What is the tolerance range of precision screws?
What is the tolerance range of precision screws?
Surface treatment process of screws 1. Types of surface treatment: Surface treatment is the process of forming a covering layer on the surface of the workpiece by a certain method. The purpose is to give the surface of the product a beautiful and anti-corrosion effect. The following methods are as follows: 1. Electroplating: Immerse the part to be electroplated in an aqueous solution containing the metal compound to be deposited, and pass the current through the plating solution to precipitate and deposit the electroplated metal on the part. Generally, electroplating includes galvanized, copper, nickel, chromium, copper-nickel alloy, etc., and sometimes blackening (blue), phosphating, etc. are also included. 2. Hot-dip galvanizing: It is done by immersing the carbon steel parts in a zinc-melting bath with a temperature of about 510°C. The result is that the iron-zinc alloy on the surface of the steel gradually becomes passive zinc on the outer surface of the product. Hot dip aluminizing is a similar process. 3. Mechanical plating: The surface of the product is impacted by the particles of the plated metal, and the coating is cold welded to the surface of the product.
1) Scope This standard specifies the lock nut (referred to as nut), the size of the locking device, technical requirements, acceptance rules and measurement methods. This standard applies to the design, production, inspection and user acceptance of nuts and locking devices for tapered bushings. 2) Terminology The terms used in this standard conform to the provisions of GB/T 6930. This standard specifies the marking system, index, test method and marking of the mechanical and working performance of the effective torque section steel hexagonal lock nut. This standard is applicable to coarse thread 6H class nuts made of carbon steel or alloy steel, the width across the sides conforming to the provisions of GB 3104, the nominal height is ≥ 0.8D, and the guaranteed load and effective torque need to be specified, and the thread diameter is 3 ~ 39mm. Except for the effective torque part, the thread size and tolerance are specified in GB 193, GB 196 and GB 197. The working temperature range of the nut should be in accordance with: All-metal nut without electroplating treatment: -50℃～+300℃. All-metal nuts with electroplating treatment: -50℃～+230℃; nuts embedded with non-metallic elements: -50℃～+120℃. This standard does not apply to nuts with special performance requirements (such as weldability and corrosion resistance). For stainless steel and non-ferrous metals with fine pitch lock nuts or thin nuts made of carbon steel or alloy steel, the performance indicators and test methods of effective torque specified in this standard may be adopted by mutual agreement.
Existing bolt and nut connections usually use threads for connection, and this connection method has two main drawbacks. First, tools are required to be used to lock it during installation, and it takes a long time to complete, which is time-consuming and labor-intensive; Second, the installed bolts and nuts are prone to loosening after a period of time, resulting in loosening and shaking between the connecting parts. Therefore, there is a need for a bolt and nut fastener that is easy to install and can effectively prevent the loose fit of the bolt and nut, so as to solve the problems existing in the prior art.
When the nut is tightened on the stud, there will inevitably be an empty upstroke. That is, when the nut has not reached the part that needs to be tightened, the nut needs to be twisted on the non-locking (working) part of the front end of the stud by hand or tool, so that the nut runs along the axial direction of the stud and reaches the part to be locked. . When the idling stroke of the thread at the front end of the stud is long or the thread pitch is small, the idling stroke before locking will waste a lot of time, resulting in a huge occupation of personnel or tools.
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