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How to choose U drill(SP or WC ) for processing?
Created on 10.20
Indexable Drill-U drills
The two most common types on the market are the SP series and the WC series.
While the drill bodies share the same precision standards, their cutting geometries make them suitable for different machining priorities.
SP series: Featuring square, four-edged inserts (SPMG), they produce a smooth hole bottom and a high-quality surface finish.
WC series: Utilizing peach-shaped, three-edged inserts (WCMX/WCMT), they deliver smoother cutting and higher efficiency.
Geometry and blade differences
Item | SP Series U-Drill | WC Series U-Drill |
Insert Shape | Square, 4-edge (SPMG) | Trigon / Peach-shape, 3-edge (WCMX / WCMT) |
Usable Edges | 4 cutting edges (rotatable four times) | 3 cutting edges (rotatable three times) |
Cutting Angle | Blunter angle — stable entry, cutting force directed upward | Sharper angle — cutting force directed downward, smooth chip flow |
Hole Bottom Shape | Flat bottom with minimal center core | Slight taper bottom for smoother break-through |
Insert Cost | Medium | Lower (cost-effective and widely used insert type) |
Surface Finish | ⭐⭐⭐⭐ High | ⭐⭐⭐ Standard |
Machining Efficiency | ⭐⭐⭐ Medium to High | ⭐⭐⭐⭐ High |
Comparison of processing characteristics
SP Series Features:
Flat drill bottom and smooth hole walls make it ideal for drilling pilot holes or blind holes.
Excellent chip breaking performance and a short chip design prevent chip accumulation at the hole bottom.
Four rotatable blades extend insert life and cost-effectiveness.
Suitable for drilling medium-depth (2D-3D) holes, balancing precision and cost.
WC Series Features:
Sharp cutting angles and smooth chip removal make it ideal for drilling through holes or through holes.
Low drilling resistance and high efficiency.
Affordable inserts offer excellent value for money.
Suitable for high-volume, high-speed, and high-capacity production lines.
Applicable scenario suggestions
Machining Condition | Recommended Series | Description |
Blind hole / Bottom hole | SP Series✅ | Square insert with short-chip geometry; flat hole bottom, ideal for bottom-hole machining. |
Through-hole machining | WC Series✅ | Trigon insert ensures smooth chip evacuation and clean hole exit. |
For smoother hole wall and flat bottom | SP Series✅ | Four-edge geometry provides stable cutting and better surface finish. |
For higher machining efficiency and lower insert cost | WC Series✅ | Three-edge design allows 10–15% higher feed rate. |
General steel or cast iron | SP / WC Both Applicable | Choose by depth (≤3D: SP; ≥3D: WC). |
Stainless steel or alloy steel | WC Series✅ | Balanced cutting force and excellent anti-adhesion performance. |
Selection recommendations
If you primarily process blind holes/bottomed holes and require a smooth and even bottom finish, then the SP series is recommended.
If you prefer through-hole processing/high-efficiency production and require feed and insert economy, then the WC series is recommended.
Flexible combinations are available depending on the processing type.
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