There are many ways to detect screws. The detection of screws requires some detection equipment. For example, ductility testing machine, torsion strength testing machine, penetration testing machine, screw-in torque test, hydrogen embrittlement testing machine, tapping speed testing machine, self-tapping screw test steel plate selection list, etc. With these testing equipment, the corresponding data of screws can be detected more scientifically.
Tools/Materials
Screws, screws, screws.
Steps/Methods
Ductility Test
1.1 Scope of application: all types of self-tapping screws
1.2 Test purpose: Check the product’s Will there be a risk of brittle fracture of the head when the assembly is rotated or tightened or is subject to impact stress during the above process?
1.3 Test device: A. Ductility test seat. B. Small hammer.
1.4 Recommended minimum test quantity: 8 pieces per batch, and each batch does not exceed 250M PCS.
1.5 Test procedure: A. Place the screws into the appropriate holes in the test seat.B. Hit the top of the head with a hammer to make the bearing surface of the test piece conform to the seat surface of the test seat. C. Inspection.
1.6 Defective: If the head and screw handle are completely separated, it is a defective test.
1.7 Product defects: A. The hardness of the core is too high. B. The carburized layer is too deep. C. The punching hole is too deep.
D. The inner diameter under the head is too small.
Torque strength test
2.1 Scope of application: all types of self-tapping screws
2.2 Test purpose: Check that the product rotates or breaks during assembly due to insufficient torque.
2.3 Test device: A. Screw clamp. B. Clamp holder. C. Screw measurement fixed base. D. Torque wrench with accuracy within 2.
2.4 Recommended minimum test amount: There are 4 pieces per batch, and the batch size of each batch shall not exceed 250M PCS.
2.5 Test procedure: A. Place the screws into the test fixture and then place the fixture into the fixture support base. The screws should have at least two teeth in the fixture. , the two teeth are outside the clamp. B. Fix the support base on the measuring fixed base. C. Twist the wrench until the screw is broken. D. Record the damage value.
2.6 Bad: The screw breakage value is less than Specified value.
2.7 Product defects: A. The core hardness is too low. B. The surface hardness is too low. C. The effective carburized layer is insufficient. D. The minimum diameter (tooth diameter) is too small.
Tapping test
3.1 Scope of application: All types of self-tapping screws except Type 25
3.2 Test purpose: Check whether the product will be damaged due to threading during assembly Collapse leading to assembly failure.
3.3 Test device: A. Test steel plate. B. Torsion tool (electric tools can be used, but cannot exceed 500rpm).
3.4 It is recommended that at least Test volume: 4 pieces per batch, each batch does not exceed 250M PCS.
3.5 Test procedure: A. Lock the screws into the test steel plate until the first complete thread passes through the steel plate. Plain screws can be slightly added Oil.B. Check whether the thread is broken.
Note: This test can be implemented together with the screw-in torque test and the hydrogen embrittlement test.
3.6 Defect: The thread after the screw is screwed in Collapse.
3.7 Product defects: A. Insufficient effective carburizing layer. B. Carburizing hardness is too low. C. Test steel plate is too hard. D. Test hole is too small.
Screw-in torque test
4.1 Scope of application: Thread-rolled (triangular thread) self-tapping screws
4.2 Test purpose: Check whether the product is damaged due to excessive screw-in torque during assembly Leading to difficulty in combination.
4.3 Testing device: A. Test steel plate. B. Torque wrench with accuracy within 2.
4.4 Recommended minimum test quantity: 4 pieces per batch, each The batch size does not exceed 250M PCS.
4.5 Test procedure: A. Screw the screw into the test steel plate with a torque wrench until the first complete thread passes through the steel plate. Plain screws can be lightly oiled. B. Record the highest Torque value.
Note: This test can be implemented together with the screw-in test and the hydrogen embrittlement test.
4.6 Defect: The maximum screw screw-in torque is greater than the specified value.
4.7 Product defective factors: A. The thread is not properly formed when rolling. B. The carburizing hardness is too low. C. The carburizing depth is insufficient. D. The test steel plate is too hard. E. The test hole is too small. F. Product Requires oiling or waxing.
>Hydrogen embrittlement test
5.1 Scope of application: All electroplated self-tapping screws
5.2 Test purpose: Early detection to prevent electroplated self-tapping screws from being damaged 24 hours after locking due to hydrogen embrittlement Breakage per hour.
5.3 Test device: A. Test steel plate. B. Torque wrench with accuracy within 2. C. Flat washer.
5.4 Recommended minimum test amount: per Batch of 8 pieces, each batch shall not exceed 250M PCS.
5.5 Test procedure: A. Based on the average torsion strength, multiply it by 80 to determine the locking torque. B. Set the flat washers Insert the screw and then screw the screw into the test steel plate, tighten it to the locking torque, and leave it for 24 hours. C. Loosen the screw and then tighten it to the locking torque.
5.6 Defect: From the test From the beginning to the end of the test, no screws should be broken.
5.7 Product defects: A. Not dried after electroplating. B. The screws are locked with too high a locking torque. C. Not inserted into the screws The clamping torque is too high. D. The hole depth is too deep.
Tapping speed test
6.1 Scope of application: only for self-drilling screws
6.2 Test purpose: to find that the tapping speed of self-drilling screws is too slow or the tapping problem is caused by production problems.
6.3 Testing device: A. Tapping speed testing machine. B. Test steel plate, thickness 0.060”-0.064” , hardness HRB 60-85.
6.4 Recommended minimum test quantity:
a. 6 pieces below 5,000.
b. 5,001- 15,000 pcs, 12 pcs.
c. 15,001-50,000 pcs, 18 pcs.
d. 50,001-250,000 pcs, 25 pcs.
Note: Each batch shall not exceed 250,000 units.
e. If one unit exceeds the minimum attack speed requirement according to the above sampling test, double inspection may be implemented according to the following sampling plan.
Number of samples Slow attack speed 1 Too slow attack speed 2
12 1 0
24 1 0
36 2 1
50 3 1
Note 1: "Slow tapping speed" refers specifically to the sample exceeding the maximum tapping time but not more than twice.
2: "Slow tapping speed" "Specifically refers to the sample exceeding twice the maximum tapping time.
6.5 Test procedure: A. Load the test piece into the testing machine. B. Adjust the testing machine so that the test piece penetrates the steel plate and exceeds a complete tooth. When, the testing machine can stop and record the penetration time. C. Record the test time.
6.6 Defect: When tested according to the above sampling table, the test time exceeds the specified value.
6.7 Product Unfavorable factors: a. Burrs at the drill end of the sample e. The test steel plate is too thick
b. The carburizing hardness is too low f. The axial load is too tight
c. The carburizing depth is insufficientg .The tapping speed is too slow
d. The test steel plate is too hard h. The surface coating is too thick
Self-tapping screw test steel plate selection table
7.1 Type A
p>Dimensional ductility test
Minimum angle and minimum torque strength
lb-in. Test steel plate (HRB 70-85)
Thickness? 0.002 Aperture?0.001