Drill jig

Drill Jig• Drill Jig Design Considerations

• Drill Jig Types

Requirement of a Drill Jig• Quick and accurate location of the workpiece

• Easy loading and unloading of the workpiece

• Prevention of wrong loading

• Prevention of bending or movement of the workpiece during drilling operation

• Ample chip clearance

• Facility for swarf removal and cleaning

• Light weight to minimise operator fatigue

• Prevention of loss of parts by using chains

• Clearance for overshoot of the drill

General Considerations in the Design of Drill Jigs

Rigidity:

• Jig must be strong enough to withstand all forces applied to it.

• It must also resist deflections that may be the result of excessive tightening of clamps that hold the w/p in place.

• The work must also be supported so that it does not bend under drilling pressure.

• Cast iron is generally used because it absorb shocks and compressive forces.


Chip Control:

• Types of chips: segmental and continuous.

• The segmental chip is preferred.

• Space should be kept between the w/p and bottom of drill bushings to allowchips to pass between the work and busing plate (1 - 1/2 * dia. of drill).

• Three ways of chip removal: coolant, manually with brush or hook, compressedair.


Jig feet and legs:

• A drill jig should stand on four feet (Or legs) rather than a flat surface.

• Jig feet may be built into the jig body or purchased as standard parts.

• They are usually placed on the extremities of the jig body.

• Feet should be ground so that they are all in one plane after they are mounted onthe jig base.


Types of Standard Jig Feet:


Drilling Machine / Wear Resistance / Loading and unloading / Ejection of w/p /Coolant accommodation:

• The type of machine in which operation is performed needs carefulconsiderations.

• The layout of the jig must provide adequate hand clearance for easily loading andunloading and process for loading and unloading must be quick.

• Errors arise in components due to wear. Therefore wear resistance surfacesshould be small and easily replaceable.

• To increase tool life and keep the components cool, a coolant is provided incutting edge in sufficient quantity. Provisions should be made for the coolant toget to the drill and holes or passages for escape of the coolant.

• Design considerations require easy ejection of the component from jig(particularly for heavy ones) to save the operation time and increase theproductivity, pneumatic devices are very suitable for easy and quick ejection.


Miscellaneous considerations:

• Sharp corners should be eliminated.

• Gripping surfaces should be knurled.

• The jig should be large enough to hold it against the torque of the drillingmachine.

• It must be easy to handle.

Drill Jig• Jigs which an be manufactured by any of the following methods:

o Machining

o Forging

o Casting and

o Welding

• Normally jigs are made of hardened steel, which are wear resistant, corrosionresistant and thermally in sensitive.

• Their dimensional accuracy directly influences the accuracy of performance of theoperations where these are used.

Types of Drill Jigs• Open Jigs:

Used for simple operations. Work is done only on one side of the part.

• Closed or Box Jigs:

Used for parts that must be machined on more than one side.

Types of Jigs• Template jig

• jig and channel jig with workpiece pots

• Angle plate jig

• Turn-over jig

• Leaf or latch jig

• Box jig

• Trunnion-type indexing jig

• Sandwich and pump jig

• Jigs for multi spindle machines

Template Drill Jig• This is a simple plate of metal or wood which has holes at correct location to be

made in the workpiece.

• Size of template jig is same as that of the workpiece.

• Plate serves as template which is fixed and overlapped with the workpiece and

drilling is done quickly.

• Use of this jig avoids the marking operation completely and to improve accuracy.

• It is simples and least expensive type od jig.

Template Drill Jig• They may or may not have bushings. When the bushings are not used, the whole

jig plate is normally hardened.

Plate Drill Jig• Open jig.

• It is enhanced form of Template Jig with jig bushes incorporated in plate.

• It consists of single bush plate with provision for location and clamping ofworkpiece.

• The flat plate containing bushing is their main structural member. All the detailsare attached and referenced to this plate.

• They have built-in clamps to hold the work.

• May or may not have legs.

• For mass production.

Plate Drill Jig• The plate jig is located and clamped directly on the workpiece.

Plate Drill Jig• Easy loading and unloading of workpiece

• Chip removal by providing clearance between plate and the workpiece.

• Thin parts are stacked one above the other for drilling at one time.

Plate Drill Jig• Workpiece profile is located by six location pins.

• Workpiece profile is clamped by two knurled screws against the location pins.

Plate Drill Jig

Table Jig

• This style is called table jig.

• The diameter of the jig feet should

be bigger than the slot of machining

to prevent the feet from falling into

the slots.

