Guides / Cost

Why Two Quotes for the Same Ceramic Part Differ by 3x

September 15, 2026

Ceramic quotes vary more than metal quotes. The same drawing sent to five shops can come back at 80 dollars and 240 dollars a piece with both shops being honest. Knowing which lines move the number tells you which quote to take, and which drawing change would halve the price.

1. Grinding hours

This is almost always the largest line. Sintered ceramic is removed by abrasion, and removal rates are a fraction of steel. Every millimetre of stock you leave on a ground surface is machine time.

Two practical consequences:

• Ask for the closest stock blank rather than the most convenient one. Grinding 4 mm off a diameter because the shop only stocks one size can double the price of a simple bushing
• A part that is 80 percent as-fired and 20 percent ground is a different product from a fully ground part, even though the drawing looks similar

2. The blank

A part ground from stock plate, rod or tube quotes in days. A part that needs its own pressed and sintered blank brings pressing tooling, a firing slot and 8 to 14 weeks of lead time.

For prototypes, always ask whether the part can come from stock. The grade might shift, for example alumina 99.5% instead of 99.7%, and that is usually a fair trade for getting the part this quarter.

3. Tolerance, flatness and parallelism

Every tight callout adds passes, wheel dressing and inspection. A tolerance of ±0.05 mm and a tolerance of ±0.005 mm on the same bore are not 10 times apart in price, but they are commonly 2 to 3 times apart once inspection is included.

The cheapest saving available on most ceramic drawings is removing tolerances that nothing depends on.

4. Surface finish

Lapping and polishing are separate operations with their own fixtures and their own scrap risk. Ra 0.1 µm on a seal face can cost more than the roughing that shaped the part.

Specify finish by face. A blanket Ra note across a part with eight surfaces is an expensive habit.

5. Geometry and chip risk

Brittle material does not forgive. Sharp internal corners, thin walls, knife edges and cross holes that break out all raise the scrap rate, and scrap is priced into the quote whether or not the shop itemises it.

Cheap fixes that shops rarely ask for but always appreciate:

• A defined edge chamfer rather than “break all edges”
• A radius in every internal corner
• A wall thickness that does not fall below roughly 1 mm without a reason
• A deburr note that acknowledges the part is ceramic, not brass

6. Quantity and route

Below a few hundred pieces, grinding from stock usually wins because there is no tooling to amortise. Above that, pressing tooling and green machining start to pay for themselves and the piece price falls in a step, not a curve. This is why an annual volume on the RFQ changes the quote even when you are ordering ten pieces today.

A worked example

An alumina 99.5% insulator ring, 62 mm outer diameter, 3 mm wall, one lapped face flat within 0.005 mm, bore held at ±0.005 mm, 40 pieces.

• Ground from a stock tube, with only the bore and one face ground: a straightforward job for any ceramic shop, quoted on grinding hours plus lapping
• The same ring with both faces lapped, an outside diameter tolerance and a fine finish on all surfaces: roughly double, with no functional gain if only one face seals
• The same ring at 2000 pieces a year: worth pressing a near-net blank, which changes the piece price entirely and adds 3 months for the first delivery

Same drawing family, three very different quotes. The difference was specified, not negotiated.

Before you compare quotes

Check that every shop quoted the same route and the same grade. If one quote is far lower, look for as-fired tolerances where you expected ground ones. If one is far higher, look for a fully ground part where a hybrid would do.

Background reading: the buyer guide and green machining vs hard machining.

The cost lines sit inside a wider buying path; the guide to buying machined ceramic parts shows where each one is decided. For how the material family changes the price, see technical ceramic material cost.

Want quotes that are actually comparable? Send one RFQ and we brief up to three matched shops on the same route. Reply within 24 business hours.

Frequently asked questions

Keep reading

• The Cheap Quote Is Usually a Different Part: Comparing Ceramic Prices
• Why the Kiln, Not the Machine, Sets Your Delivery Date