Different kinds of screws and nuts quality inspection:

Hex Cap Nuts 
Hex Serrated Nuts 
Hex Flange Nuts
Hex Coupling Nuts(High Nuts) 
Round Nuts
Square Nuts 
Pipe Nuts 
Wheel Nuts
Wing Nuts 
U Nuts 
T Nuts 
Eye Nuts 
Kep Nuts 
Clinch Nuts 
Weld Nuts 
Heigh Strength Nuts
Structural Nuts 
Stainless Steel Nuts 
Brass Nuts 
Aluminum Nuts 
Alloy Steel Nuts 
Heavy Duty Wheel Hub Nuts 
Acorn Cap Nuts 
All-Metal Prevailing Torque Type Nuts 
Anchor Nuts 
Big Size Nuts 
Closed End Acorn Nuts 
Conical Washer Nuts 
Hex Head Machine Bolts 
Hex Lag Bolts 
Square Head Bolts 
Carriage Bolts 
Eye Bolts 
Hex Socket Cap Screws 
Set Screws 
Stud Bolts 
Screw Studs 
Wheel Bolts
Wing Screws 
Self Tapping Screws 
hread Cutting Screws 
elf Drilling Screws 
Drive Screws 
Machine Screws
Wood Screws 
Furniture Screws 
Chipboard Screws 
Drywall Screws 
Foundation Bolts 
U Bolts 
Hook Bolts 
Toggle Bolts 
Flange Bolts 
Track Bolts 

Some common factors for screws and nuts quality control:

1.Appearance inspection: under the condition of appropriate illumination, open hole distance 30 cm to check by visual inspection;
2.Dimensional inspection: use vernier caliper to measure its structure size; the tolerance should be within 0.02 mm.
3.Surface electroplating: require surface electroplating is good, no oxidation, scratches,and other bad plating phenomenon.
4.Assembly effect: Select standard screw head, use electricity, wind batch screw hole in plastic or play 5 times in a row, on the standard matching nut screw groove no killing, screw not fracture, sliding wire nut: with standard screw sleeve, not smooth silk or screwing in difficulties
5.Oxidation resistance: steep In saline s after 2 hours to dry after 24 hours to see if the screw surface will have oxidation, rust 
6.Product packaging requirements products piled up neat and moisture protection.
screws and nuts quality inspection


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