Nomenclature & Design of Drill

Formula for Drilling

Cutting speed (vc)


vc (m/min) : Cutting Speed

DC (mm) : Drill Diameter

π (3.14) : Pi

n (rpm) : Main Axis Spindle Speed





Feed of the main spindle (vf)



vf (mm/min) : Feed Speed of the Main Spindle (Z axis)

f (mm/rev) : Feed per Revolution

n (rpm) : Main Axis Spindle Speed






Drilling time (Tc)


Tc (min) : Drilling Time

n (rpm) : Spindle Speed

ld (mm) : Hole Depth

f (mm/rev): Feed per Revolution

i : Number of Holes

Drill Troubleshooting Guide

Trouble Occurrences Countermeasures
Deformation of hole Becoming thread scratch in the hole 1. Check for Suitable Guide-Bush
2. Reduce relief angle
3. Check for proper point angle & length of lips
Generation of chattering & vibrationl 1. Reduce relief angle
2. Grind web thinning
3. Shortening length of drill
4. Check for proper drill
5. Check for chuck & collet & socket
6. Pre-centering
7. Inspect rigidity of the Drill Machine
Poor chip evacuation 1. Increase Feed
2. Check for proper helix angle
3. Check for proper chip space
4. Using Step feed
Defl ection of hole Drill won't enter work 1. Check for Suitable Guide-Bush
2. Reduce Feed
3. Pre-centering
Insufficient rigidity of drill Shortening length of drill
Unsuitable angle Regrinding
Excessive wear
of cutting edge
Cutting speed too high 1. Reduce cutting speed
2. Check Lip Relief
3. Increase Coolant Flow
4. Check for proper material
Poor surface
conditions
of work piece
Excessive wear of cutting edge Regrinding
Too much Feed Decrease feed
Chips clog in hole Add number of exit
the others 1. Thin Web
2. Check for Proper Guide-bush
3. Use the highly rigid spindle
Breakage Feed too heavy 1. Check for proper chip space
2. Check for proper helix angle
Chips clog in hole 1. Reduce feed
2. Shortening length of drill
3. Increasing Web thickness
Insufficient rigidity of drill 1. Reduce feed while throughout drilling
2. Check Set Up Rigidity
3. Use the highly rigid spindle
Unstable in throughout hole drilling Decrease feed rate
Chipping Feed speed too high Decrease feed rate
Tool High Lip relief Angle 1. Reduce Lip Relief Angle
2. Reduce feed in drilling
3. Check Set up Rigidity
During oversize operation 1. Properly grind point angle
2. Reduce cutting speed
Hole oversize Point angle is not properly,
large chip of one flute;
small chip of other flute
1. Regrinding
2. Thin Web
3. Properly grind point angle
4. Guide-bush

Indexable Spade Drill

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