Mechanical cutting involves splitting a workpiece into two by removing a thin slice of material. The key processes are sawing using hacksaws, bandsaws, and circular saws. Hand shears use one hand to snip and collect while long blades make them versatile. Bench shears are mounted and have a lever mechanism to increase force but cannot do delicate work. Guillotines use a heavy sliding blade for beheading. Shear machines cut stock without chips using straight or curved blades for sheet metal. Nibblers cut sheet metal with minimal distortion using punch and die or scissor-like mechanisms. Bench shears can normally cut up to 0.5mm thick mild steel.

1. WORKSHOP THEORY AND
ENGINEERING MATERIALS
MECHANICAL CUTTING
ABDUL ‘AMMAR AR-RASYID BIN RAZALI (LEADER)
HAJI MUHAMMAD ASYRAF BIN HAJI RAZALIE
MOHAMMAD ‘AIZZUDDEEN BIN HAJI MD JALALUDDIN
MOHAMMAD ZULHAFIZZAN BIN ASMALI
NOR HASMIRA BINTI WIRA ALI
HJH SITI NORZAKIAH BINTI LAPAN@OSMAN

2. INTRODUCTION
• M echanical cutting is one way of splitting a
workpiece into two, to plastically press a shape out of
it, such as with blanking.
• This entry deals with splitting a workpiece into two by
removing a thin slice of material by mechanical means
(the other main approach is removal by intense heat).
These processes are usually called "sawing" and
include: hacksaws, bandsaws, circular saws and friction
saws.

3. QUESTIONS
1. Describe the principle upon which mechanical
cutting is based.
2. Explains the basic difference between:
 Hand Shears
 Guillotine or bench shears
 Shear Machine
 Nibbler
3. Explains the maximum thickness of mild steel plate
that can normally be cut by bench shears.

4. 1. Describe the principle upon which
mechanical cutting is based.
1. Cutting Speed
• The cutting speed can be defined as the relative surface speed between the
tool and the job. It is a relative term since either the tool or the job or both
may be moving during cutting. It is expressed in m/min.
2. Feed
• It may be defined as the relatively small the cutting tool relative to the work
piece in a direction which is usually perpendicular to the cutting speed
direction. It is expressed in mm/rev or mm/stroke.
• It is more complex element as compare to the cutting speed. It is expressed
differently for various operations.
3. Depth of cut
• The depth of cut is the thickness of the layer of the metal remove in one cut
or pass measured in a direction perpendicular to the machine surface. The
depth of cut is always perpendicular to the direction feed motion.

5. 2. Explains the basic
difference between:

6. A) HAND SHEARS
• Hand shears are more efficient than the
conventional two-handed shears; here
you can use one hand for snipping and
the other for holding and collecting the
greenery, while the long pointed blades
make them far more versatile than
secateurs.

7. HAND SHEARS

8. B) GUILLOTINE OR BENCH
SHEARS
• A bench shear, also known as a le ve r she ar, is a bench
mounted shear with a compound mechanism to increase
the mechanical advantage. It is usually used for cutting
rough shapes out of medium sized pieces of sheet metal,
but cannot do delicate work.
• The guillotine is a machine for beheading by means of a
heavy blade that slides down in vertical guides.

9. BENCH SHEAR

10. GUILLOTINE

11. C) Shear Machine
• Shear machine is a process which cuts stock without the
formation of chips or the use of burning or melting. strictly
speaking, if the cutting blades are straight the process is called
shearing; if the cutting are curved then they are shearing-type
operations. Most common sheared materials are in the form of
sheet metal or plates, however rods can also be sheared.
• Shearing type
i. Blanking
ii. Piercing
iii. Roll slitting
iv. Trimming

12. SHEAR MACHINE

13. D) Nibbler
• A nibbler is a tool for cutting sheet metal with minimal distortion.
One type operates much like a punch and die, with a blade that
moves in a linear fashion against a fixed die, removing small bits of
metal and leaving a kerfs approximately 6 mm wide. Another type
operates similar to tin snips, but shears the sheet along two parallel
tracks 3–6 mm apart, rolling up the waste in a tight spiral as it cuts.
Nibblers may be manual (hand operated) or powered.
• Power nibblers are often powered by compressed air, though
electrical types also exist. A common nibbler tool is an electrical
drill attachment, which converts the rotary motion of the drill into a
reciprocating motion of the jaw.

14. NIBBLER

15. 3. Explains the maximum thickness of mild
steel plate that can normally be cut by
bench shears.
The Angle cut has a maximum rating
of 0.5mm thick mild steel and 2.6mm
round wire stock. The angle cut
feature is a 90o template with a
separate blade located on the lower
part of the shear underneath the
cutting table opposite of the handle.

16. CONCLUSION
• From this presentation you can
understand what are the
principle of metal cutting
machines used in workshops,
when they are used and at
what condition.