Sometimes you may require a specific size of wrench. If the wrench size is small, it’s not a big problem as you can buy it at a reasonable price. However, if the size you need is larger, the cost of the wrench also increases. If you need it frequently and for a lot of work, it may be useful to buy one. But if you require it only once, it becomes a huge investment. You can try to borrow one, but that is not always possible since not everyone has a wrench or BACO in a bigger size. I faced this problem while working on my boat. I needed a wrench with a size of 55 millimetres to remove the end bearing of my prop shaft. However, borrowing one was not an option as I did not know anyone who had a wrench in this size. So instead of buying one, I decided to make my own.


– The wrench should be for a nut of 55 millimetres

– The wrench must be out of steel

– the wrench should have a long solid handle

– the head of the wrench should be exchangeable

Build Process

I started by looking for some leftover materials in my shop and found a steel strip measuring 50mm x 6mm, which was long enough to make a wrench. Using Autodesk Fusion 360, I drew a design for the wrench, deciding to make the head out of two parts that would be welded together. This would provide enough material on the side of the wrench to hold the nut without bending. I carefully shaped the head so that it wasn’t too sharp and looked like a real wrench. 

To begin the drawing in Fusion 360, I first drew the nut with a 6-point polygon. I also made the sides of the wrench slightly longer than the sides of the nut. The handle side of the head was designed to be long enough for me to connect a handle with 4 bolts. I decided to use bolts that would make it easy to change to other size heads without having to look for another handle.

Next, I created a 1:1 drawing of the wrench and printed it. After cleaning and roughly cutting the steel strip, I glued these prints onto the cleaned parts. I then cut all the parts to shape, leaving some extra material on the side of the jaw of the wrench. Before making the wrench precisely to size, the two parts needed to be welded together.

After welding, I proceeded to file away the excess material carefully, testing repeatedly with the nut to ensure it could be easily loosened. It was important to keep the sides straight and parallel, as otherwise, the wrench may bind and risk damaging the nut. I also cleaned the weld to make the wrench clean and possible to mount flat to the handle.

Once the head was ready, I drilled the necessary holes for the bolts and mounted it together with the handle. The wrench was now ready to use, and I was able to successfully remove the bearing of propschaft from my boat.


Download PDF file for the wrench of 55mm form 50mm steel stripe


  • Steel stripe of 50 millimetres x 6 millimetres 
  • 2 x 135 mm
  • 1 x 500 mm

Tools used

  • Grinder with grinding wheel and sanding disk
  • drill machine
  • power file