Industrial-grade CNC feeds, speeds and Taylor tool-life calculator with per-field universal units, reference values and integrated audit trail.
Decision:Run the stated engineering model, review its assumptions and warnings, then make the release decision against the governing standard and verified source data.
The CNC Feeds & Speeds + Tool Life Calculator (SC-020) runs on FS-ENGINE v2.1.0 — an industrial parameter engine that couples extended Taylor tool-life (flank wear VB = 0.3 mm), ISO 513 material bands, Kienzle cutting-force modelling, radial chip-thinning / HEM engagement compensation, spindle power and torque verification, cantilever deflection, and Gilbert minimum-cost speed — all computed in SI with per-field universal units and a full audit trail. Results are engineering previews: calibrate Taylor C/n and kc1 against your tooling supplier before release to production.
What SC-020 computes
SC-020 is not a lookup table with imperial/metric toggles. Each input — tool diameter, overhang, cutting speed, feed per tooth, depth and width of cut, machine limits, Taylor constants, and costing fields — carries its own unit selector. The engine normalises everything to SI (millimetres, metres per minute, kilowatts, newton-metres) before calculation, then renders results and warnings against your selected display units.
A single run produces spindle speed and table feed, mean chip thickness (with thinning compensation where applicable), material removal rate, specific cutting force and tangential load, net and gross spindle power, torque demand versus machine limit, static tool deflection, corrected Taylor tool life, back-solved speed for a target life, theoretical feed-mark roughness, Gilbert economic speed, and cost-per-cutting-minute comparison. Blocking errors (RPM over limit, power exceeded, ae > D, critically low life) halt release; warnings flag envelope excursions that are physically valid but risky.
Preview caveat: reference constants loaded from ISO 513 presets are mid-band handbook values. Contract machining, aerospace release, and tooling warranty claims require supplier-specific C, n, kc1, and mc validated on your machine–tool–material combination.
Taylor tool life and VB = 0.3 mm
The classical Taylor speed–life relation describes how cutting speed Vc trades off against tool life T for a fixed tool–workpiece pair under stated test conditions. SectorCalc implements the extended form with multiplicative environment corrections:
T [min] = (C / Vc)1/n · kcool · kinterrupt
where C and n are empirically fitted constants for the selected material and tool substrate (carbide vs HSS bands differ), kcool accounts for coolant strategy, and kinterrupt penalises interrupted cuts. The implicit wear criterion is average flank wear land VB = 0.3 mm on the major cutting edge — the ISO turning-test convention. Tool life below 15 minutes triggers a blocking warning; life between half and four times the user target generates advisory messages with a back-solved speed Vc,T for the target life Ttarget:
Vc,T [m/min] = C · (Ttarget / (kcool · kinterrupt))−n
Taylor n typically ranges from 0.15 (superalloys, hardened steels) to 0.40 (aluminium). A low n means life is highly sensitive to speed — small Vc increases yield disproportionate life gains. Operating above the calibrated ISO 513 band can underestimate wear because C/n were fitted inside the recommended envelope, not at the edge of thermal failure.
ISO 513 material groups
ISO 513 classifies workpiece materials by machinability using letter groups that map to colour codes on cutting-tool packaging. SC-020 presets bundle typical Vc bands, feed-per-tooth ranges, Kienzle kc1/mc pairs, and suggested Taylor C/n for each selectable grade:
ISO 513 group
Representative grades
Illustrative Vc mid-band (carbide)
Typical Taylor n
P — Steel
1018, C45, 4140, pre-hardened tool steel
180–280 m/min (medium carbon)
0.20–0.26
M — Stainless
304/316 austenitic, 2205 duplex
150–230 m/min (304); 100–160 (duplex)
0.21–0.22
K — Cast iron
GG25 grey, GGG50 nodular
160–260 m/min (grey); 120–200 (nodular)
0.26–0.28
N — Non-ferrous
6061/7075 Al, brass, copper
400–900 m/min (wrought Al); 250–450 (brass)
0.30–0.40
S — Superalloys & Ti
Ti-6Al-4V, Inconel 718
45–90 m/min (Ti); 25–55 (Inconel)
0.15–0.18
H — Hardened
52–62 HRC hardened steel
50–100 m/min
0.18
Mid-band values are reference hints, not hard limits. HSS substrate selection automatically derates Vc to roughly 40–45% of the carbide band inside the engine.
Kienzle specific cutting force
Cutting power depends on the specific cutting force kc, which varies with undeformed chip thickness h. The Kienzle equation captures the nonlinear increase in kc as chip load decreases (rubbing regime):
kc [N/mm²] = kc1 · h−mc
kc1 and mc are material constants from the ISO 513 preset (e.g. medium-carbon steel: kc1 ≈ 1980 N/mm², mc ≈ 0.25). The engine uses mean chip thickness hm after thinning compensation, floored at 0.01 mm to avoid singularities. Material removal rate Q (cm³/min) and net cutting power follow:
Tangential force Fc = Pc · 60000 / Vc feeds the deflection model. kc from handbook tables assumes sharp tools and conventional flood coolant; worn edges, built-up edge, and cryogenic or dry extremes are not modelled explicitly — use coolant and interruption multipliers on life, not on kc, unless you recalibrate kc1 from force measurements.
Chip thinning and HEM engagement
When radial width of cut ae is less than half the tool diameter, the chip is thinner than the programmed feed per tooth fz. Programming catalogue fz for full-slot conditions in a trochoidal or HEM toolpath produces rubbing, heat, and premature wear. SC-020 applies one of two compensation paths:
CAM engagement angle θ (preferred when available): hm = fz · sin θ.
