Making (rock solid) breadboard ends

The top panel on this chest is supplemented with breadboard ends, adding structure and aesthetics. Photo: Naman Briner

Words and process photos: Damion Fauser

Breadboard ends are essentially a structural element added to a panel to aid in keeping it flat – this works because the long grain rigidity of the breadboard end is stronger than the (hopefully unlikely) cross-grain warping of a wide panel.
The issue is that you can’t simply fix the breadboard end to the panel because this would violate one of the most fundamental wood movement principles.

The issue then becomes – how to attach the breadboard end to the panel whilst also allowing the panel to expand and contract across the width. There are simple and quicker methods that can work, particularly on smaller panels, such as long slip tenons, stub tenons and sliding dovetails for example.

This article will cover the design and execution of the more traditional approach. This method takes longer but in my opinion is vastly superior in terms of strength, functionality and durability.

Alignment realities

Whichever method you choose, you must understand, plan for and accept that the edges of the panel are very rarely going
to be perfectly aligned with the ends of the breadboard end (photo 1). You must be perfectly clear with your clients about this, and even then, you may well get the call asking why things aren’t in alignment.

Cutting breadboard end boards to length will depend on the season you are making your project in. If you are making at the height of summer, size your ends slightly shorter than the width of your panel, so that when the panel shrinks during the drier winter, it will end up slightly inside the ends of your breadboards. Vice versa for making in winter.

There are species-specific formulae available for calculating the scale of wood movement, but I use a ballpark figure of 1% of total panel width. For example, a 1000mm wide tabletop will expand by around 10mm through the seasons. Note that this expansion is spread across the panel, so each edge will move around 5mm each season. You can use this to predict likely expansion and plan for your anticipated overhang/inset when cutting your ends to length – in this case I would aim for a maximum overhang of 2.5–3mm each way.

Tenon and groove

There are two main elements to a breadboarded end – the wide tenon on the panel and the groove/mortise arrangement on the breadboard ends. How you cut them will depend on the tooling you have access to and the style of woodworking you enjoy.

Design, structure and layout

Let’s start with the layout and planning. On the panel, a full-width stub tenon does the bulk of the work in keeping the panel flat. This stub tenon is housed in a matching groove on the inside edge of the breadboard ends. A series of longer tenons then provide further rigidity and lessen the risk of the breadboard ends failing along the short grain aspect of the long groove that houses the stub tenon (fig.1). It is the absence of these tenons that makes other methods significantly weaker structurally.

You generally need three longer tenons. The central one is relatively dimensionally stable so we can cut the mortise to closely match the width of the tenon, as we can largely ignore expansion in this area. The other two tenons are set towards the outer edges of the panel and will therefore move laterally as the panel expands and contracts. Accordingly, we must accommodate this movement by making their mortises longer than the tenons are wide.

Finally, you should ideally pin the breadboard ends to the tenon arrangement to prevent it from bowing along the length and coming away from the tenon shoulder at the panel. Even this requires planning for wood movement – the pin/s in the central tenon should be matched to holes of the same diameter drilled through the tenon, whereas you need to cut elongated slots in the outer two tenons to allow for the pins to slide in those slots as the panel changes dimension (photo 2).

Planning these elements will be influenced by several factors. Firstly, I like to use the rule of thirds – essentially the thickness of the tenon arrangement is one-third of the panel thickness. While not rigidly adhering to this principle, I choose the cutting method and tooling for the mortises and grooves, and then match the tenon thickness to that reality. It is far easier to make the tenon fit the mortise and groove than the other way round.

I usually like to make the stub tenon equal in length to its thickness,  creating a nice little square at the interface between the panel and the end. The length of the tenons will be largely determined by how deep you can cut your mortises with your available tooling, allowing for a couple of millimetres clearance in the bottom of the mortises. I’d recommend going as deep as you can, subject to any subsequent shaping/profiling you may wish to cut onto the ends.

The width of the tenons is a little more arbitrary – the wider you go, the more mortising you need to do and the more accommodation for wood movement you need to factor in, but the stronger the arrangement will be. The reverse is also true. I generally plan for the width of the tenons to be proportionally between 1/8–1/5 of the overall panel width.

