What RPM for a M45x4.5 tap?

RPM = 3.82 × SFM ÷ D with D = 1.77 in. With a general-purpose HSS tap that is about 150 RPM in 6061 aluminum (70 SFM) and 40 RPM in mild steel (20 SFM). Premium coated taps on a rigid CNC can run faster; see the second table.

What is the feed rate for a M45x4.5 tap?

Feed per revolution equals the pitch: 4.5 mm. Feed (mm/min) = RPM × 4.5, so at 150 RPM the feed is 675 mm/min.

How fast can I run a M45x4.5 form (roll) tap?

OSG lists 65–115 SFM for form taps in aluminum alloys, which is 140–250 RPM for M45x4.5. Form taps need a larger hole: about 43.0 mm (43.00 mm).

What speed for a M45x4.5 tap in stainless steel?

General-purpose HSS taps: 10–20 SFM, or 20–40 RPM at 90–180 mm/min. Keep the tap cutting and use 60–65% thread to cut torque.

M45x4.5 tap speeds and feeds

A M45x4.5 tap feeds one pitch per turn: 4.5 mm per rev. With a general-purpose HSS tap, start near 150 RPM and 675 mm/min in 6061 aluminum, or 40 RPM and 180 mm/min in mild steel.

ISO metric coarse thread · major Ø 45.00 mm · tap drill 40.50 mm (40.50 mm) for a cut tap, 43.0 mm for a form tap.

M45x4.5 tapping speeds by material

Cut tap = general-purpose HSS tap. Form tap = OSG form (roll) taps. RPM rounded to 10; feed in mm/min = RPM × pitch. Start at the low end.

M45x4.5 cut and form tap speeds
Material	Cut SFM	Cut RPM	Cut mm/min	Form SFM	Form RPM	Form mm/min
Aluminum 6061 / 7075	70–90	150–190	675–855	65–115	140–250	630–1,125
Free-machining / mild steel (12L14, 1018)	20–40	40–90	180–405	50–115	110–250	495–1,125
4140 alloy steel (annealed to <35 HRC)	20–30	40–60	180–270	50–85	110–180	495–810
304 / 316 stainless	10–20	20–40	90–180	15–40	30–90	135–405
Tool steel (A2, D2, O1, H13, P20)	15–25	30–50	135–225	8–25	20–50	90–225
Gray / ductile cast iron	15–30	30–60	135–270	Not listed	Not listed	Not listed
Brass / bronze	60–100	130–220	585–990	Not listed	Not listed	Not listed
Titanium (6Al-4V, CP)	5–15	10–30	45–135	8–15	20–30	90–135
Plastics and composites (acetal, nylon, G-10)	50–70	110–150	495–675	Not listed	Not listed	Not listed

Not listed = no form-tap value in the cited tables (OSG lists no form tap for cast iron; brass and plastics are not in its form-tap table).

Premium coated cut taps on a rigid CNC

OSG's starting speeds for its premium HSS-E cut taps (A-Tap family and the titanium/stainless taps it names) are higher than the general-purpose row. Use them only with that class of tap and rigid tapping.

M45x4.5 premium cut tap speeds (OSG)
Material	OSG row	SFM	RPM	mm/min
Aluminum 6061 / 7075	Aluminum alloys	70–120	150–260	675–1,170
Free-machining / mild steel (12L14, 1018)	Carbon steels <35 HRC	80–120	170–260	765–1,170
4140 alloy steel (annealed to <35 HRC)	Alloy steels <35 HRC	35–65	80–140	360–630
304 / 316 stainless	Stainless 300 & 400 series <35 HRC	15–75	30–160	135–720
Tool steel (A2, D2, O1, H13, P20)	Alloy, tool & die steels 30–40 HRC	15–30	30–60	135–270
Gray / ductile cast iron	Cast iron	50–120	110–260	495–1,170
Titanium (6Al-4V, CP)	Titanium alloys <35 HRC	15–20	30–40	135–180

Worked example: M45x4.5 in 6061 aluminum

Surface speed: 70 SFM (low end of 70–90 for a general-purpose HSS tap).
RPM = 3.82 × SFM ÷ D = 3.82 × 70 ÷ 1.77 ≈ 150 RPM (D = 45 mm = 1.77 in; or RPM = 1000 × 21.3 m/min ÷ (π × 45)).
Feed per rev = pitch = 4.5 mm.
Feed = RPM × pitch = 150 × 4.5 = 675 mm/min (26.6 IPM).

