Views: 69 Author: Site Editor Publish Time: 2022-11-17 Origin: Site
A screw is a tool used to tighten the parts step by step by using the physical and mathematical principles of the circular rotation of the inclined plane and the friction force. Screw is the general term for fasteners, everyday colloquialism. Screws are an indispensable industrial necessity in daily life. Screws have an important job in industry, and as long as there is industry on Earth, the function of screws will always be important. Screw is a common invention in people's production and life for thousands of years. According to the application field, it is the first invention of human beings. Therefore, the screw inspection is particularly important. Then how to check the screw? This article will give you a detailed introduction to the screw inspection standards and methods, I hope you have learned something successful.
I. General inspection items of screws
1. Packaging protection
The outer packing box should not be damaged, deformed or damp
The outer packing box shall be labeled with supplier name, production date, OK label, inspector, specification and model, material code, product color, quantity, etc. The incoming material name shall be consistent with the system material name
The required protective packing materials shall be used
2. Appearance inspection
2.1 Product color
Check the surface treatment (zinc plating, cadmium plating, chromium plating, nickel plating, colorful plating, paint, etc.) of screws and washers with samples according to the admission letter
2.2 Material Confirmation
Check the self-contained silk and gasket material (brass, iron, plastic, etc.) is in accordance with the acceptance of the requirements.
2.3 Product Appearance
Check the appearance of the product should not have the following problems:
(1) The screws and washers shall not have defects, burring, deformation, damage, poor processing or poor forming and other abnormal phenomena.
(2) The electrical coating on the surface of the screw and washer should be uniform, and there should be no oxidation, rust, poor electroplating, paint falling off and other abnormal phenomena.
(3) Screws and washers should not be mixed (mixed with other different screws or washers), short, lack of accessories (gaskets, washers... .). And other abnormal phenomena
a. When the above defects occur and affect the function of the product.
b. The above defects do not affect the function of the product.
3. Size inspection
Use calipers or thread gauges to check the key dimensions listed in the controlled drawings. The measured dimensions should be within the tolerance range. If the key control size is not given in the drawing, the project will not be carried out (only the size of the outside diameter will be logged in when logging in the information).
4. Actual assembly
Assemble the screws and nuts with electric batch, so that they cannot be installed or screwed tightly
After trial assembly with the nut (according to the specified torque), pay attention to check whether the screw is in place, and the slot should not slip
Feed attachment confirmation
Confirm whether the supplier has attached the "Ex-factory Inspection Test Report" or material Certificate as required in the acknowledgement when the material is imported.
2. Special inspection items of screws
1. Ductility test
1.1 Scope of application: All kinds of self-tapping screws
1.2 Test purpose: To check whether the head of the product will be brittle when the product is rotated or tightened during assembly or subjected to impact stress in the above process.
1.3 Test device: A. Ductility test seat. B. The little hammer.
1.4 Recommended minimum test quantity: 8 PCS per batch, and no more than 250M PCS per batch.
1.5 Test procedure: A. Insert the screw into the appropriate hole in the test seat. B. Hit the top of the head with a hammer to make the bearing surface of the measuring part conform to the seat surface of the measuring base. C. Check.
1.6 Bad: if the head is completely separated from the screw handle, the test is bad.
1.7 Adverse factors of the product: A. High hardness of the heart. B. The carburizing layer is too deep. C. The punching is too deep D. The inner circle diameter under the head is too small.
2. Torsion strength test
2.1 Scope of Application: All kinds of self-tapping screws
2.2 Test purpose: To check whether the product is broken during assembly rotation or tightening due to insufficient torque.
2.3 Test device: A. Screw fixture. B. Clamp holder. C. Screw determination fixing seat. D. Torque wrench with accuracy within 2%.
2.4 Recommended minimum test quantity: 4 PCS per batch, no more than 250M PCS per batch.
2.5 Test procedure: A. Place the screw into the test fixture and then place the fixture into the fixture support seat. At least two teeth of the screw should be in the fixture and two teeth should be outside the fixture. B. Fix the support seat on the measuring fixing seat. C. Twist the wrench until the screw is broken. D. Record the damage value.
2.6 Bad: The screw break value is less than the specified value.
2.7 Adverse factors of the product: A. The hardness of the heart is too low. B. The surface hardness is too low. C. Insufficient effective carburizing layer. D. The path (dental base diameter) is too small.
