7/16-14 tap speeds and feeds

    A 7/16-14 tap feeds one pitch per turn: 0.0714 in (1 ÷ 14 TPI) per rev. With a general-purpose HSS tap, start near 610 RPM and 43.6 IPM in 6061 aluminum, or 170 RPM and 12.1 IPM in mild steel.

    UNC thread · major Ø 0.4375 in · tap drill U (0.3680 in) for a cut tap, 13/32 for a form tap.

    7/16-14 tapping speeds by material

    Cut tap = general-purpose HSS tap. Form tap = OSG form (roll) taps. RPM rounded to 10; IPM = RPM ÷ 14. Start at the low end.

    7/16-14 cut and form tap speeds
    MaterialCut SFMCut RPMCut IPMForm SFMForm RPMForm IPM
    Aluminum 6061 / 707570–90610–79043.6–56.465–115570–1,00040.7–71.4
    Free-machining / mild steel (12L14, 1018)20–40170–35012.1–25.050–115440–1,00031.4–71.4
    4140 alloy steel (annealed to <35 HRC)20–30170–26012.1–18.650–85440–74031.4–52.9
    304 / 316 stainless10–2090–1706.43–12.115–40130–3509.29–25.0
    Tool steel (A2, D2, O1, H13, P20)15–25130–2209.29–15.78–2570–2205.00–15.7
    Gray / ductile cast iron15–30130–2609.29–18.6Not listedNot listedNot listed
    Brass / bronze60–100520–87037.1–62.1Not listedNot listedNot listed
    Titanium (6Al-4V, CP)5–1540–1302.86–9.298–1570–1305.00–9.29
    Plastics and composites (acetal, nylon, G-10)50–70440–61031.4–43.6Not listedNot listedNot 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.

    7/16-14 premium cut tap speeds (OSG)
    MaterialOSG rowSFMRPMIPM
    Aluminum 6061 / 7075Aluminum alloys70–120610–1,05043.6–75.0
    Free-machining / mild steel (12L14, 1018)Carbon steels <35 HRC80–120700–1,05050.0–75.0
    4140 alloy steel (annealed to <35 HRC)Alloy steels <35 HRC35–65310–57022.1–40.7
    304 / 316 stainlessStainless 300 & 400 series <35 HRC15–75130–6509.29–46.4
    Tool steel (A2, D2, O1, H13, P20)Alloy, tool & die steels 30–40 HRC15–30130–2609.29–18.6
    Gray / ductile cast ironCast iron50–120440–1,05031.4–75.0
    Titanium (6Al-4V, CP)Titanium alloys <35 HRC15–20130–1709.29–12.1

    Worked example: 7/16-14 in 6061 aluminum

    1. Surface speed: 70 SFM (low end of 70–90 for a general-purpose HSS tap).
    2. RPM = 3.82 × SFM ÷ D = 3.82 × 70 ÷ 0.4375 ≈ 610 RPM.
    3. Feed per rev = pitch = 0.0714 in (1 ÷ 14 TPI).
    4. IPM = RPM ÷ TPI = 610 ÷ 14 = 43.6 IPM.

    G84 tapping code for 7/16-14

    Rigid tapping, aluminum numbers from the example, inch (G20), depth 1.5 × D. Check your control's manual before running.

    Fanuc rigid tap (M29)

    (7/16-14 TAP - RIGID)
G20 G17 G40 G80 G90
T5 M06
G54 G00 X0. Y0.
G43 H05 Z1.0 M08
M29 S610           (RIGID TAP MODE; M-CODE SET BY PARAMETER)
G98 G84 Z-0.66 R0.1 F43.57
G80 M09
G91 G28 Z0.
M30

    Haas rigid tap

    G20 G00 G90 G54 X0. Y0.
G43 H05 Z0.1 M08
G84 Z-0.66 R0.1 F43.57 S610   (NO M03 NEEDED)
(PECK: ADD Q = PECK DEPTH; J2 = RETRACT 2X, SEE SETTING 130)
G80 G00 Z1. M09

    Floating / tension-compression holder

    Without rigid tapping, run G84 with the spindle on (M03 S610) and the same F43.57 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 7/16-14-LH taps use G74 instead of G84.
    • If the control caps rigid-tap RPM, lower S and recompute F: F = S ÷ 14.

    Notes for this size

    • 7/16-14 is in the size range most shops rigid tap every day. Run the low end of the table first, then raise speed in 10% steps while watching spindle load on the reversal.
    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 7/16-14

    Tap calculator, prefilled for 7/16-147/16-14 tap drill sizeTap drill chart

    Common questions

    What RPM for a 7/16-14 tap?
    RPM = 3.82 × SFM ÷ D with D = 0.4375 in. With a general-purpose HSS tap that is about 610 RPM in 6061 aluminum (70 SFM) and 170 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 7/16-14 tap?
    Feed per revolution equals the pitch: 0.0714 in (1 ÷ 14 TPI). IPM = RPM ÷ 14, so at 610 RPM the feed is 43.6 IPM.
    How fast can I run a 7/16-14 form (roll) tap?
    OSG lists 65–115 SFM for form taps in aluminum alloys, which is 570–1,000 RPM for 7/16-14. Form taps need a larger hole: about 13/32 (0.4063 in).
    What speed for a 7/16-14 tap in stainless steel?
    General-purpose HSS taps: 10–20 SFM, or 90–170 RPM at 6.43–12.1 IPM. Keep the tap cutting and use 60–65% thread to cut torque.

    Nearby sizes

    Sources

    SFM ranges are copied from the tables above; RPM and feed are computed for 7/16-14 (D = 0.4375 in). Speeds are starting values: your tap maker's data, coolant and machine come first.

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