Adding fine details to your work, part 1

Words and photos: Damion Fauser

Several years ago I had the opportunity to travel to Canada to attend a five day course with Garrett Hack entitled ‘Exquisite Surfaces and Details’. Aside from being a highly sought after woodworking author and teacher, Garrett is renowned for producing contemporary versions of Federal style furniture adorned with fine string inlays and other decorative details.

We each started with a single board of cherry, onto which we incorporated our own versions of Garrett’s techniques, and by the end of the week we all walked away with individually unique sample boards. This article will focus on making and using scratch stocks.

1. The author’s shop-made scratch stock with beading cutter inserted.

A scratch stock is a simple tool consisting of a small block of wood with a shop-made cutter secured in place with a threaded screw or bolt (photo 1). The simplicity of these tools, and the fact you can customise your own cutters, makes them extremely versatile. The only limitations to the profiles are the physical size of the files you can get to shape them. We were shown how to make cutters for applying fine bead profiles and for cutting grooves for inlaying decorative lines that were less than 1mm wide.

Making the scratch stock

Making these tools is very easy. Take a small offcut of hardwood that fits reasonably comfortably into the palm of your hand. Mine is 95 x 28 x 25mm, but just adjust the dimensions to fit your own hands. With a handsaw or at the bandsaw cut a kerf approximately two-thirds through the thickness of the stock at a distance from one end to allow your chosen screw to reach through to secure the cutter in place. Drill, then tap a threaded hole for the screw into one end of the stock through to the kerf you just cut. Any hardware tap that matches the thread of your screw will work for this (use a little wax to lubricate the cutting action). Once this is done, smooth and shape the corners of the stock so it’s comfortable to hold.

Making the cutters

For this you’ll need some stock steel, a mill file, and depending on what profile you wish to make, some other files such as round chainsaw files or saw-sharpening files. Suitable steel includes old handsaw plates, bandsaw blades and card scrapers. You are looking for something that is easy enough to file and stiff enough to not deform during the cutting action. Take a pair of industrial shears and cut a section from your stock of approximately 35 x 25mm. Each corner can be shaped to a different profile. Use a mill file to smooth any rough edges or remove any old bandsaw teeth etc.

Secure your stock in a vice (use a vice away from your primary workbench if you do not wish to have metal filings on your good bench) and commence filing. Remember to only cut on the push stroke or you will prematurely dull your files. When using the round or triangular files you may find it easier to start the first few strokes with one hand, using your off hand to guide the file on the stock in a similar fashion to starting a hand saw cut. The files cut quickly and with a few dozen well controlled strokes you will reach your desired profile.

Now you need to sharpen your cutter. This is just like sharpening any other cutting tool, just remember that all the facets of your cutter are involved in the cutting action and need to have their intersecting edges polished accordingly. Start by polishing the flat faces of your cutter on the stones of your choice. You don’t need to polish the entire face, just to the point where the area in the vicinity of your profile is polished.

2. Showing a custom made beading cutter with two profiles, (1/8” and 3/16” diameter) sharpened and ready for use. Note the faces are only polished in the area of the actual cutting profile.

Once the face is polished, turn your attention to the edge facets of your profile. This will likely require a combination of slipstones, all of which are available from most woodworking retailers. Concentrate on all facets of your cutting profile and once they are polished, you are ready to work (photo 2).

Setup and use

Your chances of success with a scratch stock will significantly increase if you select woods that work well with hand tools and have clear, straight grain. At time of writing I was living in the USA, and has only used these tools on cherry and tulip poplar, but I would now be confident of using them on many Australian timbers such as the Flindersias (silver ash, Qld maple), Huon pine, Tasmanian blackwood and jarrah.

Insert the cutter into your scratch stock. The scratch stock rides against the edge of your workpiece like a fence, so position the cutter relative to the stock to achieve your desired profile.

As it is a one-handed tool, you have the choice of either securing your workpiece in a vice or shavehorse, or holding it in your other hand. To begin, place the tool against your workpiece where you wish to start the cut, place the cutter down until it contacts the work, and tilt the stock in the direction you wish to cut. You don’t need to be overly concerned with the grain direction of your workpiece—one of the unique features of these tools is that they can cut both ways, so if you find the tool struggling in one direction, simply tilt it the other way and cut in the other direction. This means you can use scratch stocks on either the face or the edge of your board as well as on curved pieces. Apply gentle pressure and push or pull the tool along the edge of your workpiece.

3. Scratch-stock in use. Note the tilt of the tool in relation to the workpiece and the shavings that can be achieved with a sharp cutter.

As it is a cutting tool, you should be generating shavings rather than dust. Once you’ve successfully taken the first few shavings and established a kerf for the cutter to ride in you can start to increase the pressure—you will be surprised how quickly these tools will cut (photo 3).

