Building a violin. In part 6, Dominic Excell looks at jointing the plates, flattening the underside and more. Two-piece back...

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Building a violin In part 6, Dominic Excell looks at jointing the plates, flattening the underside and more Plane blade showing hollow ground edge Polished back surface with no rounding over

.. T he last article saw the finishing of the rib structure, which hopefully you will have completed by now the breakage of ribs having been kept to a minimum by way of luck as well as judgement!

I will now make the decision for you all, unless you are going to wait until later parts of the article are published and then take your pick!

The following instructions also apply to jointing the belly. Now, remove the glue from the hotplate and any thoughts of gluing from your head, as we have hardly started yet!

1 Building a violin In part 6, Dominic Excell looks at jointing the plates, flattening the underside and more Plane blade showing hollow ground edge Polished back surface with no rounding over Two-piece back... T he last article saw the finishing of the rib structure, which hopefully you will have completed by now the breakage of ribs having been kept to a minimum by way of luck as well as judgement! There are several directions in which we can now travel, there being no hard and fast rule as to which order the major parts are made. I will now make the decision for you all, unless you are going to wait until later parts of the article are published and then take your pick! Making the back 1 suggest that now the back is prepared which will, in due course, allow the rib structure to be freed from the mould and the remaining set of linings to be attached. The following instructions also apply to jointing the belly. Now, remove the glue from the hotplate and any thoughts of gluing from your head, as we have hardly started yet! The general plan is initially to plane the wide edges of the boards so that the inner faces are flat to each other when the two pieces are opened out like a book. This surface will, in due course, become the inside of the plate. The end view will appear as in figure 1. The underside will be planed flat, the shape of the back (or belly) will be sawn out, and outer contours will be carved to opened out to show inner faces (inside of back) shape, the inside eventually being hollowed out. A piece of cake! I hear you chorus. Well, we ll see about that... To start with, you will need to separate the two halves of the plate, which are sometimes sawn so as to leave one corner uncut. The safest way is to saw them apart using a panel saw, rather than to prise them apart, as this can especially on the belly have the unfortunate result of the narrow edge splitting away, following the grain line. Once separated, plane any high spots off, and run a couple of pencil slashes across the joint for easy recognition and orientation. Now clamp the two pieces together in the bench vice, holding them together as they were originally positioned, and plane the two wide edges as flat as you can: at right angles to the sawn inner faces of the board. If there is a difference in angle from one end to the other because of a twist, worry not; just take the average between each end, and plane at right angles to that. The plane that I recommend is the Jack plane. I have used a Record 05 for over 20 years, which has given sterling service. As long as it is perfectly flat and the blade is sharper than a razor, then you should have no insurmountable problems. Flat soles, sharp blades If you are buying such a plane, take a good straight edge along with you and pester the shop proprietor to let you check his stock for flatness of the sole.

Checking planed edges at right angles to sawn inner faces Boards held together, showing gap at end.

over. I do not recommend a mechanical sharpening device, as I feel that a degree of control is forfeited. This method is quite easy, and doesn t take long to master.

You can of course use a honing guide, but these Close up of joint about to be glued Check diagonals as well as length and width, and also make sure that the throat area is not proud.

Avoid this one like the plague. The blade now needs sharpening. I fully realise that many of you have your own way of sharpening edge tools.

2 Checking planed edges at right angles to sawn inner faces Boards held together, showing gap at end. With such a gap at each end, it will be necessary to plane away centre of each board bridging over the hollow grinding; this ensures that, in effect, this face is also flat and not rounded over. I do not recommend a mechanical sharpening device, as I feel that a degree of control is forfeited. This method is quite easy, and doesn t take long to master. The only requirements are a grinding wheel 125mm in diameter being about right ideally with a clamping device to enable the tool to be slid from side to side while being held at the correct angle. I use Japanese water-stones for honing: an extremely sharp edge can be obtained, while eliminating the danger of dirt- attracting oily deposits which can result from the use of oilstones. You can of course use a honing guide, but these Close up of joint about to be glued Check diagonals as well as length and width, and also make sure that the throat area is not proud. This latter fault should be checked for with the blade in place and the lever cap tensioned. If slight, it can readily be dressed out, however. The worst defect is a twist. Avoid this one like the plague. The blade now needs sharpening. I fully realise that many of you have your own way of sharpening edge tools. The method that I am about to describe works extremely well for all edge tools, allowing very accurate cutting, with the potential for absolute control. I have already touched on this aspect (see figure 6, page 66 of the October 95 issue). The important thing is that the flat side of the blade, be it chisel or plane, must be well polished without rounding over the edge. I cannot emphasise this detail too strongly! The blade is then hollow ground, with the final sharpening with oil or water-stones can wear troughs in the softer water stones. FIG

accurately, a very slight curvature can be beneficial; though don t overdo it, as while the joint looks good at first, a gap will appear with subsequent loss of strength as the curvature of the plate

Plane set-up A small sliver gouged away to check the joint below the surface The back glued up.

grade possible. The fine stone is used after a few strokes with a medium variety to remove 58 grinding marks on the bevelled side.

