Machining calculator
Choose the material and enter the bar to peel (or the turned or milled part) and the batch size. The calculator suggests the cutting speed and feed for the material, estimates machine time and shows the price of the machining service per part and per batch.
1You enter
2Result
- Machining per part (estimate)
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- Batch total
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- Estimated time
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- Weight per part
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Estimate of the machining service only, based on machine time with the reference cutting data below. Material, blank cutting, heat treatment, testing and freight are quoted separately; the final price comes in the quote, with the drawing. Blank left empty = finished part + 5 mm. Values with * are references from literature and tool manufacturers, to be confirmed on the part.
How the calculator estimates time
Machining price comes from machine time. For each part the calculator adds cutting time (stock to remove and finishing passes), the time for holes, threads and milled features, the secondary time to clamp, turn over and measure, and a share of the machine setup, which is divided by the batch size. It is the same costing method by manufacturing time used in machining textbooks.
| Item | Formula | Note |
|---|---|---|
| Peeling (per pass) | t = (L + 10) ÷ (f × n), with n = 1,000 × vc ÷ (π × D) | Roughing passes until 0.5 mm is left for finishing; speed limited to 1,500 rpm (conventional) or 3,000 rpm (CNC). |
| Time per part | t = cutting t + secondary t + setup t ÷ batch | Costing by manufacturing time (König and Klocke; Diniz, Marcondes and Coppini). |
| Removal rate in turning | Q = vc × ap × f (cm³/min) | vc in m/min, depth of cut ap and feed f in mm. Roughing time = chip volume ÷ Q. |
| Finishing time | t = π × D × L ÷ (1,000 × vc × f) | One pass for normal tolerance, two for precise and three for high precision. |
| Drilling time | t = depth ÷ (f × n), with n = 1,000 × vc ÷ (π × d) | Plus the time to position each hole. |
| Tool change | +10 % of cutting time (+20 % in nickel and titanium) | Approximation of the term (tc ÷ T) × tw from tool life (Taylor). |
Machinability by material
Cutting speed changes a lot from one material to another and is what weighs most on the price. The values are for carbide turning in roughing on a CNC lathe; on a conventional lathe the calculator uses 60 % of the speed and 70 % of the depth of cut, and for finishing 20 % more speed with a feed of 0.20 mm/rev (normal), 0.12 (precise) or 0.08 (high precision). The difficulty factor multiplies the time of holes, threads and features.
| Material | vc (m/min)* | Roughing feed (mm/rev)* | Factor |
|---|---|---|---|
| Carbon and low alloy steel | 180 to 250 | 0.30 | 1 |
| High alloy and maraging steel | 110 to 150 | 0.25 | 1.4 |
| Austenitic and martensitic stainless | 150 to 180 | 0.25 | 1.3 |
| Duplex and super duplex | 100 to 130 | 0.25 | 1.6 |
| Nickel alloys (Inconel, Hastelloy, Monel) | 30 to 50 | 0.25 | 3 |
| Titanium | 50 to 70 | 0.25 | 2.4 |
| Copper, bronze and brass | 200 to 300 | 0.25 | 0.9 |
| Engineering plastics | 250 to 400 | 0.30 | 0.7 |
Sources: cutting speed ranges from tool manufacturers' catalogues (ISO groups P, M, N and S) and from the literature (Sandvik Coromant, Technical guide; Diniz, Marcondes and Coppini, Tecnologia da usinagem dos materiais; König and Klocke, Fertigungsverfahren). To choose the alloy, see Dustre materials.
Setup by machine
| Machine | Setup per batch* | Includes |
|---|---|---|
| CNC lathe | 60 min | Simple programming, part zero and first part approved |
| Conventional lathe | 30 min | Clamping, tools and first part |
| CNC machining centre (CNC milling) | 90 min | Fixture, programming, zero and first part |
| Conventional milling machine | 45 min | Clamping, tools and first part |
| Off-centre drilling on a turned part | 20 min | Another clamping on the drill press or mill |
A turned part is turned over once (two clampings); a milled block, three. Precise and high-precision tolerances add finishing passes and measuring time. To know how much blank to forge, use the open-die forging calculator; for the weight, the weight calculator. See also the Dustre machining service.
Frequently asked questions
How is the machining price calculated?
From machine time: cutting time (chip volume ÷ material removal rate), finishing passes by tolerance, holes and threads, clamping and measuring time per part and the machine setup, divided by the batch. The total time is multiplied by the Dustre service hour rate. It is the costing method by manufacturing time used in the machining literature.
What is bar peeling?
It is turning the bar along its whole length, from the blank diameter to the final one, to remove the skin: scale, decarburised layer, ovality and surface defects of the rolled or forged bar. Enter the blank diameter, the final diameter, the length and the quantity: the calculator suggests the cutting speed and feed for the material, counts the passes and estimates time and price.
What is setup and why does it weigh so much on a single part?
Setup is the time to prepare the machine for the batch: mount the fixture and tools, program (on CNC), set zero and approve the first part. It is charged once per batch. On 1 part it goes fully into the price; on 50 parts, it is divided by 50.
CNC or conventional lathe: which is cheaper?
In batches, almost always CNC: it removes more chips per minute and repeats without measuring part by part. For a simple single part, conventional can be cheaper because the setup is shorter (no programming). The calculator shows both: change the machine and compare.
Why do stainless, duplex, Inconel and titanium cost more to machine?
Because cutting speed drops a lot: carbon steel machines at about 200 m/min with carbide, austenitic stainless at 150 to 180, duplex at 100 to 130, titanium at 50 to 70 and nickel alloys at 30 to 50 m/min*. Lower speed means more machine time and more tool changes.
What is and is not included?
Only the machining service (machine, operator, tooling and setup). Material, blank cutting, heat treatment, testing, certificate and freight are quoted separately. If Dustre supplies the material, the quote puts it all together.
Can I send a drawing instead of using the calculator?
Yes, and it is the best option for a complex part: send the drawing (PDF, DWG or STEP), the material and the quantity through the quote request. The calculator gives you an order of magnitude beforehand.