G84 tapping code for M45x4.5

Rigid tapping, aluminum numbers from the example, metric (G21), depth 1.5 × D. Check your control's manual before running.

Fanuc rigid tap (M29)

(M45x4.5 TAP - RIGID)
G21 G17 G40 G80 G90
T5 M06
G54 G00 X0. Y0.
G43 H05 Z25. M08
M29 S150           (RIGID TAP MODE; M-CODE SET BY PARAMETER)
G98 G84 Z-68. R3. F675.
G80 M09
G91 G28 Z0.
M30

Haas rigid tap

G21 G00 G90 G54 X0. Y0.
G43 H05 Z3. M08
G84 Z-68. R3. F675. S150   (NO M03 NEEDED)
(PECK: ADD Q = PECK DEPTH; J2 = RETRACT 2X, SEE SETTING 130)
G80 G00 Z25. M09

Floating / tension-compression holder

Without rigid tapping, run G84 with the spindle on (M03 S150) and the same F675 feed, but hold the tap in a tension-compression holder: it absorbs the overrun when the spindle stops and reverses. Leave the holder room to float at the bottom, so program the depth a little short and follow the holder maker's setting.

Peck tapping (Q) clears chips in deep or blind holes in stainless and 4140; skip it in aluminum unless chips pack.
Left-hand M45x4.5-LH taps use G74 instead of G84.
If the control caps rigid-tap RPM, lower S and recompute F: F = S × 4.5.

Notes for this size

M45x4.5 needs real torque: check that your spindle makes enough torque at 40 RPM (a gear-range spindle may need its low range). Thread milling is often the safer choice in tough material at this size.
A 4.5 mm pitch is coarse: the axis moves 4.5 mm every revolution, so check the machine can hold sync at the IPM shown before raising RPM.

4140 alloy steel (annealed to <35 HRC): Prehardened 4140 (28–32 HRC) is at the top of this band: use the low end and 50–65% thread.
304 / 316 stainless: Work-hardens: never let the tap dwell or rub, and use a tap made for stainless. 60–65% thread cuts torque sharply.
Tool steel (A2, D2, O1, H13, P20): Values are for annealed or prehardened stock. Tap before heat treat whenever you can; hardened tool steel needs a thread mill or a carbide tap.

Hole and tools for M45x4.5

Tap drill, cut tap 75%: 40.50 mm (40.50 mm)
Form tap drill (65%): 43.0 mm (43.00 mm)
50% thread drill for hard or gummy stock: 42.0 mm (42.00 mm)

Tap calculator, prefilled for M45x4.5 M45x4.5 tap drill size Tap drill chart

Common questions

What RPM for a M45x4.5 tap?: RPM = 3.82 × SFM ÷ D with D = 1.77 in. With a general-purpose HSS tap that is about 150 RPM in 6061 aluminum (70 SFM) and 40 RPM in mild steel (20 SFM). Premium coated taps on a rigid CNC can run faster; see the second table.
What is the feed rate for a M45x4.5 tap?: Feed per revolution equals the pitch: 4.5 mm. Feed (mm/min) = RPM × 4.5, so at 150 RPM the feed is 675 mm/min.
How fast can I run a M45x4.5 form (roll) tap?: OSG lists 65–115 SFM for form taps in aluminum alloys, which is 140–250 RPM for M45x4.5. Form taps need a larger hole: about 43.0 mm (43.00 mm).
What speed for a M45x4.5 tap in stainless steel?: General-purpose HSS taps: 10–20 SFM, or 20–40 RPM at 90–180 mm/min. Keep the tap cutting and use 60–65% thread to cut torque.

Nearby sizes

Sources

Productivity Inc. tool catalog, Tech Info - Taps: General Purpose & Other Tap Speeds (pp. 405-416)
OSG USA, A Brand & Premium Tooling Recommendation Guide Vol. 4 (Threading and Drilling), EDP 800313CA-V4, 2026
Haas Automation, G84 Tapping Canned Cycle (Group 09), mill G-code reference
Thread dimensions and tap drills: Machinery's Handbook, 31st ed.; ASME B1.1 Unified Inch Screw Threads.

SFM ranges are copied from the tables above; RPM and feed are computed for M45x4.5 (D = 45 mm). Speeds are starting values: your tap maker's data, coolant and machine come first.

Free for machinists & programmers

Put your skills on a free talent profile

Machines, controls, certs and saved calculations in one profile shops can find.

Create free profile

For your shop

Bring shift handoffs to your shop

Stop losing job status between shifts. Every station's notes, counts and issues, handed off cleanly.

See shift handoffs