The document discusses various considerations for designing drill jigs. A drill jig must securely hold the workpiece to prevent bending and movement during drilling. It must also provide chip clearance and ease of loading/unloading. Different types of jigs include plate jigs, turn-over jigs, and box jigs, each suited to particular workpiece geometries. Proper support, locating elements, and clearance are needed to withstand drilling forces and improve accuracy.

1. Drill Jig
• Drill Jig Design Considerations
• Drill Jig Types

2. 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

3. 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.

4. General Considerations in the Design of Drill Jigs
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 allow
chips 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, compressed
air.

5. General Considerations in the Design of Drill Jigs
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 on
the jig base.

6. General Considerations in the Design of Drill Jigs
Types of Standard Jig Feet:

7. General Considerations in the Design of Drill Jigs
Drilling Machine / Wear Resistance / Loading and unloading / Ejection of w/p /
Coolant accommodation:
• The type of machine in which operation is performed needs careful
considerations.
• The layout of the jig must provide adequate hand clearance for easily loading and
unloading and process for loading and unloading must be quick.
• Errors arise in components due to wear. Therefore wear resistance surfaces
should be small and easily replaceable.
• To increase tool life and keep the components cool, a coolant is provided in
cutting edge in sufficient quantity. Provisions should be made for the coolant to
get 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 the
productivity, pneumatic devices are very suitable for easy and quick ejection.

8. General Considerations in the Design of Drill Jigs
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 drilling
machine.
• It must be easy to handle.

9. 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, corrosion
resistant and thermally in sensitive.
• Their dimensional accuracy directly influences the accuracy of performance of the
operations where these are used.

10. 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.

11. 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

12. 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.

13. Template Drill Jig
• They may or may not have bushings. When the bushings are not used, the whole
jig plate is normally hardened.

14. 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 of
workpiece.
• The flat plate containing bushing is their main structural member. All the details
are attached and referenced to this plate.
• They have built-in clamps to hold the work.
• May or may not have legs.
• For mass production.

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

16. 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.

17. Plate Drill Jig
• Workpiece profile is located by six location pins.
• Workpiece profile is clamped by two knurled screws against the location pins.

18. Plate Drill Jig

19. 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.

20. 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.

21. Channel Drill Jig
Channel Drill Jig
• The workpiece is located and clamped to a base that is suitable for a number of
operations.

22. Channel Drill Jig
Channel Drill Jig
• The workpiece is located and clamped to a base that is suitable for a number of
operations.

23. Pot Drill Jig
• There should be enough clearance below /
ahead of the workpiece for the overshoot of
the drill after passing through the
workpiece.
• The pot is provided with bigger slots for the
passage of the drill ad disposal of chips.
• These slots are aligned with drill bushes in
the jig plate by using location pin.
• A location pin is provided in the pot and a
corresponding slot in the jig plate.
• The pot is also used for anchoring the
clamping stud.
• C Washer facilitates clamping of the
workpiece.
Pot Drill Jig

24. 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 the
workpiece bore.

25. 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 through
the 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

26. Angle Plate Jig
Angle Plate Jig

27. Turn-over or Table-type Jig
• Workpiece having no suitable resting
surface for drilling can be drilled
conveniently with turn-over jig.
• Turn-over jig is plate jig with jig feet.
• Height of the feet should ne longer
than the clamping stud.
• Turn-over jig is turned over for loading
and unloading the workpiece.
• After loading the workpiece, the jig
must be turned over to rest on the jig
feet for drilling.

28. 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.

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

30. 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 and
unloading.
• 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

31. Latch Jig

32. Box Jig

33. 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 and
unloading 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.

34. Box Jig
• The box is closed and clamped by
the latch.
• Suitable feet are provided to give
good seating
• Suitable swarf clearance ports are
incorporated.

35. 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.

36. 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 feed
of the tool.
• There should be enough clearance below / ahead of the workpiece for the
overshoot of the drill after passing through the workpiece.
• Locating and clamping elements in drill jigs are subjected to high torque in the
direction perpendicular to the axis of the cutting tool.

37. 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 on
the same side as the holes.
• Leaf or latch jigs are used for workpieces having machined surface on the side
opposite to the holes.
• Box jigs are used for drilling holes from a number of sides on light workpiece.

38. 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.

39. Thank You!
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