What is Woodruff Key?
Woodruff key is a flat semi-circular or half-moon-shaped disk with a uniform thickness, which directly fits into the semi-circular recess of the shaft. The semi-circular recess or pocket is known as the woodruff keyway. Semi-circular pocket in the shaft directly cut by plunge cutter with woodruff key cutter. The bottom circular portion is placed in the shaft by hammering & the top flat portion is inserted into the keyway of the hub. Once placed in position, it gets to align itself in the shaft.
Due to the extra depth of the key, it directly fits in the mating part, and there is no gap between those parts. These keys are easy to use and adjustable as compare to other keys.
Although, this key is easy to remove & hard to install. Because there is small tolerance between key and keyway. Due to extra depth in the shaft, there are chances of weakening of shaft strength ability.
Key is machined element using for connecting transmission shaft to rotating parts like gear.
This type of key is mainly using for light loads. It is suitable for shafts whose diameter ranges between 6mm to 60 mm.
Different Types of Woodruff Key
There are mainly two types of Woodruff keys as per application. But the difference between them is minimum.
It is full half-circular in shape and in contact with the seat of the shaft. This key requires high precision tight fit tolerance. Because small deviation in size cannot make an assembly with the hub.
It is in the same shape as the standard key, with the bottom is flat. Due to that, it can adjust in the groove easily.
High Pro Key
This key having a slightly different profile at the top. The step is at the flat portion on top to get support during assembly. The above figure gives more detailed information about high pro woodruff kay.
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How to install the woodruff key properly?
- While installing the woodruff key, first press that key in the pocket (Keyway) in a shaft manually.
- Once it gets fit in the shaft, align the flat surface of the key with the slot of the hub.
- As per the condition, we can move the hub or shaft with the key in each other to get proper assembly.
- By light tapping with a hammer, we can make an assembly of shaft & coupling.
Woodruff key material & finish.
This key is manufacture in stainless steel, alloys, and carbon. Carbon & alloys are durable. Different kinds of coating can prevent corrosion.
|Material of Key||Finish||Benefits|
|Carbon Steel & Allo Steel||Plain Finish||Corrosion Resistance|
|Carbon Steel||Zinc Plated||Corrosion Resistance|
|Stainless Steel||Passivated is Oxidation Process||Additional Resistance to Corrosion|
Advantages of Woodruff key.
- The Woodruff key is simple and easily adjustable.
- Due to the exact fit of the key, there is no gap between the shaft & key. It reduces stress concentration & improves the reliability of the shaft.
- Mostly used in the tapered shaft where all others key fails.
- It is typically useful in high-speed applications.
- It can tilt and align according to the movement of the shaft.
- Easy to remove.
Disadvantages of Woodruff Key
- Woodruff key is difficult to install because of its groove.
- Due to high depths, there are chances of reduction of strength in the shaft.
- It is not suitable to carry a high load.
- No axial movement between shaft and mating part.
Woodruff key is a flat semi-circular, fitting partly into a circular segment keyway with the remainder fitting into a longitudinal slot keyway in the mating part. It is a machined metal piece used to connect a rotating device to a shaft.
The purpose of woodruff keys is to connect a rotating device to a shaft. The semi-circular part gets fixed in the shaft & the flat parallel part is inserted into the hub for an assembly.
It is mainly using to fix the tapered shaft into the hub or gear. It gives a good fixing area for the shaft as its top flat surface gets to engage with the hub/gear to get better fixing.
The woodruff keyway is a semi-circular (Half Moon Shaped) pocket drawn in the shaft where the woodruff key is going to place. It is made by a woodruff keyway cutter.