Lathe Threading – Manufacturing Processes 4-5 (2023)

After completing this unit, you should be able to:

• Determine the infeed depth.

• Describe how to cut a correct thread.

• Explain how to calculate the pitch, depth, and minor diameter, width of flat.

• Describe how to set the correct rpm.

• Describe how to set the correct quick change gearbox.

• Describe how to set the correct compound rest.

• Describe how to set the correct tool bit.

• Describe how to set both compound and crossfeed on both dials to zero.

• Describe the threading operation.

• Describe the reaming.

• Describe how to grind a tool bit.

Thread cutting on the lathe is a process that produces a helical ridge of uniform section on the workpiece. This is performed by taking successive cuts with a threading toolbit the same shape as the thread form required.

Practice Exercise:

1. For this practice exercise for threading, you will need a piece of round material, turned to an outside tread Diameter.

2. Using either a parting tool or a specially ground tool, make an undercut for the tread equal to its single depth plus .005 inch.

3. The formula below will give you the single depth for undertaking unified threads:

d = P x 0.750

Where d = Single Depth

P = Pitch

n = Number of threads per inch (TPI)

Infeed Depth = .75 / n

To cut a correct thread on the lathe, it is necessary first to make calculations so that the thread will have proper dimensions. The following diagrams and formulas will be helpful when calculating thread dimensions.

Example: Calculate the pitch, depth, minor diameter, and width of flat for a ¾-10 NC thread.

P = 1 / n = 1 / 10 = 0.100 in.

Depth = .7500 x Pitch = .7500 x .100 = .0750 in.

(Video) Thread Anatomy- (In less than 5 min!)

Minor Diameter = Major Diameter – (D + D) = .750 – (.075 + .075) = 0.600 in.

Width of Flat = P / 8 = (1 / 8) x (1/10) = .0125 in.

Procedure for threading:

1. Set the speed to about one quarter of the speed used for turning.

2. Set the quick change gearbox for the required pitch in threads. (Threads per inch)

Lathe Threading – Manufacturing Processes 4-5 (1)

Figure 1. Thread and Feed Chart

Lathe Threading – Manufacturing Processes 4-5 (2)

Figure 2. Setting Gearbox

3. Set the compound rest at 29 degrees to the right for right hand threads.

Lathe Threading – Manufacturing Processes 4-5 (3)

Figure 3. 29 Degrees

4. Install a 60 degree threading tool bit and set the height to the lathe center point.

Lathe Threading – Manufacturing Processes 4-5 (4)

Figure 4. 60 Degree Threading Tool

5. Set the tool bit and a right angles to the work, using a thread gage.

Lathe Threading – Manufacturing Processes 4-5 (5)

Figure 5.Using the Center gage to position the tool for machining Threads

6. Using a layout solution, coat the area to be threaded.

Lathe Threading – Manufacturing Processes 4-5 (6)

Figure 6. Layout

7. Move the threading tool up to the part using both the compound and the cross feed. Set the micrometer to zero on both dials.

Lathe Threading – Manufacturing Processes 4-5 (7)

Figure 7. Compound Figure 8. Cross Feed

8. Move cross feed to the back tool off the work, move carriage to the end of the part and reset the cross feed to zero.

Lathe Threading – Manufacturing Processes 4-5 (8)

(Video) Threading: Step 5 (Setting Lathe Speed)

Figure 9.End of the part and Cross feed to Zero

9. Using only the compound micrometer, feed in .001 to .002 inch.

Lathe Threading – Manufacturing Processes 4-5 (9)

Figure 10: Compound feed in .002 inch

10. Turn on the lathe and engage the half nut.

Lathe Threading – Manufacturing Processes 4-5 (10)

Figure 11: On/Off Lever and Half Nut

11. Take a scratch cut on the part without cutting fluid. Disengage the half nut at the end of the cut, stop the lathe and back out the tool using the cross feed. Return the carriage to the starting position.

Lathe Threading – Manufacturing Processes 4-5 (11)

Figure 12. Starting Position

12. Using a screw pitch gage or a rule check the thread pitch. (Threads per inch)

Lathe Threading – Manufacturing Processes 4-5 (12)

Figure 13. Screw Pitch Gage Figure 14. Screw Pitch Gage(10)

13. Feed the compound in .005 to .020 inch for the first pass using cutting oil. As you get near the final size, reduce the depth of cut to .001 to .002 inch.

