Sunday, 17 December 2017

Here's a Thing That I Made, or, How to Hold A Lute Mold, or, The Return of the Betterizer

I have a question for all the lute makers out there: how do you hold a lute mold?

I've looked around at a lot of makers' websites and visited a few of their workshops, and I've seen a few different contraptions. Some are simple, elegant and useful, while others seem awkward and difficult. Here's a selection:

A plain stick of wood fitted in the underside of the mold, and held in a bench vice. This is the method used by Robert Lundberg, illustrated in his book Historical Lute Construction. Here is a photo of his proteg√©, Prof. G√ľnter Mark, using the same method:

(Courtesy Liuto Forte)
I once used this method, for the second lute mold I ever made, and found it pretty inadequate. The mold can be tilted forward and back in the bench vice, but that's it. (I guess in a pinch you could turn it 90° in the vice, and tilt it side to side, if you really wanted to.) Not very convenient when you're carving a mold, and want to tilt it a little to scrape a rib facet, or slightly change the angle of light from your shop window or bench lamp. I'm sure this way of holding the mold worked fine for Lundberg (and does so for Prof. Mark), but my eye needs more angles, more ways of seeing. I want a way of holding a mold that allows a full range of motion, so I can set the mold in any position.

Here's a good example of a jig that I imagine works really well: two locking hinges. I've seen quite a few makers using this type of holder; here's a shot of Malcolm Prior with his. (Malcolm thinks this method might have originated with the renowned English maker Stephen Gottlieb.)

I once tried to make one of these jigs out of stacked layers of plywood (again, early on in my lute making career), but lacked the skill or resources to do a good job. Malcolm's version looks very well made and useful--note the tightening levers on the bolts through both hinges. The mold (and lute back in progress) is held very securely, but is fully adjustable, tilting forward and back, as well as side to side, and rotating 360° where it sits in the bench vice (you can't see that part in this photo). I can't comment on its ease of use, never having used one, but it does allow a full range of motion and orientation in any position.

Here's the slickest of all the lute mold holders that I've seen. It belongs to Grant Tomlinson, and he tells me he bought it years ago from a supplier in Vancouver who's no longer in business; it was called a "universal carver's vice."

There's a big steel ball (like a trailer hitch) that bolts into a plate screwed to the underside of the mold. The ball is sandwiched between two half-inch steel plates, one of which is sunk into a big block of hardwood, which is held in the bench vice. A couple of heavy bolts cinch the plates around the ball; one of the bolts may be loosened (note the nut with lever attached in the view below), and the mold may be moved freely, and then secured in any position.

There's the owner of the mold (and mold holder) himself, Grant Tomlinson. As you can see, he's just getting ready to fit up and carve a new top block for this mold. In fact, he's getting ready to make top blocks (and bodies) for a new group of lutes. Here are the other three molds in the group:

Each is fitted with its own steel plate, so it's a fairly small matter to remove the current mold from the holder, and set up another. In this way, Grant can fit and glue a rib on one back, and while that's drying, set up the next mold, and fit and glue another. I doubt that Grant will be working on all four backs at once, but he might work on two at a time--most probably they'll be made of the same material (for instance, yew wood), so that he can set up his planes and other tools a certain way, and not have to change for a harder or softer material.

I got a chance to use this mold holder, and Grant's molds, when I worked with him in 2008-2009 (once again, my thanks to the Canada Council for the Arts for the grant that financed this residency.) One of Grant's instructions about using this piece of equipment is that it's essential to hold onto the work securely when loosening the nut and releasing the vice--if you don't, the mold will just fall over, and the consequences to it, and the back in-progress, could be devastating. (And no, in case you're wondering, I never let the mold slip!) If you've got a good hold of it, everything's fine: just re-position it, tighten the nut, and you're ready to go. 

(By the way, I've looked online for a mold holder like Grant's, and while I have found carving vices that kind of look like it, I've never found one that looked heavy-duty enough to withstand the weight of a mold and the wear and tear of using it pretty constantly for years, as Grant has done with his. If anyone has found a good version, please leave a comment and link at the end of the post--I'd love to have a look.)

What I used for years was a setup that Grant showed me a long time ago--the rig he used before finding that space-age carver's vice that he has now. A block of hardwood is screwed to the underside of the mold, and a large ratchet clamp grips the ends of that block. The bar of the clamp is encased in a built-up block of plywood, and that plywood block is held in the bench vice. It's low-tech, but effective--just the kind of thing I like. Have a look.

Everything's very secure. You can see that I've drilled through the hardwood handle of the clamp and inserted a 3/8" bolt, which gives plenty of leverage when tightening up against the hardwood block. 

Here's a look at the plywood block that holds the clamp, and sits in the vice--it's an essential part of the rig. It's built up of layers of ply, and as you can see, some thicknesses of card to ensure the clamp's held tightly. 

The setup has some drawbacks, but a few things work really well. Once you've clamped up the block a few times, there gets to be a kind of recess pressed into both ends, where the jaws almost automatically fit whenever you clamp up. Also, the clamping pressure is so good that you can tilt the mold by simply pulling it toward you or pushing it away (as shown in the photo above), without having to loosen the clamp. I've found it very handy to have this small amount of flexibility available, when carving the mold or fitting a rib. It allows a quick glimpse at the work from a slightly different angle, which can be a great help in the middle of the process.

