Two dovetails in a 3 way corner joint

[Anamika]

I am preparing to build a workbench. I have only 3 x 4 lumber and mostly hand tools.

I have made one design for a 3 way corner joint as seen in the attached image. I have some doubts whether the frame would be of necessary strength and rigidity. I wish to know if  2 dovetails actually weaken the workbench leg.

If it is OK,  I propose to add corner blocks (of solid wood) and also dovetailed corner pieces to further strengthen the frame and supplement its rigidity.

If it does  not work, I would like to know alternatives. Mortice and tenon is ruled out since with only bench chisels ( no mortice chisel), mallet and handsaw, I am not confident of cutting deep mortices accurate and square.

I solicit views from kind experts on the subject.

Thanks in advance.

 

 

 

[pkinneb]

Welcome!

Given the racking forces of a bench I would think a mortise and tenon joint where you have glue surfaces on two sides would be better.

[Tom King]

Yeah, no need to re-invent the wheel.  You can cut mortises, especially the large mortises here, with bench chisels, without needing a mortising chisel.  Just go slow, and keep checking, and you can't pry out as large of chunks as you can with a mortising chisel.

[drzaius]

What @Tom King and @pkinneb said. There's no reason you can't chop mortices with bench chisels, just take lighter cuts. If the edges are too fragile, then just grind a higher angle secondary bevel, like 35* or so. If you are capable of cutting that joint in your sketch, then chopping mortices will be a piece of cake. And that joint will be very weak.

[Ronn W]

Assuming that you wnat to stay with the dovetails, let's look at your concspt.......

1.  It appears that you are notching the aprons into the legs a little in addition to the dovetails.  I would not do that - you will get more glueing surface without the notches.

2.  It appears that your legs are taller than the tops of the aprons.   I understand that you need some leg material above the dovetails but how does your bench top sit in place on the aprons??

3.  What is the top made of?  If you are going to use 3x4's or similar they will be abel to be supported on the aprons at the ends of the bench without stting of the aprons on the long sides.  If that is the case then you could lower the long side aprons so that the dovetails do not interfere with each other.  My workbench has the long side aprons lower. 

4.  May I suggest a saddle joint (strong with lots of gluing surface and less chisel work than mortise and tenon) for the end aprons and then dovetails for the lower long sides aprons.

Good luck, take your time and do practice pieces before tackling the real thing.

[Anamika]

Keeping in mind the considered opinions offered by experts, I have remodelled the joinery as per the attached image.

The bench top would rest on the short aprons through a micro angled dovetail ( more of a dado actually ). 

I hope this frame would now be strong and rigid. The overhang on one side is for mounting the vice. But for this, the top and the frame are flush.

I thank all the masters for their advice.

I would request a final opinion on this design.

[RichardA]

Is the vise going to be on the overhang?  If so, rethink it's placement to the other end. A vise on that overhang is going to make the bench less stable.  And why the dovetails on the legs?   Visual? Or supportive?  Seems unnecessary, since it's part of a tool.

[drzaius]

I agree, if the drawing is to scale, then the bench is going to be very unstable when using the end vise. 

Rather than dovetails for the stretchers, mortise & tenon offers more glue area. For a little belt & suspenders, draw bore and glue them. Another advantage to draw bore is that you won't need clamps when gluing the joint. In this situation, a dovetail doesn't offer any advantage. Its forte is that it resists pulling apart. What is needed here is racking resistance.

[wtnhighlander]

My bench is a similar design, in that the top is flush at one end, overhanging the other. Vise is on the flush end.

I agree that the dovetails add nothing but aesthetics if the joints are glued, but they can make a nice take-down design if you leave them dry, and secure them with dowels, drilled through at slightly opposing angles, and also left dry so you can drive them out with a punch.

[Ronn W]

1.  Your long side stretchers could be a little highr if you wnat a little more room (height) under the table.    You lonly need about 1/2" of wood between the botom of you dovetails and top of the mortises.

2.  Are you planning a shelf on top of the bottom stretchers?  If so I would lower the short end stretchers a little so that the bottom of the short end stretchers are at the level fo the shelf to help contain items on the shelf.

3.  On my bench I glued ledgers on the long rains for my shelf (loose 1/4's) to rest on.

4.  I agree that you could get rid of the dovetails - try a simple saddle joint.

%.  Consder adding a little over hang on the other end so that you can clamp things to the bench.  Nothing worse that not being able clamp something down when the need arises.

[Richard Rose]

I agree with the posts recommending eliminating the dovetails and  adding overhang on the side of the table currently flush with the base.

Why are you re-inventing the wheel? There are literally thousands of designs of excellent, sturdy bench construction to emulate consisting of mortise and tenon joinery. The dovetails in your design are essentially lapped joints, lacking the strength of the enclosing side and extra gluing surface of mortise and tenons.

The purpose of dovetail construction is to resist joint movement against the angle of the tail such as used between drawer fronts/backs and sides. Are you really concerned that your legs will pull away from the stretchers in that direction? If so, your drawing already shows through tenons at some of the joints. Then, make all the tenons through tenons and wedge them.

Why is there a thin ridge along the top of the aprons supporting the top? That severely limits the support area between the top and the base and will result in bouncing between them when pounding on the top and complicates attaching the top. Or is that a spline that will fit into a cross-grain channel in the underside of the top? If so, why? Reinventing the wheel again. Attaching table tops to bases involves straight-forward techniques that allow for top movement and have been standardized for centuries for good reason.

Good luck,

Rich

[Anamika]

Well, the final version, after incorporating the suggestions from the well meaning gentlemen, would now look like this. There is a short overhang on one side for clamping purposes. The vice would on the flush side. All the joinery is through mortice and tenon. All would be through tenons. Yet to decide regarding draw boring or wedging/pinning the tenons.

A final word on validation of this design would be highly welcome.   In the meantime let me build up confidence for cutting 16 accurate pairs of deep mortice and tenons with hand tools.

My sincere thanks to all the experts who have spared time to look into the subject.

[drzaius]

Your design is evolving nicely. Both draw bore and wedged tenons will hold the joint together very well. But draw boring will also pull the joint very tight & then hold it there. With draw boring you don't need to make them through tenons. I chose to use draw boring on all the stretchers. No clamping needed.

[Wood Basher]

18 hours ago, drzaius said:

With draw boring you don't need to make them through tenons.

Just to be pedantic, you don't need through tenons to use wedges either. Click here for an example on youtube. I have successfully done joints this way before without problems.

[drzaius]

3 hours ago, Wood Basher said:

Just to be pedantic, you don't need through tenons to use wedges either. Click here for an example on youtube. I have successfully done joints this way before without problems.

True, but that is definitely an approach that requires more advanced skills to get done just right.