14. Continue this process until the tool is within .010 inch of the finish depth.

Lathe Threading – Manufacturing Processes 4-5 (13)

Figure 15. Threading operation

15. Check the size using a screw thread micrometer, thread gage, or using the three wire system.

Lathe Threading – Manufacturing Processes 4-5 (14)

Figure 16. Three wire measurement

16. Chamfer the end of the thread to protect it from damage.

Reamers are used to finish drilled holes or bores quickly and accurately to a specified sized hole and to produce a good surface finish. Reaming may be performed after a hole has been drilled or bored to within 0.005 to 0.015 inch of the finished size since the reamer is not designed to remove much material.

The workpiece is mounted in a chuck at the headstock spindle and the reamer is supported by the tailstock.

The lathe speed for machine reaming should be approximately 1/2 that used for drilling.

Reaming with a Hand Reamer

The hole to be reamed by hand must be within 0.005 inch of the required finished size.

(Video) How to Cut Multi-Start Threads - Quick Machining Tips #23

The workpiece is mounted to the headstock spindle in a chuck and the headstock spindle is locked after the workpiece is accurately setup. The hand reamer is mounted in an adjustable reamer wrench and supported with the tailstock center. As the wrench is revolved by hand, the hand reamer is fed into the hole simultaneously by turning the tailstock handwheel. Use plenty cutting fluid for reaming.

Reaming with a Machine Reamer

The hole to be reamed with a machine reamer must be drilled or bored to within 0.010 inch of the finished size so that the machine reamer will only have to remove the cutter bit marks. Use plenty cutting fluid for reaming.


1. Grip the tool bit firmly while supporting the hand on the grinder tool set.

2. Hold the tool bit at the proper angle to grind the cutting edge angle. At the same, tilt the bottom of the tool bit in towards the wheel and grind 10 degrees side relief or clearance angle on the cutting edge. The cutting edge should be about .5 inches long and should be over about ¼ the width of the tool bit.

3. While grinding tool bit, move the tool bit back and forth across the face of the grinding wheel. This accelerates grinding and prevents grooving the wheel.

4. The tool bit must be cooled frequently during the grinding operation by dip into the water. Never overheat a tool bit.

5. Grind the end cutting angle so that it form an angle a little less than 90 degrees with the side cutting edge. Hold the tool so that the end cutting edge angle and end end relief angle of 15 degrees are ground at the same time.

6. Check the amount of end relief when the tool bit is in the tool holder.

7. Hold the top of the tool bit at about 45 degrees to the axis of the wheel and grind the side rake about 14 degrees.

8. Grind a slight radius on the point of the cutting tool, being sure to maintain the same front and side clearance angle.

Lathe Threading – Manufacturing Processes 4-5 (15)

Grind front Grind side Grind radius

Lathe tool bits are generally made of four materials:

1. High speed steel

2. Cast alloys

3. Cemented Carbides

4. Ceramics

The properties that each of these materials possess are different and the application of each depends on the material being machined and the condition of the machine.

Lathe tool bits should possess the following properties.

1. They should be hard.

2. They should be wear resistant.

3. They should be capable of standing up to high temperatures developed during the cutting operation.

4. They should be able to withstand shock during the cutting operation.

Cutting tools used on a lathe are generally single pointed cutting tools and although the shape of the tool is changed for various applications. The same nomenclature applies to all cutting tools.

(Video) Threading 5


1. Base: the bottom surface of the tool shank.

2. Cutting Edge: the leading edge of the tool bit that does the cutting.

3. Face: the surface against which the chip bears as it is separated from the work.

4. Flank: The surface of the tool which is adjacent to and below the cutting edge.

5. Nose: the tip of the cutting tool formed by the junction of the cutting edge and the front face.

6. Nose radius: The radius to which the nose is ground. The size of the radius will affect the finish. For rough cut, a 1/16 inch nose radius used. For finish cut, a 1/16 to ⅛ inch nose radius is used.

7. Point: The end of the tool that has been ground for cutting purposes.

8. Shank: the body of the tool bit or the part held in the tool holder.

9. Lathe Tool bit Angles and Clearances

Proper performance of a tool bit depends on the clearance and rake angles which must be ground on the tool bit. Although these angles vary for different materials, the nomenclature is the same for all tool bits.

• Side cutting edge angle: The angle which the cutting edge forms with the side of the tool shank. This angle may be from 10 to 20 degrees depending on the material being cut. If angle is over 30 degrees, the tool will tend to chatter.

• End cutting edge angle. The angle formed by the end cutting edge and a line at right angle to the centerline of the tool bit. This angle may be from 5 to 30 degrees depending on the type of cut and finish desired. For roughing cuts an angle of 5 to 15 degrees, angle between 15 and 30 degrees are used for general purpose turning tools. The larger angle permits the cutting tool to be swivelled to the left when taking light cuts close to the dog or chuck, or when turning to a shoulder.

