REAMING.

• Reaming is an accurate way of sizing and finishing a

hole which has been previously drilled.
• In order to finish a hole and to bring it to the accurate
size, the hole is drilled slightly undersize.
• The speed of the spindle is made half of the drilling.
• The tool used for reaming is known as reamer, which is
having multi point cutting edges.
• Reamer can’t originate a hole . It simply follows the axis
of previously drilled hole.
• Metal left before reaming is 0.2mm for hand reamer
and 0.5mm for machine reamer.
ELEMENTS 0F REAMER.
A reamer consists of three main parts:-
1. Fluted portion.
2. Neck.
3. Shank.
AXIS
• The longitudinal centre line of the reamer.
BACK TAPER
• The taper of the reamer after the bevel edge for easy
entry into the hole.
BEVEL EDGE
• The angular cutting portion at the entering end to
facilitate the entry of the reamer into the hole. It is not
provided with a circular land.
BODY
• That portion of the reamer extending from the entering
end of the reamer to the commencement of it’s shank.
CIRCULAR LAND
• The cylindrically ground surface adjacent to the cutting
edge , on the leading of the land.
CLEARANCE
• Primary :- That portion of the land relieved immediately
behind the cutting edge.
• Secondary :- That portion of the land relieved from the
primary clearance of the land.
CUTTING EDGE
• The edge formed by the intersection of the face and the
primary clearance of the land.
FACE
• The portion of the flute surface adjacent to the cutting edge
on which the chip impinges as it is cut from the work.
FLUTE
• The grooves in the body of the reamer to provide cutting
edges to permit the removal of chips and to allow cutting
fluid to reach the cutting edges.
HEEL
• The edge formed by the intersection of the surface left by
the provision of secondary clearance and the flute.
BEVEL LEAD ANGLE
• The angle formed by the cutting edge of the bevel lead
and reamer axis.
CLEARANCE ANGLE
• The angle formed by the primary or secondary clearances
and the tangent to the periphery of the reamer at the
cutting edge.
HELIX ANGLE.
• The angle between the cutting edge and the reamer axis.
 ROTATION OF REAMER.
LEFT HAND CUTTING REAMER.
A reamer which cuts while rotating in a clockwise direction
when viewed on the entering end of the reamer.
RIGHT HAND CUTTING REAMER.
A reamer which cuts while rotating in anti-clockwise
direction when viewed on the entering end of the reamer.
RAKE ANGLE.
• The angles, in a diametrical plane formed by the face and a
radial line from the cutting edge.
• If the angle formed by the leading edge and the surface to be
cut (it’s tangent) is obtuse, the rake angle is said to be positive
rake.
• If the angle formed by the leading edge and the surface to be
cut is acute, the rake angle is said to be negative rake.
DIFFERENT TYPE OF REAMER.
Hand reamer.

• These reamers are operated by hand with a tap wrench,

fitted on the square portion of the reamer.
• The work is hold in a vice.
• The flutes may be straight or helical.
• Shank is straight with a square tang to hold with the tap
wrench.
• There is a starting taper of 1/3 of flute length for easy
entry of the reamer into the hole.
• Stock removal is less I,e 0.05mm to 0.2mm.
Machine reamer.

• Machine reamers also known as chucking

reamer
• Machine reamers are similar to hand
reamer.
• The shank may be straight or taper.
• Flutes may be straight or helical.
• Straight shank reamer can be held by drill chuck or by collet
adopter where as taper shank by sleeve adopter or by
sleeve.
• Machine reamer has shorter flute length than hand reamer.
• The diameter of straight shank machine reamer varies from
1.5mm to 32mm and for taper shank from 5 to 32 mm.
SHELL REAMER.

• It is a hollow round piece having standard holes to suit in an

arbor.
• It saves the cost of materials.
• The arbor has a morse taper shank and permits the various
sizes of shell into it’s body with a locking device.
• The shell may have the straight or spiral flute in it’s body.
• Shell reamers are designated for reaming bearing and other
similar items.
• They are fluted almost all their entire length.
• Less strength due to two piece assembly.
ADJUSTABLE REAMER
• Five or six cutting blades on a taper longitudinal slots
made over a round body.
• They are positioned by locking two nuts shifting the
blade upward or downward for adjusting to a desired
size.
• It is used for enlarging the holes of any odd size within
a limited range.
• Overstrain to the blades should be avoided.
• Blades can be replaced individually or sets.
• Specially designed for light cuts by hand operation.
• Blades made from high quality high speed steel.
• Properly hardened and ground blade.
• Accurately tapered slots.
EXPANSION REAMER.

