Lubrication
  • The Primus was my first attempt at using a scroll saw (or making a clock) and so the cogs were not particularly fair and needed a great deal of tidying up work. Perhaps I should have practiced on something less critical first. After many hours of sanding and filing teeth, I could get the clock to run for up to 10 minutes at a time, but had a 4+kg weight hanging on it. In desperation, I sprayed some CRC Dry Glide (P.T.F.E. – i.e. Teflon) on all of the cog teeth, arbors and arbor holes and was delighted to see that the clock was still running next morning. I have since reduced the weight to 3.4 kg and it still runs non-stop.

    The advantage of this type of dry lubricant is that it does not stain the bare plywood I used for the cogs (although I would recommend applying any varnish finish to the frame before using the spray) and as it dries to a dry surface it will not attract dust. It is used extensively on yachts and so should be readily available from any marine shop.

    This method of lubrication might be useful for those who are about to give up on ever hearing that elusive tick, or who are struggling to decrease the weight required to run the clock.

    I am now a little more skilled with the scroll saw and will no doubt make a better job of cutting out the cogs next time

    Tony Barker
  • I think the two things that really helped my clock (septimus) after I had similar problems in getting it to run for more than a few mins - was a) removing the arbours, putting them in a drill and polishing them with fine sandpaper, and b) adding the weight and allowing the clock work to run through without an escapement - this latter seemed to help force everything into the right place and iron out the kinks. Once I'd done both of those, the clock worked without problems,
  • I have two suggestions, both of which have worked for me.

    1) When I was building my first clock, I was advised to polish the shafts with polishing compound. I bought a set of blocks on Ebay, one of which was specifically for brass (it is a blue colour). With the shaft in the drill press, I go through the polishing steps as recommended by Dave, and finish off by rubbing the compound onto the shaft, and buffing it off with a rag or piece of paper roll. It gives a high gloss. When I was building the Sextus, I could get the pendula to swing for over 2 minutes by polishing the shafts in this way.

    1) Another method for use on wooden bushings is to use graphite powder. This is easily available cheaply on Ebay. Dip the tip of a fine artists brush in white spirit or some other volatile solvent, then dip it in the graphite powder to pick up a small quantity, then carefully paint it onto the contacting surfaces. The theory is that the solvent will evaporate, leaving a very slippy surface. No guarantees, but it has worked for me.
  • Just finished last cog on Primus, all arbors run in bearings and noticed on this one the arbor runs within the inner bearing as opposed to the bearing spinning. Would it be best to glue the arbor to inner bearing (nothing too strong) and let it do the work or lubricate arbor and let it spin within ? Its either down to different brass stock or over finishing shaft. I have graphite powder and looking into other dry lubes as well. A very slight finger pressure on shaft will make bearing work so we are only talking a very very slight gap.
  • @Paul

    Another good way of getting graphite into a bushing is to use a soft sharp pencil, just "draw" around the bushes walls until you have an even coating. Graphite is an incredible lubricant, but messy as hell :-)

    @ George

    All bearings have a certain inertia, and if your arbor is turning freely in the bearing without moving the inner ring then that just means that the arbor turns with less friction than the bearing would, so gluing the arbor to the bearing would be very much counter productive.

    For heavy load situations such as the drive arbor where the weight hangs then bearings are definitely the way to go as they offer a constant predictable amount of friction, but the less load on the arbor the more the bearings become redundant, as the inertia of the bearing is greater than the load of the arbor.

    But having said that, bearings are far superior to bushes as they allow for movement in the frame, when an arbor, because of frame sag, no longer centers in a bushing than it can lead to clamping, and where that ends we all know. A bearing however will keep turning.

    So to summarise, ball bearings for heavy loads and the rest in generous frame holes, and stay away from bushes.