3 accurately, a very slight curvature can be beneficial; though don t overdo it, as while the joint looks good at first, a gap will appear with subsequent loss of strength as the curvature of the plate is carved. A curvature of about 0.25mm at the centre of the blade would be acceptable. See figure 2 for details of sharpening. Plane set-up A small sliver gouged away to check the joint below the surface The back glued up. Note that the suction of the glue provides enough clamping force Once you have the flat side honed to eliminate machining marks, scratches and so on, the only stone to use on that side is the finest grade possible. The fine stone is used after a few strokes with a medium variety to remove 58 grinding marks on the bevelled side. A leather strop can be used for a final polish, but here again great care must be used, as it is all too easy to round over the edge! I disregard the sharpening instructions that come with a new plane, though these are all right for heavy-duty work. The shape of the cutting edge as well as its profile is also important. For the task of jointing boards The plane needs to be set up to cut extremely fine shavings. The shavings need to be so fine that they just hold together, like lace; but not so fine that they are just dust. If dust is produced, then the blade is probably a little blunt. Several sharpening sessions will probably be required as you proceed with the joint. The idea now is to make each board in turn as flat as possible, trying each against the other, thereby gradually eliminating inaccuracies. Hold each board in turn in the vice, the outside facing away from you, the jaws gripping about x/3 rd the way up from the narrow edge so as to avoid distortion. For the

When flattening, check with straight edge along each line A couple of steel rulers can be used as winding strips.

Remember that for these joints an accuracy of + or - 0.001mm is required!

the boards. When bringing the plane onto the board, make sure your weight is concentrated on to the front knob, almost (but not quite) lifting the rear of the plane upwards.

Needless to say, you are not going to slide the plane back for the next cut, as this will only bring forward the resharpening time, but lift the plane at the end of the stroke before cutting the next

4 When flattening, check with straight edge along each line A couple of steel rulers can be used as winding strips. The eagle-eyed will have noticed that this is a one piece back same reason, clamp the board in the vice with enough pressure to hold firmly, but no more. Remember that for these joints an accuracy of + or mm is required! You need to attempt to plane each board slightly hollow along its length this of course being impossible unless your plane is convex, but the net result should be an absence of gaps at the ends of the boards. When bringing the plane onto the board, make sure your weight is concentrated on to the front knob, almost (but not quite) lifting the rear of the plane upwards. As you proceed with the cut, gradually bring your weight back so that when the far end of the board is reached, you are almost lifting the front. Needless to say, you are not going to slide the plane back for the next cut, as this will only bring forward the resharpening time, but lift the plane at the end of the stroke before cutting the next shaving preferably checking against the other board first. It is as well to remove the shaving from the throat of the plane after each and every stroke, as it is useful to be able to see where the subsequent shaving is coming from! It can also be quite a useful technique to hold the plane by the centre of the body, and starting from the centre of the board gently shunt the plane along while applying a good downward pressure, thus picking up any high spots. Study figures 3 closely: they show how I go about checking each board against the other, and what to read into the results obtained. At all costs avoid a high ridge along the centre of the board, thus allowing a side-to-side rocking motion. Fig. 6.5 The ribs clamped to the back to mark out the outline Ready to glue When you are getting very close to perfection, it is time to put the glue on to heat up. It is as well to have fresh glue for these joints, as maximum strength is required. You will also need to be in a warm, draught-free environment. To minimise built-in stresses in the boards, I always make a rubbed joint, using no cramps, with just the suction being sufficient clamping force after applying my own body weight for 30 seconds or so. To be successful does require a perfect joint though! One important point: when you have finished planing, do not handle the surfaces, as even a small amount of handling will contaminate the joint with natural oils (or sweat!) from your skin. When you are completely satisfied with the dry joint, and are not kidding yourself that it is better than it really is (I've been tempted many times!) you will need to glue up immediately, as with no tolerances allowable, the boards tend to move quite quickly. Allow yourself the luxury of a dry run, however. Make 5 9

Illustration 1: Fig. 2.6 Marking out the outline using a sharp pencil and washer one board is thicker than the other, it helps to have the thicker one in the vice.

Slide The marking out at the corner. Note how the lines are continued For the back, do not forget to allow for the button!

Turn the board in the vice around so that the outside is away from you. If 6 0 the top board back and forth while keeping the two aligned. Only an inch or two in either direction is required.

