Diamond Blade Grit Guide for Gemstone Cutting
When choosing a diamond blade for gemstone cutting, many users focus on blade size first. Size is important, but grit can have an even bigger impact on the cutting result.
Grit determines how aggressive the blade feels, how clean the edge looks, and how much chipping may occur.
What Does Grit Mean?
Grit refers to the size of the diamond particles on the cutting edge.
A lower grit number means larger, coarser diamond particles. A higher grit number means smaller, finer diamond particles.
In simple terms:
Coarse grit cuts faster.
Fine grit cuts cleaner.
But the right choice depends on the material and the purpose of the cut.
Coarse Grit: Faster Cutting
Coarse grit is usually used when speed matters more than edge finish. It removes material quickly and is useful for rough cutting.
Typical range:
30#–100#
Best for:
- Rough trimming
- Opening rough stones
- Cutting larger pieces
- Early-stage shaping
- When the edge will be ground or polished later
Possible downside:
- Rougher edge
- More visible cutting marks
- Higher chance of chipping on delicate material
Medium Grit: Balanced Cutting
Medium grit is often a practical choice for general gemstone cutting because it balances speed and edge quality.
Typical range:
120#–180#
Best for:
- General lapidary cutting
- Small stones
- Moderate finish requirements
- Users who want both efficiency and control
This grit range is useful when you do not need a mirror-like edge directly from cutting, but you still want to avoid excessive chipping.
Fine Grit: Cleaner Edge
Fine grit is used when the user cares most about a clean edge and reduced chipping.
Typical range:
200#–400#
Best for:
- Thin gemstone slices
- Valuable stones
- Fragile materials
- Glass
- Decorative cuts
- Lower chipping requirements
Possible downside:
- Slower cutting
- More patience required
- May not be ideal for aggressive rough cutting
Grit Selection Table
| Material / Goal | Suggested Direction |
|---|---|
| Agate rough opening | Coarse to medium grit |
| Jade clean cutting | Medium to fine grit |
| Quartz cutting | Medium grit with wet cutting |
| Glass cutting | Fine grit and slow feed |
| Turquoise or delicate stone | Fine grit, light feed |
| Valuable small pieces | Thin blade, finer grit |
| Fast cutting only | Coarser grit |
| Cleaner edge | Finer grit |
Grit Is Only One Part of the Result
A fine grit blade can still chip material if the user feeds too fast or cuts without coolant. A coarse grit blade may still perform well if the cut is rough and the edge will be finished later.
Cutting quality depends on:
- Grit
- Bond type
- Blade thickness
- RPM
- Coolant
- Feed speed
- Machine stability
- Material support
This is why two users can use the same blade and get different results.
How Grit Affects Chipping
Chipping is more likely when the cutting action is too aggressive for the material. Coarse grit can remove material faster, but it can also create larger edge impacts.
To reduce chipping:
- Use a finer grit.
- Use wet cutting.
- Feed slowly.
- Support the material.
- Slow down at the end of the cut.
Choosing Grit for ToAuto Lapidary Cutting
For ToAuto G6 series users, the 6-inch sintered diamond blade is designed for gemstone and hard brittle material cutting. When selecting replacement or specialized blades, match grit to the cutting goal:
- Rough cut: faster material removal
- General cut: balance of speed and edge quality
- Fine cut: cleaner edge and less chipping
FAQ
What grit is best for gemstone cutting?
For general gemstone cutting, medium grit is often a good starting point. For cleaner edges, choose finer grit.
What grit should I use for agate?
Medium grit is usually practical for general agate cutting. Finer grit may help reduce chipping.
Does higher grit mean better cutting?
Not always. Higher grit gives a cleaner cut but usually cuts more slowly.
Can grit reduce chipping?
Yes, finer grit can help reduce chipping, especially when combined with wet cutting and slow feed speed.
