Mortise and Tenon Miter Joint?

 This sample languished forgotten in the bottom of my box of Sample CNC cut joinery.  I was sorting out that box and nearly threw it away as it appears to be a simple miter joint.

Looks Simple

Pulling it apart reveals the inner mortise and tenon that hold it together.

Surprise Inside!

The tenon was cut from what is normally cut off to make a miter joint. Mating mortise cut on the other side face. There is no weak cross grain in the tenon. This tenon also keeps the faces aligned when gluing up the miter. While I cut both sides on my CNC, I'm pretty sure this could be duplicated by a clever craftsman without using a CNC. 

Very much the best of two joint types working together to make a strong connection where there is normally a need for added reinforcement. 

With wider boards, each side can have a tenon and a mortise.  Identical cuts using a CNC.  Tenons on each side slide into the mortises on the other side. 

Comments encouraged!

4D 
 

 

Small Trays Made From Leftover Scraps

I have A CNC. I have a bottle of wood glue, and several clamps. I also have several small odd shaped wood scraps begging to be used for something useful.   

Small scraps glued up can make larger boards. Here are a few shallow wood dishes/trays all made from glued up scraps.  

This first oval dish was cut from three maple scraps glued together. I used my CNC to cut the top recess and rounded edge.  Then used my router table to bevel the side 11.25 degrees, and follow that up with a small 45 degree transition to the bottom.  

Oval Tray

This second tray was the best shape to make from two glued up corners saved from a hexagon table top cutout. 

Diamond Tray

This walnut version was made from several walnut scraps. Add in patching two screw holes with walnut dowels to increase the potential final size. For this one I used the modelling tool in Aspire to create the center recess. It also has a 45° chamfer on the bottom edge.  A rounded rectangle.

4" x 6"

This 4" x 4" Cherry example required several bit changes, and used the VCarve toolpath to make the crisp inside corners of the dish. It used up the left over corners from a round plant stand cutout. Its shape echoes the shape of the glued up corners. 

V-Carved Cherry Dish

Several bit changes were required.  Bits used (in order) were a 3/16" end mill to clear out the center area of the dish, then a 60 degree V-Bit to slope the sides and create the sharp inside corners. A 1/4" end mill cut a clearance path for the final bit and profile out the final shape.  Last bit used on the CNC was a side cutting V-bit to put a groove around the sides as shown below.

VCarved, V-cut, and beveled. 

As with all of these trays some follow up work was needed.  The waste perimeter was roughly cut off using my bandsaw.  A flush trim bit cleaned up the bottom edge on my trim router table.  Lastly a 45 degree chamfer bit beveled the bottom edge. 

Beveled bottom and side groove.

Lastly, an octagon dish. Made from one scrap board nearly 11" long and 2.6" wide.  It had a rough bark side.  I cut it in half and glued the good sides together to make a roughly 5" x 5" block close to 7/8" thick. The inner and outer sloped sides were 3D toolpaths.  The center of the top was a pocket toolpath to bring it down to the bottom of the inner sloped sides.  Hard maple with tight grain cut nicely on the CNC. 

Octa Dish

These are small examples of the value you can find from small scraps of wood left over from previous projects. Glue thin scraps together to make thicker boards that may be more useful. Any scraps with a straight edge can usually be glued up to make a larger board.  A trip across a jointer may be needed to face the edges for the best glue joint. I have a small benchtop jointer that is perfect for this task. Its small expose blade gap between tables make it safer than larger jointers with a larger expose blade gap to slide over. 

So save those odd scraps.  When boredom or inspiration strikes take a few and glue them up to make a larger board that can become something useful.  

Comment encouraged!

4D

Steep Dovetail Corner Joint

 

Face to Face

This is a sample I made to show my Furniture Design students one way to connect wood at a steep corner.   A variation was used to connect the top of A-frame legs on a CNC controller cart the students made. The parts slide together, so technically this is more of a French Dovetail solution. 

Open for Inspection

Careful layout of vectors was require to guide the dovetail bit.  Each half had to be clamped at an angle so the bit could travel level through the ends. My compound angle clamping fixture was used for that task. 

