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If you’re an avid gym-goer, then it’s very likely that you’ve worked out using a barbell. Maybe you already know that there are many different types of barbells ranging from weightlifting bars, speciality bars, Olympic barbells and even women’s bars.
All of these different bars typically offer unique features depending upon what you are trying to achieve.
For example, a squat bar tends to be used by those who favour powerlifting or squatting with heavy weight. Whilst squat bars will likely have differences depending on the manufacturer and brand, the overriding feature is that the bar is longer in length and allows for more weight to be added when compared to a regular power bar.
So, now we have an understanding that there are a range of different barbells, what are the common features you can find on pretty much all bars? Something that you may have noticed but not paid too much attention too, is barbell knurling.
What is Barbell Knurling?
Barbell knurling is the textured surface located on the shaft of a barbell. It is an engraving of a crosshatch pattern that is designed to improve grip by creating friction. Depending on the type of bar, knurling can differ in its shape, location and pitch.
In terms of its application on a barbell, this would be done with a knurling tool which is loaded onto a manual or CNC lathe. Two different types of knurling tools are the cut knurling tool and the form knurling tool.
Cut knurling is where material is cut away to form the desired pattern whereas form knurling involves pressing the pattern into the bare steel.
When it comes to the longevity of barbell knurling, you’ll likely find that knurling on lower cost barbells will wear down fairly rapidly. More often than not, this is due to the bar’s tensile strength.
In manufacturing processes, high quality barbells undergo a process known as case hardening. Case hardening is a heat treatment process that would be carried out post knurling, the aim of which is to harden the outer surface of the metal allowing it to retain its shape, whilst making it considerably more durable. If the surface area of the barbell has been case hardened, you can expect the knurling to carry a much longer lifespan.
The manufacturing process for a barbell will differ depending on the brand and materials being used, but usually low-cost imports would not have been case hardened. These type of multipurpose barbells are found in most commercial gyms and carry a passive knurling which would likely not last very long.
Furthermore, these bars tend to bend with repeated heavy use, due to the lack of heat treatment. This makes these barbells unsuitable for strength sports such as powerlifting and weightlifting.
Conversely, a high-quality barbell will likely have gone through numerous research and development tests to best determine the material to be used, it’s type of knurling and Rockwell scale. The Rockwell scale is used to establish the most suitable hardness level for a barbell. Whilst, an untreated bar is too soft for certain sports, a bar that has undergone a heat treatment process which is too high can result in a material that becomes too brittle.
Is Barbell Knurling Important?
The importance of barbell knurling is really a personal preference and tends to depend upon the user and what exercises are being performed. For those undertaking barbell exercises with a lower weight, the knurling on standard bars probably won’t make much difference and they may prefer to improve their grip simply by wearing a pair of weightlifting gloves.
However, for people such as olympic lifters and powerlifters, who tend to lift much heavier weight loads, the types of knurl available are deemed much more important with a more aggressive knurling making for a solid grip.
It’s also not uncommon for lifters to make use of chalk prior to lifting which absorbs excess sweat further improving their bar grip. When used, chalk will become lodged in the grooves of the knurling making it important to clean the barbell after use.
Always use a stiff-bristled nylon brush for cleaning a barbell as opposed to a steel brush. Using a steel brush will not only remove any bar coating (nickel or powder coating), it can also damage the knurling itself.
Why is Barbell Knurling in different places?
Most good barbells will offer some form of knurling whether it be a coarse knurl or a fine knurl. The commercial gym you attend likely has a variety of different bars and maybe you’ve noticed that knurling isn’t always consistent in its location. But, why is that?
Knurling on all barbells is located either side of the center of the barbell and is typically wide enough to allow for a wide or narrow grip positioning of the hands. However, on some bars you’ll notice that there is knurling in the center as well as either side of the shaft.
Center knurl marks are useful for providing extra grip between the barbell and the upper back during squatting and helps to prevent the bar from slipping. That being said, during olympic lifts, especially a movement such as the clean and jerk, center knurling can be somewhat of a hinderance as it can result in drag between the chest and the barbell.
A squat barbell and a power barbell will both have knurling either side and at the center. The differences between the two will be down to the size. The squat bar will be much longer than a power bar with a thicker grip and will have longer sleeves to allow for more plates to be loaded on. By comparison, the deadlift bar will only have knurling either side of its shaft and in terms of length and diameter sits midway between the squat and power bar.
Whilst most gyms will tend to offer a multi-purpose bar, some facilities who specialise in strength sports such as weightlifting and powerlifting will supply bars specific for these exercises.
Interestingly, when it comes to the sport of powerlifting, current rules of the international powerlifting federation stipulate no requirements for specific deadlift and squat bars but, instead supply dimensions that should be adhered to. This means that use of a standard power bar is OK for use in national and world competitions so long as it meets their specifications.
Barbell knurling too soft?
