Basic knowledge about drills

1. Cutting tool’s knowledge
Basic Drill’s
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2. Different type of drill’s
Stepped drill
(Drills and chamfers holes at the same time)
Gun drill
(Used for opening deep holes)
Center hole drill
(Used to open center holes in shafts)
Burnishing drill
(Used to open high-precision holes in aluminum)

3. Different type of drill’s
Twist drill
(Regular drill with good swarf removal)
Throwaway drill
(An insert is set in the end of the tool. Used primarily for finishing holes)
Formed flat drill
(Used for finishing stepped holes and shaped holes)
Flat drill
(The angle on the end is between 120 degrees and 100 degrees, !
while the end can be separately attached or shaped like a spade drill)

4. The structure of drill
Point angle
Margin
Drill diameter
Web
Chisel edge
Back taper
Tang
Thinning
Cutting edge
Neck
Shank
Margin:
This is the diameter of the drill, and improves the progress of the hole.
Chisel edge: This part joins the cutting edges at the ends of the webs.
Thinning:
This feature reduces cutting resistance.
Shank:
This is the part that is used to hold the drill, and is either straight or tapered.
Cutting edge:
Used to actually cut with the drill.
Tang:
Used to hold the drill and stop it from turning. Inserted into the sleeve socket.
Back taper: In order to prevent friction with the hole wall, drills have a smaller diameter closer to the back end.

5. Drilling
Characteristics of drilling
Characteristics of drilling
Simple mode of processing
Swarf is
ejected from
the flute
Extremely difficult
processing
Friction with the hole wall
Cutting usually occurs deep in the hole
Not very rigid
Cannot see the point during processing
- Characteristics of swarf generation -
Because the cutting edges are not outside, the
swarf has to work its way out. However, there are
limitations to the swarf ejection route.

6. The purpose of each type
Structure
Solid drill
Carbide brazed
drill
Drill with
replaceable
carbide tips
Type
How it is used
Optimum for finishing holes 20mm in
diameter or smaller
Appropriate for processing holes between
8mm and 40mm in diameter.
If the required hole precision is low, the
“NEW POINT” drill is suitable. If it is high,
the “KEY POINT” drill is suitable.
Suitable for holes between 12mm and 56mm
in diameter. It is also suitable for lowprecision holes, and because the tip is
replaceable, it does not need to be reground.

7. Different types of carbide gun drill
Type
Gun drill for machining
centers
Regular gun drill
SAMMIKA gun drill
ARROW JET gun drill
Primary characteristics
Diameter 6 to 20mm; L/D = 10, 15, 20; for cast irons, ductile cast irons, and
aluminum alloys
Diameter 2 to 30.3mm; L/D = up to 150; for carbon steels, alloy steels,
stainless steels, cast irons, ductile cast irons, aluminum alloys, and copper
alloys
Diameter 5 to 30.3mm; L/D = up to 150; for carbon steels, alloy steels, cast
irons, ductile cast irons, and aluminum alloys. Excellent for cutting swarf; high
feed rates are possible.
Diameter 6 to 30.3mm; L/D = up to 150; for cast irons, ductile cast irons,
aluminum alloys

8. Carbide drill: components & operation
Point angle
Drill diameter
Web
Groove
Margin
(1) Groove:
There are two helical grooves that guide the swarf back and eject it.
(2) Point angle: Generally 118 degrees for high-speed steel and 140 degrees or 150 degrees for
carbide.
(3) Web:
Tapered to make the drill shaft rigid.
(4) Back taper: To prevent the outer edge of the drill from contacting the hole wall, the drill is
tapered so that it narrows toward the shank.
(5) Margin:
The part of the drill that contacts the wall of the hole in order to produce the
required dimension.

9. How to lock at cutting edge
Lip height difference for
drills
0.05 or less
Lip height difference for
reamers
0.02 or less
Excessive land wear
Secondary angle
Excessive wear
Residual wear
Chipped cutting
切れ刃の欠け
edge
Chipped margin
マージンの欠け
Good
Thinning defects
シンニング不良
Asymmetry
Too deep
Off-center (runout)
Discontinuity in cutting
edge
Damaged shank
シャンクの傷
Too shallow
No cutting edge

10. Troubleshooting of drill’s
(1) Drill problems caused by swarf
During drilling, swarf can cause the following types of problems, so sufficient care is required.
(1) Swarf winding around the drill
(2) Swarf ejection problems
(3) Damage caused by too little cutting fluid
These can lead to damaged drills and
problems such as abnormal wear.
(2) Typical methods for addressing swarf removal
(1) Workpiece material: Change to a more brittle material (e.g. use free-cutting steel)
Doing this makes it easier for fan-shaped swarf particles to form, making it easier to manage.
(2) Change the feed rate
This depends on the workpiece material and the processing conditions, but changing the feed speed can
change long pieces of swarf into flakes, strips, or short pieces.
(3) Step feed
Mainly used for twist drills used for drilling deep holes. With twist drills, step feed is considered for deep
holes with a depth that is 4 to 6 times the hole diameter.
Number of steps
(guideline)
For steels, there should be one step per hole depth multiple.
For cast materials, no step feed is required for FC23.
For the FCD series, there should be one step every 5 to 6 hole depth multiples.
For aluminum, there should be one step every 5 to 6 hole depth multiples.

11. Troubleshooting of drill’s
(4) Drills with a chip breaker or nicked drills
As a countermeasure for swarf issues that are done on the drill itself, some drills have a chip breaker that
breaks the swarf up, as well as drills with nicks in the cutting edge that divides up the swarf. However, these
features must be put in every time the drill is re-ground (resulting in increased man-hours) so these methods
are not common at Toyota.
Breaker
Nick
Drill with chip breaker
Nick
Nicked drill

12. “Thanks for looking this presentation, !
for detail please visit www.frannoto.com”
–Fran Noto