01 / Identify the fastener
Start with the head style, drive and intended connection. Machine screws mate with a nut or a tapped hole. Coach and decking screws are wood-screw families. Socket cap screws have a hexagonal recess; UNF hexagon set screws have an external hexagon head.
02 / Match diameter and thread
A metric M designation describes nominal thread diameter in millimetres. Pitch is the distance between adjacent thread crests. Imperial UNF threads use an inch diameter and threads per inch (TPI). Similar-looking threads can differ; use a thread gauge or a known specification rather than forcing a connection.
03 / Check the length
For pan, hexagon and socket cap heads, length is normally measured from underneath the head to the end. Countersunk screw length is normally measured including the head. Confirm against the particular product drawing, especially for unusual head styles.
04 / Choose material, finish and pack
Material and surface finish are separate characteristics. A colour or plating description alone does not establish corrosion performance. Check the installation requirements and the number of pieces in the selected option.
05 / Check the Amazon option
Each RADSO variation has its own ASIN. The website link takes you to that ASIN on Amazon UK. Check the size, pack contents, seller, price and delivery information again before checkout.
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