If you look at many brazed diamond drill bits or diamond hole saws used for stone, tile, and hard materials, you’ll notice a common specification: most of them use diamonds around 45 grit.

This isn’t a random choice. Over years of tool development and field use, this grit size has proven to be a practical balance between cutting efficiency, diamond retention, and drilling stability.

Understanding why requires looking at how diamond size affects drilling performance.

A Balance Between Cutting Speed and Control

Diamond grit size directly influences how aggressively a drill bit cuts.

Coarser diamonds provide stronger cutting action because each individual crystal removes more material. However, they also create rougher cutting behavior and can increase vibration during drilling.

Finer diamonds produce smoother cuts but reduce material removal speed.

In practical applications:

• Coarser grit (around 30 grit) Cuts aggressively but can cause more vibration and edge chipping.

• Finer grit (above 60 grit) Produces smoother holes but significantly slows drilling speed.

A 45 grit diamond sits in the middle of this range. It offers enough cutting strength for efficient drilling while maintaining reasonable stability and hole quality.brazed drain drilling bit for countertop

Brazing Technology Also Influences Grit Choice

Brazed diamond drill bits are very different from traditional sintered tools.

Instead of being embedded inside a metal bond, the diamonds are directly brazed onto the surface of the cutting edge. This means each diamond particle must both stay firmly attached and remain sufficiently exposed to cut effectively.

If the diamond particles are too small:

• Cutting edges become less pronounced

• Chip evacuation becomes more difficult

• The brazed layer may wear flat more quickly

If the particles are too large:

• Brazing stability can decrease

• Diamonds may detach under impact

• Cutting forces become uneven

Diamonds around 45 grit provide a good compromise. They are large enough to create effective cutting edges but still small enough to maintain strong brazing support.

Drilling Stability and Tool Life

Another important factor is stability during drilling.

Large diamond particles can cause the drill bit to behave more aggressively, sometimes producing vibration or chipping—especially when drilling brittle materials like porcelain tile or ceramic.

With 45 grit diamonds, the cutting points are distributed more evenly around the edge of the drill bit. This creates a more balanced cutting action, which helps:

• Reduce vibration

• Improve hole quality

• Extend overall tool life

This balance is one reason why 45 grit has gradually become a common industry standard.

Are Other Grit Sizes Ever Used?

Of course, 45 grit isn’t the only option.

Some specialized drill bits use different diamond sizes depending on the material being drilled.

For example:

• Harder materials such as quartzite may sometimes benefit from slightly coarser diamonds for stronger cutting action.

• Glass or very thin tiles may use finer diamonds to minimize edge chipping.

Even so, for many general applications in stone and tile drilling, 45 grit remains one of the most practical and widely used specifications.