Guides / Process

How to Buy Machined Technical Ceramic Parts Without Getting Burned

September 21, 2026

Buying a machined ceramic part is not buying a machined metal part in a different material. The route, the tolerances, the lead time and the failure modes are all different. Most of the bad quotes we see come from a drawing that was written for aluminium and then had the material block changed to alumina.

This guide covers what actually drives a ceramic quote, what you can ask for, and what to put on the drawing so the shops quoting you are quoting the same part.

Ceramic is ground, not cut

A sintered technical ceramic is harder than the carbide tooling used on metal. Nothing on a standard machining centre will cut it. Material is removed by abrasion with diamond, on surface grinders, ID and OD grinders, and increasingly on machining centres running diamond tooling with flood coolant.

Two consequences follow from that, and they explain most of the price:

• Removal rates are a fraction of what they are in steel, so grinding hours dominate the quote.
• The material has almost no ductility. It does not deform before it fails, it chips. Sharp corners, thin walls, knife edges and break-out on cross holes are where parts are lost.

A good ceramic shop spends as much thought on fixturing and edge preparation as on the cutting path.

The two routes, and why quotes differ so much

Ask any ceramic shop for a price and the first thing they decide is the route.

Green or bisque machining cuts the part while the blank is still soft, then fires it. Cutting is fast and cheap. The catch is shrinkage: the part loses 15 to 25 percent of every dimension in the kiln, and the shrinkage factor depends on the grade, the powder lot and the kiln cycle. A shop with a proven model for that grade can hold roughly 1 percent of the dimension as fired. That is fine for an insulator standoff. It is not fine for a bore that has to take a bearing.

Hard machining fires the blank first, then grinds it. This is slower and more expensive per piece and it is the only way to hold a tight fit, a flat face or a fine finish. Prototypes almost always take this route because there is no tooling to amortise.

Many production parts use both: green machine the bulk, fire, then grind only the two or three features that need it. If your drawing does not say which features are critical, you are forcing the shop to either grind everything, which is expensive, or guess, which is worse. See green machining vs hard machining for the detail.

Tolerances you can actually ask for

Feature	Realistic on a ground surface	As fired
Diameter and length	±0.005 to ±0.013 mm	about ±1% of the dimension
Flatness	under 0.005 mm lapped	0.1 mm and up
Surface finish	Ra 0.1 to 0.4 µm	Ra 0.8 µm and up
Perpendicularity	0.005 to 0.02 mm	not controlled

Every tight callout is grinding time and inspection time. The cheapest ceramic drawing is the one that holds tolerance on the three features that matter and leaves the rest as fired.

Picking the grade

• Alumina 96% is the default. Insulators, wear parts, fixtures. It metallises and brazes, and it is the cheapest of the oxides.
• Alumina 99.5% buys purity and density: vacuum work, plasma exposure, higher dielectric strength. Semiconductor parts usually start here.
• Zirconia (Y-TZP) is the tough one. It survives impact and point loading that cracks alumina, which is why plungers, blades and dental parts use it. It conducts heat poorly, so keep it out of heat paths.
• Silicon carbide is for seal faces and abrasive service. Extremely hard and stiff, which also means the grinding bill is the highest on this list.
• Silicon nitride holds strength through thermal shock, which alumina does not. Bearing elements and hot section parts.
• Aluminium nitride is the insulator that still moves heat. Heat spreaders, chuck bodies, power electronics.
• Macor and other machinable glass ceramics cut on conventional tooling with no firing afterwards. Ideal for one-off fixtures and instrument parts. Weaker and less temperature capable than the oxides, so it is a prototyping material more than a production one.

If you are unsure, describe the environment instead: temperature, chemistry, load, voltage and whether the part is in a vacuum. A shop that machines ceramic every week will propose a grade.

Lead time is set by the kiln, not the machine

A part ground from stock plate or a standard tube is typically 3 to 5 weeks. A part that needs its own pressed and sintered blank is 8 to 14 weeks, because firing is scheduled in batches and a blank is not made for one customer on demand.

This catches buyers who assume that a small simple part must be quick. It is the blank that sets the calendar. If you have a deadline, say so on the RFQ so the shops quoting you can propose a stock blank or a different grade that is on the shelf.

What to put on the RFQ

• The grade, or the environment if you want a recommendation
• Which dimensions must be held, and which can stay as fired
• Flatness and surface finish only where the function needs them
• Quantity now and the annual volume, even if you are ordering five pieces
• Whether the part is metallised, brazed or assembled afterwards
• Cleanliness or packing requirements for semiconductor and medical parts

Edge chamfers deserve their own line. A drawing that says “break all edges” on a ceramic part is asking for chipped parts and a high scrap rate. A defined chamfer, even 0.2 x 45 degrees, tells the shop what to grind and gives the part an edge that survives handling.

How we match your part

We are not a machine shop. You send one RFQ and we read it, decide whether it is a grinding job or a green machining job, then put it in front of up to three shops set up for that route and that grade. They quote you directly and you order from whichever one you want. It costs you nothing, and it is faster than emailing eight shops that mostly do metal.

Before you send anything, it is worth reading what drives the cost of machined ceramic parts so you can tell a fair quote from a lazy one.

Ready now? Send your drawing and we reply within 24 business hours.

Frequently asked questions

Keep reading

• HIP for Ceramics: What the Extra Furnace Cycle Buys You
• Glazing and Sealing: Making a Porous Ceramic Part Hold Up in Service