Everything You Ever Needed To Know About Dumbbells

Unlike Cast Iron, steel is not brittle and has a higher density meaning dumbbells can be made smaller than their cast iron counterparts as they are less likely to break.

Stainless Steel

Stainless steel dumbbells can be produced in two variations, 316 stainless or 303 stainless.

There is a variation known as 304 stainless steel and although it offers slightly better corrosion resistance when compared to 303 it is not a material which is easily machined and is therefore not used in dumbbell manufacturing.

Unlike mild steel or cast-iron, stainless steels have at least 10.5% chromium which reduces corrosion significantly.  The higher the level of chromium, the less the material will degrade. 

316 Stainless Steel has a higher nickel content in comparison to 303 or 304 with the addition of molybdenum making it even more corrosion resistant.

However, 316 stainless steel is at least two to three times as expensive as 303 stainless steel and six times the cost of mild steel.

Contrary to popular belief, all stainless-steel CAN rust. The rate of corrosion though is far lower than steel or cast-iron alternatives but in an indoor gym environment this is unlikely to ever happen unless your gym is next to the sea or a swimming pool with high levels of humidity.

It’s easy to test to see if your dumbbell is stainless steel, simply place a magnet on the surface.  If its magnetic it’s not stainless steel.  If it’s not magnetic, there is a high chance you have stainless steel. 

Unfortunately, the only way to check if the dumbbell is 316 or 303 would be to perform a chemical test on it so unless you are willing to do this you must have a trustworthy supplier.

Different Shapes of Dumbbells

• Six Sided – also known as hex dumbbells
• Circular Dumbbells – the most common dumbbell Shape
• Spherical – these are globe shaped dumbbells
• Square – more common on adjustable dumbbells
• 12 Sided – less regular these offer a balance between hex and circular

Six Sided Hex Dumbbells

Six sided dumbbells, also known as Hex Dumbbells, exist to provide more stability during workouts and are typically found in home gym’s or Crossfit Box Gym’s.

Hex Dumbbells are commonly made from cast iron and coated with either rubber, urethane or neoprene. Because of their construction and low cost, hex dumbbells are better for individuals that train at home or are on a limited budget.

These six-sided dumbbells generally come in two styles

1. Studio dumbbells which are entirely coated in neoprene, vinyl or rubber and are available between 1kg and 10kg
2. Hex dumbbells have a knurled handle and only the ends of the dumbbell are coated in either rubber or neoprene and can go from 1kg to 50kg+

Hex Dumbbell Benefits

• As Hex Dumbbells are mainly made from Cast Iron they are usually cheaper than other alternatives on the market.
• The Six sides stop dumbbells rolling away during exercises where dumbbells would be placed on the floor such as push ups.
• The coating protects the dumbbell from scratching or damaging equipment.
• Because Hex Dumbbells don’t roll, it’s good for those on a budget as you don’t have to use a storage rack.

Hex Dumbbell Drawbacks

• Heavy Hex Dumbbells can be awkward when placing them down as they want to roll to their flat position.
• Because Hex Dumbbells are produced using Cast Iron and more commonly coated for protection, they are not particularly accurate and can weigh 2-3% more or less than the stated weight which can cause muscle imbalance, especially noticeable with heavier dumbbells.
• Hex Dumbbells have a higher chance of breakage due to the use of cast iron rather than steel. Because the dumbbell ends are welded first then coated for protection it makes it extremely difficult to fix them as you cannot get to the broken area without taking the coating off.  Meaning when they break, they need replacing.
• Hex Dumbbells have slightly higher centrifugal forces surrounding the dumbbell handle which is dependant on where you grip
• Limited options such as no revolving grips and they are not available in stainless steel finishes due to mass production.
• They cannot be stored in traditional dumbbell racks and require flat shelves to store the dumbbells.

Circular Dumbbells

Circular dumbbells are the most common shape on the market. They can be made from Cast Iron, Mild Steel or Stainless Steel. They also come in a range of styles of sizes.

Circular dumbbells are usually cast in a mold, or they can be machined on a lathe.

Circular Dumbbell Benefits

• When exercising with circular dumbbells it doesn’t matter how they are placed they will never move as the weight is spherical.
• Centrifugal forces are the same all the way around the dumbbell handle no matter where you grasp the handle.
• Circular dumbbells can achieve more accurate weights when machined using a lathe.
• Available in a wider range of finishes, handle diameters and shapes.