Maybe you’ve purchased a decent second-hand barbell but the knurling has all but worn away or the knurling on your current has worn reducing your grip strength. In either instance, is there something that can be done to fix soft and worn knurling?
Whilst many forums suggest simply taking your bar to a local machine shop to get it re-knurled, unfortunately it’s not always as straightforward as that. It’s not impossible to re-knurl a bar however, by going over worn knurling would likely result in double tracking.
Also, don’t forget if it’s a decent bar, it’s likely been case hardened, this makes the job of re-knurling even more difficult and expensive. As mentioned above, any shaping of metal is always done prior to heat treatment.
The bar could be re-skimmed, this means to take off the very top layer of metal then knurled. However, the downside to this is that you’ll be reducing the diameter of the shaft. Again, there’s the issue of whether the bar has been heat treated.
It’s always worth making enquiries with a machinist to find out if the work is possible and the cost. In many instances, it would be cheaper to purchase a new barbell.
Different shapes of barbell knurling
Something that often goes unnoticed is that barbell knurling is available in different shapes. Whilst all knurling has the same distinctive diamond pattern, each diamond has a specific shape. These are referred to as hill, mountain and volcano. Even though these shapes have been around in knurling for many years, the naming of them has been credited to Chris Duffin, founder of Kabuki Strength. Let’s look at the different knurling types in more detail.
A hill knurl is so called because of the rounded, smooth top of each individual diamond. In strength training, this tends to be the least favoured of the knurling patterns as it offers the least amount of grip, which can be a limiting factor in the amount of weight being lifted. You would tend to find this type of knurl on lower cost and more generic bars.
However, something to consider is that the hill knurling could simply be worn down from what was previously a mountain or volcano knurl.
Even though hill knurling is not particularly popular amongst seasoned lifters, it’s still a good starting point for beginners and those who wish to keep any discomfort at bay when training.
The diamonds on a mountain knurled bar, sometimes called pyramid knurling, will feature a sharp peak at each top. Whilst this provides for excellent grip, many users do report this type of knurling to be uncomfortable, even painful, on the skin.
Repeated use of a mountain knurled barbell can eventually result in calluses, a hardening and thickening of the skin on the hands due to the excessive friction. Even though many lifters suggest calluses allow them to lift heavier and with better grip, if you want to avoid them simply wear a pair of gym gloves. This will of course defeat the purpose of the knurling.
Volcano knurling is a newer type of knurling to be featured on barbells and can be identified by mountain like peaks that feature a concave top, as its name suggests, looking somewhat like a volcano. When compared to a mountain knurl, which has one peak, the volcano knurl has four peaks per diamond. The benefit of this is that it allows for more peaks to make contact with the skin providing excellent grip without the discomfort.
Preference for any of these bars very much depends on how important your grip strength is when lifting. If you’re a beginner to the gym and don’t tend to lift particularly heavy, then any standard bar with a hill knurling would suffice. However, for seasoned lifters who’s aim is to lift as much as physically possible you’ll want to opt for either a bar with mountain or volcano knurling.
Types of barbell knurling
As explained above, knurling is applied by way of tooling and a lathe machine and aside from the different shapes produced when knurling, its also possible to achieve different depths and spacing. These are usually categorised as aggressive, passive, fine, medium and coarse.
Aggressive and passive knurling are determined by the shape of the knurl. Most often a hill knurl will be defined as passive (smooth, flat, minimal grip), whereas a mountain knurl would be considered aggressive (sharp, pointy, maximum grip).
When it comes to fine, medium, and coarse, this is relating to the pitch of a knurl. A knurl pitch simply refers to the distance between the diamonds (the diamonds are technically known as teeth). This is known as teeth per inch (TPI). A fine knurl would have a higher TPI when compared to a coarse knurl. When it comes to knurling on a barbell, fine or medium knurling would be preferred over coarse as it offers more diamonds.
However, whilst a higher TPI should equate to a better grip, this would also depend on the pattern and the depth of the knurl as a shallow (or worn) knurl irrespective of TPI wouldn’t be beneficial for grip improvement.
What are knurl marks for?
Now that you have a pretty in depth knowledge about knurling on barbells, something else worth pointing out are the knurling marks. These are the narrow smooth rings that you’ll see in the middle of the knurling. These are there purely to help with positioning of the hands and to help you align the barbell as best you can prior to your lift.
The position of these rings can also differ depending on the type of bar. On a powerlifting bar, you’ll typically see the rings sit closer to the center of the bar when compared to an Olympic barbell. In either case, they provide a useful guide to the lifter when it comes to hand placement.
When investing in either a new or second hand barbell, always undertake sufficient research to determine which type of bar would best suit your needs and also make enquiries with manufacturers directly to find out about the production process, if the bar has been heat treated and also the type of knurling.
A high quality barbell will offer good knurling and this could make all the difference in terms of the weight that you can lift. Remember, an aggressive knurling, whilst good for grip, may not be necessary depending on the weight you’ll be lifting.