Tutorial: How to Measure Metric Hardware

This tutorial will help you understand how to read and measure metric hardware sizes so you can create your own unique hardware kits using our individual hardware selection for your vehicles. 

How to measure bolts

Thread Diameter (M6)

Thread diameter which is the width of the bolts threaded section in millimeters. This is displayed with a capital M before the millimeter measurement. For example, a 6mm diameter would be written as M6 for the thread diameter.  If using a measuring device such as a micrometer, the measurement will rarely be exactly 6mm.  In this case if the measurement was 5.75mm, you would round up to 6mm for the purpose of determining the bolt diameter.

Thread Pitch (1.00)

The thread pitch is the distance between threads measured in millimeters. For example, a 1.00 thread pitch means that the distance between one thread to the next is 1.00mm.

Thread Length (15mm)

To measure length, start from right below the head, including any shank, and measure to the tip. This rule for bolt length is applicable for the motor head, socket head, and button head types. Only measure the entire length if you are working with the countersunk head design.

How to measure nuts and washers

The easiest way to measure a nut or washer is to actually verify the thread diameter and pitch measurements of your bolt or stud that matches with the nut and washer.  

If you need to measure a nut or washer the first measurement you are going to find is the inner diameter of the nut or washer instead of the outer thread diameter that we measured for the bolt. With a nut, you will need to account for the width of the threads on the inside of the nut.  So in our example of an M6 nut, the diameter of the bolt may have been 5.86mm, but the diameter inside the nut will be approximately 1mm smaller than the bolt at around 4.86mm.  This is because the thread width on each side is 0.5mm.  

You will find the opposite is true with the inner diameter of the washer. The diameter of the hole in the washer will be slightly larger than the bolt to account for any variance in the thread width.  In our example above, the washer's inner diameter would be around 6.5mm. 

How to use a bolt gauge

Step 1

Determine your thread diameter by placing the bolt into the holes on the bolt gauge to find the one that fits best. It should be a snug fit with only enough gap for the bolt to be inserted and removed.

Step 2

Next step is to find the bolts thread pitch.  The bolt gauges on our website have a thread pitch gauge on the back side. Find the grooves that allow your bolts threads to seat perfectly in them. While there are always exceptions, the general rule is that the thread pitch will increase as the bolt diameter increases.  So an M5 bolt may have a thread pitch of 0.80mm and a M6 bolt would have a thread pitch of 1.00mm.

Step 3

Lastly measure the length of the bolt below the head. The bolt we used for this example is a M6 x 1.00 x 24mm.

If you do not have a bolt gauge tool you can Click Here to purchase one directly from us.

Other things to consider

It is important to pay attention to the amount of surface area available for your hardware. Knowing the size of your bolt is great, but doesn’t help when you go to screw it in and it turns out the bolt head, nut, or washer is too large for the small amount of space you have available. This is why we have included outer diameter hardware specs on each individual hardware size so you can determine before you purchase if you have enough room for your new titanium piece. If you do have any questions about a hardware size you are considering please email us at sales@dressupbolts.com and our team will answer any questions you have about our hardware sizes. 

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Bolt Gauge

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