Circular Dumbbell Drawbacks

• Circular dumbbells can roll on uneven floors making them a hazard in certain training environments.
• Because circular dumbbells are round it is not advisable to keep them on the floor, a specific dumbbell storage rack and saddle would be required to safely store them.  However, this not only adds additional cost but the plastic saddles can break when heavy dumbbells are thrown into the rack after a heavy workout.

Globe or Circus Dumbbell

The Globe shape is found on the circus dumbbell. This type of dumbbell is not common in home or commercial gyms and is usually found in functional training environments such as strongman.

Circus dumbbell ends and handles are generally larger in diameter in comparison to other dumbbell types. These dumbbells are generally used in single arm movements such as the overhead dumbbell press.

Globe Dumbbell Benefits

• Rounded globe dumbbells are better for overhead pressing as your forearm can rest against the dumbbell end more comfortably thanks to its rounded edge.
• They can promote better balance and grip strength due to the huge size.

Globe Dumbbell Drawbacks

• Much harder to grip.
• Cannot be used the same as a traditional dumbbell.
• Not available in light weights, mainly because of its intended use.
• Harder to press. People generally press overhead from the side of the shoulder or sitting on top of the shoulder.
• Limited variations in design of circus dumbbells.

Square Dumbbells

Less common are square dumbbells. Most square dumbbells tend to be adjustable. Examples of this are the Powerblock Adjustable Dumbbells or Ironmaster Quick Lock Dumbbells.

All square dumbbells that are on the market, as is our understanding, are made from cast iron.

Square Dumbbell Benefits

• These dumbbells will not roll making them safe in home gym environments.
• They do not require expensive Dumbbell Racks or Storage.
• More stability over Hex or Octagonal Dumbbells.

Square Dumbbell Drawbacks

• Unbalanced design, the weight is not spread concentrically around it’s center.
• You have to place the dumbbell down on its flat side, if you drop it on it’s edge its likely to jerk into position.
• Cannot be stored in a standard dumbbell rack much like the hex dumbbells and would most likely be suited to a kettlebell style rack which are not rated to as high a capacity as a dumbbell rack.
• As these dumbbells are less common they have less variations and custom options.

Octagonal or Dodecahedral Dumbbells

Octagonal (8 sided) or Dodecahedral (12 sided) Dumbbells are not particularly common in gyms. These dumbbells are usually cast iron and encased in a specialist coating such as rubber or Urethane.

They provide some of the benefits of round dumbbells whilst avoiding some of the pitfalls of Square or Hex Dumbbells.

Octagonal Dumbbell Benefits

• These dumbbells are less likely to roll like a circular dumbbell.
• Because of the multiple small edges, they aren’t as likely to jolt if they are placed down on one of the 8 or 12 corners.
• As each of the edges are so small it can be used in a standard Dumbbell Rack with saddles.

Octagonal Dumbbell Drawbacks

• Because the dumbbell has edges, it is more likely to damage the dumbbell saddles in a rack.
• These are less stable when comparing them to Hex or Square dumbbells and can still roll.
• Limited choices in materials or handle designs.

Different Dumbbell Coatings

Dumbbells come in a variety of finishes, ranging from synthetic Polyurethane coatings, through to Zinc and Nickel, which are naturally occurring metallic coatings. Each of the coatings are applied using different processes and offer different protection levels and finishes

Urethane Dumbbells

Polyurethane also known as Urethane is considered one of the best coatings in the industry for dumbbells. Urethane protects the base metal from corrosion and moisture forming a smooth covering. 

A good way to tell the difference between this coating and rubber is that it feels a lot harder to the touch when compared to rubber

Urethane Benefits

• Highly Impact Resistant
• Waterproof
• Hard material
• No smell
• Reduction in Bounce
• UV Resistant
• 50+ Year Lifespan
• Safer than Steel Alternatives
• Easier to clean the rubber dumbbells as it’s a smooth surface

Urethane Drawbacks

• More Expensive
• Do not look as high quality as chrome dumbbells
• Less accurate than steel dumbbells
• Difficult to repair if they break

Rubber Dumbbells

Rubber is a natural product that is quite often found on dumbbells. It’s quite common to see the debate Rubber Dumbbell vs Urethane Dumbbell when you search the internet. 

