Rolled vs. Cut Threads – What's the Difference?

Rolled vs. Cut Threads &#; What&#;s the Difference?

You might intuitively understand that there are multiple ways to craft a screw or bolt. But have you ever considered the exact method for creating these essential fasteners? And have you ever wondered if one method is better than another?

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You may have never even considered this question before, but perhaps you have a specific project that has forced you to wonder, &#;does it matter how the threads are made?&#;

Rolled Threads vs. Cut Threads

Threads in a screw or bolt must be consistent from top to bottom. When discussing rolled vs. cut threads, there&#;s not much difference from the perspective of the person using bolts and screws.

Strength-wise, they are very similar but there are other drastic differences in construction, costs, and finishing that may sway you towards rolled vs. cut threads or vice versa.

Rolled Threads: An Overview

A screw or bolt made with rolled threads starts life as a smooth round bar. It&#;s then forced through an extruder which forces the material into the familiar threaded screw or bolt we all recognize. Since no material is being removed, the final diameter of the threaded portion is actually larger than the original bar.

The valleys in between the threads equal the diameter of the smooth bar while the peaks stick out. This variability is an important area where rolling threads vs. cutting threads makes a difference for the user. For example, if you need a bolt or screw with threads and a body with the same diameter, rolled thread construction may not be what you want.

Rolling threads vs. cutting threads yields another interesting difference: thread strength. Rolled threads tend to be much sharper and better defined than cut threads thanks to the burnishing during manufacture, which improves fatigue resistance.

While it&#;s true that the screw or bolt body will be just as strong with either method, rolled threads tend to be stronger and more resistant to stripping than cut threads.

Pros and Cons of Rolled Threads

Benefits include:

• Less costly to make than cut thread bolts or screws
• A smaller diameter body means less weight
• No need to heat the material
• Smooth threads

The drawbacks are:

• There is a limit on the size of material, which limits the size of bolts and screws
• Material that is too hard can&#;t be rolled
• Thread diameter and body diameter are different
• Certain structural bolts can&#;t be rolled

Next, we&#;ll take a look at cut threads.

Cut Threads: An Overview

The main difference between rolling threads vs. cutting threads is that cut thread bolts and screws have the same body diameter as thread diameter. Cut threading takes a steel bar and cuts the threads into the material.

If you start with a 1-inch bar, your bolt or screw&#;s threads and body will still be 1 inch. Additionally, that bar can be just about any diameter or hardness.

When discussing the strength of rolled threads vs. cut threads, yes, the process of rolling yields stronger, smoother threads. But you can use much harder material with the cut thread method, and it can be bigger, too. Because thread cutting is a similar process to using a lathe, if the material can be spun, it can be threaded.

Pros and Cons of Cut Threads

Benefits of cut threads include:

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• Practically any size bar and thread length are possible
• Threads can be cut to almost any pitch
• Works best with materials containing lead

The drawbacks include:

• They are more expensive to manufacture
• They are slower to produce
• They are heavier than rolled thread screws or bolts
• Threads can bind and fatigue

Keep these factors in mind when making your decision.

Which One Is Superior?

The question of superiority in the discussion over rolled vs. cut threads comes down to application and budget. If the threaded portion and the body don&#;t need to be the same diameter, the dimensions required are small, and the cost is a factor, then rolled threads are the better choice.

Cut threads are preferable for precision applications that need specific body and thread diameters, bolts or screws with large or unusual sizes, and when the cost is less of a concern.

Still Have Questions? Let us help!

You might still be wondering which method is best for your application. When in doubt, talk to our team.

At Crane Point Industrial, we&#;ve been supplying fasteners to hard-working construction, pallet, and industrial customers for over 25 years. So, we know a thing or two about selecting quality screws and bolts. In addition, our fastener supply company offers tools and equipment, construction accessories, industrial safety gear, pallet building supplies, and structural hardware.

Mechanical parts can be manufactured with different techniques. These include thread rolling and thread cutting. What type of threading should be used in which case? Which threading is used for the manufacture of CODIPRO&#;s lifting rings and why? In this article, we&#;ll have a closer look at this subject.

Cut vs. rolled thread

Machined threading (cut threads) consists of removing material. The metal is cut away in several successive steps with a considerable loss of material. The fibers of the material are thus &#;cut&#; and broken.

Manufacturing mechanical parts using the thread rolling process consists of deforming a part under the force of rotating presses. The material is thus deformed by cold forming and not cut. This particularity of thread rolling results in a better tensile strength.

At CODIPRO, the threaded bolts of the standard lifting rings are manufactured using the thread rolling process. This is a significant advantage for the products and their users.

Static tensile strength

Because the metal fiber is not cut, the thread rolling process naturally increases the thread strength. The cross-sectional view below demonstrates the difference between the two techniques: rolled thread (deformed material) and cut thread (cut material).

Material hardness and fatigue strength

One of the characteristics of thread rolling is the hardening of the part. At the bottom of the thread, a zone of very high compression, the material can be deformed up to 200 percent. This greatly increases the surface hardness of the material and creates a state of compression that prevents formation of cracks and their propagation, which also results in better fatigue resistance. Concretely, the fatigue strength of cold-rolled threads can be up to 30 percent higher compared to cut threads.

Rolled vs. cut threads

The mechanical strength of a threaded element is therefore influenced by the threading process. The characteristics of a rolled thread compared to a cut thread can be summarized as follows:

• Tensile strength -> up to 10% higher
• Shear strength -> better, due to the crack propagation mode
• Fatigue strength -> up to 30% higher

The working load limits and safety coefficients of a lifting ring manufactured with a rolled thread can therefore be much higher than those of the same lifting ring with a cut thread.

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