Guides / Choosing a Supplier

Secondary Operations for Swiss Machined Parts and How to Scope Them

September 20, 2026

A Swiss-type lathe delivers a part that is finished on both ends and often needs no further machining. That is the point of the machine. What it does not do is passivate, plate, heat treat, clean or package, and on many parts those steps decide both the final cost and the delivery date.

This guide covers the operations that follow the machine, what each one adds and how to write them into an RFQ so that every shop quotes the same thing.

Why the scope matters more than the machining

When quotes for the same part come back far apart, the gap is more often in the secondary operations than in the machine time. One shop assumed passivation, another did not. One included cleaning and individual packaging, another quoted bulk. One priced heat treatment to a specific condition, another assumed material supplied ready to use.

The parts are the same. The scope is not. Writing the full scope into the RFQ removes most of the noise from the comparison, which is the practical reason to think this through before you send a drawing rather than after.

Deburring

Swiss machines produce fewer burrs than multi setup machining, because the part is cut in one continuous cycle with fresh tooling geometry. Burrs still appear in predictable places: where a cross hole breaks through, at thread starts and ends, on slot edges and at the cut off face.

Methods vary by part and by requirement:

• In cycle chamfering. The cheapest answer, because the machine does it. Designing a chamfer where a burr would otherwise form removes the problem before it exists.
• Vibratory or tumble finishing. Suits high volumes of small parts. It also rounds edges slightly and changes surface appearance, so say whether that is acceptable.
• Thermal or electrochemical deburring. For internal intersections a tool cannot reach.
• Hand deburring. Precise and controllable, but labor per part, which shows immediately at volume.

Specify the requirement rather than the method. “Break all sharp edges, no burrs on the cross hole intersection” tells the shop what you need. Naming a method you do not require can force a more expensive route than necessary.

Passivation

Machining smears free iron across a stainless surface. That iron rusts even when the base alloy would not, which is why a correctly specified stainless part can still show corrosion. Passivation removes the free iron chemically and lets the chromium oxide layer reform.

For medical, food, marine and fluid handling parts it is normally in scope. Specify the standard, typically ASTM A967 or AMS 2700, and the method where it matters, since nitric and citric acid processes are not interchangeable for every application.

Passivation removes a negligible amount of material, so it rarely affects dimensions. It does affect the schedule, because it usually happens at an outside processor with its own queue. The stainless steel guide covers which grades need it and why.

Plating and coating

Plating is where dimensions and documentation both need attention.

Common choices on Swiss parts are gold and tin for electrical contact, nickel as a barrier or for wear, zinc for corrosion protection on steel and anodizing on aluminum.

Three things have to be on the drawing:

1. Thickness and where it applies. Plating thickness is often comparable to a tight tolerance, so a diameter that was correct before plating can be out of specification after it.
2. Whether dimensions apply before or after. State it explicitly. This single note prevents one of the most common first article failures.
3. Masking, if only part of the surface is plated. Masking is labor and it needs a clear definition of where the boundary sits.

Also decide whether you need a plating certificate and thickness measurement with each lot. In electrical and medical applications this is usually yes.

Heat treatment

Heat treatment either happens before machining, after machining or both, and the choice changes the quote and the achievable tolerance.

For 17-4 PH, parts are commonly machined in the solution annealed condition and then aged to a condition such as H900 or H1025. Aging moves dimensions slightly and raises hardness. For alloy steels, hardening and tempering happen after machining and the part moves more.

What the drawing must state:

• The final condition or hardness required, with the specification
• Whether dimensions apply before or after heat treatment
• Whether any post treatment operation, such as a finish grind, is expected

Where the movement is larger than the tolerance band, the sequence becomes an engineering decision rather than a purchasing one. Raise it at quoting and let the shop propose a route.

Cleaning and packaging

Easy to leave off an RFQ and surprisingly expensive to add later.

Machining leaves cutting oil and fine chips. For general industrial parts a standard degrease is enough. For medical, optical, vacuum and some electronic applications the cleaning process is specified, validated and documented, and it is a real cost line.

