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Category Archives: jigs and holding devices

Most vices won’t let you file a nut or saddle to shape. Their jaws are too wide and get in the way. Stew Mac make a special vice with tall narrow jaws to get around the problem. I haven’t tried it but I should think that it works fine.  However, it’s quite unnecessary. A simple pair of wooden jaws does the job perfectly well.

 

The jaws in the photographs below were intended as a prototype. I was planning to make a pair of jaws out of gauge plate or aluminium sheet and wanted to check that I’d got the size about right and that the idea was feasible. It turned out that the wooden version worked so well that I didn’t need to bother.

 

 

 

As I hope can be seen in the photographs, the device is little more than a couple of pieces of maple about 5mm thick, hinged together at their lower ends with glass fibre reinforced tape.

 

 

Stewart-MacDonald has been sending me emails recently about a device which allows guitar makers to adjust the height of a guitar nut or saddle while keeping the underside both square and straight (item # 4047 in the StewMac catalogue). Here’s a picture.

I thought that this was rather a good idea.  Although it’s not especially difficult to adjust a nut or a saddle by hand with a file, it’s a tedious job and often takes a while. And the reviews on the StewMac website were positive, saying how quick and accurate the device was.

The drawback is that it’s quite expensive.  By the time I’d paid  shipping and import duty, buying one would probably cost around  $200.   So, I decided to make one for myself.

The body is a length of aluminium bar, 15mm x 30mm, drilled at each end to take an axle that carries miniature ball bearings.

Used with a sheet of P280 sandpaper on a flat surface, it worked quickly and accurately.

As I hope you will be able to see from the photographs, it’s not difficult to make, although you will need access to a drill press and a small lathe. The materials needed (aluminium bar and four miniature ball bearings) are easily available and cheap.

Mine took a bit longer to construct than it should have done because I drilled the holes for the axles too low, which meant that the body of the device ended up too far above the sanding surface. So I had to bush the holes and re-drill. If you’re making one, I’d recommend positioning the axle to give a gap of no more than 2mm between the bottom of the device and the sanding surface.

Most woodworking vices are designed to hold pieces of wood with sides that are parallel. This is a problem for instrument makers because much of the wood they work with is curved or tapered.

So guitar makers frequently use a carvers’ vice, which has adjustable jaws, to get around the difficulty.  Dan Erlewine uses one in his excellent series of videos, Trade Secrets.  And here’s one in my own workshop.
 

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But they’re big, heavy, ugly things (mine is a particularly repellent shade of green) and whenever possible I prefer the simpler solution of a moving accessory vice jaw. This is no more than a block of wood with one gently curved side that allows it to rotate to accommodate the work piece. The flat side is lined with cork and there’s a thin sheet of plywood is glued to the top to maintain it in position while the vice is tightened.

 

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I’ve written about these before (see here) so I’ll only say that they’re easy to make and that they’re very effective in gripping gently tapering (10° or less) objects.

 

The device below  is a little more complicated in having 2 jaws connected at the bottom with a flexible hinge made of leather. It was originally intended to hold the head of a violin or cello  bow while the mortise for the hair was being cut – an invention of Andrew Bellis, who is a bow-maker in Bournemouth.

The 2 jaws are slightly thicker at one end (hence the arrow on the top) which gives it a head start when it comes to accommodating a tapered shape. The flexibility of the hinge allows it to adapt to objects with complex curves. It’s easy to make, too.

 

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Here’s a similar idea but in a more elaborate form. I took the jaws off a small Record vice and substituted cork-lined wood. On one side there’s a permanent version of the moving jaw described earlier. A thin metal bar located by a 3mm rod keeps it in position. I’m hoping the photographs will make things clear.

 

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A couple of photographs of it in action. In the first it’s holding the neck of the soprano ukulele that I mentioned in a previous post. The second shows it gripping the head of a violin bow while it is being re-haired.

 

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I’m pleased with how these vice jaws turned out. And it’s certainly convenient having them immediately available to hold an awkwardly shaped work piece. However, I have to say that they’re significantly more effort to make than the simple devices described earlier. Unless you’re dealing with tapers and curves a lot, it may not be worth the time and trouble.

I’ve been a fan of Roland Chadwick’s music since hearing a performance of his trio for classical guitar, Letter from LA, a few years ago. So I was delighted when he contacted me about a guitar that needed some attention.

It was a fine instrument too – a cedar top classical guitar made by an Australian guitar maker, Simon Marty, in 1988. Quite apart from being 25 years old, it had worked hard for its living and the thin cedar top had developed some nasty cracks in the widest part of the lower bout. Some of the internal braces had come unglued too, and the guitar was more or less unplayable. To make matters worse, someone had tried to repair the cracks with superglue.

This is what it looked like after I had scraped away most of the superglue.

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With a hand through the soundhole, I could feel that the cracked part of the soundboard had become detached from a long transverse bar running across the instrument under the bridge. This explained the multiple little dowels, which were a previous attempt to fix the problem. The only thing to do was cut out the damaged wood and replace it.

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I also needed to replace some missing braces and re-glue several that were beginning to come unstuck. The difficulty here was that the braces, constructed out of balsa wood and carbon fibre, were very thin and it was almost impossible to position conventional clamps accurately enough to hold them in place without distortion. In the end, I solved the problem by making a few spring-loaded miniature go-bars. Wedged between the back of the guitar and the top of the brace, they kept everything in place while the glue cured.

