RRB JE Production Engineering: Machining & Lathes

• This text introduces a series of lectures that will cover the technical aspects of the RRB (Railway Recruitment Board) JE (Junior Engineer) exam, specifically using the Youth Competition Times' book containing previous years' questions.
• The speaker guarantees a proper solution to every book question.

Subjects Covered So Far

• Engineering Mechanics
• Strength of Materials
• Material Science

Current Subject Focus: Production Engineering

• Production is especially important in the context of the RRB JE exam due to its high weightage
• 2019 RRB JE exam sets have already been reviewed
• In some sets, Production Engineering accounted for as many as 15-20 questions out of 100 total questions

Chapter Starting Today: Machining

• The first chapter will cover Machining, with an emphasis on lathes, their functions, and their types

Question 1: Lathe Parts and Function

• The first question asks which part of a lathe serves as the housing for driving pulleys and back gears
• Four options were given: carriage, bed, tail stock, head stock.
• Answer: The head stock serves as the housing

Head Stock in Detail

• The head stock is the correct housing for both the driving pulleys and the back gear
• The Spindle is a key component of the head stock
• The chuck, which fits onto the spindle, is also part of the head stock
• The head stock also contains the gear assembly
• Driving pulley, back gear and switches are found in head stock

Other Lathe Components Discussed

• Tail stock
• Tool post
• Compound rest
• Saddle
• Lead screw

Question 2: Calculating RPM of a Steel Shaft

• The second question involves calculating the RPM of a steel shaft, given its diameter (25 mm) and cutting speed (50 meters per minute).
• Formula to use is V = πDN/1000, where:
  • V = cutting speed (m/min)
  • D = diameter (mm)
  • N = RPM
• Because the diameter is in mm, the formula includes dividing by 1000 to convert it to meters
• Therefore N = (V * 1000) / (π * D)
• Inserting the given values: N = (50 * 1000) / (π * 25) ≈ 636.73 RPM
• Answer: 636.73 RPM

Key Unit Considerations for Velocity Calculations

• 1st Velocity Formula: V = πDN / 60 (where D is in meters, N is in RPM, and V is in meters per second)
• 2nd Velocity Formula: V = πDN / 1000 (where D is in mm, N is in RPM, and V is in meters per minute)
• Remember to adjust the formula based on the units given in the question

Question 3: Composition of a Lathe Bed

• The options provided are High Carbon Steel, High Alloy Steel, Mild Steel, and Cast Iron
• Answer: Lathe beds are made of Cast Iron
• More specifically, they are made of Gray Cast Iron
• Grey Cast Iron contains 2.50 to 3.75% carbon

Advantages of Using Gray Cast Iron for Lathe Beds

• The high carbon content causes carbon to surface in the form of graphite flakes
• These graphite flakes help absorb vibrations during machine operation

Alternate Materials and Their Uses

• Mild steel is used for screws and nuts
• High carbon steel is used for files and hammers
• Medium carbon steel is used for connecting rods in internal combustion engines

Carbon Percentage in Different Types of Steel

• Low Carbon Steel: Less than 0.3% carbon
• Medium Carbon Steel: 0.3% to 0.7% carbon
• High Carbon Steel: 0.7% to 1.5% carbon

Carbon Percentage in Cast Iron

• Cast Iron: Typically 2% to 6.67% carbon
• Cast iron is made from pig iron
• Pig Iron: Contains approximately 4% carbon

Question 4: Component to Support Tools

• The question asks what component, fitted on top of the cross slide, is used to support the tool post and cutting tool
• Options are carriage, tailstock, compound rest, or saddle
• Answer: The compound rest

Components of Lathe

• Head stock
• Tail stock
  • Includes "dead center" here
• Tool post
• Compound Slide
• Cross Slide
• Saddle

Question 5: Expressing Lathe Capacity

• Asks which of the given options best represent the capacity of a lathe, of the four options given the correct answer is:
• Answer: Swing and distance between centers
• Bed length also contributes in defining capacity, but this was not an option

Question 6: Controlling Horizontal Feed

• Asks which part of lathe controls horizontal feed:
• Possible answers: cross slide, apron, tail stock, head stock
• Answer: Apron
• Apron contains levers, clutches, and gears

Question 7: Feed Direction in Lathe

• Asks what operation does not involve a straight line motion:
• Answers: form turning, counter turning, contour turning, facing, taper turning
• Answer: Contour turning
• Taper turning uses straight lines to move in the direction
• While the curvature of profile is being moved, that is still done with linear motion in some direction
• Contour turning follows the profile of the part

Question 8: Moving Carriages During threading

• The question is about which part moves the carriage automatically during threading
• Options: lead screw, hand wheel, bed, feed rod
• Answer: Lead screw
• The screw threads are typically Acme threads with a 29 degree

