What Is Fastener Thread? Selection Of Coarse And Fine Tooth Threads
The thread of the fastener plays a vital role in the fastening of parts. For fastener suppliers, many people may have some understanding of various parts of fasteners, such as screws, nuts, bolts, rivets, etc., but how much do you know about the thread? In the use of fastener thread, the choice of fine teeth and coarse teeth is the most difficult decision to make. As a professional fastener manufacturer, Xinchi Fastener Company will share the introduction of thread and the choice of fine teeth and coarse teeth thread according to the understanding of fastener thread over the years.
The definition of fastener threads
A thread is a shape with a uniform helix raised on a solid outer or inner surface.
The role of fastener threads
- Fastening and connecting function: suitable for most screw products at this stage.
- Transmission action (displacement action): such as QC to check the size of the micrometer.
- Sealing effect: such as pipe connection sealing.
The history of fastener threads
Machine tooth thread: During assembly, drill holes and tap teeth on the assembly first. The tapped inner teeth have the same specifications as the outer teeth of the screw and assemble with smaller torque.
Self-tapping thread: Drill holes on the assembly object first when assembling, without tapping the inner teeth, and use large torque for assembly.
Self-drilling thread: directly used on the assembly, screw drilling tapping a molding.
What is fine tooth thread? What is the coarse thread? How to choose coarse tooth and fine tooth thread?
To what extent can a fine thread be called a fine thread? We can try to define it this way, the so-called coarse thread can be defined as a standard thread; The fine tooth thread is relative to the coarse tooth, under the same nominal diameter, and the number of teeth contained in each inch is different, that is, the pitch is different, the coarse tooth pitch is large, while the fine tooth pitch is small. In other words, for the 1/2-13 and 1/2-20 sizes, the former is a coarse tooth and the latter is a fine tooth. So it’s 1/2-13UNC and 1/2-20UNF.
Since there are two different thread specifications for the same nominal diameter, how to choose coarse and fine thread?
Coarse tooth thread
Definition: The so-called rough teeth actually refer to the standard thread, without special instructions, generally purchased stainless steel screws and other fasteners are rough teeth.
The characteristics of coarse tooth thread: coarse tooth thread has higher strength and good interchangeability, and there are standards to compare. Generally, rough teeth should be the best choice. Compared with fine tooth thread, because the pitch and screw angle of coarse tooth thread is large, resulting in poor self-locking, need to install an anti-loose washer, self-locking device, etc. in a vibration environment. The advantages of coarse tooth thread are convenient disassembly and assembly, complete standard parts, and easy interchange.
Note: There is no need to mark the pitch when marking the coarse tooth thread, such as M8, M12-6H, M16-7H, etc., mainly used for connecting thread.
Fine tooth thread
The definition of fine tooth thread: fine tooth and the coarse tooth is the opposite, is to supplement the coarse tooth thread can not meet the special use requirements and provisions. Fine tooth thread also has a pitch series, and the pitch of fine teeth is smaller, so its characteristics are more conducive to self-locking, anti-loose, and the number of teeth, which can reduce the effect of leakage, to achieve the effect of sealing. In some precision occasions, fine-tooth stainless steel screws are more convenient for precise control and adjustment.
The disadvantages of fine tooth thread: compared with coarse tooth thread, the tensile value, and strength of fine tooth thread are relatively low, and the thread is easy to damage, it is not recommended to disassemble and assemble many times. Perhaps the precision of fasteners such as nuts and other fasteners matching fine thread is similar, but if the size is slightly wrong, it is easy to make the screws and nuts damaged at the same time.
The applications of fine tooth thread: fine tooth thread is mainly used in the hydraulic system metric pipe fitting, mechanical transmission parts, thin wall parts of insufficient strength, internal parts limited by space and self-locking requirements of the higher shaft. The pitch of fine tooth thread must be marked to show the difference with coarse tooth thread.
How to choose coarse and fine tooth thread?
Coarse tooth thread and fine tooth thread screws are used for fastening.
Fine tooth screws are generally used to lock thin-walled parts and parts with high vibration prevention requirements. The self-locking performance of fine thread is good, so the ability to resist vibration and loosen is strong, but because of the shallow depth of the thread, the ability to bear greater tension is worse than that of coarse thread.
When no anti-loosening measures are taken, the anti-loosening effect of fine thread is better than that of coarse thread. It is generally used for thin-walled parts and parts with high anti-vibration requirements.
For adjustment, the fine thread has more advantages. The disadvantage of fine tooth thread is that it is not suitable for application on material with too thick tissue and poor strength. When the tightening force is too large, it is easy to slip the wire.
Anji Xinchi Fastening Piece Co., Ltd is a one-stop solution fasteners company and is the designated fastener supplier to“STAPLE”. As a trusted fastener supplier, Xinchi can offer a wide range of high-quality fasteners, including tee nuts, bolts, rivets, washers, etc. If you want to know more about fasteners or want to wholesale fasteners, please do not hesitate to contact us. Our experienced and expert service team will reply to you as soon as possible.