5 Illustration 1: Fig. 2.6 Marking out the outline using a sharp pencil and washer one board is thicker than the other, it helps to have the thicker one in the vice. Bring the glue to the bench, and stand it next to your work, but not in the way. Now dip your brush into the hot glue, and slop it on as quickly as possible over the two edges, held side by side. You won t have time to brush it out! Then quickly bring the boards together, using your fingertips at opposite ends and sides of the top board to judge for alignment, and using your body weight to squeeze out the surplus glue. Slide The marking out at the corner. Note how the lines are continued For the back, do not forget to allow for the button!!! sure you are wearing an apron, and that you are not working directly over the best carpet in the house. The glue tends to go everywhere, and I do not want to have to answer to angry spouses! Turn the board in the vice around so that the outside is away from you. If 6 0 the top board back and forth while keeping the two aligned. Only an inch or two in either direction is required. All the time, maintain downward pressure. Make sure you do not push the board away from you, as if the air gets in and chills the glue, then you have to start again. You may get away with it if the glue has yet to gel, and you are very fast applying more, but there s no guarantee. The aim is to have the boards lining up when they suddenly bite; as long as you have enough length in hand, don t worry if it is a little out. Maintain the pressure for a little longer, then relax and carefully unpeel your hands from the board. Finally, take a small gouge, and very carefully take a small sliver away from the surface, thus exposing the join at each end and at the centre, on both sides. This is to check that you have a good wood wood contact along the join. If something has gone wrong and the joint hasn t glued up well, now is the time to prise it apart: there will be less planing later. But 90 percent of the time, the joint is successful; so go and make a drink, have a smoke, throw a party or whatever. The belly When you have recovered, repeat the above for the belly. Have patience with these joints: please resist the temptation to rush, and try to analyse what is wrong with the joint before planing. Try for fit after every pass of the plane when you are close. Just be methodical and you ll succeed. To give you an idea of the time taken to glue up a plate, I allow I1/2 hours per joint. My first one took about 12 hours, and I have taken as little as 5 minutes though there was a degree of luck with that one! Leave both plates to dry out thoroughly before you continue. The joint will be strong enough to work on after about five or six hours, but it is necessary for the water to evaporate completely before planing the underside flat, otherwise the centre area has a tendency to contract slightly as it dries. Leave for a week to be on the safe side. The boards now need to be held securely while being planed flat. I use another twopiece back or belly to fill in the slopes, with the board held in bench dogs at each end. You will have to make a couple of tapered or wedge-shaped boards, unless you have some spare unworked plates available. See figure 4.

narrow blade. Take great care that you don't cut across the points of the corners. If you only have hand saws at your disposal, then using a coping saw.

Make sure you maintain pressure against the flat surface, otherwise you will probably have two or more lines. Would you always know which one to work to?

This will allow the plate to be held in the bench vice. Two spots of glue will suffice: we will want to remove this block in due course.

belly must be worked from along the grain to the diagonal: see figure 5. Check along the length, across the width, and the diagonals.

6 narrow blade. Take great care that you don't cut across the points of the corners. If you only have hand saws at your disposal, then using a coping saw. Once you have sawn out the outline, take a marking gauge set to 4mm and scribe a sharp line parallel to the flat underside. Make sure you maintain pressure against the flat surface, otherwise you will probably have two or more lines. Would you always know which one to work to? When satisfied, mark the scribed line with a finely- sharpened pencil. Finally, glue a block of scrap wood approximately 50 x 100mm at the centre of the underside. This will allow the plate to be held in the bench vice. Two spots of glue will suffice: we will want to remove this block in due course. The back sawn out The edge thickness of 4mm being marked out The scribed line being blackened with a chisel-pointed pencil The back must be planed from across grain to about the diagonal, while the belly must be worked from along the grain to the diagonal: see figure 5. Check along the length, across the width, and the diagonals. The use of a pair of winding sticks can help: laid across the board, one at each end, they exaggerate any twist in the board a great help. Fitting the ribs Once both boards are flat, take the rib structure and clamp the back lightly in position, making sure that the joint is truly central to the ribs. Scribe lightly around the ribs. Next, find a washer whose width between inner and outer diameters is about 3.5mm, (the actual size being unimportant): run this around the outline, with a sharp pencil inside the washer. This gives an accurate marking-out relevant to your rib structure. Granted, it may not follow the template precisely, but it is more important to have an even overhang in my opinion than an exact copy of the template shape. Use the The block, enabling the back to be held in the vice, ready to be glued in place. Note small amount of glue, allowing easy removal later outline template to mark the corner shapes. Make certain that you allow enough length to include the button at the upper end of the back. You will teach yourself a few new words if you don t... Now saw out the shape outside the marked line. If you use a bandsaw or fret saw, go very carefully using a In the next instalment, I will be taking you through the process of carving the outside of the back and belly, and the beginning of the hollowing out process. In the meantime, if you require plans or materials price lists, or details of my violin-making courses, please write to me c/o The Woodworker, enclosing a SAE or IRC. 6 1

Chisels. A set of Dovetail Paring chisels from Blue Spruce Toolworks (www.bluesprucetoolworks.com).

Chisels. A set of Dovetail Paring chisels from Blue Spruce Toolworks (www.bluesprucetoolworks.com). 7 Chisels CHISELS MAKE UP A LARGE AND IMPORTANT part of the woodworker s tool kit. The apparent simplicity of a chisel a blade on a stick belies the numerous variations on that theme. At the very least,