There are many types of fasteners used in industry today, but some of the most popular and reliable are hex head fasteners. Hex head fasteners are known for their strength and durability as well as their ease of use. There is, however, a lot of confusion regarding which type of wrench should be used when trying to loosen a hex head fastener. Using an incorrect tool can result in a stripped bolt, damage to your wrench, and lots of frustration. In this article, we will take an in-depth look at what type of wrench you should use to loosen hex head fasteners and provide you with some common mistakes to avoid; we also address a number of questions most frequently asked about hex head fasteners.
Best Tool for Loosening Hex Head Fasteners
The best tool to use for loosening a hex head fastener is a box-end wrench, an open-end wrench, or an adjustable wrench. Depending on how much work or tension needs to be done to loosen the hex head fastener will determine which tool to use:
- Box-End Wrench: This type of wrench fully encloses the hex head fastener and provides the most gripping surface and reduces slippage while removing a hex head fastener. This is the best type of wrench to use when you require more torque from the wrench on a particular item.
- Open-End Wrench: Open-end wrenches also have the advantage of being able to access difficult-to-reach spots but do not give you the same gripping ability that box-end wrenches do.
- Adjustable Wrench: Although you will not be able to achieve the precision of a fixed-size wrench with an adjustable wrench, they are still flexible and perfect for use with many different sizes of hex-head bolts and screws.
When trying to find a wrench that will work with small or special types of screws and bolts, you will want to use a hex key (Allen wrench) to turn internally threaded (hex) screws rather than externally threaded hex head bolts.
Matching the Hex Head Screw/Bolt Size with Hex Type Wrench Size
One of the things to keep in mind when using hex head screws or bolts is the importance of making sure that the size of the wrench that you are using to tighten the fastener corresponds to the size of the fastener itself. A wrench that’s too big or too small can slip, causing difficulty in loosening or tightening a fastener.
Here is a general size reference for hex head fastener sizes and their corresponding wrench sizes:
Note: Measure carefully, as there can be slight variances among different manufacturers’ wrenches.
- 6mm – 8mm Hex Bolts: Wrenches can be used that range from 1/4 inch through 5/16 inch.
- 10mm Hex Bolts: A 3/8-inch wrench is usually a snug fit.
- 12mm – 14mm Hex Bolts: Use 1/2 inch or 9/16 inch.
- 16mm Hex Bolts: A 5/8-inch wrench works well.
- 18mm Hex Bolts and Larger: Wrenches that are 3/4 inch or larger will fit, depending on the size of the bolt.
When in doubt, an adjustable jaw wrench can save you time and effort to find the correct wrench size.
Tips for Preventing Stripped Hex Bolts
Stripping hex bolts is a major frustration for professionals and weekend warriors alike. To prevent this from happening, follow these helpful tips:
- Use the Correct Wrench Size: Match the wrench size to the bolt size to prevent rounding or stripping of the bolt or fastener.
- Apply Even Pressure: Too much or too little pressure can cause slippage when loosening or tightening a bolt. Use gradual and consistent pressure to tighten/loosen a stripped hex bolt.
- Inspect the Fastener: Check for rust, corrosion, or damage before trying to loosen the bolt. Using a spray such as WD-40 or PB Blaster will help loosen a rusted hex bolt.
- Use the Correct Angle: Be sure your wrench is aligned squarely on the bolt so you have equal distribution of force and reduce the chance of slipping.
- Use Quality Tools: Using an inferior quality wrench may cause it to stretch or break due to no longer gripping the bolt securely, increasing chances of damaging your fastener.
Alternatives to Loosen Stubborn Hex Head Fasteners
Hex head fasteners can be very difficult to remove due to either rust, excessive tightness, or previous damage (worn, cut, bent). Here are some alternatives to consider:
- Socket Wrenches: A socket wrench, which is the proper size for your hex head, gives you more leverage and stability when attempting to remove a stubborn fastener.
- Impact Wrenches: For heavy-duty applications, an air-powered or electric impact wrench is perfect for breaking stubborn fasteners loose.
- Penetrating Oil: By applying penetrating oil on the fastener, it will work through the rust, dirt, and/or debris, helping to make removal easier.
- Heat: In cases where the fastener is rusted into place, heating the fastener with a torch may be necessary to expand the metal and break any corrosion locking it into place.
FAQs Regarding Hex Head Fasteners and Wrenches
This section will answer some commonly asked questions regarding hex head fasteners and the wrenches used with them:
1. What is the most frequent size of a wrench for hex head fasteners?
It all comes down to how big the fastener itself is, but there are also a number of sizes of common wrenches that are used: metric 10mm, 12mm, 14mm, 18mm, and regular 3/8 inch, 1/2 inch, and 9/16 inch.
2. Can I use pliers to loosen a hex head fastener?
Using pliers—which don’t have the grip or torque of a proper wrench—wouldn’t necessarily be out of the question, but it isn’t recommended as it could cause damage to the fastener and result in stripped or rounded edges on the hardware.
3. How do I remove a completely stripped hex bolt?
For a stripped hex bolt, the most effective way to get it out would be to use a bolt extractor or a special stripped screw remover. Otherwise, the other options would be to try using locking pliers to grip the hex head of the bolt and then using a rotary tool to create a slot on the hex head for a flat-bladed screwdriver to fit into and remove it.
4. Why does my wrench keep slipping off the hex head fastener?
If you notice that your wrench keeps slipping off the fastener, most often the cause is that either you’re using the wrong size wrench or the bolt itself is no longer in good condition. Make sure that the wrench you are using is the correct size before assuming that it is a problem with the bolt. It may also be advisable to use a socket wrench rather than a standard open-end or closed-end type of wrench to achieve a better grip on the hex head fastener.
5. Are hex keys the same thing as wrenches for hex head fasteners?
No, while both types of tools can be used to turn fasteners, hex keys (also known as Allen wrenches) are intended to turn into fasteners that have internal hexagonal sockets rather than those that have external hexagonal socket heads like standard hex bolts.
All the various types of wrenches available, such as open-end wrenches, box-end wrenches, and adjustable wrenches, serve an important purpose when loosening hex head fasteners. Each of these wrench types will work well depending on the size of the hex head fastener and the circumstances of the situation. When trying to use the proper tool to loosen a hex head fastener, it is crucial to avoid stripping the head; if necessary, invest in any specialty tools you may need to help loosen difficult or stuck bolts. Knowing the sizes of hex bolts and how to pick appropriate tools to use on them can help you to do your job easier and quicker, both as a professional and as a hobbyist. In short, with the proper tools and methods, loosening hex head fasteners is not difficult to do, even if they are stubborn or difficult to work with in many situations.
