The Right Set Screw Size For Pss Shaft Seals

pss shaft seal set screw size

The PSS Shaft Seal Set Screw is a crucial component for securing the stainless steel rotor in various machinery and equipment, such as boats and propellers. When it comes to the size of the set screw, it is important to note that there are different sizes available depending on the specific application. According to PYI, the set screw sizes for their seals are 1/4-20 with a length of 5/16 and 3/8-16 with a length of 3/8. It is recommended to replace the set screws if the PSS Shaft Seal needs to be removed and reinstalled, as they are designed for one-time use. This ensures a secure grip and proper functionality.

PSS Shaft Seal Set Screw Characteristics and Values

Characteristics Values
Set Screw Size 1/4”-20 5/16” long, and 3/8”-16 3/8” tall
Number of Set Screws 4
Reusable No

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Set screw size for PSS shaft seal: 1/4 X 20 with a length of 5/16

The set screw size for a PSS shaft seal is 1/4 X 20 with a length of 5/16". This measurement is for a shaft with a diameter of 1.25". It is important to note that there are two different sizes of set screws for PSS shaft seals: 1/4”-20 with a length of 5/16”, and 3/8”-16 with a height of 3/8”.

The PSS shaft seal set screw is designed to secure the stainless steel rotor to the shaft. It is recommended to use a sharp-pointed set screw for the inner screw and avoid using Loctite on it as it can smear across the shaft and make it difficult to remove the seal collar. The set screws should also not be reused as they are designed for one-time use only. When reinstalling the rotor, it is important to use new set screws or, if not available, reverse the set screws so that an unused cup is compressed onto the shaft.

The PSS shaft seal is a mechanical face seal that utilizes stainless steel and carbon sealing components. It is designed to compensate for variable axial movement due to propeller thrust. The sealing surface is created between the flat surfaces of the rotating stainless-steel rotor and the stationary carbon flange. The carbon flange is attached to a silicone bellows, which is then secured to the vessel's stern tube. The stainless-steel rotor is fitted onto the shaft in front of the carbon flange and secured with set screws, followed by the installation of the shaft retention collar.

The PSS shaft seal is designed for applications that require increased durability and resistance to harsh, corrosive, high-pressure, and demanding environments. It offers unmatched performance and can withstand temperatures ranging from −13°F to 425°F and shaft RPMs up to 10,000. The carbon composite used in the seal has a maximum operating temperature of 500°F and can withstand short periods of dry running without melting.

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Set screws are designed for one-time use

Set screws are designed to be used once. This is especially true for knurled cup point set screws, which are commonly used to secure the stainless steel rotor of the PSS Shaft Seal. The PSS Shaft Seal is a dripless stern seal used in boats and ships.

The set screws that secure the stainless steel rotor of the PSS Shaft Seal are designed to be used once because they are made with a cup at the base that compresses into the shaft, ensuring a secure grip. Reusing the same set screw on the shaft can compromise the security of the grip.

Knurled cup point set screws have a serrated ridge that helps to reduce loosening due to vibration. When tightened, the cutting edges of the knurls are deflected, and during removal, these cutting edges are torn and no longer have the full strength to resist unscrewing. Therefore, it is important to replace the set screws each time the PSS Shaft Seal is removed and re-installed.

PYI, the manufacturer of the PSS Shaft Seal, recommends replacing the set screws with new ones each time the seal is removed and re-installed. This is to ensure the security and integrity of the seal, preventing leaks and other potential issues.

It is worth noting that set screws are not commonly used in general, as they have a specialist function: to secure one component inside another. They are ideal for this function as they lack protruding parts that would interfere with the movement of the two components, making them useful for gears on shafts.

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Two set screws in each of the two holes in the stainless steel rotor

When it comes to the PSS Shaft Seal, there are specific instructions to be followed regarding the set screws in the stainless steel rotor. The rotor features two holes, and each hole contains two set screws, for a total of four set screws. This arrangement is designed to securely fasten the rotor to the shaft.

It is imperative that you never reuse the set screws in the stainless steel rotor. They are specifically designed for one-time use. When removing and reinstalling the rotor, always replace the set screws. This is a critical step to ensure the proper functioning and security of the PSS Shaft Seal.

Each of the two holes in the stainless steel rotor serves a specific purpose. One set screw in the first hole is tightened onto the shaft, providing the initial grip. The second set screw in the same hole is then tightened onto the first, locking it in place and further securing the connection.

The unique design of the set screws enhances the overall stability of the assembly. The base of each set screw features a cupped shape. When the screws are tightened, this cupped base compresses into the shaft, creating a strong and secure grip. This compression fit ensures that the rotor remains firmly attached to the shaft during operation.

To install or adjust the stainless steel rotor of the PSS Shaft Seal, you will need a set screw kit. This kit typically includes six stainless steel cupped point set screws and thread lock. The kit may also include an Allen wrench specifically designed for the task.

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The inner set screw should have a sharp point and no Loctite

When it comes to the PSS shaft seal set screw, it is important to pay attention to the type of screw used and the installation process. The set screw plays a crucial role in securing the stainless steel rotor of the PSS Shaft Seal, ensuring a secure grip on the shaft.

The inner set screw, which is tightened onto the shaft, should have a sharp point. This sharp point is essential for achieving a secure and precise grip. It is designed to compress into the shaft, creating a strong and reliable connection. By having a sharp point, the screw can effectively penetrate and grip the shaft material, maximizing its holding power.

It is important to note that the set screws are designed for one-time use only. Therefore, when removing and re-installing the PSS Shaft Seal, it is crucial to replace the set screws. Reusing the same set screw is not recommended as it may compromise the security and integrity of the connection. Always use a new set screw to ensure optimal performance and safety.

Additionally, the use of Loctite is not advised on the inner set screw. Loctite, a type of thread-locking adhesive, is typically used to secure screws and prevent them from loosening. However, in this case, the sharp point of the inner set screw provides sufficient gripping power, rendering the use of Loctite unnecessary. Applying Loctite could actually hinder the performance of the screw by affecting its ability to penetrate and grip the shaft effectively.

By following these guidelines and paying attention to the details, such as the sharp point and the avoidance of Loctite, you can ensure a secure and proper installation of the PSS shaft seal set screw. This will help maintain the integrity of the connection and contribute to the overall performance and reliability of the PSS Shaft Seal.

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PYI sells set screw kits for PSS shaft seals

The set screw kit includes six stainless steel cupped-point set screws, an allen wrench, and thread lock. The cupped-point set screws are designed to compress into the shaft, ensuring a secure grip. It is important to note that the inner set screw should have a sharp point and be free of any Loctite, as this can smear and lock the shaft tight.

PYI offers two sizes of set screws for their PSS shaft seals: 1/4"-20 5/16" long and 3/8"-16 3/8" tall. The correct size for a 1.25" diameter shaft is 1/4 X 20 with a length of 5/16".

The set screw kit is available for purchase through PYI's website, with same-day shipping options. It is also available from authorised dealers and distributors.

Frequently asked questions

The size of the set screws in the PSS shaft seal rotor is 1/4 X 20. The length of the screw is 5/16" for a 1.25" diameter shaft.

Yes, according to PYI, there are two different size set screws for their seals: 1/4”-20 5/16” long, and 3/8”-16 3/8” tall.

There are a total of 4 set screws for the PSS shaft seal. Each set screw is backed by a second screw to lock it in place.

It is recommended to use a set screw with a sharp point for the inner set screw.

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