Chip Formation, Drilling Machines, and Drilling Operations (Week 7)

Question 1

What are the four basic types of Chips in Machining?

Answer 1

1. Continuous chip
2. Discontinuous chip
3. Continuous chip with Built-up Edge (BUE)
4. Serrated chip

The type of chip depends on material type and cutting conditions

Question 2

What Cutting Conditions create Continuous Chips?

Answer 2

• Ductile* work materials
• High cutting speeds
• Small feeds and depths
• Sharp cutting edge
• Low tool-chip friction

*Ductility is the ability of a material to be drawn or plastically deformed without fracture.

Question 3

What Cutting Conditions create Discontinuous Chips?

Answer 3

• Brittle work materials
• Low cutting speeds
• Large feed and depth of cut
• High tool-chip friction

Question 4

What Cutting Conditions create Continuous Chips with BUE?

Answer 4

• The formation of continuous chips with the BUE is caused by high friction between the tool and the chip while machining ductile metals.(nickel, copper, steel)
• Low-to-medium cutting speeds
• Tool-chip friction causes portions of the chip to adhere to the rake face

Question 5

Effects of BUE on the cutting process :
The built-up edge _____________________________. It also reduces the contact area between the chip and the cutting tool, leading to a reduction in the power demand of the cutting operation.

Answer 5

The built-up edge [effectively changes tool geometry and rake steepness]. It also reduces the contact area between the chip and the cutting tool, leading to a reduction in the power demand of the cutting operation.

Question 6

What are the 4 main parts of a Drilling Machine?

Answer 6

1. Base
2. Column
3. Table
4. Drilling Head

Question 7

What are 3 types of drilling machines?

Answer 7

1. Drilling Press
2. Upright Drilling Machine
3. Radial Drilling Machine

Question 8

What is a Drilling Press used for?

Answer 8

Used primarily to produce holes in metal

Question 9

Properties of an Upright Drilling Machine?

Answer 9

Larger and heavier

Differences from Drilling Press

Equipped with gearbox for a variety of speeds

Spindle may be advanced by: hand lever, handwheel, and automatically by the feed mechanism

Table raised or lowered by mechanism

Some have reservoir in base for coolant storage

Question 10

Advantages of a Radial Drilling Machine?

Answer 10

Advantages of this machine
* Larger and heavier work may be machined
* Drilling head raised or lowered
* Drilling head moves rapidly to any desired
* Head may swivel so holes can be drilled
* On angle
* More power

Question 11

Safety guidelines for Drilling Machines?

Answer 11

Do not support the work piece by hand

No adjustments while the machine is working

Make sure that twist drill running straight before starting the drill.

Never place tools on the machine table

Avoid loose clothing and protect the eyes.

Chips should be removed using brush.

Question 12

What is Drilling?

Answer 12

Operation of producing hole by removing metal from the solid mass using a twist drill

Question 13

Properties of a General-Purpose Drill?

Answer 13

Has two Helical flutes

Designed to perform well on a wide variety of materials, equipment, and job conditions

Can be made to suit different conditions and materials by varying point angles, speeds, and feeds

Straight-shank drills called general-purpose jobbers length drills

Two helical grooves, or flutes, are cut lengthwise around the body of the drill

Question 14

What do different Twist Drill Point Angles do?

Answer 14

60-90° used for soft material (pointer end)

135-150°used to drill hard and tough materials (flatter end)

Question 15

What are 3 common Twist Drill Types?

Answer 15

1. Solid carbide drill
   o For small diameter holes.
   o Drilling depths up to 15xD
   o Tight tolerances.
2. Brazed carbide drill
   o Alternative to solid carbide drill for large diameters and high stability is needed
3. Indexable insert drill
   o The lowest price per hole.
   o Bigger diameter than solid carbide drills.
   o Medium tolerances.

Question 16

What are 3 common Twist Drill Materials?

Answer 16

1. Carbon-steel
2. High-speed steel
3. Cemented-carbide drills

Question 17

What are 6 operations performed on the Drilling Machine?

Answer 17

1. Drilling
2. Reaming
3. Boring
4. Counter boring
5. Countersinking
6. Tapping

Question 18

What is Reaming?

Answer 18

Operation of sizing and producing smooth, the round hole from previously drilled or bored hole
o To achieve good surface roughness and good dimensional tolerances in a pre-drilled hole.
o The tool is called a “reamer”.

Question 19

What is Tapping?

Answer 19

Cutting internal threads in hole with a cutting tool called tap
o The tool is called “tap”.
o It is commonly used for small threads.
o Used for manual or automatic operations.

Question 20

What is the meaning of (3/4”x10TPI) and (M10x1.5)?

Answer 20

The 3/4′′ refers to the bolt diameter (in inches), and the 10 refers to the threads per inch meaning that there are 10 threads per inch

M10 refers to the 10mm diameter of the threaded portion 1.5 refers to the 1.5mm pitch of the threads

Question 21

What is Counterboring?

Answer 21

Enlarging top of previously drilled hole to given depth to provide square shoulder for head of bolt or cap screw

The tool is called “counterbore”, and it has a pilot to guide the cutting action.

It is commonly used for:
o Enlarging a hole to make a bolt head fit flush with the surface.

Question 22

What is Countersinking?

Answer 22

This process is like Counterboring, but the step in the hole is tapered /cone-shaped.

The tool is called “countersink”.

A common use is:
* to allow the head of a countersunk bolt or screw, when placed in the hole, to sit flush with or below the surface of the surrounding material.
* to remove the burr left from a previous drilling or tapping operation.

Question 23

What is Spot Facing?

Answer 23

Smoothing and squaring surfaces around the hole to provide a seat for the head of the cap screw or nut. The Surface machined should be a square with the hole.

Smoothing and squaring surface around hole to provide seat for head of cap screw or nut

Question 24

Drill Tool Holding Devices?

Answer 24

Most common: drill chucks, drill sleeves, and drill sockets

Straight Shank

Morse Taper Shank

Drill sleeve
o Used when the hole in the spindle of the drill press to small for the taper shank of the drill. Used also as extension sockets.

Drill drift.
Removing a tapered- shank drill with a drill drift.

Drill socket
o Used to adapt cutting tool shank to machine spindle if the taper on the tool is smaller than a tapered hole in the spindle