What Is A Set Screw? – Find The Right Screw for You
The screw is one of science’s greatest, yet simplest inventions. There are a lot of variations of this remarkable tool out there, and understandably, nobody can possibly muster each and every one of them at a whim. This brings us back to our original question - what is a set screw?
The Set Screw
Quite simply, a set screw is a headless screw - set screws are threaded fully, meaning that the entire length of the screw can be fastened to the object. The screw exerts a clamping force through its bottom tip, that projects through the hole (rather than a larger head that would otherwise remain outside). This provides the advantage of preventing relative motion between two rotating parts.
The set screw is traditionally classified within the Socket Set family of screws (screws with no heads). Set screws are set apart from other members of the family because they primarily consist of three main parts: the drive, the thread, and the point.
The traditional screw set has a hexagonal drive on one end and is pointed on the other, though this may vary according to consumer and producer specifications. The set screw is often used together with a shaft collar, and like its functional relatives, eg. the dowel pin and shoulder screw, they are used in assembly.
Who Uses Set Screws?
Set screws are mainly used in industrial and mechanical devices. Because of the mechanical advantages the set screw offers, it can often be spotted within assemblies with rotating parts such as pulleys or wheels where a component is locked onto a shaft.
How Do The Set Screws Work?
Unlike traditional screws that depend solely on threads to hold objects together, the set screw is designed to fasten one object inside the other. A threaded hole is created in the outer object, just like the norm, and the screw is tightened against the inner object. Seems normal, so far.
The difference comes about in terms of inner working. Unlike traditional screws that solely rely on threads to hold the two fastened objects in place, the set screw works by exerting a force through its tip to prevent any relative movement between the two objects, hence the mechanical advantage.
Are There Different Types Of Set Screws?
Short answer - yes. There are lots of different types of screw sets in production, each offering a different type of advantage according to different specifications. Once basic factors such as screw diameter, thread, length, and material are determined, the main differential points that come about are with regard to the drive and point style.
The most common drive style out there is the hexagonal socket drive (Allen wrench style). However, set screws are also available in slotted, six-lobe and spline drives for certain sizes.
A.Slotted Set Screws
Slotted set screws have a fully threaded body which extends over the slot to the end of each part. This slot is used for driving the screw into whatever application it is needed in.
Slotted set screws offer the advantage of relatively easy use since nearly everyone has flat head screwdrivers. Another nice feature is that if used in an outdoor environment, they are easy to clean out if debris gets in them.
B.Hex Or Allen Socket Set Screw
These are the most common type of set screws. They have a 6-sided hex on one end and the threads extend over the whole length of the screw.
The Hex Socket offers the advantage of easy adjustment with no slippage. They also allow for high torquing on the screws. This, in turn, holds objects tighter in place.
This is what makes the biggest difference when you’re picking the right set screw for production. The point of the set screw is what determines what it functions it will serve and the mechanical advantages offered. There are primarily 7 different points that are available:
The cup point screw is the most commonly used set screw. It features a cup-shaped indentation on one end, where it’s to meet the surface of the inner object.
The cup point of this screw is used mainly for quick, semi-permanent or permanent parts of an assembly where the cutting in of the cup point edge of the screw is acceptable.
The oval point is the inverse of a cup point. The small rounded surface at the end allows regular, slight adjustments without loosening the screw. This also offers minimal surface damage to the inner object.
This set screw is most practical for situations where the inner and outer objects require regular adjustments.
This is one of the many variations of the cup point and is even similar in resemblance, the only difference being it has knurls for a stronger grip.
The flat point was designed for flexibility. It is most suitable when frequently resetting or relocating objects on hard steel shafts where minimal damage to the shaft is necessary.
This is an alternative of its relative, is the full dog in this? It has a protruding tip that locks within a mating hole in the shaft, for the permanent setting.
This resembles the half-dog point, with a nylon tip used to grip curved or textured surfaces.
There are plenty of set screws to choose from, but pragmatically speaking, most of these combinations, as used by engineers out in the field, are only available on custom order.
For instance, if you’re an engineer in need of a fine thread cone point set screw that you are going to use on stainless steel, you’re probably going to be told it has to be custom made with a minimum run and a long lead time.
For which reason, you should be sure to check with a sourcing expert before you change your project requirements!
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Set screw instructions
Are There Other Factors To Consider While Choosing Set Screws?
There are plenty of set screws to choose from, but pragmatically speaking, most of these combinations, as used by engineers out in the field, are only available on custom order. For instance, if you’re an engineer in need of a fine thread cone point set screw that you are going to use on stainless steel, you’re probably going to be told it has to be custom made with a minimum run and a long lead time. For which reason, you should be sure to check with a sourcing expert before you change your project requirements!
Now that we know the setscrew points let us take a look at some factors to consider when choosing what to use. I will be listing setscrew points and how or where you should use them.
- Remember that the cup, knurled cup, cone, and half-dog are the points that hold parts permanently.
- Only the Knurled Cup resists vibration even in poorly tapped holes.
- Nylon Tip, Oval, and Flat can be readjusted without damaging the surface of the objects.
- Only the cone can work as a pivot or hanger point.
- The Flat can be used as backing for soft metal or plastic plugs.
- Remember that the Cup, knurled cup, and the cone can gouge surfaces.
- You should not use a knurled cup on very soft surfaces and anything harder than 30 RC surfaces.
Have I answered your “what is a setscrew” question now? You might have noticed that, even though there are only seven setscrews in this article, there are vast ways where you can use them.
Unfortunately, engineers don’t usually use many of the combinations that are written here. They prefer specials or those setscrews that are custom made. Like if you want a fine thread cone point set screw in stainless steel, you would probably hear “custom made” a lot.
Remember always to check what you will be doing before purchasing setscrews; you don’t want to ruin your work now would you? I hope this article helped you a lot regarding knowing what a setscrew is; I would appreciate it if you learned something from this article.
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