There are many factors that affect the quality and performance of an editing application. The spiral angle is often overlooked. It is a simple geometric feature on spiral end mills and other cutting tools. This factor can affect chip control, vibration, power requirements, etc.
In this article we will discuss what a helix is in the context of machining, its advantages and disadvantages and which helix angle solutions are ideal for your applications.
What is a propeller?
A helix, simply put, is a smooth 3D curve that rotates around a linear axis. It can best be thought of as a coil spring, whose coils form a helical curve.
Main geometric characteristics of a propeller
Four main characteristics of a helix completely define its shape:
Central axis : As explained above, a helix is always centered on an axis. Provides a reference for locating and aligning the helix in 3D space.
Helix Angle : As can be seen from the figure, the spring coils form an angle with the axis, which is called the helix angle.
pitch : The distance between two consecutive turns of the spiral is its pitch. A larger pitch means a “longer” spiral. This is an important value when designing different types of threads because their linear movement is linked to their rotational movement.
Number of trains : This is an important parameter in defining the total length of a spiral curve. The more turns, the longer the spiral.
What is the helix angle on cutting tools?
Many cutting tools have spiral grooves (cutting edges). The most common are helical end mills and twist drills. The image below shows the spiral of a cutting tool. The same logic explained above applies here – the angle of the cutting edges corresponds to the spiral angle of the tool.
The helix angle of end mills varies between 12° and 60° depending on the application. However, an angle of 30° to 40° is generally recommended for most jobs. This area offers a good balance between all the factors involved.
Small variations in this angle can change the performance of a cutting tool. Therefore, production engineers and operators need to be aware of the various impacts. Let's take a closer look at how different helix angles affect machining performance.
High helix angle cutting tool versus low helix angle cutting tool: What are the differences?
The spiral angle can be fast (high) or slow (low). In general, experts believe that the transition from low spiral to high spiral is about 40°. It influences important factors such as cutting forces, material removal rate, surface quality and chip evacuation.
Tools with high helix angle
A cutter with a large helix angle is excellent for high feed machining, better surface finish and better thermal performance.
Its sharply angled teeth gradually penetrate the cut. This also causes the forces on the tool to gradually increase, prolonging its useful life. Furthermore, due to its inclination, several grooves are in the cut at the same time, which further reduces the load on the individual grooves.
The spiral redirects part of the radial force to the Z axis of the CNC machine. As the tool is held rigidly in this direction by the tool holder and spindle, this has a positive effect on tool life and machining tolerance. Due to this reduced radial force, the tool can cut at higher feed rates. Low radial force also reduces tool deflections and improves surface finish.
When it comes to chip removal, a steep spiral tool works great. The force in the Z axis (axial force) pushes the chips out of the cutting zone, similar to a drill or tap. This is good for heat dissipation and reduces material build-up. However, the same force can sometimes pull the piece upwards, disturbing its fixation. However, this can be avoided if fixed correctly.
Low helix angle tools
Low helix angle spiral cutters have their own advantages. They have strong cores and cutting edges, allowing them to withstand higher loads. If a high material removal rate is the goal, these tools are preferable because they excavate larger, continuous chips. They are also best suited for hard materials.
However, the disadvantage of such tools is that the user has to compromise the surface quality with low helix cutters.
How do you choose the spiral angle for your application?
An experienced engineer/machinist will know which tools are best suited for your specific application. The angle of the spiral should be an important consideration when selecting a tool for a job.
We will highlight some situations in which knowing the helix angle can help in decision making.
1. Productivity requirements
The effects of the spiral on the material removal rate have already been discussed. A smaller helix angle is preferable when a lot of material needs to be removed quickly.
This can be associated with compensatory measures to reduce the negative effects of the low number of twists. For example, a high helix tool can be used for the finishing pass and a low helix tool can be used for roughing cuts.
2. Connect
When milling pockets, efficient chip removal is very important. Chips remaining in the cutting zone can have a very detrimental effect on the tool and part quality. A high spiral improves chip evacuation and is therefore suitable for pocket/slot milling work.
3. Thin walls/floors
Thin-walled structures and thin floors deform easily under shear forces. In walls, radial forces cause deformation in floors, it is the axial force that is important;
Because the spiral angle directly influences both force components, machine operators can make an informed decision about a suitable tooling solution. For example, if you are machining a thin wall, consider switching to a high spiral cutter to minimize radial forces and achieve a fine finish.
4. Service life
A disadvantage of high helix flutes is that the thickness of the center (core) of the cutter is reduced. This worsens the strength of the tool core and therefore also its service life.
However, a low twist height is also not ideal for service life. It causes problems in the form of heat build-up and shock load due to interrupted cuts. Accumulation of material on the cutting edges is also possible due to poor chip evacuation.
Different spiral angles for cutting different materials
Different materials require different spiral angles. For example, hard metals require low helix angles to get good results, while high helix angles are better for soft metals. Therefore, the type of material to be milled must be taken into consideration when selecting the appropriate helix angle.
Low helix tools are suitable for removing short chips and carbide materials. This includes steel, cast iron and easy-to-machine stainless steel. In addition, types of synthetic materials such as epoxy resin-based plastics, fiberglass panels, and abrasive plastics can also be processed better with tools with a low helix angle.
However, cutters with a large helix angle are suitable for softer materials such as aluminum, copper, plastic, etc.
Furthermore, a variable helix cutter is an ideal choice for high-performance machining. It is suitable for difficult-to-machine materials such as stainless steel and heat-resistant superalloys. Their superior cutting performance and longer tool life make them the perfect choice for even the most demanding machining applications.
University Degree
We hope this article was interesting for our readers. There are many variables in machining and helix angle is not adequately discussed in relation to its importance. An expert knows all aspects of his field and optimizes performance with this knowledge and experience.
Contact us for your rapid manufacturing needs. With our unparalleled experience, you can expect only the best!
Common questions
What is the difference between a draft angle and a spiral angle?
The tilt and spiral angles complement each other (their sum is 90 degrees). They have a common reference line that is tangent to the spiral of the screw or gear. However, the other reference line is different. For the spiral angle, this is the axis of the spiral in question. For the inclination angle, the second reference line is the line perpendicular to the central axis of the spiral.
What are end mills with variable helix length for helix angle used for?
Variable helix end mills are special cutters with different helix angles for each cutting edge. They have high dynamic stability because they can dampen vibrations at the resonant frequencies of the tool. As a result, these tools experience less chatter and produce a finer surface finish.
Why are spiral angles important in machining?
The helix angle is a central geometric parameter in milling milling. It is important because it affects material removal rate, feed rate, surface finish, cutting force distribution, strength and tool life.
