As-Sintered or Ground? Which Carbide Surfaces Actually Need Grinding
· Vanguard Carbide
Carbide shrinks by roughly a fifth when it is sintered. That single fact explains most of what a ground surface costs — and where you can save.
Why Carbide Parts Are Made Twice
- A cemented carbide part starts as a pressed powder compact, held together by a binder. Sintering turns it into a dense solid — and in doing so it shrinks substantially, on the order of a fifth of its linear dimension. The exact figure depends on the grade and the pressing process.
- Shrinkage that large cannot be controlled to a few microns. So a part comes out of the furnace close to shape but not to a tight tolerance. Anything that has to be precise is ground afterwards, with diamond.
What This Means For Your Drawing
- Every ground surface is a second operation on a material that is deliberately hard to cut. It is the part of the cost you have the most influence over.
- Surfaces that seal, locate, or run against something usually have to be ground. Surfaces that are simply there — outside diameters that clear a housing, backs that sit in a pocket — often do not.
Three Ways Drawings Cost More Than They Need To
- A blanket tolerance applied to every dimension, when only two of them matter.
- A surface finish called out everywhere, when it is only needed on the working face.
- Sharp corners specified where a small radius would do. Carbide is brittle; a sharp internal corner is a crack waiting to start, and it is expensive to produce.
What To Do Instead
- Mark the critical dimensions and let the rest be as-sintered or lightly ground.
- Say what the surface has to do rather than only what number it must hit — if we know a face seals, we can tell you what finish it really needs.
- Ask for a quotation both ways when you are unsure. The difference between "ground all over" and "ground where it matters" is often larger than people expect.
A Note On What We Confirm
The tolerances and finishes we can hold depend on the part, the grade and the quantity. We confirm them in writing for your specific part rather than publishing a general table that may not apply to it.