• Side Relief (clearance) angle: The angle ground on the flank of the tool below the cutting edge. This angle may be from 6 to 10 degrees. The side clearance on a tool bit permit the cutting tool to advance lengthwise into the rotating work and prevent the flank from rubbing against the workpiece.

• End Relief (clearance) angle: the angle ground below the nose of the tool bit which permits the cutting tool to be fed into the work. This angle may be 10 to 15 degrees for general purpose cut. This angle must be measured when the tool bit is held in the tool holder. The end relief angle varies with the hardness and type of material and type of cut being taken. The end relief angle is smaller for harder materials, to provide support under the cutting edge.

• Side Rake Angle: The angle at which the face is ground away from the cutting edge. This angle may be 14 degrees for general purpose tool bits. Side rake centers a keener cutting edge and allows the chip to flow away quickly. For softer materials, the side rake angle is generally increased.

• Back (Top) Rake: The backward slope of the tool face away from the nose. This angle may be about 20 degrees and is provide for in the tool holder. Back rake permits the chips to flow away from the point of the cutting tool.

1. What is pitch for ¼-20 tap?

2. To what angle must the compound be turned for Unified Thread?

3. Explain why you swivel the compound in Question 2.

4. What is the depth of thread for UNF ½-20 screw?

5. How would you make a left-hand thread? This is not covered in the reading—think it out?

6. What Tool bit do we use for cutting thread?

7. Please describe Center Gage.

8. What do we use to check the thread pitch(Thread Per Inch)?

9. The first and final pass, how much do we feed the compound in?

(Video) CHOOSE YOUR OWN ADVENTURE: Single Point ACME Threading!

10. Name four material that use to make Tool bits.

This chapter was derived from the following sources.

  • Lathe derived from Lathe by the Massachusetts Institute of Technology, CC:BY-NC-SA 4.0.
  • Cutting Tool Terminology derived from Lathe Cutting Tools – Cutting Tool Shapes by the Wisconsin Technical College, CC:BY-NC 4.0.
  • Cutting Tool Terminology derived from Cutter Types (Lathe) by the University of Idaho, CC:BY-SA 3.0.
  • Centering derived from [Manual Lathes Document]


What is the process of threading lathe? ›

Thread cutting on the lathe is a process that produces a helical ridge of uniform section on the workpiece. This is performed by taking successive cuts with a threading toolbit the same shape as the thread form required.

What are 5 common lathe operations? ›

The most common lathe operations are turning, facing, grooving, parting, threading, drilling, boring, knurling, and tapping.

What manufacturing processes can be done on lathe? ›

A lathe is a tool that rotates the workpiece on its axis to perform various operations such as cutting, sanding, knurling, drilling, or deformation, facing, turning, with tools that are applied to the workpiece to create an object with symmetry about an axis of rotation.

What are types of threading process? ›

There are three types: center-type grinding with axial feed, center-type infeed thread grinding and centerless thread grinding.

What are the steps of threading? ›

Check your instruction manual when threading your sewing machine for the first time.
  1. Wind a bobbin. ...
  2. Load your wound bobbin. ...
  3. Place the spool. ...
  4. Thread through the thread guide. ...
  5. Pull the thread through the U-shaped guide. ...
  6. Wrap the thread around the thread take-up lever. ...
  7. Thread the needle. ...
  8. Catch the thread.
Jun 7, 2021

What are the four 4 main parts of the lathe? ›

The main parts of a lathe machine include: the bed, headstock, carriage and tailstock.

What are 4 functions of a lathe machine? ›

Known as the "mother of machining tools," lathes can be used for a variety of purposes. These include shaping, drilling, sanding, knurling, turning, cutting, and deformation.

What are the 3 main types of lathe? ›

Types of Lathe Machines. Speed Lathe Machine. Center lathe or engine lathe machine. Turret Lathe Machine.

What are the 3 basic types of threads? ›

There are three standard thread series in the Unified screw thread system that are highly important for fasteners: UNC (coarse), UNF (fine), and 8-UN (8 thread).

What are the three methods of threading? ›

These include the hand method, mouth method and neck method. Each technique has advantages and disadvantages; however, the mouth holding method is the fastest and most precise. Threading allows for a more defined and precise shape and can create better definition for eyebrows.

What are the four basic thread operations? ›

There are four basic thread management operations: thread creation, thread termination, thread join, and thread yield.

