Drilling

Question 1

What is a center drill

Answer 1

a small twist drill used to make centers in a piece of work about to be turned

Question 2

List each center drill #s, start of hole diameter and part diameter

Answer 2

Drill #                Start of Hole           Part Diameter
#1                                 sh 1/8"                           Pd 3/16 to 15/16"
#2                                sh 3/16"                           Pd 3/8 to 1"
#3                                Sh 1/4"                           Pd 1 1/4 to 2"
#4                                Sh 5/16"                           Pd 2 1/4 to 4"

Question 3

What are the parts of a drill bit

Answer 3

1. Dead center
2. Lip or cutting edge
3. Flute
4. Margin
5. Web
6. Body
7. Shank
8. Tang

Question 4

What is the dead center?

Answer 4

The sharp edge at the extreme point should always be the center of drill axis

Question 5

What is the cutting lip or edge?

Answer 5

The portion that does the cutting

Question 6

What is the shank?

Answer 6

The portion that mounts into a chuck or spindle

Question 7

What is the tang?

Answer 7

The tang is the part that fits into a slot in a spindle, sleeve, or socket. Provides a means of separating the the taper from the holding device

Question 8

What is the body?

Answer 8

Portion of a drill between the point and shank

Question 9

What are the flutes?

Answer 9

Two or more spiral grooves that run the length of the body

Question 10

What are the purposes of the flutes?

Answer 10

1. Help form cutting edges
2. Curl the chip tightly for easier removal
3. Channel chips can escape
4. Allow coolant and lubricant to flow down to cutting edges

Question 11

What is the web?

Answer 11

The metal column that separates the flutes. gradually increases thickness toward the shank

Question 12

What sizes do the drill bits come in?

Answer 12

Numbers #80-1 (.0135” to .2280”)
Letters A to Z ( .234” to .413”)
Inches and fractions 1/64” to 3 1/2”
Metric .15 mm to 76 mm

Question 13

How to determine size of a drill?

Answer 13

Frequently have it stamped on the bit but if it wears off you can use a micrometer and measure the drill margins. If this is worn you can measure the shank at the end of the flutes.

Question 14

Types of drills?

Answer 14

1. Reduced shank drill- allows larger holes to be drilled with smaller chucks or spindle sizes
2. Micro drill- diameters smaller than .020”, special equipment required.
3. Step drill- designed to drill a hole and counterbore in same operation

Question 15

How do you sharpen drill bits?

Answer 15

Grind the drill so you have 59* on each lip for a total of 118. The relief should be 8-10 . Ensure the lips are the same length. And the dead center is accurately positioned. The angle of 59* will be more for softer metals and less for harder metals.

Question 16

How can you check the angle of your bit

Answer 16

With a drill point gage