diameter of the tube going into the sleeve. |
| Tube wall thickness | mm | Wall thickness of the tube. |
| Tube material tensile strength | MPa | Tensile strength of the tube material (annealed by brazing). |
| Shear strength of the filler joint | MPa | Shear strength of the brazed or soldered joint, from the filler supplier. |
| Safety factor on the overlap | Factor on the overlap over the length that just matches the tube wall. | |
| Overlap (socket depth) | mm | Overlap of the tube in the sleeve. |
| Axial load on the joint (0 = none) | N | Axial pull or push on the joint. |
| Clearance and filler | ||
| Diametral clearance | mm | Diametral clearance between tube and sleeve bore. |
| Smallest clearance for the filler | mm | Smallest clearance the filler supplier gives for capillary flow. |
| Largest clearance for the filler | mm | Largest clearance the filler supplier gives. |
| Filler density | g/cm³ | Density of the filler metal. |
What each input means
Open an input to see what it is, its units, the worked example and the common mistakes, with a small diagram.
What this means: Tube outside diameter
- What it is
- The outside diameter of the tube that goes into the sleeve or socket. Its circumference is taken as the width of the brazed joint, and it sets the tube’s own capacity.
- Units and format
- Enter a number in mm: millimetres. The form accepts 0.000001 mm to 2000 mm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 25 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- A larger diameter raises the joint capacity and the filler needed in proportion; the overlap needed is not changed.
- Get it right
- Use the outside diameter, not the nominal bore or the inside diameter.
What this means: Tube wall thickness
- What it is
- The wall thickness of the tube where it enters the sleeve. The overlap needed is worked out so that the joint is as strong as this wall.
- Units and format
- Enter a number in mm: millimetres. The form accepts 0.000001 mm to 100 mm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 1.5 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- The overlap needed rises in direct proportion to the wall thickness.
- Get it right
- Use the actual wall, not a schedule number; a thin-wall tube needs less overlap.
What this means: Tube material tensile strength
- What it is
- The tensile strength of the tube material in the condition it will be in after brazing, from the material data. It sets the tube’s capacity and the overlap that matches it.
- Units and format
- Enter a number in MPa: megapascals (1 MPa = 1 N/mm²). The form accepts 0.000001 MPa to 3000 MPa. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 210 MPa as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- The overlap needed rises in direct proportion to the tube strength.
- Get it right
- Brazing heat anneals many materials; use the annealed strength, not the hard-drawn figure.
What this means: Shear strength of the filler joint
- What it is
- The shear strength of the brazed or soldered joint along the overlap, from the filler supplier’s data for your joint design. It is spread uniformly over the overlap area.
- Units and format
- Enter a number in MPa: megapascals (1 MPa = 1 N/mm²). The form accepts 0.000001 MPa to 1000 MPa. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 70 MPa as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- The overlap needed falls in inverse proportion to it, and the joint capacity rises with it.
- Get it right
- Use the joint shear strength the supplier quotes, not the tensile strength of the filler alloy.
What this means: Safety factor on the overlap
- What it is
- A multiplier on the overlap beyond the length that just makes the joint as strong as the tube wall, set by your design rules or engineer.
- Units and format
- Enter a plain number with no unit. The form accepts 1 to 5. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 1.25 as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- The overlap needed rises in direct proportion to the factor.
- Get it right
- A factor of 1 gives the bare matching overlap with no margin for imperfect filling.
What this means: Overlap (socket depth)
- What it is
- The length of tube that sits inside the sleeve and is brazed, the socket depth you have or plan. It is compared with the overlap needed and sets the joint capacity.
- Units and format
- Enter a number in mm: millimetres. The form accepts 0.000001 mm to 1000 mm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 10 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Joint capacity and filler volume rise in direct proportion to the overlap.
- Get it right
- Measure the length actually filled with filler, not the full socket depth if the tube does not bottom out.
What this means: Axial load on the joint (0 = none)
- What it is
- The axial pull or push the joint must carry in service. Both the joint capacity and the tube capacity are compared with it.
- Units and format
- Enter a number in N: newtons. The form accepts 0 N to 100000000 N. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 8000 N as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Get it right
- Enter it in newtons (1 kN = 1000 N). With 0 the joint and tube capacity checks are skipped.
Clearance and filler
What this means: Diametral clearance
- What it is
- The clearance between the tube outside and the sleeve bore across the full diameter, bore minus tube. It is checked against the filler’s range and sets the filler volume.
- Units and format
- Enter a number in mm: millimetres. The form accepts 0 mm to 5 mm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 0.1 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Filler volume and mass rise in direct proportion to the clearance.
- Get it right
- This is diametral clearance; the gap on each side is half of it.
What this means: Smallest clearance for the filler
- What it is
- The smallest diametral clearance at which the filler supplier says the alloy will still flow into the joint by capillary action.
- Units and format
- Enter a number in mm: millimetres. The form accepts 0 mm to 5 mm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 0.05 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Get it right
- Check the supplier gives the range as diametral clearance; if it is per side, double it.
What this means: Largest clearance for the filler
- What it is
- The largest diametral clearance the filler supplier says the alloy will still fill reliably. Larger gaps tend to leave voids and weaken the joint.
- Units and format
- Enter a number in mm: millimetres. The form accepts 0 mm to 5 mm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 0.25 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Get it right
- Must be at least the smallest clearance, or the tool rejects the inputs.
What this means: Filler density
- What it is
- The density of the brazing or soldering filler alloy, from the supplier data sheet. It turns the filler volume in the gap into a mass.
- Units and format
- Enter a number in g/cm³: grams per cubic centimetre (1 g/cm³ = 1000 kg/m³). The form accepts 0.000001 g/cm³ to 25 g/cm³. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 9 g/cm³ as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Filler mass rises in direct proportion to density.
- Get it right
- Enter it in g/cm³; a value in kg/m³ must be divided by 1000.
Method and formulas
- Overlap needed = factor × t × S_tube ÷ τ_joint (as the lap joint length tool).
- Joint capacity = π OD × L × τ_joint; tube capacity = π (OD − t) t × S_tube.
- Filler volume = π OD × L × clearance ÷ 2 (the annular gap).
- Example: 5.625 mm overlap is needed; at 10 mm the joint carries 54.978 kN and takes 0.35343 g of filler.
Limitations
- Uniform shear along the overlap; very long overlaps do not gain in proportion.
- Strengths are for a sound, fully filled joint; voids and flux pockets cut capacity.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Size the socket depth for a brazed tube joint
- Check a soldered copper joint under load
- Estimate filler rings or wire per joint
Who it is for
- Fabrication engineers
- Design engineers
- Brazing technicians
What you get
- Overlap needed
- Joint and tube capacity against the load
- Clearance and filler quantity
Interpreting the result
- A joint whose overlap is about three wall thicknesses or more is usually stronger than the annealed tube beside it.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 1423–1430. Topic reference; no source tables or recommended settings are reproduced.
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Open the Brazed Sleeve Joint Plan (Overlap, Joint and Tube Capacity, Clearance, Filler) calculator