BIZOMAT MAKEOS · Fabrication
Angle Ring Cut Plan (Cut Length, Bars, Joints, Waste, Mass)
How long do I cut angle or flat bar to roll into rings for this shell, how many stock bars and joints do I need, and how much is wasted?
Cutting plan for rolled stiffening or flange rings of angle or bar fitted inside or outside a shell: cut length from the shell diameter corrected to the section’s neutral axis (as the length of angle bent to a ring tool), joints per ring when one ring needs more than one stock length, stock bars for the quantity with saw kerf, waste, mass of each ring and the material cost, with the waste checked against your limit.
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How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Correction from | choice | Whether the correction uses the neutral-axis distance or a length constant (as the ring length tool). |
| Section is | choice | Whether the ring sits inside or outside the shell. |
| Shell diameter at the back of the section | mm | Shell diameter at the back of the angle or bar. |
| Back of section to neutral axis | mm | Distance from the back of the section to its neutral axis. |
| Length constant | mm | Length constant from your section data. |
| Stock and cost | ||
| Rings needed | Number of rings. | |
| Stock bar length | m | Length of the stock bars. |
| Saw kerf and end trim per cut | mm | Material lost per cut, including end trim. |
| Section area | mm² | Cross-section area of the angle or bar. |
| Density | kg/m³ | Density of the material. |
| Material price | $/kg | Price of the material. |
| Largest waste | % | Largest share of bought length you accept as waste. |
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: Correction from
- What it is
- How the tool corrects the shell diameter to the length along the section’s neutral axis: from the neutral-axis distance of the section, or from a length constant in your section data.
- Units and format
- Choose one of 2 options from the list: Neutral-axis distance; Length constant.
- Example
- The form opens with “Neutral-axis distance” selected as a worked example. Choose the option that matches your case.
- Get it right
- Only the matching input is used: the neutral-axis distance for the first choice, the length constant for the second.
What this means: Section is
- What it is
- Whether the angle or bar ring sits inside the shell (its back against the shell’s inside) or outside it (its back against the shell’s outside). It decides whether the correction is subtracted or added.
- Units and format
- Choose one of 2 options from the list: Inside the shell (diameter is the inside of the shell); Outside the shell (diameter is the outside of the shell).
- Example
- The form opens with “Inside the shell (diameter is the inside of the shell)” selected as a worked example. Choose the option that matches your case.
What this means: Shell diameter at the back of the section
- What it is
- The diameter of the shell at the surface the back of the angle or bar rests against: the inside diameter for an inside ring, the outside diameter for an outside ring.
- Units and format
- Enter a number in mm: millimetres. The form accepts 0.000001 mm to 100000 mm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 6096 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Cut length rises by π times any increase in diameter.
- Get it right
- Match the diameter to the side the ring sits on, as chosen above.
What this means: Back of section to neutral axis
- What it is
- The distance from the back face of the angle or bar (the face against the shell) to the neutral axis of the section in the plane of bending, from section tables.
- Units and format
- Enter a number in mm: millimetres. The form accepts 0 mm to 1000 mm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 22.5 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- The cut length changes by 2π times this distance.
- Get it right
- Used only with the neutral-axis method; take the distance for the leg that bends, measured from the back.
What this means: Length constant
- What it is
- A length correction for the section, from your section data or shop tables, added to or subtracted from π times the diameter.
- Units and format
- Enter a number in mm: millimetres. The form accepts 0 mm to 10000 mm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 109.7 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Get it right
- Used only with the length constant method; make sure it is for the same section size and leg orientation.
Stock and cost
What this means: Rings needed
- What it is
- The number of identical rings to be cut and rolled.
- Units and format
- Enter a plain number with no unit. The form accepts 1 to 100000. Use a whole number. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 4 as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
What this means: Stock bar length
- What it is
- The length of the stock bars the angle or bar is bought in.
- Units and format
- Enter a number in m: metres. The form accepts 0.000001 m to 100 m. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 6 m as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Sets how many joints each ring needs and how many bars to buy.
- Get it right
- Enter metres; the cut length is reported in millimetres.
What this means: Saw kerf and end trim per cut
- What it is
- The length lost at each cut: the saw kerf plus any squaring or end trim.
- Units and format
- Enter a number in mm: millimetres. The form accepts 0 mm to 100 mm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 3 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Get it right
- Include the trim to remove rolled or damaged ends, not only the blade width.
What this means: Section area
- What it is
- The cross-section area of the angle or bar, from section tables.
- Units and format
- Enter a number in mm²: square millimetres. The form accepts 0.000001 mm² to 1000000 mm². Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 900 mm² as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Ring mass and material cost rise in proportion.
What this means: Density
- What it is
- The density of the section material, used to turn length and area into mass.
- Units and format
- Enter a number in kg/m³: kilograms per cubic metre. The form accepts 0.000001 kg/m³ to 20000 kg/m³. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 7850 kg/m³ as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
What this means: Material price
- What it is
- The price paid for each kilogram of the section material.
- Units and format
- Enter a number in $/kg: money per kilogram. The form accepts $0/kg to $100000/kg. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with $2/kg as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
What this means: Largest waste
- What it is
- The largest share of the bought bar length you accept as offcuts and kerf, from your costing or shop rules.
- Units and format
- Enter a number in %: percent: the number is read as a percentage, so type 8 for 8 %. The form accepts 0% to 100%. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 10% as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
Method and formulas
- Cut length = π D ∓ 2π x (or ∓ the length constant), minus for a ring inside the shell (as the length of angle bent to a ring tool).
- Joints per ring = 1 if one bar covers it, otherwise ⌈length ÷ stock⌉; total length = rings × (length + joints × kerf); bars = ⌈total ÷ stock⌉.
- Waste = 1 − rings × length ÷ (bars × stock); mass = length × area × density.
- Example: cut 19,010 mm per ring with 4 joint(s); 13 bars of 6 m, 2.514% waste; each ring 134.3 kg.
Limitations
- Cut length to the neutral axis; rolling springback and joint preparation need trial allowances.
- Waste assumes offcuts are not reused.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Order angle for tank or duct stiffening rings
- Cut blanks for rolled flanges
- Estimate joints and waste for a ring job
Who it is for
- Boilermakers
- Fabrication supervisors
- Estimators
What you get
- Cut length and neutral diameter
- Joints per ring, stock bars and waste
- Ring mass and cost
Interpreting the result
- Longer stock bars cut the number of joints; check what lengths the mill supplies.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 2593. Topic reference; no source tables or recommended settings are reproduced.
BIZOMAT tools are screening and decision-support utilities. Verify important financial, engineering, safety, legal or operational decisions using appropriate professional standards and your organisation’s approved data.
Open the Angle Ring Cut Plan (Cut Length, Bars, Joints, Waste, Mass) calculator