The Superglue Chuck, a replacement for the old wax chuck.
Sometimes, when making clock and other small parts, I forget to do a second operation before breaking down the setup. On other occasions, a part has to be machined with reference to a centre that is no longer there because I have replaced it, unthinkingly, with a hole. At other times, it seems impossible to hold a thin part for machining or handwork. Many times, the ideal holding device is a step or bell chuck, see photo 1.
Like other collets, they have a limited holding range and, in any case, for most amateurs they are prohibitively expensive. I have a few that I bought in a second-hand-tool shop but rather like policemen, the size I need is never there when I want it. Over the years I have resorted to various stratagems including using a type of glassworkers cement to glue work pieces to face plates and spigots. The easiest to use is a mixture of equal parts of rosin and beeswax cast into sticks a few millimetres in diameter. The surfaces to be joined have to be heated first, touched with a stick of cement and then held together until they cool down. The hold is not especially tenacious so heavy cuts cannot be made. Also the cement melts at 50 degrees C.
THE CHUCK DISCOVERED
Recently, while browsing a friends book on clock construction, I came across the super-glue chuck. It is so simple that I thought its use should be more widely known as a solution to some difficult machining problems. It is made from any piece of metal of more-or-less the right size for the job that can be held in a chuck and faced. Aluminium seems to be preferable to steel as, although the specific heat of steel is half that of aluminium, steel is about 2.8 times as dense. This makes aluminium quicker to heat when removing the super-glue after machining. Super-glue itself is based on methyl methacrylate and sets very rapidly in the absence of oxygen. It is reasonably cheap for a small tube.
MAKING THE CHUCK
Chuck your piece of metal. It will usually be round, but can be square. Face it and make a few shallow grooves in the face about 4 or 5mm apart. Without these, the glue will not set properly. If a part is to be located from a hole, then drill through, bore and ream to size for a plug or spigot, see photo 2.
If you are locating from a big hole, it makes sense for the spigot to have a step and the hole in the chuck to be a small one, so you can reuse the chuck. Apply a drop or two of super-glue to the back of the work piece and slide it over the spigot until it contacts the face of the chuck. Hold for a few seconds and remove the spigot or push it through into the bore of the lathe spindle. If you do the latter, retrieve it with a magnet on a stick so it does not annoy you by rattling, or score the taper in the bore, photo 3.
Within minutes, the bond will be strong enough for you to machine the part. Maximum strength is reached after about twelve hours. Do not get glue on the spigot, especially if you need to work on the bore of the part and do not get it on your fingers, as it will stick them together instantly. It has also been known for eyelids to be stuck together with super-glue, so I suppose I should add that you should wear goggles as a precaution.
EXAMPLES OF USE
Photo 4 shows an hour wheel bridge for a table clock that could have been machined using a rather uncertain set up with a four-jaw chuck, but probably at the cost of losing concentricity of the outside of the pipe. The hold was strong enough to machine the feet by turning rather than by milling, but I took only light cuts of a millimetre at a time and left the spigot in place to give extra support to the pipe.
Photo 5 shows the hour wheel itself. The teeth were cut holding the blank on a mandrel with a 4mm diameter bore. With the super-glue chuck, it is easy to re-centre the wheel and bore it out to the required 12.5mm, knowing that the bore will be square to the face. In this case, I used a piece of square aluminium scrap for the chuck and left the business end square.
CENTRING A TOOL EDGE
Sometimes it is necessary to locate a tool with reference to the centre of the work piece. To this end, when making the spigot you need to turn a sharp point on the end. Then, using a hand lens, you can locate the tool edge on centre and then reposition it using the cross slide index. Photo 6 shows where a trepanning tool is being positioned to cut a groove of the correct radius in the Vulliamy pallets of a dead-beat escapement.
It is worth noting that the correct use of a hand lens, with the lens close to the eye gives you a clear and undistorted image.
When you have finished machining, mark the super-glue chuck opposite jaw number one. My three-jaw chuck at least will hold work repeating to within 0.02mm so I dont have to bother to re-bore or re-face it each time unless doing very critical work. An old trick to find out which key position gives the best concentricity with a three-jaw chuck is to use a piece of ground bar and a dial indicator. I mark the best key position with a dab of red paint, which can be seen in some of the photos. To remove the work piece, simply heat up the super-glue chuck until the glue gives way. With brass, it seems to happen at a temperature where the marking-out blue loses its colour. A few strokes on a piece of 300 grit paper on a flat surface removes the glue residue from the work piece and the super-glue chuck itself. The chuck then lives on to be used for another day.
If you do accidentally glue your fingers together, try slowly peeling them apart in warm soapy water. This does not work for eyelids, but they usually become unstuck of their own accord within a day or two.