Packaging ranges from bulk in a bag to individually bagged parts with barcoded labels, controlled quantities per container, desiccant, anti static packaging or cleanroom packing. Each level costs labor per part.

Decide and state:

• Cleaning requirement and, if applicable, the specification and any validation
• Packaging format and quantity per container
• Labeling and identification, including lot numbers
• Any requirement for parts not to touch each other in transit

On small turned parts shipped in thousands, packaging choices can rival machining cost per part. It is worth deciding deliberately rather than inheriting a format from an unrelated job.

Assembly and other work

Some Swiss parts ship as sub assemblies: a pin pressed into a housing, an O-ring fitted, a spring captured, two parts staked together. Some need marking, such as laser engraved lot codes or part numbers.

If this is in scope, describe it precisely and say who supplies the mating components. Shops handle assembly in very different ways, and this is an area where scope confusion is common.

Who does the work

Most shops do some operations in house and send others out. Neither is automatically better.

In house means fewer handoffs, shorter transit and one party responsible for the whole part. It can also mean the shop is good at machining and less specialized at the process.

Outsourced usually means a specialist doing the process every day, with the right equipment and approvals. It adds transit each way and the processor’s queue to the lead time.

Questions to ask:

• Which operations do you perform in house and which go outside
• For outside processes, are the processors approved to any standard my application requires
• Who owns the parts and the responsibility if an outside process damages a lot
• What does each outside step add to the lead time
• Does the documentation from outside processors reach me with the shipment

The last point matters most in regulated work, where a missing certificate makes a good part unusable. The inspection guide covers documentation in more detail.

Yield, rejects and who carries the risk

Secondary operations are where a good lot can become a short lot, and it is worth agreeing what happens before it does.

A plating line can damage parts. A tumbling operation can round an edge that should have stayed sharp. A heat treatment batch can come out of specification. When parts are lost at an outside processor, three questions arise: who pays for the machining already done, who remakes the parts and what happens to your delivery date.

Settle these at quoting:

• Overage. Will the shop run a small quantity above the order to cover losses in later steps, and is that quantity charged or absorbed
• Responsibility. If an outside processor damages a lot, does the machine shop stand behind the finished part or pass through the processor’s liability
• Rework versus scrap. Which defects can be reworked and which cannot, and who decides
• Nonconforming parts. Do you want them returned, scrapped with evidence, or held for review
• Schedule impact. How a remake affects the delivery date, and whether a partial shipment is acceptable

On regulated parts, add one more: how nonconformances are documented and whether you need to be notified of any deviation, even one that was corrected.

None of this is adversarial. It is the ordinary detail of buying a part that passes through several hands, and agreeing it early keeps a problem from becoming a dispute.

Sequence and dimensions

Every operation that touches the surface potentially changes a dimension. Plating adds material, electropolishing removes it, heat treatment moves the part, tumbling rounds edges.

The rule that avoids most problems: for every toleranced feature affected by a secondary operation, state at which point in the sequence the tolerance applies. Put it in a note on the drawing rather than in an email, because the drawing is what the shop works from months later on a repeat order.

Writing the scope into an RFQ

A complete secondary operations scope for a Swiss part reads something like this:

1. Deburr requirement, stated as a condition not a method
2. Passivation, with standard and method if required
3. Plating or coating, with thickness, area, masking and before or after dimensions
4. Heat treatment, with final condition and when dimensions apply
5. Cleaning requirement and specification
6. Packaging format, quantity per container and labeling
7. Marking requirements
8. Documentation required with each shipment

Eight lines. Including them turns three incomparable quotes into three comparable ones, and it removes most of the scope disputes that surface after the first delivery.

Getting the whole scope priced

Send the drawing and the STEP file through the RFQ form with the secondary operations listed. We match your part with up to three shops that run Swiss-type lathes and reply within 24 business hours, and every shop sees the same scope.

If these steps are driving your delivery date rather than the machining, the lead time guide shows where the days actually go.

Frequently asked questions

Keep reading

• Inspection and Quality on Swiss Machined Parts
• Design for Swiss Machining: Drawing Choices That Move the Price