Working small bone pieces

Construction and repair of Classical Guitar and related instruments
Dave M
Posts: 226
Joined: Tue Aug 05, 2014 1:39 pm
Location: Somerset UK

Working small bone pieces

Post by Dave M » Wed Nov 01, 2017 9:11 pm

I was preparing the bone pieces to act as wear strips on a classical today. And it really is a bit of a struggle. Even a fairly high TPI bandsaw leaves a very ragged edge, and trying to keep the faces at right angles is difficult with such small cross sections - about 1.5 mm square with a length of around 70 - 80 mm.

I have made up various holding jigs but they haven't been particularly satisfactory.

I wonder how other people manage this?
Dave

User avatar
Trevor Gore
Posts: 914
Joined: Sun Aug 07, 2011 12:57 pm

Re: Working small bone pieces

Post by Trevor Gore » Wed Nov 01, 2017 10:11 pm

I've just done a batch of these. I went for 2mm square, 100mm long. I used a fine tooth metal working blade (think junior hacksaw) in my bandsaw, and a zero clearance insert. I started with thinned down saddle blanks. I re-flattened the edge before each cut, so there's always at least three good sides when the strip comes off. The fourth side is flattened with a few swipes on 240 grit paper.

I've done them before on my mini-table saw. That works well too, leaving clean edges, but takes a wider kerf.
Trevor Gore: Classical Guitar Design and Build

OldPotter
Posts: 1744
Joined: Thu Dec 06, 2007 7:31 pm
Location: Channel Islands

Re: Working small bone pieces

Post by OldPotter » Wed Nov 01, 2017 10:25 pm

I haven't machined such small sections but do use a sledge/vice/holder to pass saddles etc under a sanding drum. I saw the stewmac luthiers friend sanding station. Its basically a sanding drum fitted to a drill press, they also supply a holder for the saddle (or whatever part). I made my own version and ended up making a miniature thickness sander. The important part is the holder. It means you can hold a thin part and sand it flat to fairly small dimensions. If the holder is well made it also means that you can get 90 degree corners.
It would also be possible to use their nut and saddle sander. Fairly expensive though.
You can use a grade of sandpaper to give you the finish you want. I can't remember what grade I used, probably around 80 grit.
Apologies if describing this in words does not make sense, perhaps have a look at their catalogue pictures and it will all become clear.
"When I was younger, I could remember almost everything, whether it happened or not." Mark Twain

Jim Frieson
Posts: 508
Joined: Mon Jan 24, 2011 12:48 pm

Re: Working small bone pieces

Post by Jim Frieson » Thu Nov 02, 2017 7:25 am

No sanding device ? One can still work bone . With a hand plane and a small shooting board . To do edges it is a simple matter to cut grooves of various widths in a block of wood , with a stop at one end , as holding device . To maintain a perpendicular angle , plane two pieces at the same time , spaced apart for the plane to sit on , one can be of wood .

gjo
Posts: 267
Joined: Wed Sep 16, 2009 8:48 am

Re: Working small bone pieces

Post by gjo » Thu Nov 02, 2017 8:37 am

Circular saw with a fine toothed 0.6 mm jewellers blade on reduced speed works perfect for this job.

chiral3
Posts: 1720
Joined: Mon Sep 19, 2011 7:08 pm
Location: Philadelphia Area, PA / New York.

Re: Working small bone pieces

Post by chiral3 » Thu Nov 02, 2017 2:41 pm

Byrnes saw followed by sander. I built a sanding jig that's basically a small routed channel to hold the pice while sanding. Real bone smells horrible in the saw.
物の哀れ

Douglass Scott
Luthier
Posts: 489
Joined: Fri Nov 09, 2012 5:44 pm
Location: Ladysmith, Canada

Re: Working small bone pieces

Post by Douglass Scott » Thu Nov 02, 2017 3:31 pm

I do same as Trevor, but instead of a super fine tooth blade, I just use a super thin kerf regular woodworking blade at 14tpi and 0.5mm kerf. It's one that I use only for bone, since bone kills a sharp blade very quickly. I also put high grade masking tape on the bottom of the saddle blank before sawing to reduce chipout - this way the table insert doesn't have to be 0 clearance. The one rough sawn edge of each strip faces up when glued into the bridge and they get smoothed down when shaping the tie block.

Alan Carruth
Luthier
Posts: 2662
Joined: Mon Dec 24, 2007 6:56 pm

Re: Working small bone pieces

Post by Alan Carruth » Thu Nov 02, 2017 8:18 pm

Like Jim, I use plane jigs for this sort of thing. Mine may be a bit more sophisticated than his, and I use the same sort of setup to make rosette parts.

Take a piece of wood and glue a couple of rails to it just far enough apart so that your block plane will run in between them. Plane away at the wood for a while and the plane will stop cutting once it takes enough material off so that it's riding on it's side rails. Now, rout a pocket in that surface, and drop in a piece of bone or wood that sticks up. When the plane stops cutting the piece will be exactly the same thickness as the depth of the pocket.