Cutting the grooves and mortises

Once you’ve done the layout, mark up the ends of the mortises on the inside edges of your breadboard ends, allowing for the mortises to run longer than you plan your outer tenons to be. You can use similar seasonal planning methodology and ballpark calculations for this.

I cut the grooves first. Whilst you could do this with a router or even a plough plane, I find the tablesaw to be the fastest and cleanest method for this task. By setting the fence to cut one edge of the groove width and then reversing the board to run the same cut, you perfectly centre the groove on the board thickness (photo 3).

Then you simply shift the fence over and gradually nibble out the remainder (photo 4). Use a raking tooth profile so you leave a nice flat bottom in the groove.

Cutting the long and deep mortises is likely the most challenging part of the task. Creating the grooves first gives a great reference point for setting up your cutters for removing the mortise waste. Most home-based or small-operator woodworking shops will likely find it easiest to drill out the bulk at the drill press and clean up with chisels.

I would highly recommend using forstner bits where possible as they leave a much cleaner inside wall, making chisel clean-up much easier. It is essential that the mortises run perfectly aligned with the faces of the breadboard ends, otherwise the ends won’t line up flush with the face of the main panel. For this you can make some kind of paring block to assist you with accuracy during chisel clean-up.

You could also use a router to cut these mortises although you may be limited by the length of tooling you can get, and make sure you take small passes to stay accurate and allow for chip extraction.

Cutting these big mortises is far easier with either a hollow chisel mortiser (photo 5)...

...or a slot mortiser. I use a slot mortiser myself and love how clean and accurate the resulting mortises are (photo 6).

Regardless of method, ensure you accurately measure and record the width of your grooves and mortises as these are the reality to which you cut the tenon arrangement (photo 7).

Cutting the tenons

Lay out the shoulders on the faces of the main panel, and the cheeks of the tenons on the ends. If you’re cutting the tenons with hand tools, knifing and gauging these lines will help with accuracy and to prevent chipping out the cross-grain fibres at the shoulders. You’ll start with one enormous full- sized tenon from which you’ll mark out and cut the outer tenons.

There are many ways to cut this initial tenon. I form the shoulders on my sliding tablesaw, but you could also use a tracksaw and guide rail (photo 8). This prevents blow-out when using some of the other methods for removing the bulk of the waste for the cheeks.

The latter include a dado stack (photo 9)...

...handheld router with edge guide or guide rail (photo 10)...

...tracksaw and chisels (photos 11, 12)...

...spindle moulder (photo 13) and of course handplanes.

Next, place the breadboard onto the formed tenon and transfer the mortise ends, allowing for expansion. Mark out the stub and supplementary tenons and clearly mark the waste (photo 14).

Drill some clearance holes in the corners of the waste areas (photo 15)...

...and use hand and coping/ fret saws to remove the bulk of the waste (photos 16, 17).

While you’re at it, cut a smaller sample tenon in some secondary stock, ensuring the length of the tenons are identical. You can use this to check your settings by fitting the test tenon into one of your mortises, and you’re also going to need this piece again later (photo 18).

Cleaning up the tenons

The most common question I now get is ‘how do I make sure the end of the stub tenon is perfectly straight, parallel to the shoulder and matches the depth of the grooves in the breadboard ends?’ Thankfully this is one of the easiest tasks you’ll have.

Dress some strips of scrap stock to perfectly match the cheek and shoulder dimensions of the stub tenon. Fix this in place onto the roughly cut stub tenon with some double-sided tape. Dress some more stock to the same thickness as the tenon shoulders, cut some pieces to size to match the final tenon dimensions and again fix these down with double-sided tape (photo 19).

You now have a template to follow with a pattern-bearing bit (photo 20). The only task remaining is to clean out the round inside corners – this is easily done with chisels and/or a flush-cut saw.

Now you’re going to get really well acquainted with your calipers. Check the actual thickness of your tenons in several places and record this in location on pieces of blue tape (photo 21). Regardless of how you cut the initial tenon, don’t be surprised if you find variations of a tenth of a millimetre or two.

Localised and careful passes with a handplane easily and satisfyingly dial the tenon thickness in to perfectly match the mortises. Use a shoulder plane to cut right into the corners where the shoulder meets the cheeks.

