Hi Jackie et all, An interesting question! I have made compasses for replica dials and found it more difficult than I expected. If you want a quick answer, it would be to buy a cheap compass and pull it apart so that you can re-case it and make an appropriate compass card but keep the same needle and pivot. If you want to make your own from scatch, the first thing is to kind suitable steel for the needle. Too 'soft' and it won't retain the magnetism, too 'hard' (like most stainless steels) and it will be impossible to magnetize. I found a piece in my junk box so I don't know its spec. To make the needle, drill the centre hole first and then cut the needle to shape around it - using a Dremel or, if you want to be authentic, a jewellers saw with a very fine blade. The pivot has to be non-magnetic: brass being the obvious material. Really old portable dials have a pyramid-shaped pivot but I turned mine on a watchmakers' lathe. The actual suspension point needs to be significantly higher than the level of the needle. The conical hole is a tricky thing to drill.... Ideally, the pivot should be a jewel but I've yet to find a suitable source - anyone got any suggestions? The pin can be a piece of pianowire ground and polished to a sharp point. I use a solenoid to magnetize the needle. You will then need to balance it for the local angle of magnetic dip, so that it hangs level. Either carefully shorten the 'heavy' end or use a blob of wax or soft solder underneath the light end.
Good luck, John ----------------------------------------------------- Dr J Davis Flowton Dials --- On Wed, 4/7/12, Jackie Jones <jac...@waitrose.com> wrote: From: Jackie Jones <jac...@waitrose.com> Subject: making a compass To: sundial@uni-koeln.de Date: Wednesday, 4 July, 2012, 13:35 Hi All, I would like to make a small (probably about 1.5 - 3cm diameter) compass for a sundial. I have not made one before; I’m sure many of you have, can anyone give me any tips and instructions please. Many thanks, Jackie Jackie Jones 50° 50’ 09” N. 0° 07’ 40” W. -----Inline Attachment Follows----- --------------------------------------------------- https://lists.uni-koeln.de/mailman/listinfo/sundial
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