What is the tolerance range of precision screws?
What is the tolerance range of precision screws?
The lifting ring screws are generally not surface treated, but according to the requirements, surface treatment such as galvanized passivation and chrome plating can be carried out, and it is specified in GB5267-85. The chemical composition and mechanical properties of the material should be treated immediately after electro-galvanizing. The test methods are specified in GB699. During routine inspection, the grain size test may not be advanced, and the grain size test method shall be in accordance with the provisions of YB27. Thread inspection is performed with thread gauges and smooth limit gauges or universal energy tools.
Screw model Drive Code: groove on the head, characteristic model Length Code: screw length (mm) A-1: Thread Code: screw model Metric screws directly indicate the screw model with the outer diameter of the screw, such as M3, the outer diameter of the screw is 3.00mm. ; M4 means the outer diameter of the screw is 4.00mm. Metric Thread Size x Pitch: Note: The metric screw is behind the screw model, and sometimes the screw pitch is indicated. Such as M3x0.5, M4x0.70, M5x0.8, M6x1. Standard specification, usually not mentioned. A-2: Length Code: Screw length: For metric screws, the screw length is directly marked in mm. The total length of the screw is marked, only the length below the head is calculated, excluding the head height. But With the exception of flat head screws, the total length of the screw is marked with the head height. A-3: Drive Code/ Head Groove, Features.
(1) Galvanized (blue-white, multicolored, black) 1. Pretreatment: thermal degreasing tank (5 tanks) - electrolytic degreasing tank (3 tanks) - rust removal tank (4 tanks) 2. Electroplating: electroplating tank (20 tank) (ammonium chloride, zinc oxide, gloss, softener solution). 3. Post-treatment: Melting tank (1 tank) - Green medicine tank (1 tank) - (blue-white/multicolored/black) (2), blackening: 1. Pre-treatment: thermal degreasing tank (4 tanks) - rust removal Tank (4 tanks) 2. Blackening: blackening (5 tanks) (flake alkali, sodium nitrite solution) 3. Post-treatment: anti-rust oil (1 tank) (3), phosphating: 1. Pre-treatment: heat Degreasing tank (1 tank) - Derusting tank (1 tank) - Electrolytic degreasing tank (1 tank), - Surface treatment (1 tank) 2. Phosphating: Phosphating (forming a film) 3. Post-treatment: dipping in anti-rust oil (2 tanks) (4) Hot dip galvanizing: 1. Pretreatment: degreasing tank (1 tank) - rust removal tank (1 tank) - FLUX tank (1 tank) - drying 2. Hot dip galvanizing: hot Zinc immersion tank 3. Post-processing: centrifugal treatment - ammonia chloride cooling - water cooling
The lifting ring screws are generally not surface treated, but according to the requirements, surface treatment such as galvanized passivation and chrome plating can be carried out, and it is specified in GB5267-85. The chemical composition and mechanical properties of the material should be treated immediately after electro-galvanizing. The test methods are specified in GB699. During routine inspection, the grain size test may not be advanced, and the grain size test method shall be in accordance with the provisions of YB27. Thread inspection is performed with thread gauges and smooth limit gauges or universal energy tools.
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