DIY Nut and Bolt Sizer




Introduction: DIY Nut and Bolt Sizer

Ever wish that you could have one of those nifty nut and bolt thread check/sizer gauges they have at Home Depot, Ace, etc? Well with a little time, you can have your very own in your home shop. There are commercial options available, but this one cost me a whole 15 bucks in materials. So follow along and I'll show you how to make your own. As usual, the second image was my inspiration for this project.

Materials Used:
1/4" Plexi Glass sheet (had on hand from another project)
Dymo Label Maker
Super Glue
Nuts and bolts in the following sizes (bolts as short as you can get for the size it comes in)

Step 1: The Layout

The first thing I did was cut my plexi down to size. I've had mixed results doing this in the past but this time I managed to get a nice clean break. I could have used wood for the base or metal, but I had the plexi on hand so I used it.

Once I had it cut down to size my next issue was how to mark my layout without marking the plexi itself. The benefit of using the plexi came in nicely here. I just took a piece of paper and laid out a 1" x1" grid pattern on the paper and set it under the plexi on my workbench.

Step 2: Prepping the Hardware

The issue with glueing the bolts directly to the surface of the plexi is that most bolts are not flat on the heads. They come with grade or manufacturers marks cast into the heads. Obviously to ensure a secure bond, these needed to be eliminated. I just used a hand file and filed the heads down nice and flat. This has the added benefit of scuffing the surface to ensure a good strong bond, so I filed the nuts a little bit as well.

Step 3: Putting It Together

Next I laid the hardware out on my grid on the plexi. I had to make a few adjustments here for the larger nut and bolts. Luckily I did a dry lay out the first time before I glued them down to make sure I was going to be happy with the placement. Once I was, I picked each nut and bolt up and glued them in place one at a time.

For the smallest nuts, I found it worked well to use the bolt to help hold it in place as I was setting it. Just be careful not to glue the nut and bolt together by accident.

A Note here on the Super Glue, I choose to use it since I had some on hand. I did a strength test by gluing a half inch bolt to a scrap piece first. I was not able to easily break it off so I am fairly confident it will hold up just fine. Long term, well time will tell. If it ever does give I will re-set with a good 2 part epoxy.

Step 4: Labeling

Can I just say how much I love my Dymo Label maker?

Pretty simple at this point, I used white plastic coated labels in the machine. Made a label for each size as well as the labels showing SAE and Metric. Then just Peeled em and Stuck em. Simple, Clean and effective.



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    26 Discussions

    I have my nuts and bolts and screws etc. all sorted into separate labeled containers. So I grab a possible match out of one and test the unknown hardware against it, if I can't tell by just looking. I usually check though if I am tapping work or something, just you know, to make sure.

    1 reply

    That is the best way IMHO, since your accumulation of screws/nuts/bolts keeps getting added to as you go. The pull out thread gauges that allow you to count threads are a tool worth getting since it is so small you can tuck it away and pull it out when needed. Most tap and die sets come with these included. The problem with the setup here is that you could cross thread a part by putting the wrong size on, but the biggest weakness would be all the variations out there would make this board 6 feet tall. If you use an organizer for small parts it makes it much more compact and useful.

    Now, if we could only convince this country to "give in" to the inevitable and switch to metric, half the problem would be eliminated. Nice idea.

    2 replies

    On the surface, that seems like a nice idea. However, you'd lose half the choices you could make if you switched. Sometimes metric is cheaper, sometimes SAE is cheaper. If you are MAKING something however, the thread standard doesn't matter, because you can use what you have on hand.

    Nice instructable. I'll put this to use as I'm getting my work bench organized.

    When I use do work with this stuff daily, unless a metric fastener was thrown in the lot, I never need a tool to determine the size other than my eyes. 18 years out of the loop I can't trust my eyes to be correct anymore. Your version of the tool is as good as any others out there

    Add in METRIC size M3, often used in electronic apliances

    Great Idea for a project ! One thing that would have made the project easier to make is not using glue for the hardware. My solution would have been to drill the plexi and use a long enough bolt to be able to have at least 2 nuts on it. Install the bolt thru the drilled hole and secure with the first nut. Loosely put the other nut on. When checking another bolt remove the loosely installed nut; when checking a nut, thread on the stud.

    Just a thought - it'd be hard to use this on something like an engine. Why not leave a nut on the bolt and a bolt in the nut, so you can take it away to try?

    Label the loose one well to save issues.

    These will also do the same job :-]

    Note also that certain combinations of metric/imperial threads will screw onto each other (they may be a little tight or a little lose depending on the combination) so while the gauge shown here is a good quick and dirty check it's no substitute for proper measurement. BTW interestingly while Australian Propane regulator will screw onto UK propane cylinders, UK regulators won't screw onto Australian cylinders, this is because although the pitch and diameter are near enough the same the profile of the thread is different.


    If using clear plexiglass an alternative to using a label printer might be to just print all of the labeling on a single sheet of paper, and place it behind the plexi. (How to attach this to the plexi is left as an exercise for the reader -- there are numerous possibilities.) It should be pretty easy to make a nice label sheet in anything that supports text and a grid (vector drawing programs, word processors with table support and even spreadsheets are all possibilites here.)

    If going this route it'd probably be best to mount the label sheet before mounting the hardware, and use the label sheet as your layout guide.

    One disadvantage to this approach is that having the labels behing the plexi means there'll be parallax, but that shouldn't be a big issue as long as you don't place things too close together.

    Don't forget there are different thread pitches for metric sized bolts, and possibly the SAE ones too (I didn't look super close).. For example M12x1.25, M12x1.5, I think I have seen M12x1.75 around... so JUST an m12 peg is not necessarily going to allow you to get the right bolts or nuts!

    I don't remember exactly which ones are generally standard, I know some thread pitches are more common on Asian cars and others are more common on US cars now that they use metric, etc, but I couldn't give you a list offhand. But for most usefulness in the application it's something to definitely look into!!


    I'm going to do the same except add course and fine thread samples. I often have trouble figuring out whether a particular bolt or nut is "inch" but with different threads or metric. And vise-versa.

    1 reply

    I had planned to do that initially, but Ace didn't have much for fine thread in SAE. I still have plenty of plexiglas left so I may make another one for fine thread hardware

    one quick way to see if a bolt or screw is metric is to measure the length metric is in millimeters standard is decimals

    Good Job! You may have saved my partner from trouble. Every time he sees one of these used at Orchard Supply Hardware, he threatens to reach over and take it home. :-)

    I made a similar one in the past, but kept the nuts screwed onto the bolts and removable. It meant you could possibly lose them but you could also remove them and take them to the car/whatever you were working on and check the nut on the bolt.

    Must find it again!

    Thanks for the Kudos guys. This is only my second instructable so far. Obviously I like to make useful items. While this isn't really a need to have item it sure is a nice to have item. I can't tell you how many times I have needed to figure out the size of a bolt and forgotten to take it with me to the hardware store! Not anymore!