Monday, May 24, 2010

Dirt Cheap, Super-Simple Thickness Sander

Wouldn't it be nice to own one of those big wide belt thickness sanders? My tiny shop just doesn't have the space. Maybe one day.....

With the number of lute ribs I'm preparing these days, hand planing was becoming less and less efficient. I thought about putting a sanding drum on my drill press but so much axial pressure that would cause an inordinate amount of wear on the bearings. Building a traditional sander with adjustable table seemed costly, time consuming and again - there was the space issue.

I was in my local building center and spotted this little oscillating spindle sander on sale for $120. It's a Rockwell Shop Series. The sander comes with a variety of spindles. It's light enough to move around easily for storage.

I installed the largest spindle, popped on an 80 grit sleeve, planed a length of pine square and straight, and put it to work.

One nice thing about this machine is a dust port which is the correct diameter for my little 6 gallon Shopvac. I don't even have to take the wand off - it just slips in place. The vacuum is perfectly adequate and this means I don't have to find room for a large dust collector.

I feed the stock against the rotation which presses it firmly against the fence. I suppose one could set up some feather boards on either side of the drum but I haven't found it necessary. The 2" staves come out uniform and there isn't any propensity to kick back.

I stand on the fence side and use both hands to feed, one on each side of the drum wearing some grip tape on my index fingers for safety and comfort. In the photo you can see a second board clamped against the back of the fence. This allows me to accurately increase the sanding depth. To do this I loosen the fence clamps, insert two business cards, re-clamp, and finally move the rear positioning block back into place.
Works great!

Tuesday, May 18, 2010

In Which Ted Finds Splitting Hairs Would be Easier

This morning I had a frustrating experience. I've decided to make the next lute bowl of Macassar ebony. Some time ago I'd come across a stick of this rare material at the local exotic wood purveyor. My tape measure told the tale... the board was just large enough in all dimensions to yield the 14 pieces needed.

Ebony is a rare substance. It's hard, heavy, black, and it's always been glorified by those who work with wood. In fact, the French word for master cabinet-maker is "Eboniste". I paid a handsome sum for the little board.

As a person of conscience, I go through periods of some doubt where exotic woods are concerned. It's true that this little board passed through three or four pairs of hands and likely experienced a 100% markup at each stage. I'm against unregulated forestry practices. The sad fact is, this board's other likely destination was a fire pit. Unchecked population growth in its place of origin means that trees are either burned to make way for farmland, or burned for heat.

Does using such a scarce resource for a creative endeavour devalue the material? Or increase the desire for it in the buying public, thereby making worse exploitation probable? I'd like to think that through employing it in a high value object designed with longevity in mind I'm somehow making sustainable harvesting a better economic opportunity than destruction by fire.

Recently I was watching one of those "Let's make your house palatable to hip young home buyers" shows. "Crash" went the sledgehammer as the old kitchen cabinets made way for new. I was a little outraged by what happened next. The new cabinet doors were made from photo-print foil laminate in the pattern of... macassar ebony. Or, "mer-crasser", as the bubbly hostess repeatedly called it.
Sigh. I think of some materials as utilitarian in their scope. Gold-plated toilet seats are wrong on many levels. If you're going to make a plastic-faced cabinet door, it should say something about plastic as a material. Utilizing the image of a scarce and beautiful natural material for storage purposes inoculates us against what a miracle the real thing is.

I had to psyche myself up to cut the ebony. I put it off for a few days until I arrived at a morning I was feeling up to the challenge. I spent some time tuning up my rickety old band saw and made test cuts to dial in the fence just so.

Wood does not sleep. It's in constant motion, gaining water or losing it. The block had been slightly larger when I bought it and had shrunk a little though drying out. Recall, if you will, that it was just wide enough to provide 14 strips, including the material lost to the saw blade. Had it rained this morning, I'd likely have been okay. As it was, I ended up with 13 perfect slices... and one too thin. By half a millimeter. Either the saw blade expanded with friction, or the fence was misplaced. By 1/24th of a millimeter. Cumulative error is an awesome thing.

So, I'm left with a decision. I could make a so-called "beach ball" lute with alternating dark and light staves. (They always leave me cold.) I think I will take the thin stave and use it for the capping strip, padding it out with a piece of veneer on the reverse side to make up the thickness. Such is life!

Thursday, May 13, 2010

Chipping off the Old Block

Today I'll make a mate for the neck. The top block is a piece of alder, which is a relatively soft timber. It's easy to carve but has more "substance" than basswood. Poplar is another traditional choice, but it's stringy and not pleasant to cut with carving tools. I've marked the face of the block previously - here, I'm marking the face which will eventually be glued to the soundboard.

