Free Fly Cutter Surface Finish & Feed Tool
Calculate peak-to-valley cusp height, surface roughness ($R_a$), table feed rate, spindle RPM, and surface speed for large-sweep fly cutter heads.
⚙️ Fly Cutter Geometry & Workpiece
📊 Scallop Roughness & Machine Feed
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Tested hardware and components for high reliability
Mechanics of Fly Cutting Surface Roughness & Scallop Formation
A fly cutter uses a single-point toolbit rotating at a large sweep radius to generate ultra-flat planar surfaces. Because only a single cutting edge engages the workpiece, tooth-to-tooth runout errors inherent in multi-insert face mills are completely eliminated, enabling mirror finishes.
Scallop Cusp Height Equation
As the fly cutter advances across the work by feed per revolution (f_r), circular arcs generated by the toolbit corner nose radius (r_ arepsilon) intersect, leaving theoretical cusp ridges of height (h):
$$h approx rac{f_r^2}{8 cdot r_ arepsilon}$$
Center-Line Arithmetic Roughness ((R_a))
For circular arc tool profiles, theoretical (R_a) is approximately one-fourth of peak-to-valley height:
$$R_a approx rac{f_r^2}{32 cdot r_ arepsilon}$$
For example, with a standard (r_ arepsilon = 0.8 ext{ mm}) insert nose radius and a fine feed of (f_r = 0.08 ext{ mm/rev}):
$$R_a = rac{0.08^2}{32 cdot 0.8} = 0.00025 ext{ mm} = 0.25 mu ext{m} (10 mu ext{in})$$
Frequently Asked Questions
Why should the mill head be trammed slightly when fly cutting?
If a mill spindle is perfectly square, the "back side" of the fly cutter toolbit will drag across the freshly cut surface during the return arc, causing unwanted cross-hatch scuffing. Machinists intentionally tilt the milling head by 0.02 mm over 150 mm so only the front leading edge cuts.
What is the minimum cutter sweep diameter for a workpiece?
The fly cutter diameter should be at least 1.3 to 1.5 times the width of the workpiece to enable single-pass surfacing without overlap blend ridges.