What about oiling the drones?
Oiling is one of those issues that causes heated arguments. There is a "maintenance" side to oiling, discussed in this note, or a "refurbishing" aspect to oiling, discussed here. This latter reference should be read if you bring an unused set up pipes back to life.
As a maintenance issue - on a well conditioned, frequently played, well cared for pipe, not exposed to extremes of heat or humidity- you probably don't "need' to oil it. However, if you occasionally leave your pipe in the car, near a radiator, play in high humidity/rain or leave you pipes unplayed for a few weeks or more - you might want to oil them.
If we consider "oiling" to be an "answer", the underlying "question" is usually, "how do I prevent my pipes from ever cracking?". Let's understand the issue...
When you play, you put very humid air into the inside of your instrument. If the moisture is absorbed by the wood, the wood will swell to accommodate the molecules of water. Only the wood near the bore will swell, not the rest. This creates a stress in the wood which can result in a crack or split.
(Note: The part most often affected is the practice chanter top. This is why wooden PC tops almost always crack. On the pipes, the blowstick, the blowstick stock and (if you don't have a tube type water trap) the chanter stock are most likely to be directly impacted by the humidity from your lungs. Drone stocks and bores are generally affected indirectly through water condensation by playing outside when the relative humidity is very high. )
Although it is sometimes presented that oil creates a layer on the surface of the wood so that moisture can't get to the wood - more correctly, moisture can only get through the oil and into the wood "slowly". This lets the wood swell slowly. As long as the rate of swelling is slow, moisture can migrate through the wood and allow the entire piece to swell slowly. In this way there is minimal stress built up in the wood and minimal internal forces to cause a crack.
Let's first understand that we want a layer that moisture cannot easily/rapidly penetrate. This can be done in a variety of ways. In the commercial world, the most obvious approach is "paint" or varnish, but, at first glance, no manufacture would want to do that! So, various products are used including petroleum based oils and waxes, biologically derived oils and waxes and silicone oils. There are rumors that under very controlled conditions, thin plastic films and reactive silanes or polymethacrylates are used.
Commercial woodwind bore oil is often simply a particular viscosity of mineral oil. This is a simple hydrocarbon (paraffin) mixture like common motor oil. It is rather incompatible with wood and only coats the very surface. It basically never dries and seems to loose its effect after several weeks.
Oils which are biologically derived from natural sources (i.e., almond, tung or linseed) may be slightly more "soluble" in wood, but when spread out in a thin layer, will cross-link and "dry". Historically, many of these oils have been used as the basis for paints, which again emphasizes the permanent nature of some of these coatings. Drying is the result of the oxidation of the fatty acid esters in the oil into a moisture resistant, cross-linked network. Oxidation happens when you expose the oil in a thin layer to oxygen from the air. Antioxidants (a.k.a. preservatives), such as vitamin E, are sometimes added to increase shelf-life, but upon spreading over a surface these antioxidants rapidly overcome by the amount of oxygen in the air. Once the antioxidant is overcome, the oil will "dry". (The anti-oxidants do help with shelf life issues.)
Paraffin waxes or biological waxes are just higher molecular weight versions of petroleum and biological oils, respectively.
My advice would be that commercial bore oil won't hurt and can be applied once or twice a year. I'd go with the spring and fall. It is applied with a soft cloth or swab.
There are various "specialty" products out there that purport to do many wonderful things. There are arguments over mineral oil vs. almond oil vs. sweet almond oil with and without vitamin E. Once you understand that any of these products are intended to minimize the rate of uptake of moisture so that the wood doesn't swell, you've got the important bit. My feeling is that any oil that can crosslink will last longer than a similar viscosity of a non-drying oil. On the other hand, not everyone wants a permanent modification of their bore.
It would be irresponsible to not relay that there are anecdotal stories that oiling caused old drones to crack during refurbishing. However, I don't see any reason why oil should cause drones to crack and suspect that 1) insufficient oil coverage/penetration was provided followed by 2) uptake of moisture and 3) stress build-up inside the wood. Drones which are already cracked, but not humidified will reveal their cracks upon humidification. Humidification of the drone from a very dry state results in some expansion of the wood. Oiling cannot prevent an existing crack from opening up. (Personally, I don't believe that soaking a piece of wood in oil will substantively correct a crack, either.)
Some very good references include:
Copyright S.K. MacLeod 1996-2013