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Milling titanium (Ti-6Al-4V): end mill speeds and feeds

Published carbide end mill SFM and chip load for Ti-6Al-4V (Grade 5) from Harvey Tool, Kyocera SGS and 6GTools, plus HEM vs. heavy-radial test data, slot limits and worked examples.

Ti-6Al-4V, also called Grade 5 or Ti 6-4, is the most common titanium alloy: 6% aluminum and 4% vanadium [4]. The published surface speeds for carbide end mills cluster lower than steel, and the chip loads are lighter at every size. Harvey Tool's general table gives 50-250 SFM for commercially pure titanium and 6Al-4V [1]. Kyocera SGS's general-purpose end mill catalog puts titanium alloys up to 350 Bhn / 38 HRc at 180 SFM (144-216) for profiling and 130 SFM (104-156) for slotting [2]. 6GTools lists 175 SFM uncoated, 210 with TiN and 240 with AlTiN [3].

Surface speed, carbide end mills

ChiploadPro's end mill calculator doesn't cover titanium yet. Use these tables, and the formulas RPM = SFM × 3.82 ÷ D and IPM = RPM × flutes × IPT [1].

Chip load by diameter

Inches per tooth, solid carbide. Digital Machine's values assume roughly 30-50% radial engagement and are compiled from Machinery's Handbook and maker charts [7].

Keep it cutting

Harvey Performance's titanium guide boils it down to: use a lot of high-pressure coolant, keep speeds down and feeds up, keep the tool moving whenever it touches the part, and make the setup as rigid as you can [4]. A lower RPM with a larger chip load runs significantly cooler than a high-speed, light-chip approach, and titanium conducts heat poorly, so the heat stays in the edge. Dwelling in a hole or stopping against a wall makes the tool rub, which work-hardens the surface and wears the tool early [4].

Titanium also sticks to the cutting edge. Built-up edge and galling are worst in the softer, "gummy" commercially pure grades. Aim high-pressure coolant at the cut to clear chips before they get recut. A high-temperature coating like AlTiN forms an oxide layer that adds lubricity [4].

Light-and-fast vs. heavy-and-slow

High-efficiency milling (HEM) in titanium is often run around 400-500 SFM at a 6% radial stepover [5]. In a Harvey Performance test with a 1/2" 6-flute Helical end mill at 1.0" axial depth, the HEM path ran 400 SFM, .0064 in/tooth and 118 IPM. A "heavy radial" (HREM) path at 27% stepover ran 220 SFM, .0026 in/tooth and 27 IPM. Both removed the same 3.51 in³. HREM raised peak tangential force from 228 to 397 but dropped peak tool temperature from 1,218 °F to 857 °F [5]. The catch is more force on the fixture and spindle, and less radial room on long tools. Harvey caps it at 27% radial for a 2 × D length of cut and 20% for 2.5 × D [5].

Slot and profile limits

SGS's titanium row uses the same engagement limits as its steel rows. Profiling: up to 1.5 × D axial, and radial up to 0.5 × D with 2 flutes or 0.25 × D with 3-4 flutes. Slotting: full width, 1 × D deep with 2 flutes, 0.5 × D with 3 and 0.4 × D with 4. For materials harder than listed, reduce speed and feed [2].

Worked example: 1/2" 4-flute profile

SGS: 180 × 3.82 ÷ 0.5 = 1,375 RPM. At .0012 in/tooth: 1,375 × 4 × .0012 = 6.6 IPM, the same as SGS's printed feed [2]. At 0.125" wide (0.25 × D) and 0.5" deep, that removes 0.125 × 0.5 × 6.6 = 0.41 in³/min. At 1.15 hp per in³/min for titanium alloys [6] and 80% drive efficiency: 0.41 × 1.15 ÷ 0.80 ≈ 0.6 HP at the motor. Titanium is rarely a horsepower problem at these feeds. Rigidity and heat are.

With an AlTiN tool, 6GTools's numbers run hotter: 240 × 3.82 ÷ 0.5 = 1,834 RPM, and 1,834 × 4 × .0014 ≈ 10.3 IPM [3]. Start at the catalog figure for your tool and move up from the chips and the tool wear.

Worked example: 1/2" 4-flute slot

SGS slot: 130 × 3.82 ÷ 0.5 = 993 RPM, 993 × 4 × .0012 = 4.8 IPM, no deeper than 0.4 × D = 0.2" per pass [2].

FAQ

What SFM should I run a carbide end mill at in Ti-6Al-4V?

Published starting points for solid carbide in Ti-6Al-4V run from 50-250 SFM in Harvey Tool's general table, 180 SFM (144-216) for profiling and 130 SFM (104-156) for slotting in Kyocera SGS's catalog, and 175, 210 and 240 SFM for uncoated, TiN and AlTiN tools from 6GTools.

What chip load should I use for a 1/2" end mill in titanium?

For a 1/2" carbide end mill in Ti-6Al-4V the published chip loads are .001 in/tooth (Harvey Tool), .0012 (Kyocera SGS), .0014 (6GTools) and .0014-.0025 (Digital Machine).

Should I slow the feed down in titanium?

No. Harvey Performance's advice is to keep speeds down and feeds up: a larger chip load at a lower RPM runs cooler, and rubbing work-hardens the material and wears the tool. Keep the tool moving whenever it touches the part.

Chip thinning math 304 stainless guide

Related guides

• Milling 304 stainless: speeds, feeds and flutes
• Chip thinning: why light cuts need more feed
• Milling 1018 and 4140 steel: end mill speeds and feeds
• Choosing flute count for end mills

Tooling for this job

• Carbide end mills for titanium
• AlTiN-coated carbide end mills
• Cutting fluid

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Sources

1. [1] Harvey Tool, General Machining Guidelines (high-temp alloys / titanium table)
2. [2] Kyocera SGS, 2023 Global Catalog: General Application End Mills, titanium alloys speed & feed, p. 322 (PDF)
3. [3] 6GTools, Carbide end mill speeds & feeds
4. [4] Harvey Performance, Tackling Titanium: A Guide to Machining Titanium and Its Alloys
5. [5] Harvey Performance, HREM vs HEM: Titanium Milling Test Results
6. [6] 4calculators, Milling Spindle Power Calculator (unit power table)
7. [7] Digital Machine, Chip Load Chart (compiled from Machinery's Handbook and maker charts)
8. [8] Harvey Performance, How to Combat Chip Thinning