Bone (antler, horn) is the traditional material of choice for bone folders as well as tool handles , where a durable, relatively impermeable material is needed. As a material, bone has interesting properties. It is very anisotropic, meaning that the material behaves differently when worked or stressed in different directions. Wood is a good example, behaving differently when cut with (rip) or across (crosscut) the grain and splitting readily along the grain but not not across it. Bone behaves much like wood, prone to splitting along the long-axis of the bone but not across it. In addition, bone is thermoplastic- with heat it can be deformed and will retain its shape indefinitely when cooled.  Today, Teflon or other synthetic materials are used to produce folders of great durability, but traditional bone folders are still readily available and widely used. 

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I purchased a cleaned, bleached bison bone online rather than obtaining raw bone or antler. (I suspect this is why I remain married...)  I had intended to make full-size (6" long or so) bone folders.  However, as I worked the bone on my bandsaw it became obvious that it had stress cracks in the long dimension. The marrow cavity, which consists of spongy bone, also was very irregular.  In the end, I was able to obtain a number of smaller-than-desired bone sections.  

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As the purpose of the project was to learn, I decided to go ahead and make what I could. This resulted in a set of small folder and probes which in fact are quite functional and I have used them on several binding projects for small pamphlets and for probing and introducing adhesive into narrow spaces. Bone sands and polishes very nicely. 

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Learnings: 

• The isotropic nature (see above) of bone is very pronounced. 

• I do not know if the bones of other species/horn/antler or even other bison bones that have been differently processed would be less prone to splitting or have less prominent marrow cavities. 

• Bone cuts well on the bandsaw. Final shaping and polishing appears to be best accomplished by hand or machine sanding (I have a belt and a drum sander).

• NOTE: Bone dust is NASTY STUFF... very fine and mobile and very irritating as well as possibly an allergic sensitizer.  Wear a respirator and use a vacuum system if available for cutting and sanding.  (I built a hood from a cardboard box to go over my belt sander and connected it to my shop-vac specifically for this purpose.)

• Final finish can be accomplished with 400-600 grit abrasive paper or polish, followed by a coat of hard wax to eliminate any residual porosity. 

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Worth it??   Nah...  unless you want to mass- produce and sell, you are probably best off buying Teflon or bone/antler folders as needed by the time you go to all this trouble!