Underside Edge Cutters
In fact, the recorder is not a simple instrument. It evolved continuously over many centuries, from its birth, probably in early Medieval times, until its death at the end of the Baroque period. The instrument was brought back to life again less than 100 years ago, by Arnold Dolmetsch, initially in the Baroque form. The recorder probably died out originally because it could no longer compete with the louder, newer instruments of the time. The Baroque recorder is an inherently quiet instrument compared with those of the modern orchestra. However, the early makers designed these quiet instruments with a purpose. They are designed to have a wide range, play especially well in the higher register, and sound wonderful. These key attributes are due mainly to the shape of the bore, and to the design of the windway and voicing.
This article describes methods for fabricating modern special hand tools for Baroque recorder making, with emphasis on bore and windway cutting. It also lists the ordinary tools which are needed to make a recorder. All of the tools can be used to make earlier Renaissance and Medieval versions as well. The article is aimed at those who either already make recorders, or those who wish to have a go at making their own recorders. The information on tools should be of greatest value to keen amateur makers, like myself, but may also be useful to some professional makers. Everyone has a different approach to recorder making; this is mine.
Reaming the bore of a recorder to the correct dimensions is an essential part of recorder making. Recorder bores generally follow a complex profile, especially Baroque recorders. This profile is achieved by first drilling through the timber blank with a conventional drill, and then reaming the bore with special tools to produce the required shape. Some of the tools used by the original makers from the Renaissance and Baroque periods have survived to this day. Large sets of spoon reamers were used by these early makers to cut different parts of the bore separately. Indeed, the same spoon reamers were probably also used to make adjustments to the tuning of their instruments. Some surviving illustrations from these times also show what appear to be simple tapered wooden reamers, fitted with metal blades, although these were probably only used for roughing out in preparation for spoon reaming. Spoon reamer marks are visible in the bores of many surviving original recorders.
There is nothing to prevent anyone who intends making recorders from doing exactly the same as our ancestors did. However, accurately reaming recorder bores with spoon reamers is a difficult and skilled task, requiring years of patient dedication to learn properly. It is much easier, today, to produce single reamers for each joint that cut the whole section profile in one go. The idea is to make a "former" that has the same shape as the finished bore. The former then has cutting edges set into its surface to become a working reamer. Once the timber blank is drilled through, the reamer is inserted into the hole and slowly rotated by hand to cut away the bore. When the reamer has been advanced to a pre-determined depth, it is withdrawn and Hey Presto! the bore is finished. A good reamer will leave the bore perfectly smooth and polished, requiring no further attention.
The simplest home made reamer, the bargain basement model, is made from an old metalwork file. All that is needed to make this is access to a bench grinder, or at a pinch, an angle grinder. Take great care with these machines, they can be dangerous if used improperly. Remember to wear the appropriate safety equipment, and work slowly and patiently.
First lightly grind away both sides of the file so that they are as smooth as possible. This is so the finished reamer will have a good cutting edge. Any trace of the original file surface would spoil it. The next step is to grind away the edges to the required profile. It is important that both sides of the file are ground away identically and symmetrically about the centre line of the file. If one side is different from the other, the reamer cannot possibly produce an accurate bore profile. Slow, patient work will give its rewards. The finished edge should be bevelled back slightly, so that the trailing edge just clears the bore. If the bevel is too shallow, the reamer will tear the wood. If it is too steep, the trailing edge will foul the bore and prevent the cutting surfaces from working properly. Figure 1 shows how this works.
Fit a standard wooden file handle to the reamer. Drilling a hole through the handle will allow a suitable length of wooden dowel or metal rod to be inserted, making it easier to turn. The finished reamer should be advanced gently into the recorder body. If it is used too aggressively it will bind and tear the wood. Making the first few centimetres parallel and of the same diameter as the initial drill will also help to make the job easier. This type of reamer will not usually produce a perfectly smooth and polished bore. It cannot compete with the finish quality and accuracy of the steel reamers described below. However, it is simple and cheap to make, and it allows people who do not have access to metalwork lathes to have a go at recorder making. It can also be useful for quick prototype instrument development. It warrants a recommendation because of this.
The second type of reamer is made of wood, and appears to be similar to the reamers seen in surviving illustrations from the Renaissance and Baroque periods. Access to a wood turning lathe (which is necessary for recorder making anyway) is required for this reamer. It is particularly useful for bigger recorders, where the large bore size makes the reamer strong. This type of reamer is not suitable for descant or sopranino instruments. It should really only be considered seriously as an option for tenor and bass recorders. However, it produces a much better finish than the metal file version, and it is easier to use.
