![Page 1: TIPS FOR SELECTION OF A JIGnitc.ac.in/dept/me/jagadeesha/mev303/CHAPTER10_HOW_TO...4)-To drill holes in cylindrical piece , template circular jigs are used. Template jigs are normally](https://reader035.vdocument.in/reader035/viewer/2022071502/61215204d8b7c802465a0702/html5/thumbnails/1.jpg)
TIPS FOR SELECTION OF A JIG
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1)- To drill holes on the rectangular surface.
Plate jig with side and top views
Clamping screw
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*To drill holes on large work pieces we generally go for table jig*Table jigs are plate jigs with legs to raise the jig of the table
TABLE JIG
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2)- To drill a hole exactly on the diameter of the cylinder or spherical piece.
Diameter jig
jig
a)
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Box jig to drill hole at the centre of the spherical workpeice
Cam
b)
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3) For drilling holes in large rectangular piece with less accurate operation
For this operation we have to use channel jig
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*Channel jigs are used for large rectangular pieces where there is little tolerance in acuraccy.*The work is held between the two sides and machined from the third side Bush
Clamping screw
jig
workpiece
channel jig
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4)-To drill holes in cylindrical piece , template circular jigs are used.
Template jigs are normally used for accuracy rather than speed.This type of jigs can be fit over, on or into the workpiece
TEMPLATE JIGS(circular)
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RECTANGULAR TEMPLATE JIGS
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Diagram showing use of template jig
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Box jig used for drilling holes at different points at different angles
8)- To drill holes at different angles- a) Box jig
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Diagram showing box jig to drill hole at inclined angle, with unequal legs to give desired angle
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Plate jig for drilling at an angle-
Angle plate jig for driiling at 90 degree
Modified angle plate jig for drilling at angle < 90 degree
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6) For angular drill entry , angular plate jig with angular bush is used
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7)-To drill holes on the irregular surfaces at different positions can be done by making end of bushing to the workpiece contour.
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To make hole at one side of the flank , pot jig is used
POT JIGS
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*leaf jig is used for drilling two connecting holes in small plate.
*It is a type of box jig with small size which surrounds the work and have a handle
LEAF JIG
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Indexing jigs are used for accurately space holes around a circular part
INDEXING JIG
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Problem 1
• Design and draw a channel jig for mild steel component as shown in the figure to drill a hole of 18 mm diameter
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Different steps involved in design
• Selection of Bush• Selection of locator• Design of jig body• Selection of Clamps• Bill of Materials
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Selection of Bush
• Outside diameter – Push fit or Press fit
• Inner hole – Run Fit
• Bush Selection, : headed fixed type DDB 5.100
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• Given hole diameter is 18mm.• Tolerance for innter diameter
of bush: d1F7φ – running fit• From DDB 3.9 d1= 18 +0.041
+0.020
• d2=30 mm• Tolerance push fit- d2h6 φ• From ddb-3.7 d2= 30 +0.000
-0.016
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Other dimensions
• l1= 20mm• l2= 15mm• d3= 35mm
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Selection of locator
Thickness of jig plate must be equal to distance,l2 of brush= 15mm
For better rigidity- 2 locators and clamps on both sides are used
Select locating pin corresponding to jib plate thickness
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• Width of workpiece = width of jig =45 mm
• Use 2 locators for perfect alignment at a width of 45 mm
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DDB 5.92
• Locator head diameter ,D= 16mm
• h1=14mmOther Dimensions
• d=15mm, • h1=14mm, • h2=22mm, • d1=12mm, • d2=11.5
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Design of Jig Body
• W=45mm• Length of jig plate =
2tp+lw+h2+allowance = (2*15) + 75 + 22+ 13 = 140mm
• tp – thickness of jig plate
• Lw – length of workpiece
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Continued Height of jig plate =
Hw + tp + clearance for chip removal = 52+15+ clearance
Clearance= 0.5 drill dia – for ductile= 1 drill dia – for brittle
So,height of jig plate=52+15+9 =76 mm
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Selection of Clamp (DDB 5.104)
Pressure pad assembling is used to clamp right hand side of workpiece and fixed at the end of clamp.
2 clamps are selected for better rigidity
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• Outer dia of pressure pad = d1 = 16mm
• Other dimensions
• d4 = 64mm
• f=3.5mm
• h = 9.5mm
• d5 = 12mm
• d6=7mm
• d7 = 2mm
• Size of screw M8
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Bill of Materials
SL. NO Part Name Material No. o
1 Bush Gun Metal 1
2 Jig Plate Steel 1
3 Screw clamp with pressure pad
Steel 3
4 Locator Steel 2
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Problem 2
Design a jig for drilling two holes of 10mm diameter on the given workpiece
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Step 1: Selection of bush
Fixed type bushes is selected (one for each hole to be drilled)
Inner hole - loose running fit (d1=10mm f7 )
Length of the bush (l1=20mm) l1=2xd1 (general rule)
Outer diameter - press fit(d2=18mm h6)
Flange diameter - 22mm
d1= 10 +0.034
+0.016
d2 = 18-0.000
-0.013
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Step 2 : Design of locator and supporting block
For cylindrical workpiece, form locator is fabricated.
V-block locator may be used.
Drawback – height of jig will be increased
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Used to support the workpiece from bending during drilling operation
Similar to hollow pipe
Supporting Block
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Step 3 : Design of Clamp
Used to clamp the worpiece
Avoids the action of disturbance forces