Supply tolerances: forgings, cutting and machining
How much machining allowance Dustre leaves on each forging and how much a part may vary in cutting and machining. All dimensions in mm, always on the finished size you order.
Definitions
- Machining allowance: extra material left over the finished size for machining. On the section it is the total on the diameter (or side), both sides added.
- Tolerance: how much the forged or cut size may vary around the nominal size (finished + allowance).
- Disc: D ≥ 2C, diameter equal to or greater than twice the length (height).
- Bar: C ≥ 2D (D ≤ C/2), length equal to or greater than twice the diameter.
- Billet: C/2 < D < 2C, diameter greater than half the length and smaller than twice the length.
Example: finished shaft Ø 110 × 800 mm. The Ø 100 to 125 mm range (length up to 3,500 mm) gives an allowance of 7 mm on the diameter and 14 mm on the length: the forging is Ø 117 × 814 mm, tolerance +6 / −0 on the diameter and +14 / −11 on the length. The open-die forging calculator does this for you.
Forged round and square bars
Values by finished size: outside diameter of the round bar or side of the square bar. INF 002 has one table for each shape, with the same values. Up to 3,500 mm long the section tolerance is plus only; from 3,500 to 6,000 mm it is symmetrical (±) and the allowance is larger. Below Ø 40 mm there is no forged bar longer than 3,500 mm.
| Finished Ø or side (mm) | Section (mm) | Length (mm) | ||
|---|---|---|---|---|
| Allowance | Tolerance | Allowance | Tolerance | |
| 6 – 16 | 2 | +3.5 / −0 | 8 | +9 / −7 |
| 16 – 25 | 3 | +3.5 / −0 | 9 | +10 / −7 |
| 25 – 40 | 4 | +4 / −0 | 9 | +10 / −8 |
| 40 – 53 | 4 | +4.5 / −0 | 10 | +11 / −8 |
| 53 – 80 | 5 | +5 / −0 | 11 | +12 / −9 |
| 80 – 100 | 6 | +5.5 / −0 | 12 | +13 / −9 |
| 100 – 125 | 7 | +6 / −0 | 14 | +14 / −11 |
| 125 – 150 | 9 | +7 / −0 | 15 | +14 / −11 |
| 150 – 200 | 11 | +7 / −0 | 17 | +14 / −14 |
| 200 – 250 | 13 | +8 / −0 | 20 | +16 / −16 |
| 250 – 315 | 16 | +8 / −0 | 23 | +18 / −18 |
| 315 – 400 | 19 | +10 / −0 | 27 | +21 / −21 |
| 400 – 500 | 24 | +12 / −0 | 32 | +25 / −25 |
| Finished Ø or side (mm) | Section (mm) | Length (mm) | ||
|---|---|---|---|---|
| Allowance | Tolerance | Allowance | Tolerance | |
| 6 – 16 | not supplied in this length | |||
| 16 – 25 | not supplied in this length | |||
| 25 – 40 | not supplied in this length | |||
| 40 – 53 | 6 | ± 1.4 | 14 | +11 / −9 |
| 53 – 80 | 7 | ± 1.6 | 15 | +12 / −10 |
| 80 – 100 | 8 | ± 1.9 | 16 | +13 / −10 |
| 100 – 125 | 10 | ± 2.1 | 17 | +14 / −10 |
| 125 – 150 | 12 | ± 2.5 | 19 | +15 / −12 |
| 150 – 200 | 14 | ± 2.9 | 21 | +16 / −14 |
| 200 – 250 | 17 | ± 3.5 | 23 | +17 / −17 |
| 250 – 315 | 21 | ± 4.2 | 26 | +19 / −19 |
| 315 – 400 | 26 | ± 5 | 30 | +22 / −22 |
| 400 – 500 | 32 | ± 6.2 | 35 | +26 / −26 |
Forged discs
By finished outside diameter and finished height. The diameter allowance is the same in the four height ranges; the height allowance grows with the disc height. All tolerances are +x / −0.
| Finished Ø (mm) | Diameter (mm) | Height (mm): allowance / tolerance, by finished height | ||||
|---|---|---|---|---|---|---|
| Allowance | Tolerance | H 20 – 50 | H 51 – 100 | H 101 – 300 | H 301 – 750 | |
| 50 – 53 | 4 | +3.5 / −0 | 3 / +2 / −0 | 5 / +3 / −0 | 8 / +4 / −0 | 8 / +4 / −0 |
| 53 – 80 | 5 | +4 / −0 | 3 / +2 / −0 | 5 / +3 / −0 | 8 / +4 / −0 | 8 / +4 / −0 |
| 80 – 100 | 6 | +5 / −0 | 3 / +2 / −0 | 5 / +3 / −0 | 8 / +4 / −0 | 8 / +4 / −0 |
| 100 – 125 | 7 | +5.5 / −0 | 5 / +2 / −0 | 5 / +3 / −0 | 8 / +4 / −0 | 8 / +4 / −0 |
| 125 – 150 | 7 | +6 / −0 | 5 / +2 / −0 | 5 / +3 / −0 | 8 / +4 / −0 | 8 / +4 / −0 |
| 150 – 200 | 7 | +6.5 / −0 | 5 / +3 / −0 | 7 / +4 / −0 | 10 / +5 / −0 | 10 / +5 / −0 |
| 200 – 250 | 8 | +7 / −0 | 5 / +3 / −0 | 7 / +4 / −0 | 10 / +5 / −0 | 10 / +5 / −0 |
| 250 – 300 | 8 | +8 / −0 | 5 / +3 / −0 | 7 / +4 / −0 | 10 / +5 / −0 | 10 / +5 / −0 |
| 300 – 450 | 9 | +8.5 / −0 | 6 / +5 / −0 | 8 / +5 / −0 | 11 / +6 / −0 | 11 / +6 / −0 |
| 450 – 600 | 9 | +9 / −0 | 6 / +5 / −0 | 8 / +5 / −0 | 11 / +6 / −0 | 11 / +6 / −0 |
| 600 – 750 | 9 | +9.5 / −0 | 6 / +5 / −0 | 8 / +5 / −0 | 11 / +6 / −0 | 11 / +6 / −0 |
Band saw cutting
Tolerance on the length of the cut piece, by bar diameter. Plus only: the piece is never shorter than ordered.
