Two turned parts that look alike at first glance can differ in price many times over. This is rarely down to the costing, but almost always to a few features of the part. Knowing them lets you save a lot of money at the design stage.
The five building blocks of the price
1. Setup and programming. Before the first chip falls, the machine is set up: writing the program, loading tools, mounting the workholding, measuring the first part. This time is incurred once per order — whether you order 1 or 1,000 pieces.2. Cycle time. The time the machine works on each part. It depends on the geometry: how much material is removed, how many diameters, grooves, holes and threads there are, and whether milling is required.3. Material. What counts is not the finished part but the raw material — the next larger bar diameter plus allowance. Stainless steel costs several times as much as free-cutting steel and also machines more slowly.4. Accuracy and surface finish. Tight tolerances and fine surfaces need additional finishing passes, slower feeds and more inspection.5. Post-processing. Hardening, coating or anodising come on top, usually with their own minimum charge per order.Why quantity matters so much
The setup time is spread over all parts of an order. If it is, say, one hour, a single part carries the whole hour; at 100 pieces it is only 36 seconds per part. That is why the unit price falls sharply with quantity at first and then levels off once cycle time is almost all that counts.
From a few hundred pieces upwards, bar work with a bar feeder often pays off for small parts: the machine then also runs without an operator, which lowers the cost per part further.
Seven ways to make a turned part cheaper
- Tolerance only what the function needs. ISO 2768-m is enough for everything else.
- Specify surfaces realistically. Ra 3.2 is standard for turning; Ra 0.8 costs considerably more.
- Choose easily machinable materials where possible: free-cutting steel instead of structural steel, 1.4305 (303) instead of 1.4301 (304), free-cutting brass instead of special brass.
- Use standard bar diameters. An outside diameter of 39.5 instead of 40 mm saves some machining; 41 instead of 40 mm requires the next larger bar.
- Allow inner radii and undercuts instead of sharp inside corners.
- Design threads and holes to standard — special threads need special tools.
- Bundle quantities. One call-off of 200 pieces is cheaper than four of 50.
How to get a reliable price quickly
Send us the STEP file and a drawing with material, quantity, tolerances and surface finishes. The more complete the information, the more accurate the quote. It is worth asking for several quantities at once: you will see straight away at which quantity the price drops.
We have built the way we derive cycle time from geometry into our own quoting tool, Nemero — find out more here.