BTW, as I mentioned.....Walnut Oil can be found in any well stocked health food store, large stores with a "Gourmet" section, possibly, Trader Joe's, etc. It is used primarily to dress greens and salads. It's always sitting next to other specialty oils, e.g.....Avocado, Olive, Grape Seed, Flax Seed....etc....all food-grade oils...so nothing toxic is in them.
Oils used for furniture/wood finishes like Formby's/Minwax, etc, contain spreaders, resins, siccatives/dryers, colorants, and God knows what else. I would not use it on any part of a briar/wood/Meerschaum pipe. Just the fumes coming off a hot pipe would turn me off. Who wants to smell paint/varnish/resins while sipping some smoke?
One caveat....organic oils can and do go rancid after many months/years, especially if kept in a warm storage area. closet, garage.... Keep your oils in a cool/dark storage area, even in a refrig'. Walnut oil is delicious when used to dress fresh salad greens, so just use it for it's intended purpose. It's cheap, always available, and you'll not need very much for your pipes.
BTW, Pure, UNPERFUMED, Cocoa Butter works just as well. It must be raw, pure, unrefined, and contain no scents/perfumes/fragrances, skin/hair lotions, essential oils. Pharmaceutical grade = 100% Cocoa Butter.
Try: (Bulk Apothecary.com) for waxes, oils, etc....but, there are other sources for these products.
Frank