Chip Thinning Calculator

Quick start

1. Pick Radial or Axial mode with the top toggle.
2. Set tool Ø, engagement (ae/% or ap + κ), desired chipload, flutes, and RPM.
3. Read h_eff, the feed multiplier, and adjusted feed in the big numbers.
4. Flip in | mm in the header anytime — it rewrites the whole board (angles, Z, RPM stay put).
5. Open Convert under Results for SFM↔rpm / ipt↔ipm, then tap Use this… to push into the calc.

Radial mode

Side-milling / circular engagement. Factor = 2·√((ae/D)·(1−ae/D)) when ae/D < 50%, else 1 (the chip reaches full ipt once the tool engages half its diameter). Example: 12.7% stepover gives a factor of 0.666, so feed × 1.50. Source: Harvey Performance, Combat Chip Thinning and HEM Guidebook p.20. Light ae thins the chip. Diagram: tool circle with shaded ae wedge.

Axial mode

Lead / entering angle thinning. Factor = sin(κ). Inputs: Ø (for surface speed), ap (axial DOC), κ (presets or free), ipt, Z, RPM. Diagram: side-view depth + lead-angle geometry. Source: Sandvik Coromant, Entering angle and chip thickness (h_ex = f_z · sin(κ_r) for straight-edge inserts).

Compensate

Radial only. When ON, the calc multiplies table feed so programmed IPM puts effective chip thickness back to the ipt you typed — light side cuts thin the chip, so you feed faster to keep load. When OFF, you still see the thinning math, but programmed feed stays ipt × RPM × Z.

Axial has no Compensate button on purpose. At small lead angles (like 12°) that jump can be 4–5× and unsafe for tools, spindle, and people. You still see h_eff and a theoretical × (info only) — raise feed yourself after checking machine load and the insert card. Never treat the Axial × as a one-tap program value.

Lead / entering angle κ

What to type into κ. Open the insert or cutter catalog (or the box). Find one number labeled lead angle, entering angle, approach angle, or κ / κr — how many degrees the cutting edge leans off the machined face. Type that number into κ. Example: FFQ4 high-feed ≈ 12°.

What it is (picture it). Look at the tool from the side, like the diagram. The work is flat. The insert’s cutting edge either stands tall or lays flatter on that face. κ is that lean, in degrees — not how deep you cut, not how wide sideways.

• 90° — edge stands square to the face (shoulder mill). Almost no axial thinning.
• 45° — common mid lean. Factor ≈ 0.707.
• 15° or 12° — high-feed: edge lays nearly flat on the face. Chip gets much thinner (sin 12° ≈ 0.208). Catalogs list high table feeds — you raise feed yourself against spindle load; Axial will not auto-jump feed.

Do not type these into κ: ap (depth of cut), ae (side engagement), rake, clearance, or a “chip thinning factor” from CAM. Those are different fields. κ is only the lean angle from the insert card.

Math: Axial factor = sin(κ). Smaller κ → thinner chip → bigger theoretical × (shown as info only). Match the preset to your real card — don’t leave 15° on if your tool is 12°.

Convert + units

in | mm lives in the header and flips every length field and label on the board (×25.4). Convert is a violet accordion under Results: SFM↔RPM needs Ø; ipt↔IPM needs Z + RPM. In mm mode it shows m/min ↔ rpm and mm/tooth ↔ mm/min. Gold stays on DEMO $ only — never next to Convert.

Convert math: RPM = 12 × SFM ÷ (π × Ø), which Harvey Tool prints as 3.82 × SFM ÷ D, and feed = chipload × flutes × RPM. Source: Harvey Tool General Machining Guidelines.

DEMO costs only

DEMO costs only. Blank $, burden rate, and scrap totals are sample numbers so you can see how scrap burns cash. They are not anyone’s real shop rates. Toggle the panel off if you only want the thinning math.

What’s not in this build

What’s not here yet. Setup / PM due board and arrive-by timers stay parked for a later tab — not missing, just not shipped.