Question for Clockmakers about oilsinks

I'm just completing my first clock - an 8-day skeleton. I want to make oil sinks for the pivots in the plates, but I have no info about size and shape. Looking at photos of other skeleton clocks, the oil sinks seem to have a maximum diameter around 3-4 times the pivot diameter, and a depth of 1-2 times the pivot diameter. All those I've seen also appear to have been cut with a round nose cutter.

I'd be very grateful if one of the clockmakers in this group could give me some guidance on preferred sizes and shapes for oil sinks, and tips on how to cut them (i.e. what kind of tool).

Incidentally, the plates on my clock are 4mm thick, and the pivots vary from 6 mm at the barrel, to 1.2 mm at the escape wheel.

Mike

Reply to
mike.crossfield
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Mike -

I believe that oil sinks in clock plates are one of those "that sounds like a good idea" kind of things that really isn't terribly useful. In reality, if the oil is thick enough to "stay put" in an oilsink, then you probably don't want it near anything more delicate than the back axle of your truck. Clock oil has a nasty tendency to creep across the surface of plates pretty rapidly by capillary action, and putting an oilsink around the pivot doesn't stop that happening.

So, if you want to do them for decorative reasons, or because it is traditional, then go ahead, but don't feel that you have to do it for any other reason.

Regards, Tony

Reply to
Tony Jeffree

The usual tool has a hardened steel disc pivoted at the end of a slit rod. You can buy sets of these

Bergeon do a set

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As supplied they are designed to be used by hand, probably after rebushing. Some people saw these double ended tools in half so that they can be used in a drill press.

However I, for one, usually make my own. If you take a bit of silver steel and turn the end hemispherical (usually I do this with a graver on the T rest) and then file from both sides to make a "slice", followed by more filing to give clearance to the cutting edge, then harden and temper to a straw it works fine. I usually size them on an aesthetic basis by comparing with a similar clock.

I'm sure it goes without saying that the pivot length must be such that the end is proud of the bottom of the whole with endshake fully taken up. Otherwise in no time at all the pivot will wear into the side of the hole.

Alan

Reply to
Alan Bain

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Thanks Alan

I note Tony's comments, but since oil sinks can only have a beneficial effect (as far as I can see), and they are traditional, I want to know how to cut them.

I've seen the Burgeon roller cutters advertised, but they only come in sets which are rather pricey for what will be very limited use. I'm also surprised they are efficient, since there is presumably no relief on the cuttng edges. Your cutter design clearly gets around this. I had thought about making a D-bit with a hemispherical end, but since your design works I will give it a try.

Mike

Reply to
mike.crossfield

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You are right that they don't cut efficiently, nor do they centre themselves well over a pivot hole. I solve both problems by cutting most of the brass away with a twist drill in my fingers, then dress the hole with the roller cutter.

As for size, aim for a width that looks right and will hold enough oil, and a depth that will leave the active length of pivot approximately equal to its diameter. Despite Tony's reservations about the value of oil sinks, they do hold the oil in place providing they are not filled up. (If you can actually see a drop of oil in the hole it is too much.) My suspicion is that oil sinks, originally a French idea, were designed to provide square proportions to the pivot hole rather than act as oil resevoirs, but the latter property was found to be a useful bonus.

Cliff Coggin

Reply to
Cliff Coggin

Thanks Cliff, that's very helpful.

Mike

Reply to
mike.crossfield

Mike -

One of the questions I have had in the back of my brain about clock lubrication is whether it has any real benefit. There are a number of aspects to this:

- In some parts of a clock train, the power being transmitted is extremely small, and factors such as oil viscosity may well outweigh any lubricating property the oil may have

- If you are using leaded (engraving) brass for the plates, then a well-made hard steel pivit should run with pretty low friction anyway, regardless of whether oil is used

- Oil acts as an excellent trap for dut particles, so over time the oil becomes lesse ffective as it turns into a grubby paste, with not terribly good lubricant properties

- Oils tend to thicken over time as they oxidise

So if you feel the inclination to do so, it would be an interesting experiment to try measuring the difference in running friction in your clock train with and without lubrication. This should be simple enough to do - temporarily run it as a weight driven clock (I assume it will eventually be spring driven?) so that you can determine what force is needed for the clock to run without oiling, then do the same after oiling the pivots.

Regards, Tony

Reply to
Tony Jeffree

Not built one meeself...

If you have not seen the Laurie Penman book on clock design and manufacturing, it's worth a look. If I recall correctly, he discusses the issue at some point.

