Great observation - Super time and error saver !!

Thank you as well. :-)

Thanks guys! I love these positive comments. The gauge is very well made. Most customers are surprised at how sturdy and durable they are. Have a great day!

You probably won't find a bolt that is 9/16 long. That would be considered very uncommon. Maybe someone out there offers it but I recommend getting a bolt 5/8 long and grinding/cutting it down to 9/16". (Remember that length is measured from underneath the head. Do not include the head when determining length unless the bolt has a countersunk flat style head) The written size description depends on what type of bolt or screw you have. You are using the word bolt so I'll assume that it has a machine thread. If it's standard course thread bolt then your bolt size would be written as such: 1/4-20 x 9/16. The 20 is the thread pitch (20 threads per inch). If it's a wood or sheet metal screw then the size description would be written this way: 1/4 x 9/16 or sometimes #14 x 9/16. The thread count is less important for a wood or sheet metal screw. 1/4" bolts will have either a 20 or 28 thread pitch. 20 is coarse and 28 is considered fine thread. This is important if you need to use a nut or screw it into a threaded hole. It's really a lot more simple then it seems. I hope this helps. MarineBoltSupply.com

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10, 8, 6, 5 and 4 are industry standard sizes for screws that are smaller than 1/4”. Your screw is a #6 size. If your screw was 1” long than you would need a #6 x 1”. If you had a #6 machine screw that needed a nut then you would use the thread finder and see that you had a 6-32 x 1” machine screw. Hope this helps. If you have more questions about this please feel free to email me directly. sales@marineboltsupply.com Thanks!

@@cmcindustrialsupply3804 I know I'm coming here a year late. This one answers what those numbers mean. However, it doesn't answer what the actual sizes are, for example if I needed to drill a hole prior to putting a screw a #6 screw what size would that be? I've goggled those sizes, but I only get the metric for 10,8,6,5,4, but my understanding is that these are NOT the equivalent of the metric sizes.

@@fabioqa The gauge has size holes on two sides. One side is for metric sizes and the other is for machine screw sizes and fractional sizes. You need to use the #6 hole on the fractional side. Hope this helps.

@@marineboltsupply3786 Actually I was trying to find the actual sizes of the fractional side... I found the following, in case anyone was looking for similar information: Size closest fraction inch mm #4 7/64 0.11 2.8 #5 1/8 0.12 3.1 #6 9/64 0.13 3.3 #8 5/32 0.16 4.2 #10 3/16 0.19 4.8

The tabs on the sides are for the nuts. You just slide it over the tab that fits. For nuts it will only measure fractional sizes. Thanks for the question.

Great question! That's exactly what this gauge is used for. Choose the hole that fits the bolt or screw perfectly and then you'll know whether it's metric or fractional. No hole on the gauge is exactly the same size. They can be close but your bolt will fit one better than the other. You can also use the thread pitch gauge on the back. If the bolt is metric it will fit the metric pitch option better than the fractional pitch option. The hole along with the thread pitch will leave no doubt to what size you have. Thanks for the question! Marine Bolt Supply

I'm sorry but I don't understand the question. 4:14?

Sure. In the box there are 3 rows titled Inch, UNC & UNF. The "Inch" row lists the different diameter sizes of a screw or bolt. The "UNC" row lists the coarse thread option for each size. The "UNF" row lists the fine thread option for each size. So for example, if you have a 1/4" bolt your two thread options are 20 (coarse thread) or 28 (fine thread). Just helps you identify the screw after you know it's size. The MM box does the same thing for metric sizes. Hope this helps. Thanks! Marineboltsupply.com

Oh, perfect! Thanks

Those are standard machine/sheet metal screw sizes. For sheet metal screws #4, #5, #6, #8, etc. For machine screws 4-40, 6-32, 8-32, etc. These are commonly used sizes and they are not to be confused with metric sizes like 4mm, 6mm, 8mm, etc. Hope this helps. Thanks for the question!

@@marineboltsupply3786 Thank you very much for answering, greetings!

The screw or bolt will only fit one size hole. Whichever one that is will be your size.

The top row in the box titled "INCH" & "MM" are the fractional (INCH) and metric (MM) screw and bolt sizes. Underneath each size are the coarse (UNC) and fine (UNF) options for thread pitch. The thread finder is on the back of the gauge. So for example the bolt size 1/4 has two thread options underneath it: 20 (coarse thread) or 28 (fine thread). The thread finder on the back will show you which one you have. Very important to know whether you have a coarse or fine threaded bolt or machine screw. Hope this helps. Thanks for the question.

It doesn't have the #12 size. #14 is the same as 1/4 so that one is there. If the screw/bolt that you are trying to measure seems to be in between the #10 and 1/4" holes and it fits the 24 thread pitch on the back you will know that it is the 12-24 size. Hope this helps. Thanks for the question.

The gauge has both options. The fractional holes and length marks are on one side and the metric are on the other. The bolt/screw will only fit into one hole correctly. That will tell you if it’s fractional or metric. It makes it easy. Thanks for the question.

Those are for metric screws and bolts (3mm through 20mm)

Hi Joe. The example we showed did include a fractional bolt and not a metric bolt. The video shows that the bolt will fit snug into the correct size hole. If the bolt doesn't fit snug into any of the fractional holes then I would assume the person would try the metric side next where they would discover that the bolt is metric. Some fractional sizes are close to metric sizes but none are exact. Thanks for the question.

The tabs on each side of the gauge are for the nuts. Simply push the nut over the tab and you've got the size. Hope this helps.

It's a nut & bolt gauge. For checking size and thread pitch.

Marine Bolt Supply thank you

5/16" = 7.937mm and 3/8" = 9.525mm 3/8 is closer.

Actually 5/16 is closer to 8 mm than 3/8 it's closer to anything, no?