Short answer: Gas-cut (oxy-fuel) MS circles are cut from mild steel plate with a torch, so they need a machining allowance if the final part has tight dimensions. In your enquiry, give the outside diameter (OD), inside diameter (ID) for rings, plate thickness, quantity, grade (for example IS 2062 E250) and whether the sizes are finished or rough-cut. Weight in kg = 0.006165 × (OD² − ID²) × thickness ÷ 1000, with all sizes in mm. For example, a 500 mm OD × 200 mm ID ring, 25 mm thick, weighs about 32.4 kg.
This guide is for fabricators, flange makers, machine shops and traders in India who buy MS circles and rings cut from plate.
Should MS circles be gas-cut or plasma-cut?
Oxy-fuel cutting heats the steel and then blows a jet of oxygen through it. The oxygen "chemically combines with the iron" and the molten oxide is blown out, which is what makes the cut. Plasma cutting melts the metal with an electric arc and a jet of ionised gas.
| Oxy-fuel (gas) cutting | Plasma cutting | |
|---|---|---|
| Materials | Low- to medium-carbon steel and wrought iron. Stainless steel and cast iron need powder injection. | Steel, stainless steel, aluminium, brass, copper and other conductive metals |
| Thickness range | 0.5 mm to 250 mm (TWI) | Up to 38 mm hand-held and up to 150 mm on CNC machines (Wikipedia) |
| Cut edge | Some hard oxide slag ("dross") that is removed by tapping or grinding (Wikipedia) | The kerf is "wider at the top surface … than at the bottom", so edges can have a slight bevel |
| Equipment | Low cost, manual or mechanised (TWI) | Higher equipment cost; usually CNC for accurate parts |
Swipe sideways to see the whole table.
Sources for the rows without their own link: Wikipedia, Oxy-fuel, TWI and Wikipedia, Plasma cutting.
Rule of thumb: for thick MS plate, oxy-fuel is the usual method. Plasma is used for thinner plate, for stainless steel or aluminium, and where speed on thin sheet matters.
Heat-affected zone (HAZ). Any thermal cut heats the edge. The fuel gas and flame setting change how wide the heat-affected zone is and how much the part distorts (TWI). If the edge will be welded or machined to a fine finish, allow for removing this layer.
What tolerance does a gas-cut MS circle have?
There is no single "standard tolerance" for a gas-cut circle. The accuracy depends on:
- the plate thickness (thicker plate means a wider kerf and more edge taper);
- whether the circle is cut by hand torch, a profile machine or CNC;
- the torch condition, gas purity and cutting speed. TWI notes that a 1% drop in oxygen purity typically reduces cutting speed by 25% (TWI).
The international standard for classifying thermal cuts and their quality tolerances is ISO 9013. If you need a stated tolerance class, name it in the order.
The plate thickness has its own tolerance too. IS 2062 says rolling and cutting tolerances follow IS 1852 unless the buyer and mill agree otherwise. A "25 mm" plate is not exactly 25.00 mm.
How to handle this in practice:
- Decide whether you are ordering finished size (cut to your final OD/ID) or rough size (oversize on the OD and undersize on the ID, so you can machine to final size).
- If you will machine the part, state the machining allowance per side you want on the OD, the ID and, if needed, the faces.
- State the tolerance you need on OD and ID (for example "+X / −0 mm") and ask the supplier to confirm it in writing before cutting.
- For stacks of the same size, ask for a first-piece check before the full batch is cut.
Which IS 2062 plate grade should you ask for?
Most structural MS plate in India is made to IS 2062:2011, "Hot rolled medium and high tensile structural steel". The key points for a circle buyer:
- Grades are named by minimum yield strength in MPa: E250, E275, E300, E350, E410, E450, E550, E600 and E650.
- Sub-qualities A, BR, B0 and C show the impact-test requirement. A: no impact test. BR: test optional, at room temperature. B0: test at 0 °C. C: test at −20 °C.
| Grade | Min. tensile strength (MPa) | Min. yield stress (MPa), <20 / 20–40 / >40 mm |
|---|---|---|
| E250 | 410 | 250 / 240 / 230 |
| E350 | 490 | 350 / 330 / 320 |
Swipe sideways to see the whole table.