• It is drilled for a taper plug at the lower end and the

sides are slotted.
• The expansion form is split up through fluted section.
• A slight amount of expansion can be had from 0.15mm
to a maximum 0.3mm over the nominal diameter , by
screwing in a tapering plug.
• The reamer can be expanded and re-sharpened to it’s
original size several times when the reamer worn.
• Used for reaming abrasive material where tool
becomes blunt frequently.
ADVANTAGES OF SPIRAL FLUTED REAMER OVER ST FLUTED REAMER.
1. The spiral fluted reamer avoids chattering since it contacts
all over the body of the hole.
2. It gives best finishing.
3. It enters freely and easy for engagement.
4. The chips come out freely.
5. The cutting edges engage progressively without giving a
hammering effect on the job in case of straight fluted
reamer.
6. Load on the spindle due to cutting force is evenly
distributed rather giving a jerk.
CARE OF REAMERS.
• Keep reamers absolutely clean to do accurate work.
• Do not use the reamer to remove more than to 0.2mm of
metal.
• If the proper pressure is applied in use and the reamer
chatters, replace it to insure accurate work.
• If the reamer edges are only slightly dulled, honing the edges
on an oilstone may restore the sharpness.
• On an adjustable reamer, the blades may be replaced.
• To prevent chipping or dulling, turn the reamer in the cutting
direction only.
• To prevent damage, ensure reamers are stored where they
will not come in contact with each other, or other tools.
• Use suitable grade of coolant/lubricant oil while reaming.
• Use half of the drilling speed while doing reaming.
 COUNTERSINKING.
• Countersink tool is similar to a twist drill but it has
a multiple toothed cutting edge on a angular
surface.
• It is used for beveling the mouth of a hole to
provide a seat for the countersink screw or rivets.
• The countersinks are available with include angle
60⁰,82⁰,90⁰,100⁰,110⁰ and 120⁰. Out of which 82⁰
and 90⁰ are the most commonly used angles.
 COUNTERBORE
• A drilled hole to be enlarged to a required depth in the
same axis of the previous hole using proper seating of the
headed bolts or screws.
• The counterbore has 3 parts as Pilot
Cutter head.
Shank.
• The pilot enters into a drilled hole and the cutter head
makes the recess enlarging the drilled hole to a required
depth.
THREAD
Thread is a helical groove having a definite cross-
section with constant helix angle that has been cut on
a cylindrical job internally of externally.
Threads generally cut on a machine called as
“lathe” on a small size screw. Thread is often cut by
means of tool called as die.
The principal uses of thread are :-
1. For fastening such as nut, bolt and screw etc.
2. For transmitting power such as lead screw.
3. For lacking accurate measurement.
4. For adjusting.
5. For applying pressure.
THREAD NOMENCLATURE.
 TYPE OF THREAD.
METRIC THREAD.
It is used where light fits are necessary e.g steam fitting, pipe
fittings etc.
Angle of “v” thread is 60⁰. Depth = 0.866 x Pitch
H = 0.866 x P.
BSW THREAD.
BRITISH STANDARD WHITWORTH THREAD (BSW).
It is used for general engineering work as bolts & nuts,
screw etc. Angle of “v” thread is 55⁰.Depth (H) = 0.6403
x Pitch (P).
Radius at the root and crest (R) = 0.137329 x Pitch.
BRITISH STANDARD FINE (BSF)THREADS.

It is similar to BSW having fine pitch. It has more number of

TPI than BSW on the same size. It is used largely on the bolts,
nuts and parts of automobiles.
BRITISH STANDARD PIPE THREAD.(BSP)

It is a standard screw thread that has been adopted

internationally for interconnecting and sealing pipe
ends by mating an external (male) with an internal
(female) thread and has been adopted as a standard
scale used in plumbing fittings. It is similar to B.S.W
used on pipes only.
SQUARE THREAD.
It’s shape is square at an angle of 90⁰. It is strong enough
to transmit heavy loads on both directions. It is used on the
spindle of vices, Presses, screw jacks etc. it has no definite
size and number of threads per inch. It is fixed according to
the capacity required
ACME THREAD.
It is similar to square thread but it’s include angle is 29⁰. It is
considerably stronger, used in automatic working machines
since it gives easiest engagement. Ex. Of lead screw of
lathes.
BUTTRESS THREAD

