CHAPTER 3 - DRILLING HOLES IN MATERIALS Flashcards
PREPARATION AND MARKING OUT
What does the helical fluting provide on a drill?
Provides the cutting edges of the drill with a rake angle
Assists in clearing waste material (swarf) and a path down for lubricant to follow.
PREPARATION AND MARKING OUT
Which is the most efficient drill used in metalwork?
Why?
Twist Drill because of the helical fluting
PREPARATION AND MARKING OUT
What do the initials HSS mean?
What do the initials CS mean?
High Speed Steel
Carbon Steel
PREPARATION AND MARKING OUT
What are the advantages of a HSS drill?
HSS drills are made from alloy steel and can cut at much inherent speeds without sustaining damage to their cutting edges
PREPARATION AND MARKING OUT
If a drill is too small to have its size written on its shank, what can be used to check its size?
By using a drill gauge
PREPARATION AND MARKING OUT
What type of shank does a drill under 12.5mm have?
Usually has a parallel shank and carried in the chuck of the drilling machine
PREPARATION AND MARKING OUT
What is the maximum size of drill that can be fitted to a pistol drill chuck?
12.4mm
PREPARATION AND MARKING OUT
Name the two grades of twist drill in common use?
- Carbon Steel
- High Speed Steel
PREPARATION AND MARKING OUT
Which type of lubricant is used on mild steel?
Soluble oil
PREPARATION AND MARKING OUT
Name 3 properties of a lubricant…
-Improve the quality of the hole
-Assists In dissipating the heat produced from the drill
-Improves the cutting efficiency
-Prolongs the life of the drill
PREPARATION AND MARKING OUT
Which type of lubricant is used on Aluminium?
Kerosene
PREPARATION AND MARKING OUT
Before drilling, what must you ensure?
-Item is supported by a suitable piece of scrap material to avoid drilling into the machine table or the body of the drill vice
PREPARATION AND MARKING OUT
What 3 situations could happen if the work isn’t properly supported before drilling starts?
-Broken drills
-Damaged work
-Personal Injury
PREPARATION AND MARKING OUT
Why do we centre punch before drilling?
In order to position the drill
PREPARATION AND MARKING OUT
What 2 things must the centre-punch mark be?
- Accurate in position
- Large enough to take the chisel edge of the drill
DRILLING PROCEDURE
When drilling deep holes, what must you do frequently?
Lift the drill from the hole at frequent intervals, stop the machine and use a brush to sweep the swarf from around the hole
PREPARATION AND MARKING OUT
Why do we Pilot Drill?
-Large drills have a large chisel edge, so centre-punch marks of the proportional amount could not be positioned accurately enough
-The above scenario also means a greater pressure being applied. This is relieved by a pilot hole
-Permit small tolerances before drilling holes to their final dimensions
DRILLING PROCEDURE
When drilling is complete, what should you continue to do when removing the drill?
Keep the drill turning clockwise as it is withdrawn
COUNTERSINKING
What is a countersinking tool used for?
Used to cut a seating around a drilled hole for flush-fitting countersink screws, bolts or rivets
REAMERS
What are reamers used for?
Reamers are precision-ground cutting tool. They are used to enlarge drilled holes to accurate dimensions and give a good smooth finish
REAMERS
What is a tapered reamer used for?
Type of reamer is used to produce, from a normally drilled hole, a tapered hole suitable for the fitting of taper pins.
REAMERS
How would you check the size of a hand expanding reamer?
Checked by a ring-type gauge of the required size or by using an outside micrometer calliper
REAMERS
How would you check the size range of a hand expanding reamer?
Stamped on its shank
REAMERS
On an imperial reamer, what does fractional number mean?
Shows the taper between the reamer and its taper pins
