This little tool—whether you refer to it as a hex key, hex wrench, Allen key, or Allen wrench—can be pretty valuable. Well, it might be if you can locate the appropriate size, and it can be a little frustrating when you are left trying to fit each of them into the hex bolt head to get the proper size.
Trial and error may also be a mistake since you risk damaging the hex screw or bolt and being unable to fasten or loosen it. Let’s avoid it by understanding how to determine the precise size.
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How to Determine the Hex Key Size

There are numerous valuable sizes available for an Allen wrench. The variety of sizes can also be confusing when you are in the middle of a project. You can choose the type of Allen wrench you need for a project using several methods. The screw’s diameter determines the size of the hex wrench. When selecting an Allen wrench, pay close attention to this.
The best ways to determine the size of your hex wrench are as follows.
Stay Organized
Hex key sets often come in packets or containers with each size clearly labeled for you when you purchase them. You may always refer back to those labels if you can put each back after use.
Of course, if you have young children or other people who want to borrow your tools, this is no help. You might want to keep an additional set hidden somewhere only you are aware of. Regardless of how hard you try, your “secret set” never stays a secret for very long.
Examine the Tool Closely
Most hex keys have the size etched on the side, which is incredibly useful. But nothing is perfect. Those numbers can occasionally be challenging to see, particularly if you already have a visual impairment. An additional item to remember to maintain would be a magnifying glass, which you could keep nearby to help.
Furthermore, after being used repeatedly, those numbers start to wear out.
You could always try writing labels on it with a Sharpie or something else. Create a color chart that you can store in your toolbox, for instance, by using nail polish or permanent markers to color-code the sizes.
Use a Size Chart for Hex Keys

Additionally, there are helpful tiny charts that you may find online. The hex key heads on the charts are the correct size, implying that you can measure the size by placing your key directly next to the picture.
To ensure that the chart is always available when you need it, consider printing it out, laminating it, and putting it with your equipment.
Measure Hex Key
You can always determine your size if you know how to measure a hex key. Measurements for hex keys are made across-flats or AF.
Simply put, they are measured from one flat side of the head to the one right across it. So, if you have a digital caliper or a measuring tape, you can actually measure the hex key size.
Also Read: How to unclog a garbage disposal with standing water
How Do I Determine the Size I Need for My Garbage Disposal?
You are most likely covered if you purchased a project-in-a-box, such as furniture from Walmart, Target, or Amazon. The majority of those sets include the proper size hex key. If not, the instructions will likely provide a list of the required materials.
But as we all know, sometimes essential items might be missing from these crates. It’s not entirely hopeless if you don’t have the instructions or the hex key. You have two options:
- Measure the screw hole that the hex key is intended to fit into.
- Use the old-fashioned trial and error method.
There are a few crucial things to perform if you use the trial-and-error approach. Start by using a medium-sized hex key first. You won’t have to try on as many sizes because of this, which will help you determine the one you need.
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Which Way Does an Allen Wrench Go on the Garbage Disposal?

If you have figured out the size of the Allen wrench and your disposal hex hole, you are all set to fix the garbage disposal. Here’s how you do it.
Step 1: Insert the Allen wrench into the hex hole on the underside of the disposal.
Step 2: Crank it back and forth until the food is dislodged.
Step 3: You have successfully fixed the problem when you can effortlessly move and turn the wrench in one direction in a circular motion without encountering any obstructions.
Step 4: If you’ve been rotating the Allen wrench for a long time but haven’t been able to clear the clog completely, don’t be afraid to apply some force while cranking the wrench. The shaft that reaches into the garbage disposal can withstand quite a bit of strain.
SEE: How to Unclog a Garbage Disposal
Allen Wrench Not Rotating Garbage Disposal Blades: How to Fix
Having trouble turning the Allen wrench when repairing the garbage disposal is not unusual. To turn it, all you need is a strong force.
Typically, it turns improperly and feels like it won’t spin right after the Allen wrench is inserted.
This is because it could be difficult to remove the impediment. Even though you would think that trying to force the Allen wrench to spin could damage it, that won’t happen.
The Allen wrench is made to withstand a lot of strain and dislodge even the hardest jams and obstructions. Therefore, if it doesn’t turn, don’t be afraid to use all of your strength to turn it.
Simply ensure that you provide a solid support for the garbage disposal unit while spinning the Allen wrench forcefully.
Also read: What is a garbage disposal
What Can I Use in Place of a Garbage Disposal Wrench?
There are generally three sorts of wrenches that are suitable for garbage disposal. So, you can substitute the product-specific tool for the garbage disposal wrench or use the Allen wrench instead.
The disposer wrench was explicitly created to fix and unclog various types of garbage disposals.
These wrenches differ significantly from the product-specific Allen wrench in structure and usage.
As a result, if there is no product-specific wrench for the model of disposal you are using, you may be unable to use it as a replacement for a garbage disposal wrench.
However, using an Allen wrench with a diameter of 1/4 inch is the ideal choice for replacing the garbage disposal wrench. In most cases, a quarter-inch Allen wrench fits precisely into the hex hole of a garbage disposal, and it is the finest choice for all sorts.
SEE: How to Fix a Garbage Disposal
FAQs
What range of sizes is an Allen key available in?
Hex key sets come in two different sizes: metric and standard. Typical sizes for standard include 1/8 inch, 3/32 inch, 7/64 inch, 5/32 inch, 3/16 inch, and 14 inches. The most popular metric sizes are 2.5 mm, 3 mm, 4 mm, 5 mm, 6 mm, 8 mm, and 10 mm. Various sizes are available for some sets.
Half sizes are also available for certain sets. Additionally, remember that typical hex keys have a short arm, and you may get long-arm hex keys if you want a little more length.
What if the size I require isn’t precisely what I have?
You have a few more options if your hex key set doesn’t contain the size of hex wrench you require. The first is only helpful if you have a screwdriver that can have its head changed or an interchangeable screwdriver. Sometimes the head tips come with hex keys, so you might find what you’re looking for.
What if the size I require isn’t exactly what I have?
You have a few more options if your hex key set doesn’t contain the size of hex wrench you require. The first is only helpful if you have a screwdriver that can have its head changed or an interchangeable screwdriver. Sometimes the head tips come with hex keys, so you might find what you’re looking for.
The flathead screwdriver is the next option. This will only help if you have one with tips that fit into the sides of the hex screw or bolt. You can attempt to spin it with the screwdriver if it fits tightly. If these techniques fail, you should wait until you can purchase or borrow the appropriate size.
Second, don’t try it out with a lot of power. If you do this, the screw may distort. To test each size, hold the screw in your hand. You know you’ve got a winner when you get one that fits snuggly.