What are the different types of machining manufacturing processes? ›

There are three main kinds of machining: turning, milling, and drilling. There are other processes that also fall into the category of machining, but when it comes to modern machining processes, turning, milling, and drilling cover the majority.

How many types of machining process are there? ›

The three principal machining processes are classified as turning, drilling and milling. Other operations falling into miscellaneous categories include shaping, planing, boring, broaching and sawing.

What is the manufacturing method of machining? ›

Machining, also known as subtractive manufacturing, is a prototyping and manufacturing process that creates the desired shape by removing unwanted material from a larger piece of material.

What are the 4 types of threading dies? ›

What types of thread die are there? The external shape of the thread die can be round, square, hexagon or tubular and can be further classified as solid, split or separable. Round dies are the most common and, depending on their size, have three or more serrated cutting edges and geometrically represent the nut thread.

What are the 4 main types of threads used on fasteners? ›

Metric, UNC, UNF and More: Thread Types for Fasteners
  • Metric Thread. Metric thread is the most widely used today, and can otherwise be referred to as 'ISO Metric' or 'M'. ...
  • UNC. UNC stands for 'Unified Coarse' and is the most commonly used thread type in the United States of America. ...
  • UNF. ...
  • BA. ...
  • BSF.
Aug 21, 2019

What are the 2 main types of threads? ›

There are two common forms of threads: straight threads and tapered threads. Straight threads have a parallel profile that remains the same diameter throughout the part. Tapered threads taper along with the thread profile and become smaller in diameter as the part moves down.

What is threading process in manufacturing? ›

Threading is a manufacturing and metal processing method used to create the helical detailed edges of a screw to enable it to be fastened to another piece of wood, metal or material. Threading may be the source of corrosion in some materials due to the crevices created by the process.

What are the 6 major parts of a lathe machine? ›

While there are different types of lathes, most feature a few basic parts to facilitate their operations.
  • Bed. The bed is a large horizontal structure or beam that's used to support other parts of a lathe like the headstock and tailstock. ...
  • Headstock. ...
  • Tailstock. ...
  • Carriage. ...
  • Legs. ...
  • Cross Slide. ...
  • Saddle. ...
  • Apron.
May 9, 2019

What is a 4 jaw chuck in a lathe? ›

4 jaw lathe chucks are a particular type of chuck designed to safely and securely hold square, hexagonal, wound, and irregular-shaped workpieces. One of the benefits is that 4 jaw lathe chucks are highly accurate, making them preferable to 3 jaw lathe chucks and other options.

What is the 4th axis on a lathe? ›

Index 4-axis CNC machining is when the 4th axis (A-axis) rotates whilst the machine is not cutting material. Once the correct rotation is selected, a brake is applied and the machine resumes cutting. In continuous 4-axis machining, the machine can cut material at the same time as the A-axis rotation, simultaneously.

Why is knurling done? ›

Knurling allows hands or fingers to get a better grip on the knurled object than would be provided by the originally smooth metal surface. Occasionally, the knurled pattern is a series of straight ridges or a helix of "straight" ridges rather than the more-usual criss-cross pattern.

Which is the most basic of the manual lathes? ›

The original and most basic type of manual lathe. An engine lathe holds a cylindrical workpiece on one or both ends. A flat, round workholding device often used to mount flat-bottomed workpieces. A faceplate is the most basic means of mounting a workpiece on the spindle of a lathe.

What are the 3 axis on a lathe? ›

In addition to movements along the X, Y and Z axes, this type of machine can also choose two of the three rotational axes. The three rotational axes are also denoted by A-axis, B-axis, and C-axis. These three additional axes together can perform a 180-degree rotation around the X, Y and Z axes.

What is the most common lathe? ›

The engine lathe is considered as the most common type of manual lathes, which are widely used in all machine shop applications. The engine lathe or center lathe can perform operations such as turning, end face, grooving, knurling, and threading.

Which 3 of the 6 operations can be done when filing in a lathe? ›

The three basic operations that can be performed on both a metal or wood lathe machine are turning, boring and facing.

What does 3 4 thread mean? ›

For example, a 3/4" NPT pipe thread has an outside diameter of 1.050 inches. Each thread size has a defined number of threads per inch (TPI). The 3/4" NPT pipe thread has 14 threads per inch.

How many types of threads are used in mechanical industry? ›

SIX most common types. Metric ISO threaded screws are V-shaped at the outer edges, and are self-locking so do they not need a screw lock. The flank angle of a V thread is 60° and it is commonly used for all places where fine adjustments with leads as fine as 0.0125inch (0.3175mm) are critical such as microscope stages.

