Question

REVISIONS DESCRIPTION ZONE REV DATE APPROVED 4 X 0.375 THRU 2.250 1.062 1.750 B ,0.437 0.562 0.500 0.750 1.375 2.500 - 3.000 - 4.000 NOTES: 1. UNLESS OTHERWISE SPECIFIED, ALL DIMENSIONS ARE IN INCHES. 2. MATERIAL: STEEL 350 BHN TOLERANCES DECIMALS ANOLES GEORGIA SOUTHERN XX 1 X.X +0.1 UNIVERSITY X.Xox - 0.01 X.XX - 0.01 X.XOOX 0.001 DESCRIPTION X.XXX - 0.0001 THIRD ANGLE PROMOTION A SZE PARENT ASSEMBLY OWO NO. SEE NOTE 2 LA PLATE DESIGNED BY SCALE 1.1 RELEASE DATE: 08-22-2017 SHEET 1 OF 1

Answer 1

Ans: -

Given : Drill bit material : Mild steel grade 350 BHN steel has a nominal yield strength of 350 MPa

Material : Alloy - 300 to 400 Brinell Steel 350 Recommended Speed (SFM) is 20 to 30  

For Steel drill 350 SFM will be taken from data sheet =30

Feed inches /rev for Diameter of Drill - Inches 1/4 to 1/2 is .004 to .010 inches (0.254 mm/rev)

R.P.M. = Revolutions Per Minute	I.P.R. = Inches Per Revolution
S.F.M. = Surface Feet Per Minute	Feed Stroke = Drill Depth + 1/3
I.P.M. = Inches Per Minute	Car Reamer = 1/2 Speed of Drill

• Tool diameter (D) : For Diameter size 0.375 inches (9.525 mm) - HSS dill bit reuired is 3/ 8( As per drill bits data sheet) .
• Length of Cut ( L): 0.750 inches
• Allowance (A) : 0.0019 inches
• Speed (V) : vc=π×D×n (Main Axis Spindle Speed)÷1000 =3.14×9.5 ×1350 /1000 = 40.27 m/min
• Feed (Ff) : 0.254 mm/rev
• Spindle RPM (Ns): 305 RPM
• Spindle Feed rate (Fm ) :vf=fr×n= 0.254×1350=342.9 mm/min
• Drilling time /hole (Tm) : Tc=(L×No of holes)÷(Main Axis Spindle Speed×Feed)
  Tc=(19.05×4)÷(1350×0.254)=0.226 min
  =0.226×60 = 13.6 sec
• Metal removal rare (MRR ) : MRR = (π(D)² / 4) (fm) =mm3 /min

=MRR = (0.25π (9.5)² / 4) × (342.9) = 24305.50 mm3 /min

Formula :

1. R.P.M. = (3.8197 / Drill Diameter) x S.F.M. =305 RPM
   • S.F.M. = 0.2618 x Drill Diameter x R.P.M. =30 SFM
   • I.P.M. = I.P.R. (feed) x R.P.M. (speed) =3.1 IPM