One half slide down into the other

There is a taper to one side of the cuts to compensate for the wide top sliding down to the narrow base of the dovetail shape. This joint only slides together in one direction. 

Tails into Slots

Once together there is no play between the halves,  Snug tight.  This sample has been abused for inspection by students and is a bit worn.  A little glue and the dovetail interlocking would make a very strong steep corner joint. 

Snug Together

I am considering using this joint for the corners of a triangular mantel clock box frame.  With a shallow dovetail corner variation at the top of the triangle. 

All Stood Up

Ends were trimmed so when assembled the end would be flat across. At the top the dovetail pattern is evident and interesting. 

I realize this steep angle is a rare occurrence in projects.  Knowing this joint is possible and how to cut it though keeps it on my menu of options when designing furniture and accessories.  

Comments are encouraged. 

4D

The Accidental Line. One Key to Original Designs

Design Process.

While I sketch (pencil on paper) out design ideas it is often an accidental elbow bump or mental distraction that results in an accidental line. That line sometimes leads to the freshest details or at least a new iterative path to pursue.  This is the magic blessing that comes from sketching on paper.  It is a feature I miss having when drawing out ideas on the computer using any CAD program.  I remember a conversation with a former head of the Architecture Department at KSU where he shared a similar respect for the accidental line. On a page full of quickly drawn iterative sketches an imperfect arc or misplaced line stands out.  It is the attention it draws to stand out that hints at the potentially unique creation. 

I believe many of the new and inventive original ideas are the product of pursuing an unexpected inspiration or accidental line.  That old solutions survive for so long without improvement doesn't mean they are good,  It means no one has stumbled across a simple but vastly better alternative.  My patented inverting TV tray table design was the outcome from an accidental sketch line.  TV Tray Table

So sketch, Sketch a lot.  Don't trust using a mouse with a PC app to leave an accidental line.  I concede that there are tablet apps that you can sketch on with a stylus or your finger, and some come close to mimicking what is possible with pencil on paper.  Don't get distracted with the color options and line width options and so on as they steal attention away. There is grace in a simple session between your hand and a piece of paper via a simple pencil. Shy away from mechanical pencils with skinny leads. The relatively fat lead in a wood pencil that you have to sharpen is where line width and shading and random marks live. I know there are tools in most drawing programs for effective iteration. I have yet to see any app that occasionally puts a line somewhere you didn't intend or expect it to be then lets you start a new iterating branch of sketches inspired by that accidental line.  

Sketch pads (the paper kind) come with blank pages to sketch on. There are also pads of graph paper with a light grid you can use to maintain relative scale of your sketches on.  I prefer the latter.  On a blank white page a beautiful sketch of something you want to make may prove less appealing when adjusted to fit actual final dimensions. I often start my sketches with a light rectangle or perspective cube drawn to desired scale on the grid. Then I know what I sketch within will remain constrained to the desired final proportions.  

4D 

Stretching Stretcher

 

Identical halves

Slide together

On occasion I've bumped into the conflict of a solid wood small table top that has grain running 90 degrees from the direction of the stretcher(s) below.  As wood likes to swell or shrink in width as the seasons change the distance between attached end leg frames changes.  In theory any stretcher between would need to grow or shrink in length to accommodate that structural flex. A tenon on each end keeps the stretcher square to the end frame, and a sliding dovetail embrace between the two halves should allow this stretcher to stretch. Tight together in the winter when the humidity drops, and slid open as much as 1/4" when spring arrives and humidity rises. 

This isn't a common problem as experience fabricators know how to orient wood grain to reduce conflicts on assembled wood furniture.  In fact it was only one past student of mine who's design could have benefited from this idea.  That was more than 2 years ago before I retired. I post it here to rid it from my creative mind.   

4D

Great Projects to Start a Furniture Design Class With.

Plant Stands (Workshop 2) or 

Stools (Workshop 3).  

Two Weeks to complete.

No drawings need to be submitted.

Any number of floor contact points other than 4 are allowed. 

Plant stands must hold at least one potted plant at least 6 inches above the support surface (table or floor). 