Although rubber is inferior to urethane, it is highly recyclable and delivered at a more economical price compared to its urethane equivalent.

Rubber is a natural product harvested from rubber trees with the main producers of rubber being Thailand and Indonesia followed closely by Vietnam, Africa, and then China.

Rubber Benefits

• Because of their soft texture rubber is considered one of the safest coatings for dumbbells.
• Rubber is recyclable making it an environmentally friendly option.

Rubber Drawbacks

• Recycled rubber (Non Virgin Rubber) has a very strong odor.
• Short life span when compared to Urethane but more durable than steel finishes such as Nickel or Zinc.
• Very difficult to repair if they get damaged or break because of the rubber coating.
• Less accurate weight than their steel counterparts.
• Very hard to clean because of its textured surface.
• Rubber can mark equipment when it’s dropped.

Nickel Dumbbells

Steel Dumbbells which are machined using a lathe are normally left bare. Without any form of coating they would rust and corrode so Nickel is a finishing option added to the higher priced dumbbells such as Custom or Personalized Dumbbells

As you can see from our section on material selection, Nickel makes up almost 10% of rust resistant materials such as stainless steel.

Nickel is a hard metal which is applied to the dumbbell by electroplating (there is an electroless version but this is not decorative in its appearance).  A copper base is applied to the metal followed by Nickel in Ultra Thin layers of approximately 13 to 20 microns (0.013 – 0.020mm thick).

For mineral based protective coatings, we can use the Mohs scale which tests hardness with a rating from 1 through to 10 with 10 being the hardest and 1 being the softest. Nickel is a level 4 on the Mohs scale.

Nickel Benefits

• Nickel is a highly reflective material giving you a consistent luxurious finish.
• Unlike Zinc coating, Nickel does not degrade or breakdown and acts as a barrier between the metal and the environment.
• Because it is extremely thin it is easier to obtain accurate weights and tolerances.
• Easy to repair these dumbbells when they get damaged.
• Long life span if looked after correctly.

Nickel Drawbacks

• It’s a difficult finish to achieve consistently.
• It’s a costly process which is why some dumbbell manufacturers use zinc plating instead of Nickel.
• If the Nickel Coating is chipped or removed, the underlying surface can corrode if not kept dry.
• Nickel coated dumbbells are louder than rubber or Urethane alternatives.
• Steel Dumbbells can dent and mark unless they are heat treated.
• More expensive than other dumbbell finishes.
• This material can be scratched but to a lesser degree than Zinc.

Zinc Dumbbells

At first glance Zinc Dumbbells look very similar to Nickel Plated Dumbbells.  However, there are some very big differences. Nickel is applied as a coating that sits between the external environment and the base metal.

Zinc plating is achieved in a similar way where the dumbbells are suspended in a chemical solution and using positive and negative electrical currents the material, in this case zinc, is drawn to the metal.  Zinc plating is thinner than nickel and deposited around 5 microns (0.005mm thick).

Zinc Plating is designed to sacrifice itself, breaking itself down to protect the steel underneath. Over time Zinc plating will first start to go black and after a period of time will eventually disappear exposing the bare metal beneath.

Zinc is softer than Nickel and is a level 2.5 on the Mohs scale.

Zinc Benefits

• Lower Cost
• Offers a reasonable level of rust protection
• Easy to repair dumbbells when they get damaged
• Does not chip or flake off as it chemically bonds with the Dumbbell Steel

Zinc Drawbacks

• Will sacrifice itself and breakdown over time resulting in rust and discoloration
• Shorter lifespan in a sweaty gym environment
• Not as bright a finish as Nickel
• Does not offer the same protection as Rubber or Urethane
• Not resistant to scratching so will mark much easier
• Regular wiping with cleaning solutions will push moisture into the steel resulting in rust

Enamel Dumbbells

Enamel is a protective paint layer applied to the dumbbell and most widely used on cast iron dumbbells or weight plates. It consists of a tough paint that adheres to the surface.

Enamel is a thick coating and although is available in an almost infinite variation of colors and textures it is most commonly applied to dumbbells as grey or black.

Enamel is harder than Nickel and achieves a level 5 to 7 on the Mohs scale.

