Technical Tools Incorporated
Home Line Page Promotions Page New Page
    Useful Information    

 

Useful Formulae To Make Machining Easier

Right Angle Triangle
SIDES & ANGLES KNOWN FORMULAS FOR SIDES & ANGLES TO BE FOUND
sides a & b c = (a2 - b2)1/2 sin B = b ÷ a C = 90° - B
sides a & c b = (a2 - c2)1/2 sin C = c ÷ a B = 90° - C
sides b & c a = (b2 + c2)1/2 tan B = b ÷ c C = 90° - B
side a, angle B b = a x sin B c = a x cos B C = 90° - B
side a, angle C b = a x cos C c = a x sin C B = 90° - C
side b, angle B a = b ÷ sin B c = b x cot B C = 90° - B
side b, angle C a = b ÷ cos C c = b x tan B B = 90° - C
side c, angle B a = c ÷ cos B b = c x tan B C = 90° - B
side c, angle C

a = c ÷ sin C

 b = c x cot C B = 90° - C

 

CIRCLE CIRCUMFERENCE = DIAMETER x 3.1416
CIRCLE DIAMETER = CIRCUMFERENCE x 0.31831
SIDE OF SQUARE INSIDE OF CIRCLE =  DIAMETER OF CIRCLE x 0.70711
DIAMETER OF A CIRCLE AROUND A SQUARE = SIDE OF SQUARE x 1.4142

 

TO FIND INCHES PER MINUTE FOR TAPPING (INCH)
IPM = RPM ÷ # T.P.I. OR IPM = RPM x PITCH

TO FIND INCHES PER MINUTE FOR TAPPING (METRIC)
IPM = METRIC PITCH x RPM x 0.03937

PITCH = 1 ÷ # T.P.I.

ABBREVIATION TABLE
B.M.D. BASIC MAJOR DIAMETER
D DIAMETER OF PART
d DIAMETER OF CUTTER
DIA. DIAMETER OF TOOL OR PART
DOC DEPTH OF CUT
D.S. TAP DRILL (HOLE) SIZE
FPT FEED PER TOOTH
H.P. HORSE POWER
IPM INCHES PER MINUTE
K KEY VALUE # PER MATERIAL
L.O.C. LENGTH OF CUT
MRR METAL REMOVAL RATE (CUBIC IPM)
RPM REVOLUTIONS PER MINUTE
SFM SURFACE FEET PER MINUTE
# TEETH NUMBER OF TEETH (FLUTES)
# T.P.I. NUMBER OF THREADS PER INCH
W.O.C. WIDTH OF CUT

 

RPM = SFM ÷ DIA.  x 3.82
SFM = RPM ÷ DIA. x 0.262
IPM = FPT x # TEETH x RPM
FPT = IPM ÷ # TEETH ÷ RPM

 

INCH CUT TAP D.S. = B.M.D. - (1.299 x % THREAD ÷ # T.P.I.)

METRIC CUT TAP D.S. = B.M.D. - 1.299 x METRIC PITCH x % THREAD
(TO CONVERT TO INCH SIZE, TAKE RESULT FROM ABOVE x 0.03937)

INCH THREAD FORMING TAP
D.S. = B.M.D. - (THREAD % VAR. ÷ # T.P.I.)
(55% VAR = 0.375) (65% VAR = 0.4375) (75% VAR = 0.500)

METRIC THREAD FORMING TAP
D.S. =  METRIC B.M.D. - (THREAD % VAR. x METRIC PITCH)
(55% VAR = 0.375) (65% VAR = 0.4375) (75% VAR = 0.500)
(TO CONVERT TO INCH SIZE, TAKE RESULT FROM ABOVE x 0.03937)

 

AVERAGE CHIP THICKNESS (MILLING)

FOR A NEW PROGRAM

(d ÷ RAD. ENGAGEMENT)1/2 x DESIRED EFFECTIVE FPT = PROGRAMMED FPT

TO CHECK A EXISTING PROGRAMMED FPT

(RAD. ENGAGEMENT ÷ d)1/2 x PROGRAMMED FPT = EFFECTIVE FPT

 

 

I.D. CIRCULAR MILLING IPM = D - d ÷ D x STRAIGHT IPM

O.D. CIRCULAR MILLING IPM = D + d ÷ D x STRAIGHT IPM

 

METRIC CONVERSIONS
INCHES x 25.4 = MM MM x 0.03937 = INCHES
MM ÷ 25.4 = INCHES INCHES ÷ 0.03937 = MM

MATERIAL KEY VALUE CHART
WORKPIECE MATERIAL K
FREE MACHINING STEEL (200 BHN MAX.) 1.0
SOFT ALLOY STEEL (150-220 BHN) 0.8
MEDIUM ALLOY STEEL (220-320 BHN) 0.5
HARD ALLOY STEEL (320-400 BHN) 0.5
HEAT TREATED STEEL (400-500 BHN) 0.3
S1-S7, P20 TOOL STEEL (175-225 BHN) 0.5
A2-A10, O1-O7 TOOL STEEL 9200-250 BHN) 0.5
D2-D7 TOOL STEEL (200-250 BHN) 0.4
FERRITIC STAINLESS (405,430,442,446) 1.1
AUSTENITIC STAINLESS (300 SERIES) 0.8
ANNEALED STAINLESS (404,410,420,431,440) 0.9
TEMPERED  STAINLESS (404,410,420,431,440) 0.5
17-4PH, 15-5PH, 13-8MO, STAINLESS (200 BHN) 0.7
TITANIUM 6A1-4V 0.5
INCONEL 600, 625, 718 0.6
RENE # 41 0.5
A-286 0.4
GREY CAST IRON (170-220 BHN) 1.2
GREY CAST IRON (220-270 BHN) 1.0
GREY CAST IRON (270 BHN & UP) 0.7
NODULAR CAST IRON, ANNEALED 0.9
ALUMINUM & MAGNESIUM 3.0
COPPER