Category: Drills
How to Choose the Right Drill for CNC Machining
Drilling is one of the most-performed operations in any machine shop. Choosing right between solid carbide drills, indexable drills, and HSS-Co drills determines hole quality, cycle time, and cost-per-hole. Hooguu stocks drills from Sandvik, Walter, OSG, YG-1, Mitsubishi, and Iscar.
Decision Matrix by Diameter and Depth
- Diameter < 12mm → Solid carbide drill always wins (better hole quality)
- 12-25mm, depth ≤ 3×D → Indexable drill (lowest cost-per-hole)
- Diameter > 25mm → Indexable drill or specialty Spade drill
- Depth > 5×D → Solid carbide with through-coolant or gun drill
- Tolerance H8 or better → Solid carbide + reaming
Solid Carbide Drills
Sandvik CoroDrill 460, Walter A3782, OSG ADO series. Hole tolerance IT9-IT10 straight from the drill. Premium AlTiN coating extends life 3-5× over uncoated. Best for production drilling of repeating hole sizes.
Indexable Drills
Replaceable carbide inserts mean lower cost-per-hole and one body covers a diameter range. Hole tolerance IT12 typical, surface finish rougher. Sandvik CoroDrill 880, Iscar Chamdrill. Run 30-50% faster cutting speeds than solid carbide because chip evacuation is easier.
Material-Specific Selection
| Material | Drill Type | Coating |
|---|---|---|
| Mild steel | Solid carbide or indexable | TiAlN |
| Stainless 304/316 | Solid carbide w/ internal coolant | AlTiN |
| Cast iron | Solid carbide, no coolant needed | TiAlN |
| Aluminum | Solid carbide, polished flutes | Uncoated or DLC |
| Inconel/Titanium | Solid carbide w/ HP coolant | AlTiN nano |
| Hardened steel | Solid carbide micrograin | nACo |
Through-Coolant vs External Coolant
For depths over 4×D, through-coolant is mandatory. External coolant cannot reach the cutting edge in deep holes; chips re-cut and damage the drill. Modern HMC and HSK spindles deliver coolant at 70+ bar through the tool — pair with through-coolant drills for 200-400% tool life vs flood-only.
Speed and Feed Starting Points
- Steel 1045, 12mm carbide drill: 80-120 m/min, 0.20-0.30 mm/rev
- Aluminum 6061, 12mm carbide drill: 200-300 m/min, 0.30-0.40 mm/rev
- Stainless 304, 12mm carbide drill: 50-70 m/min, 0.15-0.20 mm/rev
Browse our drill catalog below. See also our complete indexable vs solid carbide comparison.
How to Choose the Right Drill for CNC Machining
Drilling is one of the most-performed operations in any machine shop. Choosing right between solid carbide drills, indexable drills, and HSS-Co drills determines hole quality, cycle time, and cost-per-hole. Hooguu stocks drills from Sandvik, Walter, OSG, YG-1, Mitsubishi, and Iscar.
Decision Matrix by Diameter and Depth
- Diameter < 12mm → Solid carbide drill always wins (better hole quality)
- 12-25mm, depth ≤ 3×D → Indexable drill (lowest cost-per-hole)
- Diameter > 25mm → Indexable drill or specialty Spade drill
- Depth > 5×D → Solid carbide with through-coolant or gun drill
- Tolerance H8 or better → Solid carbide + reaming
Solid Carbide Drills
Sandvik CoroDrill 460, Walter A3782, OSG ADO series. Hole tolerance IT9-IT10 straight from the drill. Premium AlTiN coating extends life 3-5× over uncoated. Best for production drilling of repeating hole sizes.
Indexable Drills
Replaceable carbide inserts mean lower cost-per-hole and one body covers a diameter range. Hole tolerance IT12 typical, surface finish rougher. Sandvik CoroDrill 880, Iscar Chamdrill. Run 30-50% faster cutting speeds than solid carbide because chip evacuation is easier.
Material-Specific Selection
| Material | Drill Type | Coating |
|---|---|---|
| Mild steel | Solid carbide or indexable | TiAlN |
| Stainless 304/316 | Solid carbide w/ internal coolant | AlTiN |
| Cast iron | Solid carbide, no coolant needed | TiAlN |
| Aluminum | Solid carbide, polished flutes | Uncoated or DLC |
| Inconel/Titanium | Solid carbide w/ HP coolant | AlTiN nano |
| Hardened steel | Solid carbide micrograin | nACo |
Through-Coolant vs External Coolant
For depths over 4×D, through-coolant is mandatory. External coolant cannot reach the cutting edge in deep holes; chips re-cut and damage the drill. Modern HMC and HSK spindles deliver coolant at 70+ bar through the tool — pair with through-coolant drills for 200-400% tool life vs flood-only.
Speed and Feed Starting Points
- Steel 1045, 12mm carbide drill: 80-120 m/min, 0.20-0.30 mm/rev
- Aluminum 6061, 12mm carbide drill: 200-300 m/min, 0.30-0.40 mm/rev
- Stainless 304, 12mm carbide drill: 50-70 m/min, 0.15-0.20 mm/rev
Browse our drill catalog below. See also our complete indexable vs solid carbide comparison.
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