How to specify 316L Stainless Steel on a drawing

316L Stainless Steel is a low carbon austenitic stainless steel with molybdenum, for corrosion resistance. It is used for medical, food and marine parts, and anything that has to be cleaned aggressively. This entry explains what it is, what the numbers on a data sheet mean, and what to put on a drawing.

It is written from the point of view of the buyer and the drawing office: the values that are realistic in production, the ones that cost money, and the way the result is verified. Where an industry sets the requirement, rail is used as the example: documented welds, coatings and fire smoke toxicity compliance.

What belongs on the drawing

A clear drawing for 316L Stainless Steel states the function, the tolerance and the verification, and leaves the route open where the function allows it.

• The feature and its tolerance: ±0.01 mm, applied to the features that locate the part.
• The material and its condition: 316L stainless steel, with the certificate requirement.
• The surface finish: Ra 0.8 µm achievable, electropolishing available, called out only where it does something.
• The verification: EN 10204 3.1 with ISO 13485 where applicable, and the standard the report is written to.

Mistakes that cost money

• Dwelling the tool, which work hardens the surface and kills the next pass, which makes the part more expensive without making it better.
• Assuming it is magnetic like a ferritic stainless, so a magnetic chuck will not hold it, which makes the part more expensive without making it better.

A workable note

Where a general note is used, say so once in the title block and keep the feature level call outs for the dimensions that matter. State the finish and the passivation requirement for a contact surface

Applications

316L Stainless Steel is used for medical, food and marine parts, and anything that has to be cleaned aggressively, and in practice it appears most often in medical instruments, food equipment, marine hardware, chemical plant parts.

How it fits into a machining route

The route is fixed before the first part is cut, and it is the route rather than the individual setting that holds the result: cutting time, because the feed and speed are limited. Where a drawing calls for something the route cannot hold economically, that is raised at quotation rather than after the parts are made.

Standards, documentation and what is issued

The documentation requirement is EN 10204 3.1 with ISO 13485 where applicable. Material is supplied against a certificate where the application calls for it, inspection results are recorded with the job, and the records are kept so that a repeat order can be compared with the first instead of being measured from scratch.

Dimensional inspection plus a material certificate is the verification step. Where a customer format or a standard report is required, it is agreed before the batch starts, because a report written after the event is a report nobody can use.

Frequently asked questions

What tolerance should be specified for 316L Stainless Steel?

±0.01 mm is realistic in production. Tightening it beyond the functional requirement increases cost without improving the part.

Which material is usually used?

316L stainless steel is the usual choice, supplied against EN 10204 3.1 with ISO 13485 where applicable.

How is the result verified?

Dimensional inspection plus a material certificate, with the results recorded so a repeat order can be compared with the first.

What is the most common mistake?

Assuming it is magnetic like a ferritic stainless, so a magnetic chuck will not hold it.

How long does it take and what does it cost?

A realistic cycle is slow cutting, high tool wear, and the cost driver is cutting time, because the feed and speed are limited.

Related capability

If you are specifying 316L Stainless Steel on a drawing and want a second opinion on the route, send the model and the quantity. The first response is a manufacturability review with the likely risk points and a quotation, so the decision can be made on facts rather than on a price alone.

Machining, inspection and documentation are handled in one place, which is why the dimensional report and the material certificate arrive with the parts rather than after them.

Related entries

These entries sit next to 316L Stainless Steel in the encyclopedia: Inconel 718, C3604 Brass, Heat Sinks. Reading them together gives a fuller picture of how the process, the material and the measurement affect each other.