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Machine Screws Uncovered




Machine Screws are essential fasteners used in many industries including automotive, aerospace and marine. Also known as metric screws, they are used to attach many important pieces of engines, foils, extremities, etc. So, making sure you order the right fastener is important! Simply follow this step-by-step guide to make sure you are getting what you want.




Machine Screw Diameters

Screw SizeDecimalNearest Fraction
2.093/32
4.117/64
6.149/64
8.165/32
10.193/16
12.217/32
1/4.251/4
5/16.315/16
3/8.383/8
1/2.501/2



1. Sizing- Sizing machine screws correctly is a difficult procedure that needs to be done with some accuracy. To get the diameter, use calipers or fastener guide. Measure from the outside of the thread and use our chart below (for standard sizes). Metric fasteners correspond with the appropriate millimeter measurement.

Along with screw length, you'll need to determine thread count and length. Thread count is determined by the number of threads per inch (or #of threads/ 1/4 inch * 4). Length is measured depending on the head style. Flat head and oval heads (and anything else countersunk) is measured from the top of the machine screw. All other styles are measure from beneath the head.


2. Head Style- Choosing the appropriate head style is made easy through our Fastener Head Style Decoder. This simple guide will allow for easy pictoral references and descriptions of the styles of heads.


3. Driver Style-Use our Fastener Driver Head Decoder.


4. Metal- We specialize in 4 types of metal finishes in our fasteners: Stainless Steel, Silicon Bronze, Brass and Galvanized. To determine the appropriate metal for your machine screws, please use the two decoders: Fastener Metals and Compatible Metals.





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