carbide drill feeds and speeds chart. Get instant Number of Passes, Total Cycle Time (min) for your machining parameters.
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Request a Proposal →Every seasoned CNC machinist knows that getting the numbers right means the difference between scrap and a perfect part. Slot Milling is no exception. When Seco Tools application engineers walk a customer through process optimization, this is one of the first parameters they check — because even a 5% error here can cascade into tool failure or out-of-tolerance parts.
The formula at work here is deceptively simple but carries deep implications. Sumitomo Electric publishes reference tables for this parameter across their full turning and milling catalog, and YG-1 integrates it directly into their ToolGuide app. The underlying principle hasn't changed in decades, but modern coated carbides have pushed the usable range significantly.
Always cross-reference your calculated values against your tool manufacturer's recommended ranges. Seco Tools's CoroPlus ToolGuide and Sumitomo Electric's NOVO app provide material-group-specific upper and lower bounds. When in doubt, start conservative — you can always push harder on the second part.
Scenario: Machining 4140 alloy steel (HB 280) on a Haas VMC, using a Seco Tools solid carbide end mill.
When a slot is wider than the tool diameter, multiple passes are needed. This calculator determines the number of passes and estimates cycle time based on slot width, tool diameter, feed rate, and number of depth steps.
For width ≤ tool diameter, slot in one pass at 50-70% of normal feed rate. For width > tool diameter, multiple passes allow higher feed in each pass and produce straighter slot walls. Never slot at full diameter and full feed -- the 180 deg engagement overloads the tool.
For roughing wide slots: trochoidal or adaptive clearing (especially in hard materials). For finishing: contour passes with 0.1-0.2 mm radial stock. Avoid plunging directly into the slot -- ramp or helix entry reduces impact on the tool centre.
Down-milling (climb milling) produces better surface finish and lower cutting forces. However, in a full slot, both up and down occur simultaneously (one side climbs, the other side conventional mills). For wide slots with multiple passes, use climb milling on each pass.
Enter the slot width, tool diameter, feed rate, and number of Z-level passes. The calculator shows how many lateral passes are needed and estimates the total machining time for the slot. For deep slots, also use the peck drilling calculator for drilling before slotting.
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Use the calculator freely. If the result points to a tooling or process problem, we can source the exact carbide tooling you need from vetted factories in China. Compare factory-direct pricing.
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