Enamel Benefits

• Superior corrosion resistance
• Easy to repair and refurbish
• Low Cost
• Very Resistant to scratching
• Smooth Surface makes cleaning easy

Enamel Drawbacks

• Brittle and can chip
• Dull Finish
• No impact protection like Rubber or Urethane
• It will wear away over time
• Because of it’s thick coating, it is not very accurate

Vinyl Dumbbells

Vinyl, also known as PVC (Polyvinyl Chloride) is a synthetic rubberized substance applied by dip transfer onto the dumbbells. Vinyl is generally applied anywhere from 0.5-5mm thick and is available in a variety of colors.

Vinyl Benefits

• Soft to the touch
• Easy to clean
• Resistant to impacts and scratches
• Resistant to water
• UV resistant
• Thicker Coating than Neoprene

Vinyl Drawbacks

• Some users report the surface being slippery
• More prone to splitting than Neoprene
• Not as hard wearing as Urethane or Virgin Rubber

Neoprene Dumbbells

Neoprene is a soft synthetic rubber which is applied using a dip transfer. The thickness of the coating is approximately 0.3mm – 0.7mm thick. Neoprene is available in a wide range of colors and is usually only found on lighter dumbbells.

Neoprene Benefits

• Soft to the touch
• Resistant to impacts and scratches
• High Tensile Strength
• Resistant to water
• UV resistant

Neoprene Drawbacks

• Higher cost
• Polymer can crystalize under 10 degrees causing it to become brittle
• Textured finish makes cleaning harder
• Thinner Coating than Vinyl
• Will not stand up to abuse as well as Urethane or Virgin Rubber

Different Dumbbell Handles & Grips

Dumbbell handles and grips form the core of any dumbbell. Length is crucial, too long and the dumbbell doesn’t feel balanced in your hand, too short and it can interfere with your forearms during certain lifts such as the flat chest press.

Dumbbell handles can get slightly confusing because of the variations available, from fat grip through to standard grip, knurled or rubber, rotating or fixed. To help differentiate the features of a grip we have broken them down into five main categories

Revolving or Fixed Handles

Dumbbell handles are produced in two styles

The first, and most common, is a fixed grip handle where the relationship between the grip and the dumbbell ends are fixed and do not rotate.

The second style is a rotational grip, like the function of an Olympic Barbell this is where the grip spins separately to the dumbbell ends and is designed to offer less torque on the wrists during movements such as the snatch.

Fixed Grip Dumbbells

This type of handle is the king of all Dumbbell grips. Found on most Dumbbells in existence the fixed grip handle has a relationship between itself and the dumbbell end plate that does not rotate. The handle can either be welded into place or mechanically joined using a bolt or fixing to keep the weight ends attached to the grip.

These fixed grips can be knurled, smooth or coated in rubber. They can be ergonomically shaped or be formed with a consistent shape along the entire length of the handle.

Fixed grip dumbbell handles can range in diameter from standard and come in a range of diameters to suit every different type of user imaginable.

Revolving Grip Dumbbells   

To rotate, dumbbells must use either a composite bush or a bearing to reduce friction between the grip and the steel ends and allow them to spin. The main problem with this is that in a gym environment weight gets dropped, quite often from height, resulting in large stresses being placed on the dumbbell components which can easily damage bearings.

During construction dumbbells are either welded together or mechanically fixed using bolts. A revolving dumbbell which is fully welded will provide the best strength in a gym environment however the problem occurs if the bearings fail as it is almost impossible to get access to the bearing as it is sealed inside the dumbbell.

Alternatively, a bolted dumbbell allows you to get access to the bearing to change it, but bolted dumbbells are notorious for working themselves loose which is not great for a gym environment.

The Revolving Dumbbell Myth

It appears the appeal of the free revolving dumbbell, and its sudden rise to fame is that it ‘disconnects the weight from the rotational forces of the dumbbell while being used’.

While this is true, there are only two exercises in existence that would benefit from a rotating dumbbell. Those two exercises are the dumbbell snatch and the dumbbell wrist curl.

The reason for this is because during both these exercises the angle and relationship between your wrist and forearm changes throughout the movement, on almost all other dumbbell movements your wrist stays completely parallel to your forearm so there is no torsion on your wrist.