What does 16 TPI mean? ›

TPI stands for Threads Per Inch. This is simply a count of the number of threads per inch measured along the length of a fastener.

What are the 2 methods to create threads? ›

There are two ways to create a thread:
  1. By extending Thread class.
  2. By implementing Runnable interface.

What are three 3 differences between process and thread? ›

Process means a program is in execution, whereas thread means a segment of a process. A Process is not Lightweight, whereas Threads are Lightweight. A Process takes more time to terminate, and the thread takes less time to terminate. Process takes more time for creation, whereas Thread takes less time for creation.

What is a Class 4 thread? ›

The Class of a thread indicates the tolerance allowed in manufacturing. Class 1 is a loose fit, Class 2 is a free fit, Class 3 is a medium fit, and Class 4 is a close fit. Aircraft bolts are almost always manufactured in the Class 3, medium fit.

What are the 4 basic thread operations associated with a change in thread state? ›

Thread operations associated with a change in thread state are: Spawn Block Unblock Finish The key states for a thread are: Running Ready Blocked THREAD STATES As with processes, the key states for a thread are Running, Ready, and Blocked.

What is the meaning of 4 threads? ›

All CPUs have active threads, and every process performed on your computer has at least a single thread. The number of threads you have depends on the number of cores in your CPU. Each CPU core can have two threads. So a processor with two cores will have four threads. A processor with eight cores will have 16 threads.

What are the 6 main manufacturing processes? ›

  • 1 Casting.
  • 2 Labeling and painting.
  • 3 Moulding.
  • 4 Forming.
  • 5 Machining.
  • 6 Joining.
  • 7 Additive manufacturing.
  • 8 Other.

What are the 6 main categories of manufacturing processes? ›

What are the 6 types of manufacturing processes?
  • Repetitive manufacturing.
  • Discrete manufacturing.
  • Job shop manufacturing.
  • Continuous process manufacturing.
  • Batch process manufacturing.
  • 3D printing.
Oct 19, 2022

What are the 10 machining processes? ›

Types of Machining Operations
  • Turning. In the turning process, the cutting tool remains stationary while the workpiece rotates. ...
  • Milling. ...
  • Drilling. ...
  • Grinding. ...
  • Sawing. ...
  • Broaching. ...
  • Planing. ...
  • Electrical Discharge Machining (EDM)
Nov 30, 2022

What is 3 2 machining? ›

3+2 machining is a technique whereby a three-axis milling program is executed with the cutting tool locked in a tilted position using the 5-axis machine's two rotational axes, hence the name, 3+2 machining.

What are the 3 types of manufacturing? ›

There are three types of manufacturing production process; make to stock (MTS), make to order (MTO) and make to assemble (MTA).

What are the three most common machining processes? ›

Comparing the 3 Primary Machining Processes
  • #1) Turning. Turning is a machining process in which a fixed, non-rotating cutting tool removes material from a rotating workpiece. ...
  • #2) Milling. ...
  • #3) Drilling.
Apr 5, 2019

What are the steps in manufacturing process? ›

Steps of the Manufacturing Process
  • Develop the Product Vision. The product vision is the seed the finished goods will grow from. ...
  • Research the Vision. ...
  • Design the Product. ...
  • Finalize the Design. ...
  • Test the Prototype. ...
  • Manufacture the Product. ...
  • Get Feedback and Do More Testing. ...
  • Official Release.
May 11, 2022

What is the process of threading used for? ›

A thread is the basic unit to which the operating system allocates processor time. A thread can execute any part of the process code, including parts currently being executed by another thread. A job object allows groups of processes to be managed as a unit.

What is the process for threading metal? ›

A tap is used to cut or form threads on the internal surface, while a die is used to cut threads on the external surface. The process of using a tap to cut threads is called tapping, while the process involving a die to form threads is called threading. Tapping can be done using a drill machine or tap wrench.

How does a threading machine work? ›

Pipe threading machines use a die head, which the pipe is placed through. The die head is a ring-shaped component which contains lots of teeth and attaches around the pipe. Once the die head is turned, the teeth cut the threads into the pipe.

What are the 2 methods of threading? ›

Thread production: Methods for the production of threads

formed. drilled. rolled. shot.

What are the thread cutting methods? ›

Two cutting tools are normally used for thread cutting; taps and dies. Dies creates external threads, and taps are for internal threads. Cutting the external threads is known as threading or in some cases chasing, meanwhile cutting internal threads is called tapping.

Which method is used for producing thread in? ›

There are two methods for making threads, viz., thread cutting and thread rolling. Thread cutting is done on automatic machines called 'screw' machines.


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