Radial fallback when ae/D < 0.5 and no angle is supplied: hm = fz · 2√(ae/D · (1 − ae/D)).
hm [mm] = fz · sin θ or hm = fz · 2√(ae/D · (1 − ae/D))
The engine reports the compensated hm and the fz you should program to achieve a target chip load. High-efficiency machining (HEM) typically runs ae/D between 0.10 and 0.25 with ap ≈ 1–2 × D and elevated fz after thinning correction — the calculator verifies that corrected loads still respect power, torque, deflection, and life envelopes.
Spindle power and torque
Gross spindle demand divides net cutting power by spindle efficiency η (typically 80–90% for belt- or direct-drive VMC spindles):
Ps [kW] = Pc / η ; M [N·m] = 9550 · Pc / n
Utilisation above 100% of rated power or torque is blocking; 80% power or 85% torque triggers warnings. Critical preview limitation: the engine applies a single torque limit at operating RPM — it does not interpolate the machine's torque–speed curve. High-speed spindles deliver far less torque near maximum RPM than the nameplate peak at base speed. Always cross-check M against the manufacturer's curve at the calculated n, not the catalog maximum alone.
Tool deflection and L/D stability
Static cantilever deflection treats the tool shank as a circular beam with second moment I = πD⁴/64 and Young's modulus E (580 GPa carbide, 200 GPa HSS):
δ [mm] = Fc · L³ / (3 · E · I)
Overhang ratio L/D governs chatter risk: L/D ≤ 4 is generally stable; 4–6 requires feed derating; L/D > 6 is flagged as critical for regenerative chatter. Deflection above 0.05 mm blocks release; 0.02–0.05 mm warns. Fluted end mills are 10–20% more flexible than the solid-cylinder assumption — treat δ as a lower bound. Finish passes with reduced ae and shorter L are standard mitigation when roughing deflection is acceptable.
Gilbert economic cutting speed
Maximum metal-removal rate is rarely minimum cost. Gilbert's model minimises cost per cutting minute by balancing machine time against edge consumption. Edge cost in machine-minutes is tool cost divided by machine rate plus changeover time. Economic tool life:
SC-020 compares cost per minute at your current Vc versus Vecon and reports potential savings on the machining-cost component only — scrap risk, surface-finish rework, and downstream operations are excluded. Currency selector sets display symbol; no FX conversion is performed.
Coolant and interruption multipliers
Environment corrections scale Taylor life and Gilbert economics multiplicatively. They are engineering factors from machining-handbook practice, not measured data for your shop:
Heavy interruption applies to cast skin, welds, cross-holes, and entry/exit breaks where thermal cycling accelerates thermal-fatigue cratering. Dry machining of steels may need more aggressive derating than 0.75 on life — validate with toolmaker tests.
Ball-nose effective diameter
Surface speed at the tool tip of a ball-nose end mill is near zero if nominal diameter is used in n = 1000·Vc/(πD). SC-020 replaces D with effective diameter at depth of cut ap:
Deff [mm] = 2 · √(R² − (R − ap)²) where R = D/2
When Deff < 0.3D, a warning recommends 10–15° tool tilt to bring the cutting zone onto a larger-radius section of the sphere. RPM, feed, power, and life all use Deff and the resulting Vc,eff.
FS-ENGINE SI core and units
FS-ENGINE v2.1.0 computes deterministically in SI regardless of per-field display units. Conversion factors applied at input:
Length: in → mm × 25.4
Speed: SFM → m/min × 0.3048
Power: HP → kW × 0.7457
Torque: ft·lb → N·m × 1.3558
Every report embeds engine version, UTC timestamp, FNV-1a integrity hash, entered values with units, SI values used internally, formula catalogue, and explicit assumptions. Identical inputs always yield identical outputs — no hidden state or stochastic variation.
SC-020 assumes ISO-style flank wear with average land width VB = 0.3 mm on the major cutting edge. C and n constants from the material preset were conceptually fitted to that endpoint. If your shop uses a different criterion — crater wear on stainless, maximum flank for aerospace, or surface-finish-driven change — refit C and n from your own tool tests or apply a safety factor to predicted life.
Why is my programmed feed per tooth higher than the chip load shown?
When ae < 0.5D or a CAM engagement angle is supplied, the physical chip thickness hm is less than programmed fz. The engine displays compensated hm and suggests the fz to program for a target load. This is expected in HEM and rest-machining strategies — always size fz from hm, not from full-slot catalogue values.
Why can spindle power pass while torque fails (or vice versa)?
Power P = M·ω couples torque and speed. Low-speed, heavy cuts are torque-limited; high-speed, light cuts are power-limited. SC-020 checks both against your entered limits at the operating RPM. Because torque curves droop with speed, a pass at nameplate torque may still fail on machine — verify against the OEM curve for the calculated spindle speed.
Should I always run at Gilbert economic speed Vecon?
Not necessarily. Vecon minimises machining cost per minute for the stated tool cost, change time, and machine rate. It does not account for scrap risk from tight tolerances, required surface finish, unstable setups, or contractual cycle-time caps. Use Vecon as a benchmark — if your current speed sits far below it with life ≫ target, there is often room to increase Vc without violating life or power limits.
Can I mix metric and imperial inputs?
Yes. Each dimensional field has its own unit selector; the engine converts to SI before calculation. Mixing SFM for Vc with millimetre tool dimensions is supported — the audit trail records both as-entered values and SI internals. Use global “All Metric” or “All Imperial” toggles for consistency, then override individual fields where needed (e.g. inch tools on a metric machine).
