Designing and making a ferrule

This small part of a bow frog can have a huge effect on the bow’s final overall style

Bow maker based in Montreal, Canada

Lutherie

There is a reason why the ferrule is the first part I make when I start a new bow: it is the key piece that acts as my guide through the whole bow making process. As such, for me, the design of the ferrule shapes the whole concept of the bow. I find that ferrule characteristics are central to the bow making process, as much as they influence the final result – they embody the artistic spirit of the bow.

I use the ferrule’s shape, proportions and curvature as guides to determine the bow’s overall style. If its proportions are strongly connected to those of the frog, and then to the bow itself, the ferrule ultimately influences its playability.

For example, the width of the ferrule will give the width of the hair, while its height influences frog height, then head height, then hair height, then camber possibilities. This is why I project the ferrule’s lines and volume into the frog’s profile and shape.

Ferrules also have some mechanical aspects that I find can contribute to lengthening frog longevity. These are among the things I keep in mind when I design and make a ferrule.

Cutting out the two parts

1 The first thing to know is that ferrules were originally designed by a clock maker. For this reason, I find it easier and more appropriate to refer to jewellery making techniques, which are probably the same as those used by clock makers since time immemorial. A bow maker creating a ferrule follows very similar steps to a jeweller making a ring for a customer. They require the same tools and techniques, only the ferrule is a half-ring.

Tools: Cutting board, jewellery saw, callipers

For the flat part, I use a sterling silver plate prepared at 1.1mm thickness. After filing and sanding the frog, this flat part will have a finished thickness closer to 1mm. It will make a stronger ferrule. For what will become the curved part, I use a 0.6mm thickness. It’s approximately 1/3 thinner than the flat part, and as it is thinner, it will also be easier to bend and shape in the next step. I find that a 2/3 : 1/3 ratio is a good proportion to create between the flat and curved parts.

Annealing

ALL PHOTOS ÉRIC GAGNÉ

2 Tools: Spirit lamp, jewellery tweezers and a small pot filled with alcohol

Basically, annealing is a process by which the atomic structure of the silver can be decompressed. It’s like releasing all the internal stress that results in making silver harder. In brief, the annealing process is used to soften the silver and make it easier to cut and bend.

Shaping the round part

3 Tools: Bending block with different curve diameters and a mandrel (I personally use my ring mandrel, the one I make my button rings with)

I use two different diameters to make the curve of my ferrule: a bigger diameter for the top part of the curve and a smaller diameter for the side parts of the ferrule, to obtain a ‘D’ shape. This leaves more wood to specific parts of the frog, making it stronger at the tongue and near the wings of the hair channel. At the same time I can still keep my ferrule to a height within the proportions I like. The D shape also allows me to maintain a relatively low ferrule height, which is a personal aesthetic choice.

Preparing to solder

4 The goal of this step is to prepare a perfect fit between the flat part and the curved part of the ferrule. I achieve this by filing one facet of the flat part and the two ends of the curved part perfectly flat. I also add extra small chamfers to the interiors of the extremities of the curved part, to help the solder paste penetrate and to facilitate the cleaning and filing of the soldered ferrule’s interior later on. When the flat and curved parts are perfectly mated, I wire them together tightly and I am ready for soldering.

Clamping with wire

5 Tools: Spirit lamp, small pliers, solder p aste syringe, pot with water The impact of a good or bad solder can be revealed after years of bow use. When I am very confident with my pre-soldering preparation, thinking that no one will be afraid of rehairing my bow for fear of breaking a weak and/or visible solder joint, I am ready to solder.

Soldering

6 I use a medium-rate soldering paste in a syringe that I apply with a very big needle. I apply the paste through the whole length of the joint, inside the ferrule, as well as on the previously made chamfer. I heat everything up with the spirit lamp until the paste melts and soaks into the joint. Solders are not only used to ‘glue’ two parts together. They act as a kind of silver melter. This is especially needed at the level of the joints. So, when the soldering is done correctly, there are no longer two pieces and the joints have become silver.

Soldering with a lamp

7 I know the soldering is perfect when I have a very thin line of solder (which is in fact melted silver) on the outside of the joint. At this exact moment I know I have approached the melting point of the entire piece, so I drop everything very quickly into water to cool it off.

Cleaning inside the ferrule

8 Tool: Half-round needle file After the soldering process, there are two things inside the ferrule that I want to remove. Since solder paste is made of solder and flux, the flux residue needs to be taken out after burning. Secondly, there is a small layer of oxidation on the silver caused by the heating process. I remove both the flux and the oxidised layer with the needle file and make a nice, clean surface. I clean the round part with the file’s rounded edge, then use the flat part of the file for the ferrule’s flat surface. Finally I use the corners of the file for the flux residue.

The finished ferrule

Shaping and hardening

9 Tool: Ferrule mandrel, hammer I took a course at the Montreal Jewellery School on fine metal making and the physics of non-ferrous metal working. A discussion with the professional jeweller who was giving the masterclass confirmed my feeling: the hardest and strongest silver is a well-hammered one.

A ‘cooking process’ can also be used. But the teacher herself recounted having been brought both a hammered wedding ring and a moulded ring that had been run over by a car. While the hammered ring was still in reparable condition, the moulded ring had been completely destroyed.

Whether you decide to hammer or cook the silver, the hardening process is very important as it gives strength, resistance and durability to the ferrule. Personally, I hammer it with a self-made mandrel which has the exact interior shape of my ferrule. I simply slide the ferrule on to it and hammer the ferrule all over, to fix my shape and obtain a hardened silver piece. I stop hammering when I feel that the ferrule is not going down the mandrel any more, which means the silver has hardened enough and the ferrule is now finished.