At the beginning of a semester class, when students haven't yet decided what they want to make or at least aren't ready with drawings or dimensions, these quick projects get their creative juices flowing, keeping them active in the workshop rather than sitting at their studio desk staring at their computers. Their semester project development can develop outside of class time, with a quick review each class day with the professor, one at a time for 10 minutes each while others continue working on their plant stand or stool. 

This is NOT recommended for their first workshop class given that students aren't yet familiar with where tools and materials are to use or how to use the power tools safely. A great project to teach them the tools, joinery, production sequence, etc., is this Joinery Box project. 

Projects from One Class

The leg limit (not 4) is intentional to encourage the students to think outside the 4-legs box.  Any number of legs are allowed from 0 (hanging), 1 (wobble base), 2 (rocker), 3 (tripod), 5 or more. Just not 4!

The stool project has a higher expectation given that their design must support the dynamic weight of humans. This is where a one-point (shallow dome) base or a two-point (rocker) design makes sense. 

Students enjoy this project!

With department head approval, a competition could be held asking departmental faculty to inspect all stool or plant stand designs to pick their favorite(s). The winning design might earn the student designer free printing/plotting for the semester.  Or perhaps a free t-shirt with the latest department logo on it. 

End the two week project with a photo session.  Have workshop 2 students bring in plants to adorn their stand designs with.  

I was asked one semester if a 3D printed plant stand was allowed.  My answer was yes, but only if it consists of at least 4 parts that need to be assembled after they are printed. 

This project turned the first two weeks of what had been a slow starting semester into a busy shop and enjoyable project making time.  The biggest challenge was getting the students to work on their semester project designs during that first two weeks.  Project drawings for that project should be submitted the first day of the 3rd week.  Materials should be on their way. 

4D

A Table Lamp that Tips

Tipped to the Right.

Why a lamp that tips?   

Not for momentary joy or by a design mistake. With a way to keep the lamp leaning over at least a few obvious benefits become available.  Park the lamp on a corner of a table, then let it tip toward the middle to better illuminate the table surface.   Have kids that like to play on the floor?  Tip the lamp out to better illuminate the floor beside the table.  Using one or more 1"d steel balls and a rim of dished pockets you can move the Center Of Gravity around so the lamp will stay leaned in the direction the ball(s) are positioned at. Maximum lean angle is 12.5 degrees. 

Maximum Lean

This design consists of three wood parts.  A hub that the light hardware connects to. A simple center post. Lastly a domed base. Simple. Three parts. The lamp can tip but won't fall over. The base is a larger mimic of the top hub. The power cord runs up through the center post which is done in two halves. It exits the side of the base which is also cut in top and bottom halves.  The 1" steel balls were ordered from the jungle store, along with the 12mm threaded brass balls.  I used two halves each for the post and base to make it easy to route the power cable through. Base is 2.25" thick and the center post large diameter is 1.5". 

Almost Straight Up

A 12mm diameter brass ball screws down onto the harp. The shade ring with a 3/8" diameter hole rests on it and stays level no matter how far the lamp tips.  

I used the modelling tools in Aspire to make the pockets for the 1" steel ball on the curved surface of the base top. The moulding toolpath was used to shape all the other parts. Nine pockets evenly spaced around the perimeter allow just 3 steel balls to vary how far and in which direction the lamp tips.  

Undecided

This project, as many do, threw a few challenges to me when making the parts.  2-sided CNC projects must be perfectly aligned when flipped over.  Even when I think I have that challenge solved it is worth verifying alignment before each new cut. 

First try making the bottom of the base proved my design theory was wrong.  The curve was so flat the weight of the base itself was so heavy it wouldn't tip even with the steel balls all on one side.  

Second try I recut the bottom dome using 1/2 the previous radius.  It still was harder to rock the base than I want it to be.  Adding the light hardware, bulb, and shade might have made a difference so I added them to check. Testing proved the weight of the light hardware and shade weren't enough to make a difference.   

I had a cherry block that was large enough and thick enough to make a new base bottom. 1+5/16" thick.  Third try did indeed tip with the steel balls rather easily.   A bottom dome with close to a 6" radius center works well. 

This concludes my chase to see if this crazy idea works. I'll throw some maple stain and a top finish on the parts next time I have my finish table set up.   

Comments welcomed and appreciated. 

4D