3. Enter the test
3.1 Scope of application: All kinds of self-tapping screws except Type 25
3.2 Test purpose: To check whether the product will lead to assembly failure due to screw breakage during assembly.
3.3 Test device: A. Test steel plate. B. Torsion tool (Power tool can be used, but not exceed 500rpm).
3.4 Recommended minimum test quantity: 4 PCS per batch, no more than 250M PCS per batch.
3.5 Test procedure: A. Lock the screw into the test plate until the first complete thread passes through the plate. Plain screws can be lightly oiled. B. Check whether the thread is broken.
Note: This test can be performed together with the torque test and the hydrogen embrittlement test.
3.6 Bad: screw screw screw screw breakage.
3.7 Adverse factors of products: A. Insufficient effective carburizing layer. B. The hardness of carburizing is too low. C. The test steel plate is too hard. D. The test hole is too small.
4. Rotary torque test
4.1 Scope of application: threaded rolling (triangular teeth) self-tapping screws
4.2 Test purpose: To check whether the product is difficult to assemble due to the high rotary force during assembly.
4.3 Test device: A. Test steel plate. B. Torque wrench with accuracy within 2%.
4.4 Recommended minimum test quantity: 4 PCS per batch, no more than 250M PCS per batch.
4.5 Test procedure: A. Screw the screw into the test plate with a torque wrench until the first complete thread passes through the plate. Plain screws can be lightly oiled. B. Record the high torque value.
Note: This test can be performed together with the screw test and hydrogen embrittlement test.
4.6 Bad: the high torque of the screw is greater than the specified value.
4.7 Product defects: A. Thread rolling is not properly formed. B. The hardness of carburizing is too low. C. Insufficient carburization depth. D. Test steel plate is too hard. E. The test hole is too small. F. The product should be oiled or waxed.
5. Hydrogen embrittlement test
5.1 Application: All electroplated self-tapping screws
5.2 Test purpose: Early detection to prevent electroplating self-tapping screws from collapsing 24 hours after locking due to hydrogen embrittlement.
5.3 Test device: A. Test steel plate. B. Torque wrench with accuracy within 2%. C. Plantarus Division.
5.4 Recommended minimum test quantity: 8 PCS per batch, and no more than 250M PCS per batch.
5.5 Test procedure: A. Take the average torque strength as the benchmark and multiply it by 80% to represent the locking torque. B. Insert the flat washer into the screw, screw the screw into the test plate, tighten it to the locking torque, and put it in place for 24 hours. C. Loosen the screw and tighten it to the locking torque.
5.6 Bad: From the beginning of the test to the end of the test, there should be no broken screw.
5.7 Product adverse factors: A. Not dried after electroplating. B. The screw is locked with too high locking torque. C. The clamping torque is too high because it is not inserted into the Washers. D. The hole is too deep.
6. Attack speed test
6.1 Scope of Application: Only for self-drilling screws
6.2 Test purpose: To find the tapping speed of self-drilling screw is too slow or the tapping problems caused by production problems.
6.3 Testing device: A. Attack rate testing machine. B. Test steel plate, thickness 0.060 "-0.064", hardness HRB 60-85.
6.4 Recommended Minimum Test Quantity:
a. 6 units under 5,000 units.
b. 5,001-15,000 PCS 12 PCS.
c. 15,001-50,000 cells 18 cells.
d. 50,001-250,000 sticks 25 sticks.
Note: Each batch shall not exceed 250,000 pieces.
e. If one of the above sample tests exceeds the low attack rate requirement, double inspection may be performed according to the following sampling plan.
Sampling number Slow attack speed 1 is over slow attack speed 2
12, 1, 0
24 1 0
36 2 1
50 3 1
Note 1: "Slow attack rate" refers specifically to the sample exceeding but not exceeding twice the high attack time.
2: "Over-slow attack rate" refers to the sample more than twice the drilling time.
6.5 Test procedure: A. Mount the specimen on the test machine. B. Adjust the tester so that the tester can stop and record the penetration time when the specimen penetrates the steel plate and exceeds one complete tooth. C. Record the test time.
6.6 Bad: When testing according to the above sampling table, the test time exceeds the specified value.
6.7 Product adverse factors: a. sample drill tail hair edge e. Test steel plate is too thick
b. Carburizing hardness is too low f. Axial load is too tight
c. Insufficient carburizing depth g. Slow attack speed
d. The test steel plate is too hard h. The surface cover is too thick