Now the drawbacks. The mold tilts away or toward you, or forward and back in the bench vice, but it doesn't rotate, which means it's always facing in the same direction--unless you release it from the clamp or the vice, lift it up, turn it about in your hands, and then clamp or vice it again. (That's what you have to do if, for instance, you've fitted and glued a rib on one side of the body, and want to do the same on the other.) It's a royal pain--I did it for years, and while it's a good workout for your biceps, it's also pretty awkward, and potentially hazardous to the ongoing back assembly.

The main problem, though, is that like the Lundberg/ Mark setup, there's no way to alter the orientation if you want a slightly different view when carving a mold--to see how light and shadow fall upon the complex shape, or to follow a rib facet as it comes up in a long, graceful curve from the neck joint toward the abrupt transition at bottom end. I find mold carving to be a very demanding and difficult process, and as I said above, I need as many different angles and ways of seeing as possible in order to do a decent job of it.

So, a little while ago, I put the betterizer part of my brain to work, and came up with a solution that performs very well. I've talked about "betterizing" before in this workshop diary--I define it as a specific kind of improvement one makes to a tool or a jig in response to a displeasure one has felt building up, almost unconsciously, over many years, toward a certain shortcoming in the tool. It's like a burr under the saddle or a stone in your shoe, an irritation that can be ignored or withstood for a long time, but once decisive action is taken... there is only the freedom and sheer joy of having a tool that performs exactly as you want it to.

Here's what I came up with--a turntable that allows the mold to rotate 360°, and can be locked firmly in any position. As you see, it fits in between the mold and the hardwood block.

Here's a look at it separate from the mold.

There are two knurled nuts, on two bolts, one on each side of the hardwood block. Remove those nuts, and the top plate (along with the hardwood block) can be lifted off, to show the inner workings.  

The turntable base is made up of two thicknesses of 1/2" birch plywood, with one extra thickness of 1/8" ply on the bottom. The upper layer of 1/2" material, as you see here, is cut in two pieces in the bandsaw--an inner circle and an outer ring--to leave a channel about 1/2" wide, wide enough for the shanks of a couple of carriage bolts to travel freely around it. The lower 1/2" layer is cut in two pieces in the same way, but the space between the outer ring and the inner circle is a little more than 1" wide--wide enough to allow the head of the carriage bolt to travel freely. If you flip the base over, this is what you see: the outer 1/8" plywood layer. All of these wood screws are what hold the layers and pieces of the base plate together.

One other crucial feature of the turntable is the length of 1/2" maple dowel which centres all the layers, connecting the top plate and base plate together. It's the axis upon which the turntable turns. This is the underside of the top plate, showing the centre hole into which the dowel fits; the #12 screws that attach the top plate to the hardwood block; and the two holes through which the carriage bolts will fit up when the two plates are put together.

Here are the carriage bolt, spacer disc (made of 3/8" ply), and knurled nut.

Just a word about the knurled nut: it's simply a hexagonal-head nut which I embed within a couple of layers of ply (you can see the threads of the nut winking in the photo below.) I "knurl" the outer edge of the disc in the band saw, and then relieve the rough corners with a file. I could use wing nuts for this purpose, I suppose, but I prefer these shop made nuts because they are secure and easy to twist, which you end up doing a lot with this rig. I think wing nuts would be harder on the fingers, after a long day at the workbench carving a mold.

And here's what it's like, with the plates fitted together, waiting to be fixed to the underside of the mold--

Which I do with a couple of stout #12 wood screws on each side of the turntable (so there are four screws altogether holding it to the mold.)

Once it's fixed to the underside of the mold, just clamp the hardwood block into the big orange ratchet clamp and get to work. To turn the mold around, just back off the nuts about a half-turn, rotate the mold to the desired position, and tighten the nuts back up again. It really is that simple.

I remember the day I first made one of these things and tried it out: I was so thrilled, I must have spent an hour just loosening the nuts, repositioning the mold, tightening the nuts again. The turntable, and the mold, could be spun effortlessly, but there was no danger of anything falling over or falling apart; and when I tightened up the nuts, with only moderate finger pressure, the mold would stay very securely in its position. I could tell I had made a good jig, one that worked and would be safe and durable to use, whether I was carving a mold, or fitting and gluing a rib, or as I'm doing here, carving a top block for a new lute back.

It's like a miracle--I can position this mold in any direction I want, except, perhaps, upside down (but I will work on that.)

So there it is, another troublesome operation in the shop all betterized. It really is not an exaggeration to say that this invention has made my work with molds and backs much easier and more satisfying in so many ways. It's like a toothache is suddenly gone. I can't believe I made lutes before I started using this rig.

If anyone reading wants to make one of these things for him or herself, please be my guest. If you need any further hints on how it's done, just leave a comment here. And if you make any improvements to this rig, please let me know.

Go forth and betterize!

1 comment:

  1. Check out the Panavise stuff. I think I got the 300 base and a couple of 337 fixturing heads. It seems pretty sturdy, even with big solid moulds. Here's my setup in action-