Some manufacturers even claim that the rotating dumbbell handle puts less stress on joints during movements such as bicep curls. However, we cannot think of a single scenario during a bicep curl where a rotating handle would benefit as the centre of mass (the handle) always stays parallel to your forearm. As the mass stays concentric to the grip on the handle the dumbbell will not spin, and therefore place no torsion on your wrist

Grip Thickness

The diameter of a dumbbell handle not only reflects the dumbbell’s strength but also the users ability to grip the dumbbell during a workout. Most dumbbells use a standard grip handle however some custom dumbbells offer fat grips as an optional upgrade.

Standard Grip Diameter

A Standard grip dumbbell will range from 20mm up to 35mm, diameters under 30mm will almost always be used in home gym environments.

A standard grip will allow you to wrap your fingers almost entirely around the handle until they touch your palms and for your thumb to be placed over your index finger for additional support. This makes them ideal if you have poor grip strength.

A grip size between 36mm and 39mm could be considered either standard or a fat grip depending on the user that’s lifting the dumbbell. Someone with large hands may feel comfortable at this diameter whereas those with smaller hands may struggle to maintain a strong hold.

Thick Grip Diameter

As thick grip dumbbells have a larger diameter handle, using them can help to develop natural strength in sporting movements where users either tackle, grapple or wrestle.

They also stimulate muscle growth in the hands, forearms and biceps because the user is at a disadvantage when gripping the weight.

This happens because the point at which your fingers grasp gets further away from the center of the handle makes it harder to grip, meaning you have to stimulate more muscle fibers just to maintain your grip.

By using fat grips independently, you can try to fix imbalances on lagging body parts by making them work harder.

Grip Shape

The type of grip on a dumbbell can come in two forms, an ergonomic grip or a straight grip.

An ergonomic grip (sometimes known as a contour grip) has a thick central section of handle which gently tapers down at each end, they are manufactured to allow an even distribution of grip across your palm.

The theory is that our middle finger is the longest while the fingers either side are shorter and therefore would be better suited to smaller diameter handle which is provided with a contoured handle.

The problem with this is that when you close your grip your fingertips align therefore making the entire purpose of the ergonomic handle futile.

The main drawback of the ergonomic handle is that they are never fully knurled and most commonly consist of three narrow strips of knurling. One length at the largest diameter and two small strips either side.

The reduction of knurling is due to the manufacturing process which only allows knurling to be performed across even surfaces. Another downside to ergonomic handles is that they are simply not as robust.

Because the diameter of the grip is smaller at either end these would produce points of weakness when dumbbells are dropped in a gym environment which could lead to breakage. This could be overcome by carrying out heat treatment to strengthen the bar however this is a costly exercise and would increase the cost of the dumbbell.

Grip Texture

Smooth Grip

A smooth grip is self-explanatory. The handle would offer no texture to assist in gripping the dumbbell. Whilst it is usually coated in a coarse finish such as textured powder coat to improve grip there are only a few reasons why a manufacturer would opt for this type of handle

• To Reduce Cost – producing knurling is a slow and refined process which adds cost to the item.
• Not Required – one of the few movements which normally don’t require knurling is pushing movements as the grip is being forced into your palm rather than pulled away from it.
• Specialist Reasons – The product is designed for children, women or for those who find knurling uncomfortable

Knurled Grip

When you have a look at dumbbells, you may notice a textured appearance on the handle. This is what is known as knurling, or diamond knurling, as it forms a diamond shape or cross hatch pattern.

To manufacture this, a tool which comprises of two hardened wheels is pressed against a rotating bar which either cuts the steel or forms the material depending on the particular process.

You can read more about knurling in our post; what is barbell knurling.

When this procedure is carried out, the surface of the bar is altered by producing tiny peaks and troughs and serves two main purposes:

• To increase surface area therefore reducing friction and increasing grip.
• To allow sweat to drain away from the main point of contact.

Rubber Grip

A rubber grip is used to increase friction and improve the feel of the dumbbell handle. Whilst rubber is one of the best ways to reduce friction, there are several drawbacks to consider:

• Sweat is less likely to drain away from the grip potentially making the handles slippery and difficult to handle.
• Rubber can wear over time therefore increasing the cost of repair or replacement.
• Rubber is flexible and will change shape when gripped.