bone for a bridge patch or a patch inlay?

[Bob Hammond]

Hello,

Has anybody ever used bone for a bridge patch, or as an inset/inlay in a wooden bridge patch?

What are the opinions about that?

[Clay Schaeffer]

Hi Bob,
My thoughts would be that it might be too stiff and may not glue as well as wood to wood would. It might also chip more easily (brittle) when drilling and from the ball ends of the strings. Weight might be another concern, but probably not a big one.
It might be an interesting experiment, and could be replaced if it didn't work out. I would be interested in hearing your thoughts on it.

[Bob Hammond]

Clay, this notion came after a I made a bridge patch from ipe, that is one of the hardest woods known. Since it is very tough and resistant to machining, I made the patch thin, and I liked the sound. So I began to think of other hard materials, and bone came to mind.

Ipe, aka 'brazilian walnut' , is not an endangered species and is used for flooring and decks (I made the patch from piece of tongue & groove). I think it could be used for fingerboards also, but the particular piece that I have is olive brown in color and that doesn't appeal to me. And it's quite true that it is a tough wood to machine. It was difficult to saw with a thin asian pullsaw and it had a slippery feel when I handplaned it.

As for drilling and gluing bone, I've been considering how to do that. It may be, that a drill bit might do better with a different geometry. The orthopedic surgery literature indicates that point angles of 118 to 90d might better, but that's for drilling through living bone and tissue. I've also thought about using a traditional method for drilling glass or tile, which entails using a metal tube and abrasive grit. I'll give it some more thought and do an experiment on a saddle blank.

[Bob Hammond]

Oh, and for gluing, good old hot hide glue holds the nut in place just fine, and I think it would work well for a bridge patch/inlay. Also, the string tension would keep it clamped too.

[David King]

Bone has a grain to it and having all the strings lined up parallel to the grain could result in a fracture. I wouldn't worry about drilling bone, my preference would be to use a slow spiral drill with an 118º point. Just make sure you have a backer board underneath. The stuff is very brittle and not all that strong if you try to bend it.

[Barry Daniels]

I have been grinding my drill bits cutting faces so they are parallel to the drill bit. This is the preferred angle for brass because it makes a less aggressive, scraping type of cut. It also seems to work well in other materials like hardwood and steel. I am sure it would work well in bone too which has a consistency not unlike brass. Grinding the bits is easy with a dremel cut off disc.

[Bob Hammond]

Barry, I'm not sure I'm getting it right. Are you grinding the bits at 90d relative to the longitudinal axis (a transverse grind), and maybe with a slight center point? That's is an old trick that ham radio guys did to cut holes in a sheetmetal chassis That will work up to about 1" diameter.

[Bob Hammond]

For once, I have the proper tool for the job and don't need to improvise. This item was discarded when high quality battery powered drills became available. it's machined aluminum, with a precision Jacobs stainless steel chuck with a rotation lock and an adjustable depth stop, and it's autoclavable.

[David King]

No you want to grind parallel to the length. you just knock the leading edge angle from whatever the spiral angle is to about 90º. I do it with a small diamond hone. It will work on split point drills as well as the regular 118º tips.

Cool bone drill!

[Bob Hammond]

Yes it's a well-balanced beauty. the chuck key is stored in the grip, and the tool can be easily reconfigured for Lefties. The rotation 'safety' lock button is placed conveniently under the thumb. It's an example of superior handmade workmanship. I'd guess it's about 40— 50 y/o.