Feed for a Target Turned Finish
The fastest feed per revolution that still holds a target surface finish.
Example
You enter
- Target finish (microinches) 25
- Finish basis ra
- Tool nose radius r (in) 0.03125
You get
- Max feed per rev 0.005 IPR
Details, formula, and sources
f = sqrt(8 x nose_radius x Rt) (a target given as Ra converts with Rt = 4 x Ra). Holding 25 microinch Ra with a 1/32 in nose radius allows 0.005 IPR; a finer 16 microinch Ra drops it to 0.004 IPR. A larger nose radius lets you feed faster for the same finish. Answers 'how fast can I feed' instead of the finish at one feed. Theoretical; leave margin for tool wear and deflection.
f = sqrt(8 x nose_radius x Rt); Rt = 4 x Ra if the target is an Ra. The inverse of Rt = f^2 / (8 x r).
Theoretical surface roughness from feed and nose radius - first-principles scallop geometry as in Machinery's Handbook (Industrial Press), by name; public domain.
Pure geometry, public; the measured finish is rougher than this theoretical value, so leave margin.
Estimate. AHJ and licensed professional govern.
Field names used by the API: target_finish_uin, finish_basis, nose_radius_in, max_feed_ipr
- Round-nose scallop the round nose scallops the surface (the dominant regime); Ra ~= Rt / 4 converts an Ra target to Rtscallop geometry
- Theoretical only built-up edge, tool wear, deflection, and vibration roughen the measured finish; leave feed marginmachining practice