China OEM Sz65 Rubber Extruder Double Reduction Parallel Twin Screw Barrel High Precision Gear Shaft threaded shaft and captive nut

Product Description

Single Screw Parallel Shaft Reducer for Plastic Extruder (JHM/ ZLYJ/ ZSYJ)

PTT extruder gearboxes have 2 popular series for 2 types screw extruders:
ZLYJ/ZSYJ Series Extruder Gear Units for Single Screw Extruders
SZ Series Extruder Gear Units for Conical Twin Screw Extruders
For parameters of SZ series gearbox and other extruder gearboxes applications, please consult our sales representatives and engineers.
1. Housing: Cast Iron or Steel Plate Welding
2. Gear Set: Hardened Helical Gear Pairs, Carburizing, Quenching, Grinding, Gear Hardness HRC54-62
3. Input Configurations:
Keyed Solid Shaft Input
4. Output Configurations:
Hollow Shaft Output
1. High strength alloy steel gears and shafts, sturdy and wearable
2. Hollow output shaft integrated with strong thrust bearings to withstand axial force of the screw
3. Large load capacity, superior performance for screw extruders applications
4. High efficiency, high reliability, long service life, low noise
5. Optional international brands of bearings and oil seals (ZheJiang CZPT Oil Seals)

Plastic Extruders
Rubber Extruders
Single Screw Extruders (ZLYJ/ZSYJ Series Extruder Gearbox)
Conical Twin Screw Extruders (SZ Series Extruder Gearbox)
Horizontal Mounted
Vertical Mounted
Oil Dip and Splash Lubrication
Forced Lubrication (Additional Oil Pump)
Natural Cooling
Auxiliary Cooling Devices

Company Introduction

Get the right gearbox for your equipment.

PTT knows gearbox. As the leading industry gearbox manufacturer, PSS offers the best power transmission solutions to perfectly meet your specific industry application. On gearbox, CZPT has a lot more to share.

We always satisfy all industries with our gearbox

PTT strives for 100% satisfaction from customers of all industries. We welcome challenges to offer tailored design or special solution to satisfy customers’ Special needs on applications. We like to make impossibility become possibility.

Key features

Turbine gearboxes and planetary gearboxes are our advantages. Most companies can only manufacture Helical Bevel gearboxes, and we have a strong design team that has now designed turbine gearboxes up to 70, 000 rpm.


PTT offers a vast diversity of gear reducer, geared motor and gearbox. No doubt you are CZPT to find what you need with PTT.


PTT is a trustworthy manufacturer you can rely on, no matter in terms of quality, delivery, pricing, service, etc. It becomes our name tag during our history of servicing our customers.


PTT is CZPT to manufacture 200, 000 sets of gear reducers yearly and keeps investing on development of new series product.

We have a large list of our satisfied clients

Among the large list of our satisfied clients, there are many trend-setting top brands in various industries.

Mian products

Helical Gear Units

Bevel-Helical Gear Units

ZYJ Series Gear Units

DY Series Gear Units

P Planetary Gear Units

MLX Series Mill Gear Units

High Speed Gear Units

Non-stand Gear Units
Q:Are you trading company or manufacturer?
A: We are manufacturer with over 20 years’ experience.

Q: How long is your delivery time?
A: Generally it is within 10 days if the goods are in stock, for goods produced as per order, it is within 35 days after confirmation of order.

Q: How long should I wait for the feedback after I send the enquiry?
A: Normally within 12 hours.

Q: What information should I give you to confirm the product?
A: Model/Size, Transmission Ratio, Speed, Shaft directions & Order quantity etc.

Q: Hong long is your product warranty?
A: We offer 12 months warranty from departure date of the goods.

Q: What is your payment terms? T/T 100% in advance for amount less than USD10000.-, 30% T/T in advance , balance before shipment for amount above USD10000.

If you have any other questions, please feel free to contact us below:

Send your Inquiry Details in the Below, click “Send” Now!

Shipping Cost:

Estimated freight per unit.

To be negotiated
Application: Motor, Machinery, Agricultural Machinery, Plastic and Rubber Extrusion
Function: Change Drive Torque, Speed Changing, Speed Reduction
Layout: Helical


Customized Request


Screw Sizes and Their Uses

Screws have different sizes and features. This article will discuss screw sizes and their uses. There are two main types: right-handed and left-handed screw shafts. Each screw features a point that drills into the object. Flat tipped screws, on the other hand, need a pre-drilled hole. These screw sizes are determined by the major and minor diameters. To determine which size of screw you need, measure the diameter of the hole and the screw bolt’s thread depth.

The major diameter of a screw shaft

The major diameter of a screw shaft is the distance from the outer edge of the thread on one side to the tip of the other. The minor diameter is the inner smooth part of the screw shaft. The major diameter of a screw is typically between two and sixteen inches. A screw with a pointy tip has a smaller major diameter than one without. In addition, a screw with a larger major diameter will have a wider head and drive.
The thread of a screw is usually characterized by its pitch and angle of engagement. The pitch is the angle formed by the helix of a thread, while the crest forms the surface of the thread corresponding to the major diameter of the screw. The pitch angle is the angle between the gear axis and the pitch surface. Screws without self-locking threads have multiple starts, or helical threads.
The pitch is a crucial component of a screw’s threading system. Pitch is the distance from a given thread point to the corresponding point of the next thread on the same shaft. The pitch line is one element of pitch diameter. The pitch line, or lead, is a crucial dimension for the thread of a screw, as it controls the amount of thread that will advance during a single turn.

