chip_breakers.ppt

8/10/2019 CHIP_BREAKERS.ppt

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CHIP BREAKERS



Chip Curling and Breaking

methods

(a) by means of grooves formed on the

tool face;

(b) By means of steps or shelves ground

on the tool face;

(c) by means of separate chip breakers

fastened to the tool point; and

(d) by the kinematic method.



Chip breaker grooves

• Grooves and

depressions formed

on the tool face by

abrasive grinding orelectrospark erosion,

curl the chip into a

tight spiral or break it

into small pieces



Depressions on the tool face



• Along with the in-creased use of

cemented carbide, a disadvantage ofgrooves is that they are difficult to make

since they are ground with thin wheels

that wear rapidly, lose their form and

require frequent truing.

• The electrospark erosion method of

forming grooves with the use of a

copper or brass electrode is quite

complicated.



• These

shortcoming

s were

eliminated intools with a

sha llow ch ip-

breaker

groove



• These

grooves are

made on the

face of

cementedcarbide tips

by lapping

with a bronze

or cast irondisk charged

with boron

carbide.



Sep Type Chip Breakers



• Steps are made on

the tool face by

grinding orelectrospark

erosion.

• As the chip flows

against the

shoulder of the

step or ledge it iscurled into a tight

spiral and breaks

into short lengths



Separate Chip breakers Fasten

to the Tool Point

• The main advantages of a separate

chip breaker is that it can be

readily adjusted to achievedependable action.

• It requires no additional grinding of

the cemented carbide tip of thetool.



on tool face 1 is chip breaker 2

made of steel and having a

curvilinear working surface

which is hard-faced with a layer

of stellite 2 or 3 mm thick toimprove wear resistance.



The chip breaker has a milled slot

through which fastening screw 3

passes.



Universal Chip Breaker



• This allows the head

to be set at various

angles λ.

• Head 1 can be easily

replaced if it is

worn or has been

damaged.



Kinematic Method of Chip

Breaking

• Chips can be broken into short pieces

if a supplementary reciprocating

motion is imparted to the tool in the

direction of the feed motion. This hasbeen called kinematic chip breaking.

• Owing to tool reciprocation, the chip

will vary in thickness and breaks easilyat the thinner places.



Ceramic Tipped Tools



A slot with sides at angles of 70° and

80° is shaped at the front end of holder

1.Ceramic insert 2 is forced against the

holder by wedge 3 which is drawn up by

screw 4 .



This method of clamping the insert

from the sides is expedient since,

owing to the high brittleness of the

ceramics, the insert can be easily

broken if clamped from above.



The insert is backed up by screw 6

which is screwed into pin 5. This pin

is press-fitted in the holder.



Each time the insert is

sharpened, it becomes shorter

and is advanced by screw 6 tomaintain an overhang which

should not exceed 0.5 to 0.8 mm.



DIAMOND TOOLS



Speeds, Feeds and Depths of Cut for

Single-Point Diamond Tools



• The tool bits of diamond boring tools

are usually of round cross section ,

from 6 to 20 mm in diameter.

• The bits and holders of turning tools

may be round, square or rectangular in

cross section (16x16, 20x20, and 16x25

mm).



• Drawbacks are the difficulty in dismounting

the tool (removing the diamond) and the

danger of overheating the diamond which

acquires defects at temperature over 720° Cthat lower its strength and shorten its service

life.

• For these reasons, brazing should be

resorted to only when the small size of thediamond does not allow it to be clamped

mechanically.



1- tool bit

2- insert

3- clamp

4- screw

5- diamond



1- holder

2- clamp

3- diamond

4- insert

5- screw

6- pin



• The provision

of the pin 6

enables the

clamp to bear

more tightly

against theface of the

diamond

which

projectsslightly from

insert 4.



• The diameter

of pin 6

should be

selected in

accordance

with theamount by

which the

diamond

projectsabove the

insert.



• A mechanical ly clamped diamond can

be easily removed from the bit orholder, examined, reground (if

necessary) and replaced for further

operation.

• There is no danger of overheating the

diamond.

• The main shortcoming of mechanical

clamping is that larger diamonds must

be used.

chip_breakers.ppt

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