Clear passivated inserts offer a high level of resistance to corrosion.

With competitive price and timely delivery, Guangzhou Ruiyi Technology Co., Ltd. sincerely hope to be your supplier and partner.

Passivation is the application of a protective coating to a material to make it more passive - less reactive to its environment. If this coating is entirely or mainly transparent, it is referred to as clear passivation.

By contrast, galvanised inserts feature a protective coating of zinc to prevent oxidation or rust from forming.

Threaded inserts are available with a range of thread sizes for compatibility with differently sized screws and bolts. Whether inserted into wood or metal, a threaded insert needs to match the diameter and threading of the screw or bolt that it will host.

The most used international screw thread standard is the ISO metric screw thread, as defined by international standard 68-1.

ISO metric screws are designated with the letter M, for millimetres, followed by the major diameter of the thread. This is the longest gap between the uppermost part of each thread (the crest). So, for example, M8 indicates a major diameter of eight millimetres.

Variations in pitch can also be indicated with a multiplication sign. For example, M8x1 would indicate a major diameter of eight millimetres with a change in pitch of one millimetre per rotation.

How to choose the thread turning insert and shim

When choosing the most suitable thread turning insert for your application, you need to consider the insert type, flank/radial clearance, and insert geometry. These are all factors that influences chip control, insert wear, tool life, and thread quality.

How to choose the insert type

When turning a thread, there are three main insert types to choose from: full profile, V-profile, and multi-point inserts. Each type has its advantages and disadvantages.

Full profile insert

The full profile insert is the most common insert type. It is used to cut a complete thread profile, including the crest.

Advantages

• Ensures correct depth, bottom, and top profile for a stronger thread
• No deburring of the thread profile needed
• Fewer passes required compared to a V-profile insert thanks to the larger nose radius
• Gives a productive threading performance.

Disadvantage

A separate insert is required for each pitch and profile.

Note: Extra stock/material should be left on the workpiece for topping the finish diameter of the thread (0.05–0.07 mm (0.002–0.003 inch)).

V-profile insert

V-profile inserts do not top the thread crests. Therefore, the outer diameter for screws and inner diameter for nuts must be turned to the right diameter prior to threading.

Advantages

• Flexibility: the same insert can be used for a range of pitches, provided that the thread profile angle (60° or 55°) and radius are the same
• Minimum tool inventory needed

Disadvantages

• The insert nose radius is smaller to cover the range of pitches, which reduces tool life
• Burr formation can be a problem

Multi-point insert

Multi-point inserts are similar than full profile inserts but have more than one insert point (NT>1). A two-point insert doubles the productivity, and a three-point insert triples the productivity, etc.

Advantages

• Requires fewer passes, which gives better tool life, productivity, and lower tool costs

Disadvantages

• Stable conditions are needed as a result of increased cutting forces as the cutting edge has a longer contact length
• Needs sufficient room behind the last thread to clear the last tooth of the insert, generating a full thread depth

Are you looking for tool recommendations?

Find our cutting tools here chevron_right

Need advice?

Ask us a question chevron_right

Want to learn more about the basics of metal cutting?

Register for our free e-learning chevron_right

How to choose the insert geometry

Selecting the correct insert geometry is important when thread turning. The geometry influences chip control, insert wear, thread quality, and tool life.

Flat geometry

• All-round, can be used for most materials
• Edge rounded cutting edge for edge strength

Sharp geometry

• For sticky or work-hardening materials, e.g., low-carbon steel, stainless steel, non-ferrous materials, and super alloys
• Sharp cutting edge for low cutting forces and good surface finish

Chip-breaking geometry

• For long-chipping materials, e.g., low-carbon materials. Can also be used for stainless steel, alloyed steel, and non-ferrous materials
• Chip-forming geometry that enables a more continuous and unsupervised machining
• Not to be used with radial infeed

Read more about threading inserts and grades

Insert clearance angles

Angular clearance between the insert and thread is necessary for precise, accurate thread turning. There are two types, radial clearance (ALP) and flank clearance (ALF).

Radial clearanceFlank clearance

Flank clearance

Cutting edge clearance between the sides of the insert and thread flank is essential to ensure even tool wear and consistent, high-quality threads. The insert should therefore be tilted to gain maximum symmetrical clearance from the flanks (flank clearance angle) and get the correct thread profile. The tilt angle of the insert should be the same as the helix of the thread.

If you are looking for more details, kindly visit Threading Inserts.

Flank clearance

Selection of shim

Insert shims are used to give different tilts to the insert, so that the angle of insert inclination (λ) is the same as the helix of the thread. See table below for methods on how to select the correct insert shim.

• The standard shim in many holders is 1°, which is the most common angle of inclination
• Negative shims are used when turning left-hand threads with right-hand tools, and vice versa

Lead (pitch) mmThreads/inch Workpiece
diametermm
inch

Example:

• Pitch = 6 mm and workpiece = Ø 40 m: a 3° shim is required
• Pitch = 5 threads per inch and workpiece = Ø 4 inches: a 1° shim is required

Threads with small profile angles

ALP = Radial clearance
ALF = Flank clearance

For ACME, trapezoidal, and rounded threads, it is especially important to choose the correct shim to tilt the insert, because the pressure on the cutting edge is higher, and the flank clearance is smaller.

Flank clearance (ALF) depends on profile

Flank clearance
(ALF)Flank clearance
(ALF) Metric, UN60°7.6°5° Whitworth55°7.1°4.7° Trapezoidal30°4°2.6° ACME29°3.8°2.5° Buttress10°/3°2.7°/0.8°1.8°/0.5°

Radial clearance

To set the correct radial clearance, the inserts are tilted 10° or 15° in the tool holder. It is important to use internal inserts with internal tool holders, and vice versa, to ensure that the correct thread form is achieved.

Insert sizes:
11, 16, and 22 mm
(1/4, 3/8, and 1/2 inch)

Insert size:
27 mm (5/8 inch)

Are you looking for tool recommendations?

Find our cutting tools here chevron_right

Need advice?

Ask us a question chevron_right

Want to learn more about the basics of metal cutting?

Register for our free e-learning chevron_right

Related information

Choosing Thread Mills

Discusses thread milling concepts, insert types, and tool holder options. chevron_right

Choosing Turning Inserts

Learn how to choose turning inserts for various machining operations. chevron_right

Threading Techniques

Discover threading methods for diverse profiles and machining scenarios. chevron_right

Thread Turning

Explores challenges and methods in external and internal thread turning processes. chevron_right

For more CNC Cutting Toolsinformation, please contact us. We will provide professional answers.