The pitch diameter of a screw shaft

When choosing the appropriate screw, it is important to know its pitch diameter and pitch line. The pitch line designates the distance between adjacent thread sides. The pitch diameter is also known as the mean area of the screw shaft. Both of these dimensions are important when choosing the correct screw. A screw with a pitch of 1/8 will have a mechanical advantage of 6.3. For more information, consult an application engineer at Roton.
The pitch diameter of a screw shaft is measured as the distance between the crest and the root of the thread. Threads that are too long or too short will not fit together in an assembly. To measure pitch, use a measuring tool with a metric scale. If the pitch is too small, it will cause the screw to loosen or get stuck. Increasing the pitch will prevent this problem. As a result, screw diameter is critical.
The pitch diameter of a screw shaft is measured from the crest of one thread to the corresponding point on the next thread. Measurement is made from one thread to another, which is then measured using the pitch. Alternatively, the pitch diameter can be approximated by averaging the major and minor diameters. In most cases, the pitch diameter of a screw shaft is equal to the difference between the two.

The thread depth of a screw shaft

Often referred to as the major diameter, the thread depth is the outermost diameter of the screw. To measure the thread depth of a screw, use a steel rule, micrometer, or caliper. In general, the first number in the thread designation indicates the major diameter of the thread. If a section of the screw is worn, the thread depth will be smaller, and vice versa. Therefore, it is good practice to measure the section of the screw that receives the least amount of use.
In screw manufacturing, the thread depth is measured from the crest of the screw to the root. The pitch diameter is halfway between the major and minor diameters. The lead diameter represents the amount of linear distance traveled in one revolution. As the lead increases, the load capacity decreases. This measurement is primarily used in the construction of screws. However, it should not be used for precision machines. The thread depth of a screw shaft is essential for achieving accurate screw installation.
To measure the thread depth of a screw shaft, the manufacturer must first determine how much material the thread is exposed to. If the thread is exposed to side loads, it can cause the nut to wedge. Because the nut will be side loaded, its thread flanks will contact the nut. The less clearance between the nut and the screw, the lower the clearance between the nut and the screw. However, if the thread is centralized, there is no risk of the nut wedgeing.

The lead of a screw shaft

Pitch and lead are two measurements of a screw’s linear distance per turn. They’re often used interchangeably, but their definitions are not the same. The difference between them lies in the axial distance between adjacent threads. For single-start screws, the pitch is equal to the lead, while the lead of a multi-start screw is greater than the pitch. This difference is often referred to as backlash.
There are two ways to calculate the pitch and lead of a screw. For single-start screws, the lead and pitch are equal. Multiple-start screws, on the other hand, have multiple starts. The pitch of a multiple-start screw is the same as its lead, but with two or more threads running the length of the screw shaft. A square-thread screw is a better choice in applications requiring high load-bearing capacity and minimal friction losses.
The PV curve defines the safe operating limits of lead screw assemblies. It describes the inverse relationship between contact surface pressure and sliding velocity. As the load increases, the lead screw assembly must slow down in order to prevent irreversible damage from frictional heat. Furthermore, a lead screw assembly with a polymer nut must reduce rpm as the load increases. The more speed, the lower the load capacity. But, the PV factor must be below the maximum allowed value of the material used to make the screw shaft.

The thread angle of a screw shaft

The angle between the axes of a thread and the helix of a thread is called the thread angle. A unified thread has a 60-degree angle in all directions. Screws can have either a tapped hole or a captive screw. The screw pitch is measured in millimeters (mm) and is usually equal to the screw major diameter. In most cases, the thread angle will be equal to 60-degrees.
Screws with different angles have various degrees of thread. Originally, this was a problem because of the inconsistency in the threading. However, Sellers’s thread was easier to manufacture and was soon adopted as a standard throughout the United States. The United States government began to adopt this thread standard in the mid-1800s, and several influential corporations in the railroad industry endorsed it. The resulting standard is called the United States Standard thread, and it became part of the ASA’s Vol. 1 publication.
There are two types of screw threads: coarse and fine. The latter is easier to tighten and achieves tension at lower torques. On the other hand, the coarse thread is deeper than the fine one, making it easier to apply torque to the screw. The thread angle of a screw shaft will vary from bolt to bolt, but they will both fit in the same screw. This makes it easier to select the correct screw.

The tapped hole (or nut) into which the screw fits

A screw can be re-threaded without having to replace it altogether. The process is different than that of a standard bolt, because it requires threading and tapping. The size of a screw is typically specified by its major and minor diameters, which is the inside distance between threads. The thread pitch, which is the distance between each thread, is also specified. Thread pitch is often expressed in threads per inch.
Screws and bolts have different thread pitches. A coarse thread has fewer threads per inch and a longer distance between threads. It is therefore larger in diameter and longer than the material it is screwed into. A coarse thread is often designated with an “A” or “B” letter. The latter is generally used in smaller-scale metalworking applications. The class of threading is called a “threaded hole” and is designated by a letter.
A tapped hole is often a complication. There is a wide range of variations between the sizes of threaded holes and nut threads, so the tapped hole is a critical dimension in many applications. However, even if you choose a threaded screw that meets the requisite tolerance, there may be a mismatch in the thread pitch. This can prevent the screw from freely rotating.

China OEM Sz65 Rubber Extruder Double Reduction Parallel Twin Screw Barrel High Precision Gear Shaft   threaded shaft and captive nutChina OEM Sz65 Rubber Extruder Double Reduction Parallel Twin Screw Barrel High Precision Gear Shaft   threaded shaft and captive nut
editor by CX 2023-09-06