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What is fluting?

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The Fluting is a technique for manufacturing parts that consists in creating flutes, also called grooves, on cylindrical surfaces using machines specially developed for this technique. At LGC Industries, we apply this method to parts such as nails or Pins for example, but it is possible to obtain a spline for any type of cylindrical part.
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The mastery of this technique allows the manufacture of fasteners having 1, 3 or 6 splines, depending on the final application. However, the most common is to find ones with 3 splines at 120 degrees apart for reasons of uniform distribution of forces around the assembly without excessive stresses.

This configuration allows so-called isostatic maintenance, ensuring operation without excessive stresses and effective transmission of forces within the assembly.

On the other hand, with only 2 splines in the assembly, at least one part has a possibility of movement that is harmful to operation: it is a hypostatic maintenance.

With 4 splines in the assembly, operation is carried out with more constraints than is strictly necessary. It's hyperstatic support.

How do you get fluting on a cylindrical part?

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The principle consists in cold printing in a cylindrical part 3 flutes according to 3 generators at 120° from each other. In this way, the initial diameter of the part is swollen, which is called the bulge diameter.

The bulge diameter (Dr) is measured at the ring and corresponds to the diameter of the circle circumscribed at the most prominent points.

This diameter will be slightly larger than the nominal diameter of the hole in the part that will accommodate the part.

When this part is pressed into a hole simply drilled to the nominal diameter, the splines partially close and the metal flows between the flutes and towards the flutes, thus achieving a perfect fit between the part and the hole. The tightening thus obtained is an elastic tightening and not a simple seizure, as would be the case for an elastic pin for example.

Elastic tightening means that it is able to withstand vibration and shock forces without loosening.

What are the different types of flutes?

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At LGC we offer two types of fluting different. The constant flutes as well as the progressive flutes. The choice between the two depends on several factors, the nature of the application as well as the pressure, tightening, and precise adjustment requirements between the splined pin and the hole into which it will be inserted.

• The constant flutes have the same depth and the same spacing throughout the cylindrical part. There is therefore no significant variation in diameter along the part. They are preferred when the clamping pressure is significant and when it is desired to obtain a uniform distribution of this pressure.

• Progressive flutes have a depth and spacing that increases along the room.
  They are preferred when the part must be inserted into a hole with a diameter slightly smaller than that of the part. The progression will allow easy insertion of the fluted pin then tightening more and more strongly as the diameter increases with the spline.
  
  

The advantages of splining on fasteners.

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The advantages of Fluting are numerous, in particular the ease of use, the increase in adhesion, an increase in the contact area and a reduction in the wear of parts:

• Improvement of the contact surface : splining increases the contact area between parts within the assembly, which improves power transmission and reduces wear. According to a study conducted by the National Institute of Standards and Technology, splining can reduce gear wear by 80% compared to non-splined surfaces.
• Improvement of the adhesion between the parts: which reduces the risk of slipping and damaging the parts thanks to the bulge diameter mentioned above.
• Reduced wear and tear on parts: Flutes distribute stress more evenly across parts, reducing the risk of cracks and breaks. In addition, fluted pins have a high shear resistance thanks to the solid cross section, when compared with an elastic pin for example.
• Ease of use: The installation of a fluted pin, for example, can be done using a simple chamfered drilling. Reaming is not required. The elastic tightening is then located at the location of the splines.
• Elastic tightening: Elastic tightening is a real advantage because the pins are much more resistant to vibrations and they are removable and reusable several times before being worn out. It should be noted that few bulky tools are required to install these parts, which saves time and money! The installation can be done manually or automatically and the driving forces are moderate, so it is also a physical gain!
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Did you know that?

Automatic installation can be done using a hydraulic press powered by a vibrating bowl and manual installation can be done using a hammer.

Depending on their use, the fluted pins serve to immobilize them in translation and in rotation. This means that they do not need a lock washer or additional locking piece in the assembly. They can also be used as an axis by locating the smooth range.

Fluted pins are completely customizable at LGC Industries, you can choose the protection of the workpiece, that is to say heat treatments and coatings, as well as the choice of materials according to your applications.

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The importance of the choice of material and treatments

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You should know that the choice of metal must be made according to the mounting conditions and according to the conditions of use. The hardness must be at least equal to that of the parts crossed to avoid levelling the tops of the flutes and a fluted part must be mounted in parts whose thickness is at least equal to the diameter, except in special cases.

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For standard parts, we offer:

• Free-cutting steel
• Striking steel
• Half hard
• Stainless steel

For projects on request, we offer you in particular:

• carbon steel
• Alloyed steel
• Stainless steel
• Brass
• Light alloys

Conclusion

For 85 years, at LGC Industries, we specialize in cylindrical fastening solutions and we are committed to helping our customers co-design the product that suits their needs. We are at your disposal to support you in your project. Do not hesitate to contact us via our website for any request for information.

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Thank you for reading and see you soon at LGC Industries!

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