The reamer is made by first turning a length of timber to the exact dimensions of the finished bore. The timber must be very well seasoned, to avoid warping and distortions occurring later, and it must be very strong and hard. Suitable timbers are Lignum Vitae (Guaiacum officinale), Greenheart (Ocotea rodiae), Brazilwood (Caesalpinia echinata) and other timbers with similar properties. The surface finish should be as smooth and polished as possible.
The next step is to fit a metal blade; a hacksaw is ideal. The blade can be fitted in one of two ways. Either a 90 degree quadrant is removed (by sawing, by routing, or with an edge plane) so that the blade can be screwed to the reamer, or alternatively by carefully cutting a narrow slot along the reamer and gluing the blade in place. If the latter method is chosen, it is good practice to plane away a small flat area immediately in front of the blade to allow the shavings some clearance. The first method allows the blade to be changed easily, while the second method gives a slightly better finish. Figure 2 shows the general idea for both options.
Once the blade is fixed in place, grind away the protruding excess until it is just level, or very fractionally above the wooden surface. The last grinding should be done with a fine grit wheel, or with a hand slip-stone so that the edge is left as sharp as possible.
Finally, drill a hole through the thicker end so that a suitable wooden or metal dowel can be inserted to act as a handle. Do not apply any kind of varnish or wax to the finished reamer, as this will cause it to jam in the bore. Instead, liberally apply a non-drying oil, like almond oil, which will prevent any warping and make reaming process much easier. Any excess oil should be wiped off before reaming commences, otherwise the shavings will stick together and clog the reamer.
A third type of reamer is based around a linear metal taper (i.e. a shallow cone). A linear taper is easy to turn on a metalwork lathe, by simply off-setting the tailstock and taking straight cuts along a metal bar. The metal used for the taper will not be used to form a cutting edge, so it can be relatively soft. Brass is free-cutting and is ideal for this purpose. The degree of taper should be sufficient to clear the finished bore profile at all points.
The next step is to cut a narrow slot along the entire length of the reamer, into which will be set a cutter. In this respect, the reamer is similar to the wooden taper described above, except it is strong enough to be made small. Again, a hack-saw blade makes an excellent cutter. The slot needs to be narrow, and it is best to cut this using a small slitting saw. I do this using an electric drill (fitted with a speed reduction gear or electronic speed control), mounted onto a vertical slide which is attached to the cross-slide of the lathe. The cut is made by gradually lowering the drill and making repeated passes back and forth. Providing the drill mounting is robust and cannot flex, an excellent finish can be achieved.
Once the slot is completed, the hack-saw blade can be fitted to the reamer. It can be glued, but it is better to drill and tap some grub screws fixings through the reamer for this, so it can be replaced easily. The grub screw holes must be carefully de-burred to avoid scoring the bore. All that remains is for the blade to be ground to the correct dimensions and sharpened.
The linear taper reamer is best suited to gently tapering bores, like renaissance instruments. If the bore shape changes rapidly, the blade will stick out too from the surface of the reamer, and the finish quality will suffer. Also, the side opposite to the blade will tend to ride on the high spots of the bore. This can cause an eccentric cutting action and an inaccurate profile if the blade sticks up too far. It is best to choose recorders that allow the blade to be no more than 1 or 2mm proud of the surface at any point.
The last, and best, reamer design is the so-called "D-bit". Most professional wind instrument makers use this design. It gives supreme accuracy and finish and lasts for a very long time. D-bit reamers can be re-sharpened hundreds of times before they need to be replaced. The principle is very similar to that used for the wooden reamer described above. An exact bore profile is turned from a piece of steel and the cutting edge is machined directly into the surface. The type of steel used depends on what timbers are to be reamed. Mild steel is OK with softer timbers like Maple or Cherry, but stainless or silver steel should be used for cutting harder woods. Silver steel rusts easily if not protected in storage, but it can be readily hardened by heating and quenching to produce a longer lasting cutting edge. Brass could also be used, but a suitable steel blade would have to be fitted, and it is easier to make the whole thing from steel.
The first stage is therefore to accurately form the reamer shape. This is best done by turning a series of small steps, of about 0.1mm depth, in a steel bar. The length of each step is chosen so that the inner corner corresponds to the bore diameter at that point. Remember to add a suitable length to each end of the reamer to allow for a handle, and for transitioning from the minimum bore diameter to the drill size used to make the initial hole through the timber.
Once this is done, the small steps need to be removed to leave the finished profile. I do this by hand using a fine metalwork file while the lathe is running. Take care to avoid loose clothing etc. while doing this, and use a chuck guard! As soon as the steps have almost disappeared, swap the file for some emery cloth/paper glued onto some scrap wood. Once the step marks have just gone, polish the reamer to a mirror finish using wet & dry paper and some metal polish. Figure 3 shows the idea.