Cutting edge beads

4. Progress shot of a bead profile being cut. Note the bold use of crayon to act as a depth stop.

A round chainsaw file used to cut a semi- circular profile set in from the corner of your cutter will result in a cutter that will cut a bead on the edge of your workpiece. These tools do not have inbuilt depth stops other than bottoming out at the base of your cutting profile, however to avoid unnecessary wear and tear on your cutting edges, a good way to know when you’ve reached full depth, particularly when cutting edge profiles such as beads, is to initially mark your workpiece with a pencil or crayon line where the bead is to go (photo 4).

Once the tool has removed your mark, you’re finished. When cutting beads, another trick that Garrett taught us to reduce wear on cutters was to use a block plane to make a small chamfer on the corner on which the bead is to be applied, effectively reducing the amount of material that your cutter is required to remove. Be careful of going too far with the block plane, particularly if your bead profile is a small radius.

5. Finished 1/8” diameter bead profile, straight off the tool.

I was surprised how clean and polished the resulting beads were, but if necessary, a little sanding will remove any blemishes (photo 5). You can also use your beading cutter to make custom cock-beadings to apply to drawer faces for example. Simply run a bead on some wide stock and rip the bead off on the tablesaw.

String inlay

Whilst there are string inlay cutters of various widths available commercially, these cut kerfs with vertical sides, requiring you to make your string stock absolutely perfect to avoid unsightly glue lines. Garrett’s method avoids this risk by cutting a kerf that is tapered vertically, using a wedged shaped cutter. The stringing stock is tapered with a small plane to give a wedging fit in the kerf and seamless joinery.

Making this cutter requires nothing more than a mill file. Start by holding the file at an angle by lifting the edge of the file furthest from the corner of the cutter off the stock. Aim for a shallow angle of approximately 10°. Push forward with the file for a few strokes and you will notice a wedge-shaped profile being cut into your stock. Keep going until you have reached a depth of approximately 5mm at the base of this wedge. Then hold the file flat and remove more steel from the cutter stock towards the other corner. This is to provide clearance so the cutting point doesn’t bottom out.

Now very carefully file the corner of the cutter to match the angle of the inside face of the cutting tip. Note that you must leave a flat facet at the tip of your cutting profile, so do not file it to a sharp point.

6. Freshly made and sharpened string inlay cutter.

You should end up with a shape like the one shown in photo 6. Sharpen the cutter as described earlier, noting that as the profile has only flat facets, you will only need flat stones rather than slipstones.

Insert the cutter into the scratch stock, ensuring you set the profile the desired distance from the face of the scratch stock. Pay particular attention to ensuring your cutting profile is plumb in relation to the face of the scratch stock. Align the tool to your work as previously described and commence cutting. Again, you should be aiming for shavings. With no depth stop, you will have to rely on visual judgement to ensure you maintain a consistent depth of cut, but with a little practice this is relatively easy. Long smooth cutting strokes will assist with this.

Cutting with the grain is relatively straightforward. Cutting across the grain requires a little more finesse however. Be patient and use light, very gentle strokes.

7. Using a knife to sever fibres when cutting crossgrain kerfs.

Take one or two initial passes and then take a freshly sharpened marking or exacto type knife and score the fibres at the base of your shallow kerf against the walls of the kerf (photo 7). This will reduce the risk of tearing the crossgrain fibres and ruining your workpiece. Through cuts are straightforward, you just run the tool off the end of the workpiece.

Making a stopped cut requires a second tool, a micro chisel with a cutting edge the same width as the kerf at the surface of your workpiece. We made ours from cut nails but you could also use an old allen key for example. Take a small offcut of hardwood approximately 150 x 20 x 20mm. Drive the cut nail into one end so that approximately 30mm remains proud, and then grind each side of the nail down.

8. The author’s self-made chisel next to the commercial equivalent from Blue Spruce Tools.

Go slowly and when you’re close to the mark, start testing the fit in the kerf left by your scratch stock cutter. Once you’ve reached a good fit, grind some steel away from the base of the chisel up towards the tip to create a bevel and a sharp edge and also to allow for clearance (photo 8).

Sharpen on your stones as you would any other chisel. Alternatively, commercial mini-chisels are available from Blue Spruce Tools in the US in four sizes—0.61, 0.81, 1.17 and 1.57mm.

Mark the desired stringing pattern on your workpiece. Make your straight cuts as described earlier, stopping just shy of the ends. Use a chisel with the bevel facing your existing kerf to sever the fibres at the very end of the marked line and then use the chisel to gently lift the waste away. Be very careful as it is extremely easy to lift away the fibres at the edge of your kerf, potentially ruining your piece. I used a marking knife to further sever the fibres at the edges of the kerf when cutting cross grain and then used the chisel to remove the waste.

To make your stringing stock, choose some straight-grained, clear stock of the desired colour and clearly mark the grain direction. Rip a wide strip that is slightly thicker than the profile of your cutter.

9. Zero clearance cutting fine strips at the bandsaw.

Turn this on its side and rip thin strips that are slightly wider than the depth of the scratch stock kerf. I prefer to use the bandsaw for this, first creating a zero-clearance insert by sliding a piece of this ply or MDF into the blade and clamping it in place on the table (photo 9).