For the most part, though, these are going to be as much an esthetic addition as a practical one, or even more esthetic than practical.

I would think that a D bit cutter, carefully ground to radius, and quite scary sharp would be the tool of choice.

Cheers Trevor Jones

Reply to
Trevor Jones

I have built a couple of clocks, but am really more interested in LDT Sterling engines, and have been struggling for years with the _oil_ to use for these types of mechanism, which have very little power to spare. In my experience the "Clock" and "Watch" oils generally available, may reduce friction fine for a relatively short time, then (presumably as something evaporates) actually cause viscous drag. In the LDT Sterling application I find that "dry" bearings (leaded brass, or solid graphite, with well polished surfaces) work much better. I'm not sure what that would mean to a clock which might be expected to work for decades if not centuries - I don't suppose my LDT engenes will be of any interest to anyone in couple of decades!!

Anyone got any thoughts about the sort of oil to use ?

Mike D

Reply to
Mike D

Tony,

Some interesting observations.

Since this is my first clock I have so far simply been following accepted wisdom, and assuming that lubrication was essential. I take your point about oxidation etc, and contamination degrading the oil, but if the oil is regularly replaced I would expect it to be far better than running the bearings dry. Certainly I wouldn't dream of running my Super 7 lathe without lubricating the headstock bearing, and that has a hardened spindle running in a bronxe bearing. A somewhat larger scale than a clock, but why should the same principal not apply?

Mike

Reply to
mike.crossfield

Thanks Trevor. I'll try to get a look at the Penman book you mention.

D-bits seem a good solution, As someone else suggested, starting off with an ordinairy twist drill would be helpful for centring.

Mike

Reply to
mike.crossfield

Think you are meant to remove movement and put the movement horizontal ...and the reservoirs then let the oil get into the bearing surface.

that's what i do when oiling a clocks ...

30 Min's on one side ...30 Min's on the other ...

observations after.....the clocks definitely slowed down after oiling ...and had to tweak the weight for weeks after .

all the best.mark

Reply to
mark

Is camellia oil any good for this kind of application?

Reply to
Charles Lamont

Very droll. What about fitting nipples so you can connect a gun and squirt grease into the pivot holes at 200 psi.

Cliff.

Reply to
Cliff Coggin

Tony,

I wasn't going to respond publicly because whatever I write (and no matter how I write it) it's going to look like I'm poo-poohing another's legitimately held opinions (which we are, of course, all entitled to).... but I have to say the notion that oil sinks are nothing more than some archaic hang-over from ill-informed past times was bad enough.... but to suggest that a clock might not need lubricating at all is, (I'm sorry) just plain 'sillyness'. You may (probably would) get away with it on the low speed barrel or fusee, in fact it is fairly common to leave the barrel and fusee arbors dry if the finish is of high quality, (and in that instance the oil sink does become redundant)... but for the rest of the clock... the answer to is it safe to run it dry.. is 'no'. By all means though if you wish to build a clock yourself and run it dry (or 'attempt to run it dry' might be closer to the reality that will ensue), then that might indeed be an interesting experiment for you to undertake, .... but I wouldn't advocate it for anyone else on a clock they have spent months making.

T>

.=2E.. errrr ... yes Tony possibly ... IF you are using (relatively) cheap generic industrial oils... but that's why we have specialist lubricants in horology that cost the anything up to the equivalent of =A310,000, or more, a litre. They have been developed specifically to overcome the special-case issues involved in horology.

.=2E.which is why you should regularly clean and lubricate ANY mechanism ... do you not change the oil in your car as it degrades.... what about the oil in your lathe headstock....???

Of course it degrades... that's when you clean the clock and apply fresh oil.... but that's not a reason for not using it.

.=2E...see above comment .... same response....

.=2E..ouch!

.=2E...........ouch!!

.=2E.....................ouch!!!

|:-{

MIKE..... Cliff's suggestion of using a drill as the pilot for your oil-sink is of course the bit (ouch .,.. no pun intended) I left out of my reply to you. Use it sparingly though so that you don't go too deep.

Ian

Reply to
ticktock

well thats me ...like to make sure ...all the old contaminated oil is flushed out and is replaced with new ... :)...i do wipe off any excess after.

each to his ways ..

all the best.mark

Reply to
mark

Interesting...well at least that confirms that the oil was doing some good (more power transmitted to the escapement = bigger angle of pendulum swing = longer period of oscillation).

Regards, Tony

Reply to
Tony Jeffree

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