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After re-polishing, it was ready to perform again. All well worth the trouble because, despite its age, it’s an excellent guitar which produces a big warm sound.

 

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In his book Violin Restoration (ISBN 0-9621861-0-4), Hans Weisshaar has a photograph of a self-adjusting jig that will hold violin bridges while they’re being planed. I was rather taken by the simplicity and ingenuity of the idea and I thought that I’d make one to see if it worked any better than the very basic holder, shown below, that I use at the moment.

The clever part about Weisshaar’s jig is that one side is free to rotate which means that it can adjust itself to fit bridges of different geometry, holding them all equally tightly. It’s easier to show how it works with a few photographs than it is to describe it.

Extra holes allow the swivelling side to be mounted closer to the fixed side to accommodate three-quarter and half size bridges.

A small block glued to the bottom helps to hold the jig against the edge of the bench or in a vice.

Although the device works well, it’s probably not going to be much use anyone except a violin maker. Still, I thought that the idea of using a freely moving arm or jaw to grasp pieces of wood when the sides aren’t parallel had wider applicability. You might be able to use a scaled up version for planing tapers on table legs, for example. And the accessory jaw for holding tapered shapes in a vice that’s shown on the Tools and Jigs page of this site (scroll down to the second item) draws on the same principle.

 
 
 

Larger versions of these photographs are available by clicking on the thumbnails below.

Although I was sure that I’d read somewhere that there was a way of using a mirror to help judge when a drill bit was truly vertically, I struggled to find an account of how it was actually done. Eventually, after a lot of googling, I came across this letter and illustration published in Popular Mechanics nearly 80 years ago.

To find out if it worked, I bought a cheap handbag mirror.

First I cut off the hinge and trimmed back the plastic mount along one edge.

Placed next to the drill bit, the mirror showed when the drill was vertical…

… and when it wasn’t.

It’s a simple idea but I was impressed by how well it worked. A problem though, is that the mirror only tells you whether the drill is vertical in one axis. You have to move the mirror around the drill to check whether it’s vertical in the other axis and while you’re doing this, it’s easy to lose the vertical on the first axis.

One solution might be to have an L-shaped mirror or, perhaps better still, a mirror with a hole in its centre. Then, all you’d have to do to check that the drill was truly vertical in both axes would be to move your head.

So I ground a small hole in the centre of the other mirror and tried it out.

This is the view when the drill is vertical.

And when it’s miles off.

Of course, you don’t need a mirror to see when the drill is as far out as that. The benefit is that it makes it easy to spot small deviations from vertical.

Does it work in practice? As a test, I drilled ten 2mm diameter holes at 10mm intervals along a line in a piece of MDF and stuck cocktail sticks into them.

Not perfect – but not bad either. Certainly better than I was able to do in a repeat of the experiment when I used a small try square instead of the mirror as a guide, as you can see below.

Obviously, the best way to drill a truly vertical hole is to use a drill press. But there are occasions when this is impossible because the work piece is too large or too awkwardly shaped. It’s then that this trick with mirrors might come in handy.

A comment on the previous post asked about setting the honing angle.

Here’s one way of doing it. Set a sliding bevel to the angle you’re after. (I chose 30°.) Then, after fitting the chisel into the mould, adjust the position of the mould in the honing jig, by eye, so that the longitudinal axis of the chisel runs parallel with the blade of the sliding bevel.

 

 

I glued a strip of wood across the underside of the mould so that it can be located in the honing jig at the same angle every time. And that’s it.

 

 

Eventually, I suppose, repeated honing will shorten the chisel and increase the angle of the secondary bevel. That will mean that it’s time to regrind the primary bevel and repeat this process to restore the angle of the secondary bevel.

A point I forgot to mention in the earlier post is that it’s worth creating a stop in the moulding at its upper end to prevent any tendency for the chisel to slide up while it’s being honed. Here you can see a stop formed by the lip that mirrors the indentation between the socket and the handle of the chisel.

 

A couple of years ago, I wrote about a simple device that made it easy to plane a taper on small pieces of wood – something that’s hard to do accurately if you try to hold the wood in a vice. (The piece is still available in the Tools and Jigs section of the website.) After I’d posted it, Jeff Peachey, who specialises in the conservation of books, sent me a photograph of a rather similar jig that he had made, which had the advantage of an adjustable endstop. I’ve been meaning to incorporate this modification ever since, but have only now got around to it. Below is a photograph of the original jig with a glued endstop of 1.5mm plywood.

To add a adjustable endstop, I inserted two short lengths of 6mm studding, drilling the pilot holes under size and then tapping the holes before screwing in the studding. Because the studs are inserted into endgrain, I was doubtful if they would hold so I glued them in too. And, to be doubly sure, I cross drilled the studs in situ and popped in a nail shank, the end of which is visible on the side of the jig.

Then I cut slots in a small piece of maple to make the endstop and fixed it in place over the studs with washers and nuts.

Here is the modified jig, ready for action.

A worthwhile improvement, I think. It will be possible to match the height of the endstop to the size of the end of the wedge and, should the endstop get damaged, it will be easy to true it up again.

In the meantime, Jeff Peachey has made a much bigger and better device, which is primarily intended for planing thin boards although it can cope with wedges too. There’s photograph of it on his website here.

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