I'll saw off the excess material. You can see a screw hole that goes through the block. It will help secure the block to the mold. Later, it will house a screw that will aid in affixing the neck to the block.

More sawing, to angle the top of the block. I like these Japanese dozuki saws. They glide like butter.

There now. Much better. A couple of licks with the block plane left this interesting faceted form.

Here's the 2" wood screw that pulls the block to the mold. The protruding plywood landing houses two more short screws that pull the block down to line up with the plane of the mold.

Out comes the flat-bottomed spoke shave to bring the block into round.

A pattern-maker's rasp further refines the shape. I'm aiming for a smooth flowing curve that continues the shape of the bowl down to the neck profile tracing. Some masking tape protects the waxed surface of the mold somewhat from dings and scuffs. I'll use a broad chisel to perfect the transition from mold to block, and then file to smooth out the rough surface left by the rasp.

Here's a flexible drafting curve to mark out the shape of the facets. These aren't really set in stone - I'll sometimes file the surface to refine the shape when fitting ribs.

A smooth file makes a very slight concavity. This aids in achieving a tight joint between each rib.

An almost finished surface.

Tuesday, May 11, 2010

Passionate Necking Session

This morning I cut a number of neck shafts and blocks. Complementary angles are fashioned on both parts. The neck material here is Spanish cedar and the block is alder.

I've made up a load of jigs to make this operation less of a head-scratcher. Some luthiers lavish attention on their jigs, making them of precious materials. I'm not one of those. They're a little on the ugly side, but they work to keep things consistent.

Here I'm marking the joining surface of one of the blocks using this template that has the forward angle built in. There's a matching jig for the neck side of the joint. There will always be a little fussing to get things mated up perfectly, but this gives me a concrete guideline to work from.

Little notches on the template surface show the joint positions between each rib. I originally envisioned using these jigs with a router to machine the appropriate ends. I decided that besides being noisy and dusty, it wasn't that much faster than cutting things by hand.

Here's the neck blank marked up in similar fashion. The profile is a segment of a circle.

I've extended lines between top block and nut head surfaces.

Making shavings on the shooting board. Spanish cedar is special stuff! Historical lutes often have spruce or poplar neck shafts under the veneer. I like the cedar because it's very strong, stable and light. It also has the most wonderful spicy cigar-box aroma. The scent lingers in the shop like incense. It's easy to plane, but contains tiny sandy grains of crystallized resin so I'll need to sharpen the blade when I'm done.

I'm tapering the blank in thickness down to the lines fore and aft.

And there we have it. All squared up. Lots of potpourri too.

I've drawn some angles to denote the bulk of material to be removed. This is done with a block plane. I suppose one might use a spokeshave for this, but the short registration surface makes it more difficult to maintain good straight lines. I'll retract the blade and take smaller shavings to get down to the finished profile.

That's close enough! You can see the little fixture I made to hold the blanks off the bench. It also helps when the time comes to glue on the veneer. It's countersunk from below for two screws that just barely protrude. These hold the blank in place.

The surface is refined using a mill file. This perfects the profile at each end and smooths out the plane tracks. I'll follow this up with a "shoeshine" using 150 grit garnet paper.

This neck is destined for an all-white lute mimicking the ivory instruments reserved for Renaissance royalty. Rather than subject an elephant to the indignity of tuskless living, I've decided to use American holly, the whitest of woods. This lute will have an all-black sister made with ebony. I'm scraping down to 1.2mm.

A template eliminates the guesswork. After cutting the veneer to size, I'll bend it using my electric iron. It's almost supple enough to go around the neck by itself, but as soon as the glue hits it, it'll want to curl up in the opposite direction as the fibres on the wet side swell. Pre-bending will counteract that.

A generous coat of glue.

Surgical tubing makes an excellent clamp. It provides even pressure over the entire gluing area. I'll let this sit overnight and trim off the excess tomorrow.

Sunday, May 2, 2010

A Sticky Subject!