The next step is to machine a cutting edge along the length of the reamer. The traditional way is to machine away a quadrant from 12 o'clock to 3 o'clock from the cross-section. If access to a milling machine is available, this is straight forward. This can also be done using the lathe mounted electric drill described above, but fitted with an end-mill cutter. The reamer is sharpened by raising a slight burr with some tool steel on one of the machined faces. Alternatively, either an end-mill or slot-drill can be used to machine away a wide trough along the middle of the reamer. This is my own preferred method. The slot can be any width, but the reamer works best when the slot gap is wide. It should not be too wide though; limit the cutter width to approximately half the diameter of the reamer at its narrowest point. This also means that less metal needs to be machined away than with the traditional D-bit. Figure 4 shows the cross-sections of the two alternative methods.
You will notice that the latter method produces a more acutely angled cutting edge. This is why I make my reamers this way. The traditional D-bit, and indeed all of the other reamers described here, cut by scraping the bore. My design cuts the bore, leaving a superb finish. The shavings look like they have been planed away.
One last practical note on machining the slots/quadrants in these reamers. Most small metalwork lathes, like my Myford ML7, do not have the facility to separately drive the leadscrew while the headstock chuck is locked. This makes it impossible to automatically feed the milling cutter along the reamer using the leadscrew, because the reamer has to be held static by the locked chuck. After spending hours manually traversing the cutter back and forth, I found a solution. Grip the reamer by its smallest end using a drill chuck mounted in the lathe tailstock. Support the other end at the headstock by using a live centre. This allows the headstock spindle to rotate freely, so that power can be applied to the leadscrew, while the reamer remains static and supported at both ends.
Most professional makers, and certainly all of the larger volume producers of recorders, use special machines to cut the windway roof into recorder heads. This consists of some form of cutter, usually a broaching tool, mounted onto a reciprocating drive bar which moves the cutter back and forth into the head joint. The recorder head is held in a jig which is gradually lowered down onto the moving cutter until the desired depth of cut is reached. Sometimes, the broaching tool also has an extension which simultaneously cuts the underside of the edge as well.
Although I do not own a windway cutting "machine", I can appreciate how useful they must be to volume producers. Some makers of hand built recorders might also find them attractive as a labour saving device for roughing out the windway shape. All of the cutters that I will describe here are intended for hand use, because that is the way that I use them. However, anyone who owns a windway cutting machine could easily fit most of these cutters onto their devices.
The easiest windway cutter, suitable for school-style recorders which have flat windways, can be made from an ordinary flat file. Grind the sides away until the file is of the required width for the windway. A couple of files, one coarse and one fine, will usually be enough for each size of recorder. Make sure the file is seated accurately within the bore before starting to cut. Do this by making sure the file is parallel to the bore axis, and by gently rocking the file from side to side while holding it against the bore wall. If it rocks easily, it is not seated properly, so that it is resting in the bore on just one corner and one edge. Waggle it about slightly and it will seat itself properly. When it is seated, it will feel stable and a gentle cut can be made. Once the cut has been started, it will guide itself. Carefully inspect the cut regularly to ensure that the cut is indeed flat, is not becoming slightly convex, is cutting evenly on both sides and is not slanted up or down.
Finish the windway with some fine abrasive like wet & dry paper, 600 and 1000 grits, or some very fine (0000 grade) wire wool. Wet the windway surface and allow it to dry out completely, then re-finish the windway again. This is because the windway will become wet when the recorder is played. If it is finished only once, the first playing will raise the severed wood fibres at the surface and make it look "hairy". The tone quality will suffer if this happens. Pre-wetting allows the hairy windway to be shaved off so that it doesn't become a problem. Don't put any kind of wood finishing like oil or varnish in the windway. This would cause the condensation to form beads and quickly block the instrument. An untreated surface allows the condensation to develop as a flat film which is partly absorbed by the timber, and does not block the windway. Cheaper wooden recorders, which are make from pressure treated timber (usually with paraffin wax) to stop cracking, and plastic recorders, suffer acutely with blocking because the condensation cannot film properly.
Curved windways usually give a much better tone quality to recorders. Half-round files could be used to make curved windways, but I have found the finish they leave to be inferior to the curved cutters described below. Most curved files also have a radius that is too small for larger recorders, They can only really be used for sopraninos and descants, but I wouldn't recommend them.
