Milling Fixture

Overview• Fixtures

• Types of fixtures

• Milling fixture

• Elements of fixtures

Fixtures • Fixtures are strong and rigid mechanical devices which enable easy, quick and

consistently accurate locating, supporting and clamping of workpieces againstcutting tool(s) and result faster and accurate machining with consistent quality,functional ability and interchangeability.

• Fixtures are designed specifically for an operation and so these are named on thebase of the operation to be carried out with their help.

• Fixtures are used to hold the workpiece properly to carryout the operations.

Types of Fixtures• Different types of fixtures are listed below.

o Turning fixtures

o Milling fixtures

o Fixture for grinding

o Fixture for broaching

o Tapping fixture

o Fixture for welding

o Assembling fixture

o Inspection fixture

Elements of Fixtures • Fixtures are manually or partially power operated devices.

• To fulfil their basic purposes, fixtures are comprised of several elements such as,

o base and body or frame with clamping features

o locating elements for proper positioning and orientation of the blank

o supporting surfaces and base

o clamping elements

o auxiliary elements

o fastening parts

Milling Fixture• Fixtures used to perform different types of milling operations are called milling

fixtures.

• Milling fixture is accurately located and bolted on the machine table by usingbolts and nuts.

• The cutter is not guided during cutting operation.

• Location and clamping systems are similar to those used for drill jigs.

• Cutting forces in fixtures are high and tend to lift the workpiece therefore theclamping forces need to be high too.

• The fixtures for milling operations are designed and described on the basis ofmilling operations, milling techniques and clamping power techniques.

Types of Milling Fixtures• On the basis of types of operations the milling fixture may be of different types

are - face milling, slot milling, plain milling, side milling, form milling and gangmilling fixtures, etc.

• On the basis on technique of milling machining, milling fixtures are named assingle piece milling fixture, string milling, index milling, etc.

• On the basis of clamping power and clamping method milling fixtures are namedas fixture with mechanical clamping, hydraulic clamping, pneumatic clamping,automatic clamping and vice jaw clamping fixture.

Setting Block• Table of the milling fixture is positioned relative to the cutter with the help of

setting block.

• The setting block is located relative to the workpiece location system

• It is retained on its position on the fixture by using screws.

Setting Block• It has two hardened setting faces.

• The table setting is done with 0.25mm feeler between the cutter and setting face.

• Feeler is used so that block will not be damaged while machining.

• Setting block is positioned so that the cutter is between the vertical face of the block and the operator during setting.

Tenons• Two tenons are located on the underside of the fixture base.

• They are made from casehardened steel.

• Tenons sit in T-slots that run along the length of the machine table.

• They locate the fixture relative to the table feed.

• Two tenons are placed as far as possible to have maximum accuracy.

Milling Machine Table and Tenons

Base of Milling Fixture• Milling fixture has a heavy base on

which the complete fixture isconstructed.

T-bolt• Fixture is bolted / secured to the machine table by two or four t-blots.

• T-bolts are placed in t-slots on machine table.

• They are not a part of the fixture.

Machine Vice• The machine vice is simplest milling fixture.

• Location system can be incorporated in it.

• It can be adapted to accommodate awkwardly shaped workpieces.

Machine Vice• The machine vice is mounted on

the machine table T-slots by usingT-bolt, hex nut and washer.

Machine Vice

Machine Vice• Special jaws-shaped to accommodate the workpiece and with workpiece location.

Milling Fixture

Simple Milling Fixture• The fixture is located on machine table by two tenons that locate in the same

machine slot.

• Fixture is bolted to the machine using T slot.

Simple Milling Fixture• The workpiece is located from two holes by using one location pin and one

diamond pin.

• Workpiece is clamped using two spanner-tightened heavy duty clamps because of the high forces during milling.

• The cutter is set using setting block. Setting block has two setting faces one for the depth and other for the transverse-setting.

Line or String Milling Fixture• Five cylindrical workpiece are located in line.

• The workpieces are located and clamped with one spanner-tightened screw.

Line or String Milling Fixture• The fixture is located on machine table by using two tenons.

Thank you!

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