It has one surface normal to the axis and the other side is
inclined at an angle of 45⁰, so the shearing strength is twice
as great as square thread. It is only used where the forces
acts one direction such as quick release vice , hand press
etc.
KNUCKLE THREAD.
The shape is half round on crest and it is used for uses
,in the part of coupling etc. It is also used on hard
woods for light fitting purpose.
TAPS
TAPPING.
Tapping is the operation of cutting internal threads by
means of a cutting tool called tap.
TAPS
• A tap is a screw like tool which has threads like a bolt and
three or four flutes cut across the thread.
• It is used to cut threads on inside of a hole .
• The edge of the thread formed by the flutes are the cutting
edges.
• The lower part of the tap is slightly tapered as it can enter
into the hole easily.
• The upper part of the tap consists of a shank ending in a
square for holding the tap by tap wrench.
• They are made up of carbon steel or high speed steel.
HAND TAP

• The hand taps consists 3 nos. as roughing, intermediate

& finish tap respectively.
• All hand taps are straight fluted.
• The end of the roughing tap has 6 threads tapered. This
is used to start the thread so that the threads are
formed gradually.
• The intermediate is tapered of 3-4 threads. This is used
after the roughing tap.
• The finishing tap has 1-2 threads tapered. This is used to
finish the thread, which is prepared by other two taps.
 MACHINE TAP.
Machine taps have straight or helical flute. In machine
tapping it is necessary to see that the chips always clear the
cutting edges.
MATERIAL
Taps are made from carbon steel or from high speed steel
and are hardened and tempered.
METHOD OF TAPPING.

• Check the size of the hole and hold the job firmly in the vice
setting the hole to be vertical.
• Select the set of taps and use proper wrench.
• Insert the first tap at right angle and turn it to clockwise
applying even pressure putting of oil if required.
• Check up the position to stand vertical to base with a try-
square. The inclined position should be rectified before the
formation of thread.
• Turn the tap forward for making threads and backward to
get relief.
• Change the series of tap, I, II & III often before feeling the
strain. Repeat the procedure till the whole threaded part of
the tap passes into the hole.
• Be careful while threading into blind hole. Chips to be
removed during the threading process to achieve the
required length of thread in the work-piece.
CAUSES OF THE BREAKAGE OF TAPS.
• The hole is smaller than the required size.
• The hole is inclined or tapered.
• The pressure is over and uneven.
• The wrench is non-stand.
• The cutting edges of the tap are dull.
• Failed to hold the job firmly.
• Failed to concentrate with the work to know the
sensitivity of feel.
• Failed to turn back the tap to get relief.
• Failed to remove the cutting chips.
• Failed to apply coolant.
• Failed to use series of taps in order.
• Failed to minimise the force on the blind hole.
METHOD OF REMOVING BROKEN TAP.
• If the height of the broken tap is enough to grip for a
wrench or a plier, turn to left with it.
• Insert a tool which has 3 to 4 knobs into the grooves of
the tap, and turn it to left.
• Insert a prick punch into the grooves and give light
blows on the head for unscrewing.
DIES & STOCKS.
• Dies are used to cut threads on a round bar of metal, such
as the threads on a bolt.
• It is a round or square block of hardened steel with a hole
containing threads and flutes which form cutting edges.
• The dies are of two types as solid die & adjustable die.
• A solid die is one which has fixed dimension and can’t
be adjusted for larger or smaller diameter.
• An adjustable die can be set to cut larger or smaller
diameter.
• A circular adjustable die is very common.
• In adjustable die the die is splited through one side and
a slight adjustment is made by means of the set screw.
• Another common type is two piece rectangular die. In
this type of dies are fitted into a special stock and
closed by means of the adjusting screw.
• The size of the die is specified by the outside diameter
of the thread to be cut and pitch of thread.
STOCK.
• The tool for holding and turning the threading die is
called a die stock. It is often just called a stock.
• Die stock are provided with small screws.
• When the threading die has been inserted into the
stock, the thread screws are tightened so that they
engaged in the drill holes of the die to hold it.