At this point you’ll have to decide whether to square out the mortises or round the edges of the tenons. It’s really a personal choice – as I use a slot mortiser for the mortises I tend to round the tenons, and this is easily done with a rasp (photo 22). I’m not overly concerned about locally damaging the end of the stub tenon in this case as this area will be inside the grooves.

Pinning it all down

The pins form a crucial function as mentioned earlier and can be visible or unseen. If unseen, then ensure you do everything I’m about to describe from the bottom face of the main panel and the breadboard ends, and don’t drill your holes all the way through the breadboard ends.

Here the photos and processes are for visible pins. You can use contrasting species or leave them proud and soften them. You could go all out and make square and chamfered pegs á la Greene and Greene, but of course this would require squaring out the holes. It’s really up to you.

I usually plan for 1/4" to 1/2" pins (6–12mm), ensuring I have a router bit and drill bit the same size – this will make sense later. I also like to make my own pin stock with a dowel/draw plate as I find I can get much better consistency in diameter, as well as being able to choose species.

Position the holes and slots on the cheeks of the tenons – I prefer to keep them closer to the panel to avoid shortgrain weakness from the holes to the ends of the tenons.

Mark out and drill the holes in the breadboard ends, placing a sacrificial scrap board inside the mortise to prevent blow-out (photo 23).

Fit the breadboard end to the tenons and transfer the hole locations to the tenons with a brad point or forstner bit (photo 24). Remember that test tenon? Fit this one and mark out a hole location here as well.

On the main panel, drill through the marked points in the central tenon only, using the same drill bit you used to drill the holes in the breadboard ends. Now also drill the test tenon. Set up a router with an edge guide and load the correct diameter straight bit into the collet.

Using your test tenon, set the tool so the router bit cleanly passes through your drilled hole and then tighten the locking screws so your edge guide runs against the end of the tenon (photo 25).

By doing this, you perfectly match the location of your elongated slots to the fixed pin holes, in terms of distance from the shoulder. Take the strip of dressed material that you used as a routing template to size the tenons and stick this down to the tenons, ensuring you don’t foul the edge guide of the router. Now it’s a simple task

of cutting the slots in the two outer tenons, either using visual marks or stops to define your start and stop points. Again, use your seasonal expansion calculation to size the slots, but it won’t hurt to make them longer than you think you need.

I’m often asked about drawboring at this point. I personally don’t, as I’ve found that with careful planning, layout and cutting, the edges of the breadboard ends will nicely cinch down the panel shoulders. If you do decide to drawbore, I’d advise against drawboring the two outer tenon slots, as this may prevent the pin sliding nicely in the slot.

Assembly

You can accent the interface between the panel and the breadboard ends with tiny chamfers. This is best done prior to assembly and is short work with a block plane and diligent chisel work. Set up your gluing area by elevating the assembly onto some platforms to allow clamps above and below – this will prevent the breadboard ends flexing out of alignment with the main panel.

I often wax the outer two tenons at this point, after all, we want them to slide inside their mortises. I also often use epoxy glue for the lubricating effect on those larger tenon cheeks. Speaking of glue – only glue the central tenons! Tighten the clamps and tap your pins home, applying glue to the central pins only (photo 26).

Surface preparation

Large wide belt and wide drum sanders are best avoided as they will leave prominent cross-grain scratches on the breadboard ends. Orbital sanding is fine. If you choose to finish sand long grain, or if you choose to prepare the surface with edge tools, you need to follow the direction of the grain on either the panel or the ends.

Through the seasons

Careful and proactive planning with regards to tooling choices and methods of work will bring breadboard ends into the realm of possibility for most woodworkers. They can add significant visual interest to a piece, but just remember they’re done for a structural reason. Remember to account for wood movement and you’ll delight in seeing how your panel shifts at the interface through the seasons – a marvellous and visual verification that wood movement is indeed real.

First published in Australian Wood Review, issue 124, September 2024

Damion Fauser @damionfauser is a furniture designer maker and woodwork teacher in Brisbane and a regular contributor to Australian Wood Review. Learn more at http://damionfauser.com/