| Diameter (mm) | Length tolerance (mm) |
|---|---|
| up to 100 | +5 / −0 |
| 100 – 200 | +5 / −0 |
| 200 – 300 | +7 / −0 |
| 300 – 400 | +10 / −0 |
| 400 – 500 | +12 / −0 |
| over 500 | +15 / −0 |
Machined parts
General tolerance for turned parts when the drawing states no other. Tight tolerances (ISO 286, H7/h6 fits) follow the drawing.
| Diameter (mm) | Diameter tolerance | Length tolerance, by length (mm) | ||
|---|---|---|---|---|
| up to 500 | 500 – 1,000 | 1,000 – 1,500 | ||
| 6 – 30 | +2 / −0 | +2 / −0 | +5 / −0 | +7 / −0 |
| 30 – 120 | +3 / −0 | +2 / −0 | +5 / −0 | +7 / −0 |
| 120 – 300 | +4 / −0 | +3 / −0 | +7 / −0 | +10 / −0 |
| 300 – 500 | +5 / −0 | +5 / −0 | +10 / −0 | +15 / −0 |
Waterjet cutting
Diameter allowance for parts cut from plate (discs, rings, flanges), by plate thickness. The outer contour is cut oversize and the bore undersize, so there is material for machining on both faces.
| Plate thickness (mm) | Allowance on diameter (mm) | Outer cut: contour, outside Ø (mm) | Core removal: bore, inside Ø (mm) |
|---|---|---|---|
| up to 20 | 2 | +2 / −0 | −2 / +0 |
| 20 – 30 | 3 | +3 / −0 | −3 / +0 |
| 30 – 40 | 4 | +4 / −0 | −4 / +0 |
| 40 – 50 | 5 | +5 / −0 | −5 / +0 |
| 50 – 60 | 6 | +6 / −0 | −6 / +0 |
| 60 – 80 | 8 | +8 / −0 | −8 / +0 |
| 80 – 100 | 10 | +10 / −0 | −10 / +0 |
| 100 – 150 | 15 | +15 / −0 | −15 / +0 |
| 150 – 200 | 20 | +20 / −0 | −20 / +0 |
| 200 – 250 | 25 | +25 / −0 | −25 / +0 |
- Rule: tolerance = 10 % of thickness, minimum 2.0 mm, applied on the DIAMETER (half the value per side).
- Allowance = tolerance: it is the material left for subsequent machining.
- Cutting size: outside Ø = finished Ø + allowance; inside Ø (core) = finished Ø − allowance.
- Outer cut: the contour is cut oversize, tolerance always positive (material is left outside).
- Core removal: the bore is cut undersize, tolerance always negative (material is left inside).
- On rings and bushings both conditions add up: OD +tol and ID −tol, ensuring allowance on both faces.
- Maximum cutting thickness: 250 mm. Above that, ask our engineering team.
- The values cover jet taper, jet exit deviation and plate clamping misalignment.
Maximum thickness: 250 mm.
Related calculators and services
Frequently asked questions
What is the machining allowance on a forged bar?
Under Dustre's INF 002, from 2 mm on the diameter (Ø 6 to 16 mm finished bars) to 24 mm (Ø 400 to 500 mm), for lengths up to 3,500 mm. On length, the allowance ranges from 8 to 32 mm. Bars from 3,500 to 6,000 mm have a larger allowance and a symmetrical (±) section tolerance.
Is the allowance per side or on the diameter?
On the diameter (or on the side of a square bar): it is the sum of both sides. An allowance of 7 mm on a Ø 110 mm finished bar means forging to Ø 117 mm nominal, or 3.5 mm per side.
What is the difference between a disc, a billet and a bar?
By the INF 002 definition: a disc has a diameter equal to or greater than twice its length (D ≥ 2C); a bar has a length equal to or greater than twice its diameter (C ≥ 2D); a billet sits in between (C/2 < D < 2C).
What is the band saw cutting tolerance?
On length, −0 / +5 mm up to Ø 200 mm, rising to +15 mm above Ø 500 mm. The tolerance is plus only: the piece is never shorter than ordered.
How does the allowance work in waterjet cutting?
The diameter allowance is 10 % of the plate thickness, minimum 2 mm. The outer contour is cut oversize (+) and the bore (core) undersize (−); on rings both rules add up. Maximum cutting thickness: 250 mm.
Do these tolerances apply to every alloy?
Yes. Dustre's tables are the same for carbon steel, alloy steel, stainless, duplex, nickel alloys, titanium and copper. Different, tighter or standard tolerances (ASTM A484, A788, EN 10250) can be agreed in the order.