I first saw this being used to make bone saddle pieces. I'd been trying to think of a way to shape pieces of wood to fit together and make a braid pattern, and this was the key. It's the technique that was used a hundred or more years ago to make bamboo fly rods: you make six triangular strips of bamboo and glue them together to form the hexagonal shaft. The strips can be tapered to an exact profile for the flex you need.

For bone tie block strips I will use a plane jig to thin out a piece of bone to the appropriate thickness. On edge is squared up on a shooting board, and a small hand saw is used to cut a narrow strip off the edge; a jeweler's saw works well. Then you square up the edge and have at it again. The strips are made a bit wide, and trimmed up with a file after they've been glued on.

I'll note that I've had much better luck planning bone with my old Stanley block plane than with the newer ones that have harder irons. The Stanley has softer steel which doesn't chip as easily, so it actually holds an edge a bit better. I put on a pretty short bevel for this (since it's a block plane the bevel is up, and there's no chip breaker). Then I put a small back bevel on the bottom at about 3 degrees which helps back the edge up better. You do have to touch up the edge from time to time, but it holds up surprisingly well.

Dave M
Posts: 226
Joined: Tue Aug 05, 2014 1:39 pm
Location: Somerset UK

Re: Working small bone pieces

Post by Dave M » Thu Nov 02, 2017 10:06 pm

Thanks everyone. Although I was sort of aware of most of these techniques I was more used to applying them on a larger scale. But yes the same principles apply at this smaller scale.

So I need to improve my jig making, and the fine-ness of my cutting tools as well as the general organisation of the task.

This reminds me of a thread - I suspect on another forum - about the skills needed for guitar building and I am again reminded that you can't coast, you have to constantly think about the task in hand and consider the results you are going to get using a given technique. The technique might be correct in general but may need serious refining given the tighter tolerances required for instrument building.

And yes we really do not like the smell of bone being machined. It is exactly what the dentist does to our teeth with their horrible drills!
Dave

User avatar
Trevor Gore
Posts: 914
Joined: Sun Aug 07, 2011 12:57 pm

Re: Working small bone pieces

Post by Trevor Gore » Sat Nov 04, 2017 12:19 am

gjo wrote:
Thu Nov 02, 2017 8:37 am
Circular saw with a fine toothed 0.6 mm jewellers blade on reduced speed works perfect for this job.
If you don't mind me asking, where do you source your blades? TIA.
Trevor Gore: Classical Guitar Design and Build

gjo
Posts: 267
Joined: Wed Sep 16, 2009 8:48 am

Re: Working small bone pieces

Post by gjo » Sat Nov 04, 2017 7:05 am

Trevor Gore wrote:
Sat Nov 04, 2017 12:19 am
gjo wrote:
Thu Nov 02, 2017 8:37 am
Circular saw with a fine toothed 0.6 mm jewellers blade on reduced speed works perfect for this job.
If you don't mind me asking, where do you source your blades? TIA.
Either in a jeweler´s supply or from the metal trade with a diameter of max. 100 mm. Larger blades tend to "flatter" very quick

I had them coated with TiAl... and they can be used forever, at least more than a year and I cut a lot of everything - bone, mosaic tiles, purfling, binding, etc. - with the same blade.

chiral3
Posts: 1720
Joined: Mon Sep 19, 2011 7:08 pm
Location: Philadelphia Area, PA / New York.

Re: Working small bone pieces

Post by chiral3 » Sat Nov 04, 2017 3:10 pm

Try Victor Machinery also. I also have a few from Byrnes himself.
物の哀れ

User avatar
Trevor Gore
Posts: 914
Joined: Sun Aug 07, 2011 12:57 pm

Re: Working small bone pieces

Post by Trevor Gore » Sun Nov 05, 2017 12:37 am

Thanks, gentlemen.

"flatter" = flutter?
Trevor Gore: Classical Guitar Design and Build

Jim Frieson
Posts: 508
Joined: Mon Jan 24, 2011 12:48 pm

Re: Working small bone pieces

Post by Jim Frieson » Sun Nov 05, 2017 7:43 am

From the odds and sods department .
Pictured blades are slitting saws , 0.20 " approximately .5 mm .
Spacers of wood are 2.5 mm
I made this tool for cutting bone and pearl , don't use it much because of the set up time , but it works .
DSCF6770.JPG
DSCF6775.JPG
You do not have the required permissions to view the files attached to this post.

gjo
Posts: 267
Joined: Wed Sep 16, 2009 8:48 am

Re: Working small bone pieces

Post by gjo » Sun Nov 05, 2017 8:32 am

Trevor Gore wrote:
Sun Nov 05, 2017 12:37 am
Thanks, gentlemen.

"flatter" = flutter?
Sorry, I used the german word "flattern", "wobble" might be better !?!?

Return to “Luthiers”