I was rinsing out the stiffened washcloth I use for wiping my glue brushes when a thought occurred. If I was to take a completed lute and immerse it in the laundry sink, in about five minutes the entire thing would delaminate and undo ninety hours of work. I started mentally calculating. Following the swim I'd be left with 87 pieces of wood, 23 pieces of gut and one hunk of bone. Oh, and one brass screw.
Carrying the thought further, I realized that with some patience and appropriate drying time it should be possible to put the whole thing back together again into a recognizable facsimile of the original.
After this conclusion, I meditated on the fact that I'm engaged in producing what is for all intents and purposes - a biodegradable object! This led to pondering the paucity of original lutes that have come down to the present day, when one takes into account lists like the Fugger inventory- hundreds of instruments. All to have vanished with the passing of time. Exceedingly fine, handcrafted ephemera. I don't quite know why, but it made me feel good to realize things from this perspective.
My current instruments are stuck together with protein-based, animal derived glues. Ostensibly this makes them easier to repair, and it's a historically informed approach to working. I've been using hide glue and a less well known substance called "fish glue". Hide glue has a reputation. It's decidedly old fashioned stuff that requires soaking and heating. It has a very short working time before it cools and seizes up. I've read that it stinks something fierce. I don't find this to be the case, at least not with the refined glue I use. I do recall the somewhat fetid stench of "rabbit skin glue" used back in art school days for making gesso and wax encaustic painting. This is altogether different. Fish glue is made from fish skins and is remarkably similar to hide glue when dry. It's benefit? - No heating necessary. No stink here either, unless one forgets to change the water in the brush-rinsing jar for a week or so. Even then it's not fishy, more like a hockey equipment bag.
Hide glue isn't all that hard to work with, really.
The glue pellets are soaked in cold water to soften for a few hours. (Cold water is important!
Hot water cooks the granules before they can soak up the moisture. They become case-hardened little pearls not unlike the tapioca balls one finds in Tai bubble tea.)
Here's my rig. Small quantity of glue in a baby food jar nestled in a double-boiler situation on the old hotplate. I cook it with care, adding finest Swiss chocolate and rich, creamery butter...
Well, to be honest I just make sure it doesn't go above 150 degrees F. I adjust the viscosity by adding water from the pot until it drips from the brush in a continuous stream the consistency of light machine oil.

Why use fish glue instead, if hide glue's not so bad? Mostly because I have a basement shop. I've managed to regulate the humidity but it's still a cool place. I could get around it by heating parts to be joined, but I've found the fish glue makes tricky assemblies less nerve racking.

Time for some informal, decidedly unscientific testing to compare the adhesives I use in the shop. Aliphatic glue -yellow carpenter's glue, works fine for putting jigs together. It does have a reputation for drying to a somewhat rubbery state. It also tends to let go if left in a hot car. I've seen the effects. I also find uses for cyanoacrylate superglue in several viscosity's. It works well in repair situations. This photo isn't the greatest. The warm incandescent glow hides the colours but I didn't feel like going back and shooting it again. When dry, the carpenter's glue is indeed, yellow. It sticks reasonably well to this slick piece of melamine laminate but with a little work it bends away from the surface. Fish and hide glues are both pretty pale in comparison and decidedly brittle -they crackle like hard candy when stressed. The superglue is water clear.

There's a well established opinion in luthiery circles the the brittle nature of animal glues makes for better transmission of sound across joint areas. There's no "give" to impede vibration. It's also supposed to be easier to reverse if things need repair. I'm not so sure about this, personally. I've removed dozens of steel string guitar bridges using a regular clothes iron to heat them up. The two bridges stuck down with hide glue took a lot more effort. Heat wasn't enough. I had to get in with a palette knife and water before they'd give way.

Let's make like Professor Julius Sumner Miller and devise a practical experiment. I've glued up similar lengths of beech to a block with the various glues. I'll use these hefty c-clamps on the end of the lever to put some strain on the joint. I suppose this is a problem of torque, though I have no idea of what the rotational distance is, nor the clamps' mass in newtons to calculate force, so I don't suppose I'll publish this in "Science". I'll give credit for the setup to repair guru Frank Ford, who did this with hide glue and Titebond a few years ago.
All loaded up and in the oven at about 200 degrees F. (Incidentally, the temperature your guitar would experience in the trunk of a great red Cadillac just outside Barstow...) As suspected, the aliphatic yellow glue gave way first, at about the six minute mark. The others just kept on holding. I raised the temp to 250. Still nothing, other than a pleasant roasty Christmas tree smell. I spritzed a little water in there as if preparing a rustic Italian crusty loaf. That did it. In two minutes both the fish and hide glues let go with a satisfying "clank!".
So, what of the cyano? It did continue to hold for an additional five minutes, when I reminded myself that this wasn't being funded by a research grant and I turned off the oven. When things had cooled, I inspected the joints.
The superglue holds fast, but the bond was super weak. I nudged it and it fell apart. The hide glue let go entirely. The fish glue seems better, but it too is loose. I suspect that it re-gelled when it cooled down. The carpenter's glue has little strands connecting the two halves of the joint. Will I switch to super glue for all my adhesive needs? No. The expense, toxic fumes, embarrassing finger-sticking calamities, all mitigate against adopting it for general purpose use. I still love it for sticking down loose frets and filling cracks in polyurethane finishes though!