Guides / Design

Twelve Rules for Drawing a Ceramic Part That Can Actually Be Ground

June 8, 2026

A ceramic drawing is not a metal drawing with the material block changed. These twelve rules cover most of what separates a part that quotes well from one that comes back with questions.

1. Give every edge a defined chamfer

“Break all edges” means nothing useful on a brittle material. Put a dimension on it, for example 0.2 x 45 degrees. Unchamfered edges chip in handling, in fixturing and in service, and a chip is a crack starter.

2. Put a radius in every internal corner

A grinding wheel cannot make a sharp internal corner and a brittle material does not want one. Specify a radius the shop can reach, and if the mating part needs clearance, use an undercut or chamfer the mating part instead. More detail in why sharp corners are expensive.

3. Keep walls above roughly 1 mm

Thin walls flex, chatter and chip during grinding. If the design needs a thin section, say why, so the shop can fixture and support it properly, and expect to pay for the care.

4. Avoid long slender features

An aspect ratio above about 10 to 1 on a pin, fin or rib makes fixturing hard and breakage likely. Split the part or support the feature.

5. Tolerance only what function needs

Every tight tolerance is grinding time plus inspection time. Leave the rest as fired, which is around 1% of the dimension. Mark clearly which is which. See realistic tolerances and surface finishes.

6. Choose datums on ground surfaces

If your datum is an as-fired face, everything measured from it inherits that face’s variation. Pick datums the shop will grind anyway and say so.

7. Specify flatness and parallelism by face, not globally

A blanket flatness note across six faces multiplies the lapping bill. Name the one or two faces that seal, slide or mount.

8. Treat threads as a last resort

Ground threads in ceramic are possible and expensive. Consider a through hole with a metal fastener, a clamped joint, a brazed insert or a metal collar. See holes, slots and threads.

9. Chamfer both ends of every hole

Breakout chipping at hole exit is one of the most common scrap causes. A chamfer at both ends gives the tool somewhere clean to leave.

10. Keep holes away from edges

A hole close to an edge leaves a thin ligament that cracks in grinding or in service. As a starting point, keep at least one hole diameter of material between the hole wall and the nearest edge.

11. Design for the blank, not for the ideal shape

Ask what stock plate, rod or tube sizes exist in your grade. A part designed 2 mm under a standard thickness grinds fast. A part designed 2 mm over the standard forces the next size up and throws the difference away.

12. Say what the part does

One sentence on the drawing or in the RFQ, for example “seal face runs against carbon, vacuum on one side”, changes the quote more than any other single thing. It tells the shop which surfaces matter and which are structure.

The short version

Ceramic likes: generous radii, chamfered edges, uniform sections, few tight tolerances and simple fixturing. It dislikes: sharp internal corners, knife edges, thin unsupported walls, threads and blanket tolerance notes.

If you apply nothing else, apply rules 1, 2, 5 and 12. They account for most of the avoidable cost we see on incoming drawings. The rest of the buying process is in the buyer guide.

Send your drawing and we match it with up to 3 shops that will tell you which rules your part breaks before they quote it. Reply within 24 business hours.

Frequently asked questions

Keep reading

• Joining Ceramic to Metal Without Cracking It on the First Cycle
• What Is Possible and What Is Painful: Features in a Ceramic Part