A curved windway cutter can be easily made on a metalwork lathe. Fix a cutter blank, a rectangular bar of steel of the right width and length, to a hexagonal support bar, mounted between centres. This is best done by screwing through the support bar, into the underside of the cutter blank. Make the mounting holes blind so that the fixing screws don't break through. The same screw holes can be used later to fix the cutter to a handle. Several blanks can be mounted onto the same support bar so that more than one cutter can be produced at once. A simple straight cut, taken along the rotating blank, will produce a nice uniformly curved surface. The radius or curvature can be varied simply by inserting a spacer between the blank and hexagonal bar. As with the reamers, the best material for the cutter is either stainless steel, or silver steel.
Once the blanks are correctly shaped, a cutting edge needs to be put into the curved surface. Either machine a series of simple slots across the cutter, or alternatively a saw-tooth profile using a shaped lathe tool. Figure 5 shows the two schemes.
The saw tooth profile is slightly trickier to machine accurately, but it cuts very quickly. However, it wears out fast because the cutting edges are narrow ridges with little surface area. The multiple slot style lasts indefinitely, but requires constant sharpening. Do this by raising a slight burr edge at the top of the slots with a slim piece of tool steel.
The best surviving examples of Baroque recorders had windways which were not only curved, but which had a radius of curvature that varied continuously along the length of the windway. The windway starts off curved at the beak, and gradually flattens out towards the exit at the chamfers. It took me a while to figure out how to make a cutter to reproduce this effect. What is needed is a cutter whose radius of curvature varies along its length, just like the recorder windway. As long as the cutting surface is relatively fine, a very short cutting stroke (a few mm back and forth) can successfully reproduce this type of windway in one operation. The reduced stroke length prolongs the cutting time, but the results are worth it.
A cutter with a varying radius of curvature can be made in a similar way to the previous uniform radius cutter. All that is needed is to mount the blank at an angle onto the hexagonal support bar. One end is closer to the lathe axis than the other, so the radius of the finished cutter will be smaller at this end than the other, and it will gradually change along its length. The beak end of the finished cutter is the end closest to the lathe axis, with the smallest radius. The same choice of cutting surfaces as before can also be used here. Figure 6 shows the tooling arrangement.
I find the cutters easiest to use by fixing them to a short flat handle, using the tapped mounting holes in the underside. The finished tool looks a bit like a metal toothbrush, but is very effective. Figure 7 shows the finished device.
|Abrasives||A range of abrasives is essential, 240 - 600 grit for most uses. "0000" grade wire wool is also useful.|
|Beam drills||A range of sizes for initially drilling through the timber blanks before reaming.|
|Block plane||For block making (the name is a coincidence!). Use one with a shallow blade angle and an adjustable mouth, such as 9 1/2 and 60 1/2 sizes.|
|Callipers||Vernier, dial or digital, take your pick. Use to accurately measure turned diameters. If you can find one, an internal calliper with a dial gauge is ideal for checking the windway depth. If you can't get hold of one, make your own using a standard dial gauge fitted to a pair of thin "scissors" arms. The gauge fits on one side, while the other end of the scissors arms is inserted into the bore.|
|Chisels||For cutting the ramp. Use a range of sizes from 4mm to 12mm to suit.|
|Coping saw||To cut the beak underside profile.|
|Dowel||Lengths of dowel are useful for removing the block.|
|Drills||Lip and spur type is best for drilling the tone holes. Metal drill-bits are next best. Pack the bore with a wooden former made from scrap timber to prevent internal splintering.|
|Files||A range of needle files is always useful. Use round needle files to undercut he tone holes, but break off the sharp point and grind the end smooth first, to avoid damaging the opposite side of the bore.|
|Forstner drills||Forstner bits are used for seating thumb bushings. Larger Forstner bits, or preferably saw-tooth bits can be used to cut tenon sockets. However, I prefer to use a metalwork lathe for the job, to get a good fit.|
|Gents saw||Cutting block blanks.|
|Plug cutters||Used to make thumb bushing blanks. Use in conjunction with Forstner bits for a perfect fit.|
|Scalpels||Use for delicate cutting of the chamfers, cutting the step in blocks and preparing cork strips for the joints.|
|Steel rule||Ditto callipers, but for lengths.|
|Turning tools||Make miniature scrapers, parting tools and beading tools from short lengths of slim tool steel set into wooden handles. Grind to shape as required. Use to form the delicate beading and detail on Baroque recorders.|
The most important tool is patience! A good recorder can take a long time to make. Count on at least 30 hours labour for an alto; 50 if the timber is difficult or the recorder has embellishments like contrasting wood fittings. A hand made recorder is a thing of beauty. Enjoy creating it.