We previously published a blog post detailing our production methods and techniques for our signature weight plate collection. Now it’s time to talk about our dumbbell collection. We are doing this series as we get a lot of questions about how our products are hand-crafted, what machinery is used, and how we run a small-scale production line. The process is similar to how we produce our plates, with a couple of additional steps and complexities.

Step 1 – Machining the carbon steel stock.

Each dumbbell features a 34mm knurled handle which is attached to two equally sized discs. As with our weight plate collection, the dumbbells start life as rough-cut circular steel discs, which are flame cut by our steel stock provider. The dimensions of the discs are a few millimetres larger than what the final disc sizes will be. The discs are then machined down to size using one of our lathe machines to within a very small tolerance. Each one has a 2mm groove machined into one side of the disc. This is where the round walnut wood disc will fit. The other side is a plain steel face, and the edges feature a 3mm chamfer. A 20mm central hold is then drilled so that the handle can be attached to each disc when the individual components of the dumbbell are assembled.

The handle starts life as a 40mm carbon steel rod which is cut to 155mm in length. This is then mounted to one of our lathe machines and cut to a diameter of 34mm. Two further cuts are then completed, which start from either end and are 17.5mm long going towards the centre of the rod. These cuts reduce the diameter from 34mm to 20mm. The result is a machined handle which has a 34mm diameter and is 130mm long, with two smaller diameter (20mm) ends which are 17.5mm long. The ends slot into the 20mm central holes on both machined discs. The handle is then finished with a medium diamond knurl.

Step 2 – Nickel plating.

The individual components are then transported to our nickel-plating workshop where they receive a lustrous nickel coating. The parts undergo a three-step cleaning process, ensuring there are no marks or dirt/grease particles on the surface as this would reduce the quality of the coating. The parts are then activated using an acid bath and placed into the plating bath, individually receiving a thick nickel coating. Nickel is not only an aesthetic, shiny metal, it is also one of the hardest and most corrosion resistant metals, making it perfect for this application.

Step 3 – Preparing the walnut facing.

Rough sawn planks of walnut are delivered to our facility and that’s when the processing begins. The rough sawn planks are planed and cut into sheets around 5mm thick. They are then planed again to 3mm thickness. These sheets are then placed on a CNC cutting machine which cuts out circular designs and are sized to fit inside the groove cut in each steel circular disc (dumbbell ends).

After cutting, the walnut pieces are sanded and finished with a glossy OSMO oil, before our logo and weight number is applied to the surface of the walnut.

Step 4 – Welding the components.

After the nickel-plating process, each component is prepared for final assembly. They are treated to remove any nickel plating in areas that will be used to weld the components together. They are also covered in a heat resistant welding tape to protect the surface during the welding process. The ends of the handle component are placed into the central holes in each circular disc, and they are subsequently welded together to create the final dumbbell piece.

Step 5 – Fixing the walnut onto the dumbbells.

Once final preparations have been completed, the walnut discs are then attached to the surface of each end, inside the machined groove. This is done using a specialist industrial adhesive and the dumbbells are then left to cure for 48 hours.

Step 6 - Cleaning and packaging.

The dumbbells are then cleaned and prepared for packaging and shipping.

This gives you an insight into the production methods and processes taken to produce our walnut-faced nickel-plated dumbbells. We currently offer these in sizes from 4kg to 12kg, although larger weights can be requested. We also work with several local specialists and contractors to help with various aspects of the production methods outlined above. If you have any questions regarding the processes above, or about our dumbbell product, please do contact us at contact@mannixsports.co.uk and we will be happy to help.