Figure out how many passes you need to cut a shoulder, and at what depth. Straightforward numbers for the shop floor.
Start ↓For right-angle shoulder operations on a milling machine. Enter your shoulder height and let the calculator split it into optimal passes.
Cutting a shoulder on a VF-2 or VC-5 means taking the right number of passes. Too few and you overload the spindle. Too many and you burn cycle time. The depth per pass for shoulder milling depends on the shoulder height, tool diameter, and material. For a 20 mm shoulder in 304 stainless with a 12 mm end mill, three passes at 6-7 mm each is the sweet spot on most 40-taper machines. On a lighter machine like a Mini Mill, you might need five passes. The calculator above adjusts for this automatically.
Shop Rule: Shoulder depth per pass should never exceed 1.5× tool diameter for aluminum, 1× for steel, and 0.5× for titanium. These limits prevent the tool from deflecting under side load.
When programming a shoulder, leave 0.3-0.5 mm per side for a finish pass. The roughing passes should stay inside this boundary. The finish pass runs at the same RPM but at 60-70% of the roughing feed rate to achieve the required surface finish. For a surface callout of 1.6 μm Ra or better, the final finish pass depth should not exceed 0.3 mm.
On a Mazak with smooth acceleration, you can combine the rough and finish passes in a single toolpath using HSM-style contouring. Older machines with abrupt acceleration benefit from separate rough and finish programs to avoid leaving witness marks at the pass boundaries.
How do you calculate step milling passes? Passes = shoulder height / max safe depth per pass. The safe depth depends on material and tool diameter. This calculator does it automatically.
What is the difference between step milling and shoulder milling? Same operation. Step milling describes the axial passes; shoulder milling describes the feature geometry. A 90° shoulder is the most common form.
Should I use climb or conventional milling for shoulders? Climb milling for shoulders whenever possible. The cutting forces push the tool into the workpiece rather than away from it, producing a better surface finish and reducing chatter.
How does tool runout affect shoulder accuracy? Runout above 10 μm produces a visible step pattern on the shoulder wall. A quality holder with runout below 4 μm is essential for shoulders with tolerance under ±0.05 mm.