An end mill can open shallow holes or mill holes by interpolation, but it should not be treated as a universal drill replacement. Hole depth, chip evacuation, flute count, material, and surface finish all decide whether the method is safe.
Direct plunging has limits
Most standard end mills are not optimized to drill deep, straight holes. They may cut at the center poorly, pack chips in the flutes, or leave a rough wall if the hole is deep. For shallow holes around half a tool diameter, the method may work under stable conditions. For deeper or critical holes, drilling, boring, or reaming is usually more controlled.
Helical interpolation is different
Helical hole milling uses the side and end of the cutter while the tool moves in a circular path. It can create larger holes with one cutter and allows diameter adjustment by toolpath. The tradeoff is cycle time, programming, and the need for enough machine rigidity.
- Use two or three flutes for soft materials when chip space is important.
- Use four or more flutes for harder materials when rigidity and finishing are priorities.
- Avoid deep direct plunging when chips cannot escape.
- Use a drill or guide operation when hole position and straightness are critical.
Surface finish expectations matter
A drilled and reamed hole is built for hole quality. A milled hole may be useful for flexible sizes or shallow features, but it can show tool marks or taper if the cutter deflects. A common shop-floor mistake is to mill a deep hole with an end mill and then expect reamer-like surface quality.
For slotting and pocketing context, see HEYI’s U-slot end mill guide. For cutter review, start from carbide tools and submit hole depth, diameter, material, tolerance, finish target, and machine power through the RFQ page.