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Guide to Identify Bolts before Replacement

Supa-Cheap assumes the average customer knows all there is to know about a bolt. However you know what they say about what happens when you ass-u-me. Given how critical the humble bolt can be, especially when it's clamping down tremendous forces, it pays to know how to determine the right stuff for the job before buying large bolts online.

So for the unitiated, we thought it'd be prudent to post an ever-so-brief guide to identify the bolts you want to use/replace with the range you'll find for sale on the Supa-Cheap site. To that end, here we go.

 Bolt Thread

bolt thread pitch

The spiralled groove machined out of the bolt shaft is the thread. The measurement of the thread determines its pitch. Just to keep things simple, the number of threads per inch is the imperial pitch measurement and the distance between the threads is metric. The imperial measurement is a thread-count and the metric measurement is in millimeters.

There are various special thread specifications used for precision instruments and specialist equipment. However the range of bolts at Supa-Cheap include the most common thread specifications.

Size Pitch mm (std) Pitch mm (fine)
M5 0.8  
M6 1.0 0.75
M8 1.25 1.0
M10 1.5 1.0 or 1.25
M12 1.75 1.5
M16 2.0 1.5
M20 2.5 1.5
M24 3.0 2.0
M30 3.5 2.0

Metric Standard and Fine Pitch Threads

The most common thread and pitch count for bolts found at Supa-Cheap can be found in the table:-

Bolt strength grade markings


Bolt Strength Grade

Bolt strength grades indicators appear on all but the lowest grade bolts. Most bolt grade indicators appear on the bolt head, somtimes on the side. The top letters will be the manufacturer initials and the grade number appears on the bottom.

The first number indicates the strength of the steel. The second number indicates load before the bolt starts to stretch. Grades are fairly simple at Supa-Cheap - you just look for High Tensile and Low Tensile.

Just to make identifying bolt grade more challenging, there's the "Clock Face" grade marking. The dot goes to the 12 O'clock position and the dash indicates the grade. Typical grade markings are shown in the diagram.


This guide is not intended to replace expert knowledge. Perhaps get an expert-mate's advice before you select a replacement for that bolt holding up a 2 tonne weight from the rafters.

Checking out our Range of Bolts

We know you dont want to mess about - time is important. So to make it quick and easy to find the bolts you're after, mouse-over/touch "Bolts"  in the top menu to see our range.