Channel Drill Jig• The cross section of the jig resembles a channel.

• The component is fitted within the channel is located and clamped.

• Simplifies location and clamping.

• Four location pins and rectangular surface for location. Single screw for clamping

• Drill is guided through the drill bush

• They are economical.

Channel Drill Jig

Channel Drill Jig

• The workpiece is located and clamped to a base that is suitable for a number ofoperations.

Channel Drill Jig

Channel Drill Jig

• The workpiece is located and clamped to a base that is suitable for a number ofoperations.

Pot Drill Jig• There should be enough clearance below /

ahead of the workpiece for the overshoot ofthe drill after passing through theworkpiece.

• The pot is provided with bigger slots for thepassage of the drill ad disposal of chips.

• These slots are aligned with drill bushes inthe jig plate by using location pin.

• A location pin is provided in the pot and acorresponding slot in the jig plate.

• The pot is also used for anchoring theclamping stud.

• C Washer facilitates clamping of theworkpiece.

Pot Drill Jig

Pot Drill Jig• The workpiece is located from its

outside in a bush.• The workpiece is only placed in the pot

to support the flange.

• Drill plate is located directly in theworkpiece bore.

Angle Plate Jig• The locators are generally fixed to the vertical wall of the angular body.

• The central locator has groove for the passage of the drill after passing throughthe workpiece.

• The cylindrical locator and diamond pin locator are fixed to the vertical wall.

• C Washer and hexagonal screw is provided for clamping.

Angle Plate Jig

Angle Plate Jig

Angle Plate Jig

Turn-over or Table-type Jig• Workpiece having no suitable resting

surface for drilling can be drilledconveniently with turn-over jig.

• Turn-over jig is plate jig with jig feet.

• Height of the feet should ne longerthan the clamping stud.

• Turn-over jig is turned over for loadingand unloading the workpiece.

• After loading the workpiece, the jigmust be turned over to rest on the jigfeet for drilling.

Turn-over or Table-type Jig• Commonly used for flanged workpieces.

• Swarf clearance is not a problem.

• Main disadvantage is the lack of support beneath the point of cutting.

Leaf or Latch Jig• This jig has an open construction.

Leaf or Latch Jig• Leaf jig has hinged jig plate.

• Drill bushes are fitted on the jig plate which is hinged at one end.

• The jig plate can be swung aside to provide clear path for workpiece loading andunloading.

• Clamping screw and drill bushes are accommodated in jig pate.

• The jig plate must have positive resting surface.

• The jig plate is clamped against the resting face by an eyebolt.

• Quick clamping and unclamping of the jig plate is possible.

• Handknob is provided to facilitate clamping

Latch Jig

Box Jig

Box Jig• When the holes are to be drilled from more than one face of the component,

there shall be more than one jig plate.

• All the jig plates shall be assembled as a box with one side open for loading andunloading of the component.

• Opposite to each jig plate, there shall be resting feet provided.

• Box jig shall be as light as possible to enable to lift and shift again and again

• Some of the clamps may have to take the drilling load also.

Box Jig• The box is closed and clamped by

the latch.

• Suitable feet are provided to givegood seating

• Suitable swarf clearance ports areincorporated.

Summary• A good jig facilitates precise location and easy fool proof loading / unloading of

the workpiece.

• It prevents bending of the workpiece.

• It has ample space for chip accumulation.

• It is light in weight.

Summary:• The workpiece should be supported against bending which occurs due to the

downward thrust of the drill.

• The jig and the workpiece are also subjected to thrust in the direction of the feedof the tool.

• There should be enough clearance below / ahead of the workpiece for theovershoot of the drill after passing through the workpiece.

• Locating and clamping elements in drill jigs are subjected to high torque in thedirection perpendicular to the axis of the cutting tool.

Summary: Types of Jigs• Plate jigs are used for the workpieces having parallel machined faces on sides to

be drilled and used for resting.

• Turn-over or table jigs are used for workpieces having the machined surface onthe same side as the holes.

• Leaf or latch jigs are used for workpieces having machined surface on the sideopposite to the holes.

• Box jigs are used for drilling holes from a number of sides on light workpiece.

References• Jig and Fixture Design Manual, Erik K. Henrikson, Industrial Press.

• An introduction to jig and tool Design, M.H.A. – Kempster, III Ed. Pub ELBS.

• Jigs and Fixture, P.H. Joshi, THM.

• Jigs and Fixture, ASTME.

Thank You!

Any suggestions?

Engineering

Drill jig