Source: IS 2062:2011, Table 2.
Traceability matters. IS 2062 requires heavy and plate-mill products to be marked with the cast number (clause 20.2) and the ladle analysis to be reported in the test certificate (clause 8.1). The standard also says material "for which the metallurgical history is not fully documented or not known" is not acceptable under it (clause 6.3). So:
- if your drawing calls for IS 2062 E250BR (or any named grade), ask for the mill test certificate that traces the plate to its cast number;
- if the plate has no mill certificate, for example recovered or surplus plate, buy it by thickness and size. If the grade matters, agree a chemical and tensile test at a lab before you use it.
What should an MS circle enquiry include?
Copy this list into your message:
- Shape: solid circle (disc) or ring
- OD in mm
- ID in mm (for rings)
- Thickness in mm
- Quantity of each size
- Grade (for example IS 2062 E250BR) and whether a mill test certificate is needed
- Finished or rough size, with the machining allowance per side if rough
- Tolerance needed on OD, ID and flatness, if any
- Drawing (PDF or a clear photo) for anything beyond a plain circle or ring: holes, a PCD, slots or bevels
- Delivery location and the date needed
A clear enquiry gets a clear quote. Missing the ID or the quantity is the most common reason a quote comes back with questions.
How do you calculate the weight of an MS circle or ring?
Steel weight in India is calculated at a density of 7.85 g/cm³ (IS 2062:2011, clause 18).
Formula for a ring or disc:
Weight (kg) = π ÷ 4 × (OD² − ID²) × T × 7.85 ÷ 1,000,000
with OD, ID and T (thickness) in mm. This simplifies to:
Weight (kg) = 0.006165 × (OD² − ID²) × T ÷ 1000
For a solid disc, ID = 0.
Worked example: ring, OD 500 mm, ID 200 mm, thickness 25 mm
- OD² = 500 × 500 = 250,000
- ID² = 200 × 200 = 40,000
- OD² − ID² = 210,000
- × thickness 25 = 5,250,000
- × 0.006165 ÷ 1000 = 32.37 kg
More examples
| Size (OD × ID × T, mm) | Weight (kg) |
|---|---|
| 300 × 0 × 20 (disc) | 11.10 |
| 500 × 0 × 25 (disc) | 38.53 |
| 500 × 200 × 25 (ring) | 32.37 |
| 900 × 0 × 100 (disc) | 499.40 |
Finished weight vs blank weight. A 500 mm disc is cut from at least a 500 × 500 mm square of plate, which at 25 mm weighs 500 × 500 × 25 × 7.85 ÷ 1,000,000 = 49.06 kg, against 38.53 kg for the finished disc. When you compare quotes, check whether each is on finished weight or on plate/blank weight, and who keeps the offcuts.
At J.S. STEEL we send photos of the exact material before every load, and every truck load goes with a GST tax invoice (an e-invoice for GST-registered buyers), an e-way bill when the consignment requires one, and a weighbridge slip.
Frequently asked questions
Is there a standard tolerance for a gas-cut MS circle?
No single standard tolerance applies. Accuracy depends on the plate thickness, on whether the circle is cut by hand torch, profile machine or CNC, and on the torch condition, gas purity and cutting speed. ISO 9013 classifies thermal cuts and their tolerances, so name the tolerance you need in the order and ask the supplier to confirm it in writing before cutting.
What is the difference between a finished-size and a rough-size circle?
A finished-size circle is cut to your final OD and ID. A rough-size circle is cut oversize on the OD and undersize on the ID, so that you can machine it to the final size. If you order rough size, state the machining allowance per side you want.
How do I calculate the weight of a gas-cut MS ring?
Weight (kg) = 0.006165 × (OD² − ID²) × thickness ÷ 1000, with all sizes in mm. For a solid disc, ID = 0. A ring of 500 mm OD, 200 mm ID and 25 mm thickness weighs about 32.4 kg.
Are MS circles quoted on finished weight or plate weight?
Check every quote. A 500 mm disc 25 mm thick weighs about 38.5 kg, but the 500 × 500 mm square of plate it is cut from weighs about 49.1 kg. Ask whether the rate is on finished weight or on blank weight, and who keeps the offcuts.