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Suggested Cutting Speeds With HSS Tools

MATERIAL BRINELL DRILLS
S.F.M.
TAPS - S.F.M.
THREADS PER INCH
 3-8  9-15 16-24 25 UP
Aluminum (die cast) 95-105 250 50 100 130 150
Aluminum 95-105 200 50 100 130 150
Bakelite --- 80 50 100 130 150
Brass 192-202 200 50 100 130 150
Bronze Common 166-183 200 40 80 100 150
Bronze Phos. 1/2 hard 187-202 175 25 40 50 80
Copper 80-85 70 40 80 100 150
Cast Iron - soft 126 140 30 60 90 130
Cast Iron - hard 300 45 10 20 30 40
Cast Iron, Malleable 112-126 85 20 30 40 50
Duralumin 90-104 200 50 100 130 150
Nickel 187-202 75 25 40 50 80
Rubber - hard --- 100 50 100 150 200
Steel - mild .20-.30C 170-202 115 40 55 70 90
Steel - .40-.50C 170-196 80 20 30 40 50
Steel, Stainless 460-520 20 8 10 15 20
Steel, Tool 241 50 15 15 20 20
Zinc 110-125 200 50 100 130 150

Feeds For High Speed Drills

Drill Diameter Inches

Feed Inch Per Revolution

1/16 to 1/8

.001 - .003

1/8 to 1/4

.002 - .006

1/4 to 1/2

.004 - .010

1/2 to 1"

.007 - .015


Useful Formulas

RPM = 3.82 x SFM
                 Dia.

SFM = .262 x D x RPM

1 ÷ Pitch = Tap Lead


% of Threads (cut taps) = threads per inch x (major dia. of tap - drill dia.)
                                                                              .01299
Example for 1/4-20 tap, using # 7 drill.
.250 - .201 = .049 ÷ .01299 = 3.77 x 20 = 75% thread
Note: Use .0068 divisor for roll form taps.


Tap Drill Size (cut taps) = major Dia of tap - (.01299 x % of full thread)
                                                                                TPI
Example for 1/4-28 with 70% required threads.
.01299 x 70 = .909 ÷ 28 = .032
.250 - .032 = .218 drill size


Tap Drill Size (form taps) = major Dia tap - (.0068 x % full thread)
                                                                            TPI
Example for 1/4-20 tap with 65% required threads.
.0068 x 65 = .442 ÷ 20 = .022
.250 - .022 = .228 drill size


Calculation of tapping cycle time for Procunier tappers.

Inch cycle time (seconds) =
(90 x TPI x travel)
                                                   RPM
MM cycle time (seconds) =
(2286 x travel)
                                        MM (pitch) x RPM

Example for 10-32 at 1140 RPM
90 x 32 x .625 ÷ 1140 = 1.6 seconds

Example for M10 x 1.25 at 860 RPM
2286 x .950 = 2171.7
1.25 x 860 = 1075
2171.7 ÷ 1075 = 2. seconds

Notes:
Formulas include 2:1 reverse found on all Procunier tappers.
Travel includes tap clearance above piece part and total depth into hole

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