Additional Notes on Threads

• Tumbler gears are also used in lathes

Question 9: Lathe Mandrel Function

• Asks what a lathe mandrel can be described as
• Answers given: template, gauge, fixture, jig
• Answer: Fixture
• Mandrels as well as Jigs and fixtures are all holding devices
• Mandrels are lathe accessories which hold the workpiece
• Mandrels (hollow holding devices) are similar to Fixtures during operation

Jigs vs. Fixtures

• Jigs guide the tool, while fixtures don't

Question 10: Lathe Accessories Impact

• Explores the effect of lathe accessories
• Answer: Accessories improve versatility
• Accessories such as chucks enable many operation

Examples of Lathe Accessories

• Chucks (3-jaw, 4-jaw)
• Angle plates
• Centers (dead and live centers, mentioned in reference to the tail stock)

Question 11: Center Punch Angle

• The question is about the point angle of a punch
• Possible answers: 90 degrees, other options were not specified
• Answer: Center punch

Additional Punch Types and Angles

• Prick punch: 30 degrees
• Dot punch: 60 degrees

Question 12: Standard Drill Angle

• The question is about the standard angle for a drill
• Answer: 118 degrees
• 118-degree drill is used for ductile (tensile) materials
• 135-degree drills are used for brittle materials

Question 13: Lathe Center Angle

• Angle is needed to make adjustments
• Most lathe centers are 60 degrees

Question 14: Back Gearing in a Lathe

• Asks about purpose for back gearing:
• Possible answers relating to achieving low/high speed
• Answer: Back gearing allows obtaining many speeds with low magnitude

Question 15: Controlling Apron Moments

• Asks what part of the apron controls movements:
• Answer: Carriage
• Apron is made from cast iron

Question 16: Lathe Operation With Straight Paths

• Asks what operation does not involve straight path motion
• Answer: Contour Turning

Question 17: What is used to move the Carriage Automatically

• Answer: Led Screw

Question 18: Lathe Spindle Accessories

• Also called tool accessory
• They help ensure it useful
• Helps increase accuracy and efficiency

Question 19: Point Angle Of...

• Prick punch 30 degrees
• Center punch 90 degrees
• Common question and should be studied

Question 20: Standard Drill Angle

• Point of standard drill
• 118 degrees

Question 21: Included Angle of Center

• Center
• 60 degrees

Question 22: Back Gearing Arrangement

• Is provided because;
• To obtain the low speed which are lower in magnitude

Question 23: Machine With Apron On

• Controls
• Carriage

Question 24: Machine Where Wheel Is Fed

• A straight pass
• Answer: Contour turning

Question 25: How Is The Carriage Controlled?

• Automatically while threading
• By the leadscrew

Question 26: What Can Lathe Mandrel Be Terms As?

• Termed As;
• Fixture

Question 27: Lathe Accessories Does What?

• Improve the versatility, do more work
• To support tooling

Question 28: Angle of Punch Degree?

• Prick punch 30
• Center Punch 90
• And other punches

Question 29: Ground drill angle

• Standard point:
• 118 degrees

Question 30: Angle of Lathe Included..

• The angle is;
• 60 degrees

Question 31: Gearing Arrengement

• Is for;
• More number Of Speed

Question 32: Apron...

• Is to do;
• Controll the movement of carriage

Question 33: Usually Maid Of?

• What is the late best maidd of?
• Cast Iron

Question 34: No Lubricant Needed?

• In thred cutting steel:
• Cast Iron

Question 35: Not Part Of Mechanical Press

• Which follows
• Civil Table

Question 36: Align Cutting Tool Gauge?

• With work
• Center gauge

Question 37: Given This How Much Time?

• How to give Time
• Time = Volume/Speed

Question 38: General Purpose Follows What?

• It follows
• Geometric Progression

Question 39: Serve Purpose Follow..

• Dead center.. and can support the work that
• Tailstock

Question 40: Method Of Start Thread Is Cut?

• By the multi start thred
• This leads to single point tool.

Question 41: Not On Tool

• Called as :
• Body Clear

Question 42: Machine Of Threading Is Defined!

• Cutting halical Groovers

Question 43: Speed Is Called :

• A cuttting Speed Is Called:
• Feed

Question 44: Number Of Gaze and Chucks

• Piza Chuck 3 gaze system to Self Centered

Question 45: Collate Is Can Be Called As?

• Self Centering Chuck

Question 46: Spindel Tool What?

• Tools Room and Spindel
• What Direct

Question 47:

• NOT done on work held between centers?
• Parting Off

Question 48: Increasing Cutter Tool?

• For cutting steel:
• Diamond

Question 49: Is NOT Work Holding Device!

• For Lathes device not?
• Tool post

Question 50:

Question 51::

• Not Done of Held
• Parting Off

Question 52:

• Standard Grind Is
• 118

Question 53: Control of What?

• Movement Of a What?
• Carriage