Alternatively you can turn this strip on its side and use a straightedge and a knife to slice your stock into strips. Use a sheet of ply, MDF or a self-healing cutting mat for this.

10. Using a block plane to taper stringing stock. Note that one side of the plane is allowed to run on the workbench surface to generate the taper.

Now you need to taper your strips to match the tapered kerf. All you need for this are a flat surface and a small plane such as a block plane. Place the block plane on the stock at the edge of the tool and let the other edge of the tool rest down on your flat surface. This angle is close enough to that of the profile of your cutter. The strips are too thin to butt up
against a stop and plane because the compression will make them bend and snap. Rather, make them long enough so you can hold one end while you push the plane with the other, thereby keeping the stock in tension (photo 10).

Test the fit as you go. You are aiming for a friction fit that produces a slight amount of resistance when removing the strip from the kerf.

The biggest challenge when gluing the strips in is getting the glue into such a narrow space. Garrett taught us to slightly dilute yellow or white glue to reduce the viscosity. Fill your chosen applicator bottle with 50ml glue, add 4–5 drops of water and shake to mix thoroughly.

With the friction fit of your strips you don’t need much glue in the kerf. Apply the glue sparingly, position the string pieces into their kerfs and gently push down with finger pressure. As you have cut them slightly wider than the depth of the kerf, they should sit proud of the surface. Take a block plane and trim them down until they are just proud. Note that yellow and white glues will very quickly rust tool steels so clean your plane as soon as you are finished.

11. Burnishing the stringing stock down into the kerf.

The next step is critical, and it becomes evident now why you shape your cutter and plane your strip stock to a taper. Take a round piece of steel such as a screw-driver or burnisher and use it to force the string further down into the kerf in a motion similar to turning a hook on a card scraper, but pushing straight downwards (photo 11). This action fully seats the string into the kerf and will result in invisible glue lines.

12. The end result, with the rule illustrating the micro scale achievable with this technique.

Take your block plane again and true your workpiece surface. This is where careful attention to staying aware of grain direction pays off. The levelling of these details should only be done by handplane or scraper, as sanding will result in cross-contamination of multi-coloured dust and will significantly reduce the colour contrast of the workpiece. If you get the grain direction wrong, you risk having the blade of your tool rive the grain of the string inlay, pulling it out of the kerf and ruining the workpiece. You should end up with nice clean lines and a clear colour contrast (photo 12).

Curved string inlays

You can use the same cutter to apply curves, you just need to make yourself another tool to hold it. Start with a scrap of hardwood that is wide enough to hold the cutter and long enough to cut your desired radius. Drill a hole at one end and insert a point to act as the base of the radius. I glued in a small nail with the head filed off for mine.

13. Shop-made radius cutter.

At the other end of the stock, bandsaw a stopped kerf, stopping shy of the location of your pivot or base point. Place the cutter in the kerf so the tip protrudes at your desired radius and mark for a screw hole on either side of the cutter. Drill and insert two screws that once tightened slightly will secure your cutter in place. Remove some material at the bottom corners near the far end of your stock to allow for clearance when tilting the tool to generate the cutting action (photo 13).

14. Showing the radius cutter in use.

Mark the curves onto the workpiece, determine the base point, secure the tool’s point there and take light shavings into your workpiece. Grain direction is paramount as you quickly transition from long to crossgrain, and downhill to uphill cutting as you move around your curved profile, so pay close attention. If necessary, use a knife and chisel to ease the process by severing the fibres and remove the waste as you go (photo 14).

One concern, depending on your design, may be the mark left by your base point. Where possible, design your pieces so the base point is actually off the workpiece, thereby eliminating the problem. Where this is not possible, try to minimise the pressure you apply at the base point so that it may be planed out during your final surface preparation.

The radii you can produce are limited somewhat by the species you choose for your stringing stock. You will be able to cut tighter curves with a flexible species such as holly than with a brittle species such as ebony. You can slightly increase the bendability of your stock by applying heat by soaking in hot water or bending over a heated pipe, but experimentation will tell you how far you can go without risking breakage.

15. Use a chisel to achieve neat junctions.

Treat the junctions of curved or straight lines as stopped cuts, using your knife and chisel as previously described to assist you. When joining two lines at a corner, use a chisel to gently chop the appropriate bevels on the end of each piece to achieve a refined joint at the junction (photo 15).

Now, I haven’t covered everything (you’ll have to travel to the USA for a course with Garrett for that!), but you have enough tools, tips and techniques to proceed. The only limit to what you can achieve is your own imagination. You will also quickly notice how clunky even a 1/8” line made by a tablesaw blade or router bit now looks to your eyes when compared to the delicate lines and edge profiles you can achieve with these techniques. Play around and you will be surprised at the patterns and details you can come up with that will take your work to another level.

In part 2, we will look at making and inlaying shapes and patterns and creating fine edge profiles.

First published in Australian Wood Review magazine issue 77, December 2012.

Damion Fauser @damionfauser is a furniture designer maker and woodwork teacher in Brisbane.