Chip Formation, Drilling Machines, and Drilling Operations (Week 7) Flashcards
What are the four basic types of Chips in Machining?
- Continuous chip
- Discontinuous chip
- Continuous chip with Built-up Edge (BUE)
- Serrated chip
The type of chip depends on material type and cutting conditions
What Cutting Conditions create Continuous Chips?
- 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.
What Cutting Conditions create Discontinuous Chips?
- Brittle work materials
- Low cutting speeds
- Large feed and depth of cut
- High tool-chip friction
What Cutting Conditions create Continuous Chips with BUE?
- 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
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.
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.
What are the 4 main parts of a Drilling Machine?
- Base
- Column
- Table
- Drilling Head
What are 3 types of drilling machines?
- Drilling Press
- Upright Drilling Machine
- Radial Drilling Machine
What is a Drilling Press used for?
Used primarily to produce holes in metal
Properties of an Upright Drilling Machine?
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
Advantages of a Radial Drilling Machine?
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
Safety guidelines for Drilling Machines?
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.
What is Drilling?
Operation of producing hole by removing metal from the solid mass using a twist drill
Properties of a General-Purpose Drill?
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
What do different Twist Drill Point Angles do?
60-90° used for soft material (pointer end)
135-150°used to drill hard and tough materials (flatter end)
What are 3 common Twist Drill Types?
- Solid carbide drill
o For small diameter holes.
o Drilling depths up to 15xD
o Tight tolerances. - Brazed carbide drill
o Alternative to solid carbide drill for large diameters and high stability is needed - Indexable insert drill
o The lowest price per hole.
o Bigger diameter than solid carbide drills.
o Medium tolerances.
What are 3 common Twist Drill Materials?
- Carbon-steel
- High-speed steel
- Cemented-carbide drills
What are 6 operations performed on the Drilling Machine?
- Drilling
- Reaming
- Boring
- Counter boring
- Countersinking
- Tapping
What is Reaming?
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”.
What is Tapping?
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.
What is the meaning of (3/4”x10TPI) and (M10x1.5)?
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
What is Counterboring?
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.
What is Countersinking?
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.
What is Spot Facing?
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
Drill Tool Holding Devices?
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
