When I sold my workshop machinery, `knowing’ that I would never finish building the clock, the raw materials went out as well. What was the point of keeping it anyway? In particular, all my round brass bar went with the ML7 lathe, a variety of brass off-cuts went with the Taig CNC micro-mill, while several strips of various sizes of gauge steel still in their wrapping went to a friend. Although I had forgotten, it turned out that I had also given him my butane gas torch.

In contrast, if you have seen a couple of my other postings, you will know that I have decided to complete the clock after all, even though I have very limited workshop facilities, ie. a garage and a borrowed HobbyMat lathe.

Upon trying to work out what was still to be made, at the last count there were several steel items and about twenty in brass.

For various reasons, none the least being the hip-pocket nerve and the nearest supplier’s limited thickness range of brass strip, I decided to split some of the remaining brass components into two or three pieces and then fabricate these by silver soldering. I’d discovered that I still had several lengths of silver solder, along with an old tobacco tin containing borax. Another negative issue was the purchase price of a new butane cylinder, and the difficulty in getting cylinders re-filled. However, remembering where my old butane torch had gone was to become an important issue.

As it happens, the parts in question have a limited stress level. They just need to look nice.

One of the more obvious parts for this silver soldering approach was the irregular shaped maintaining detent. If you are not into clocks, its purpose is to engage in a toothed wheel while the rundown main spring of the clock is being re-wound. Along with several other parts including what is called the maintaining spring, this part helps to keep the clock ticking during winding.

So I `borrowed’ a 4″ vice, brought home the butane torch, some of the gauge steel, and began to put some thought into the silver-soldering exercise.

How would I accurately hold together the tiny bits of brass while applying heat? The general idea was to make the parts fit closely to each other and rely upon capillary action to `pull’ the melting solder into place. But what about the heat-sink effect exerted by the `gripper’ holding the parts in place? Would it make sense to try holding them in a small vice or between snipe-nosed pliers? I certainly didn’t want silver solder reaching the vice or the pliers.

There was the question of whether to go for a simple butt joint between each piece, and how many pieces to split the item into in the first place.

And then there was the issue of thermal expansion which, although there wouldn’t be much movement for the size of the parts, I would still need to make allowances for some movement.

I decided for my first attempts to tackle the awkward shape of the maintaining detent and split it into three pieces with butt joints. However, after an overnight change of mind, I elected to make it in two pieces. Also on the positive side, there is plenty of thinking time when cutting out odd shapes by hand.

During the initial preparation, I decided that a flat butt joint would be more difficult to align and a two-face joint would be far stronger, hence the reason for the `V’. It was easy to cut by hand, and was surprisingly `willing’ to line up. I couldn’t imagine being able to hold this lot together and still enough while applying the relatively low-temperature butane flame, so I built a small steel jig. See my Pictures 1 and 2.

The left-hand end of the jig would be gripped (minimally) in the vice to reduce the heat-sink effect. The large hole through the middle serves two purposes. It allows enough of the gas flame to play onto the brass from underneath, and also reduces some of the heat from the right-hand end of the jig from travelling across to the vice.

Picture 3 shows the results before an initial polishing and Picture 4 is the almost finished maintaining detent on its arbor.

The lessons from this were applied to silver-soldering three pieces which make up the minute wheel cock. See Picture 5. This time however, I took a chance and held one piece of brass in the vice having first filed an oversize step in it to receive the second piece. The theory being that this step would reduce by 1, the degrees of freedom. With a weight applied to the loose piece to keep things in place, and a tiny quantity of borax spread around the joint, I snipped off about 3mm of silver-solder wire. This was placed on the extra ledge of the step. After about a minute, the borax began to spread around the joints, and after a further three or four minutes the solder suddenly melted. It’s delightful to see this stuff run around forming a meniscus where it’s supposed to do.

The same process was carried out with the second joint, before applying the necessary shapes and clean-up. As can be seen in Picture 5, this part has still to be polished.