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

WORKSHOP THEORY AND

ENGINEERING MATERIALS

INTRODUCTION• Mechanical 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.

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.

QUESTIONS

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.

 

2. Explains the basic difference between:

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.

HAND SHEARS

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.

BENCH SHEAR

GUILLOTINE

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. Blankingii. Piercingiii. Roll slittingiv. Trimming

SHEAR MACHINE

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.

NIBBLER

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. 

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.