So, my first proper instructable.....
This is one of the very few designs that I have actually built, and the one I am most satisfied with both design wise and construction wise. To say I was surprised that I could build it (and do it well) would be a bit of an understatement. What surprised me most were the very basic tools I could have built this with. I cheated a bit and used a CNC for part of it, but it really isn't necessary. All you really need is a jig saw, drill, router and a few hand tools.
This instructable is split into two main parts, design and construction. The design section is brief and more of an explanation of how the concept came about than an attempt to describe the design process.
For more pictures of the finished coffee table see the slideshow: https://www.instructables.com/id/Coffee-Table-Mackintosh-Inspired/
Step 1: Design
I cant remember exactly what the design brief was now, my memory of it is hazy and I cant find it either. What I do remember was that it was entitled "Past to Present" and the object of it was to choose a 20th century furniture designer and sample their style and create a design for a piece of furniture from it. The only constraint was that it had to be prototyped. So in practical terms that meant that it had to be able to be made using the college workshop, which in a furniture college means you gotta use wood unless you can get outside facilities. I actually built most of at home, where I had even less facilities.
I chose Charles Rennie Mackintosh for no particular reason at all. Dont even like the Glasgow style all that much though I have a much greater appreciation of it now after studying it a bit. Lucky for me I happened to find myself in Scotland for a few days mid-semester and got to visit the magnificent Willow Tea Rooms and take in a bit of the atmosphere, have some tea and take a few pictures.
When I got back home I wrote a personal brief to guide me ("Create a piece that evokes the modern atmosphere of a social gathering. Much like the atmosphere of The Willow Tea rooms in CRM's time") and started drawing Mackintosh decorative motifs to see if I could get some inspiration. I didn't want to try and sample directly by creating a piece that looked as if CRM himself had designed it because the style doesn't appeal to me, and the table was after all for me. So I looked at all the elements that appear again and again in his work, sketched them and tried to extrapolate out of them something out of scale with the original.
At that stage my personal brief and those little motifs converged and screamed at me to make a coffee table to bring people together. So to make this long story short this design as born.
Some of the models and the full scale mock up are pictured. Originally I wanted to have the sides/legs perpendicular to the ground but I realised that no one would be able to sit up to it if that was the case. These models were as important as the CAD models for refining the design.
If I was going to make this again I would make it slightly smaller for better usage of materials. I could cut the amount of 6mm MDF needed in half with a simple design change.
Step 2: Materials & Tools
You are going to need:
Working Drawing (should be attached to this step)
5 sheets 6mm MDF
2 sheets 18mm MDF (about €19.50 each)
3 pieces of 6mm toughened glass (€40 total)
1 roll window tint
High Gloss White PC Lacquer - about 2 Litres
10 x steel dowels
Lots of Cascamite glue
Dowel rod/threaded rod
scrap wood for making jigs
A Jigsaw, a Cordless Drill, sander and various hand tools. A heavy duty router and the following cutters: 1 mortising straight bit (3/4 dia or similar), 1 bearing guided bit and 1 long straight bit like the kind used for cutting kitchen counters, I had a single flute 70mm long one. As it turned out it needed to be so that I could use the edge of the shaft against the template as my bearing guided bit wasn't long enough. This is obviously not ideal from a safety point of view because not enough of the shaft was in the router....
Jigs are very important for this design and I really couldn't have made it without them. If you have any better ideas on jigs then please share them. If you make this then you will spend most of your time on this project making jigs. Make sure you make them well so that your parts will be accurate.
Step 3: Make Former
Right first step:
Make the former for bending the legs. It is roughly something like that pictured. The sketchup model should give you a better idea. It should be 1650mm long about 500mm wide and have an arc of radius 1640mm. The ideal former is not what I built, but I just used what was on hand really. The former pieces were 18mm unfinished chipboard on a baseboard and skinned in 6mm MDF. 12mm dowel rod was used for aligning the pieces. You are gonna need 28 or so identically sized chipboard pieces if you make it this way. I made it with about 16 former pieces with spacers between them and then skinned it all over with 6mm MDF after.
I wanted to CNC the parts but I couldn't get access to the machine so I made the former in my house instead. I printed out a pattern at full scale with the plotter because I had no room for a beam compass in my tiny house and it was raining outside.
Just mark out your first piece with the beam compass. Mark some holes for the dowel rod so that you can line up all the former bits afterward. If you had threaded rod instead of dowel that'd be even better... Then drill the holes out with the appropriate sized bit. Cut out the arc with your jigsaw and use a rasp and some sandpaper and elbow grease to get it smooth (maybe even a belt sander if you are brave). Mark that piece and use it as your template. Call one side the face side also.
Line up a blank on top of your template, clamp them to something secure like a proper workbench. Dont use your kitchen table like me. Rough out the arc with your jigsaw and use your router and bearing guided bit to finish the job. Mark the face side on the freshly cut former piece. Flip both over and clamp again. Drill through the holes again using the template as your guide. Now wash, rinse, repeat until you have enough pieces to make up in their combined thicknesses the height of the leg plus a fair bit for waste seeing as we are going to be cutting off some angles later on.
Stand up the former parts so that the face sides are all facing the same direction. Line up the first two pieces and pass the dowel rod through the holes to keep them lined up. Screw them together with 30mm screws. Push the rod through a bit more and add the next former piece, screw that to the others. Repeat this until the former is finished. It might be hard work to get the rod through because of all the friction. Your trusty hammer will be useful here!!!
Step 4: Break Out Parts
Break out your 6mm panel pieces to form the laminates for the legs. Lucky for me I had a panel saw to do this on. You can use whatever means you have at hand because accuracy is not super important. So use a hand saw, jig saw or circular saw. Cut 10 pieces 1700mm x 480mm, that's 5 for each leg, giving a total leg thickness of 30mm. You only get 2 of these from an 8' x 4' sheet which is very inefficient in material usage, but you have tons of little bits left over to use for jigs.
While you are at it you might as well break out the pieces for the top as well. You will need 2 pieces 1630mm x 700mm from 18mm MDF. Again this is wasteful because you only get one from each 8' x 4' sheet. But you will make use of the scrap for jigs so it's not all that bad really.
Step 5: Form Legs
Prepare for laminating the legs. Get your former and clamps etc. ready. I used a vacuum bag for this process. It wasn't my first choice as you can see from the picture of my former which has a ton of holes in it where the clamps were supposed to go. Being a college environment though I couldn't find enough clamps as the majority were in use..... I actually could only find the amount that is in that picture. 6mm MDF will bend to this radius pretty easily so you shouldn't be too worried about that end of things.
You will need a helper for this, it is next to impossible to do it correctly alone. I had to do 2 trial runs before I was satisfied that I had the process down.
The process is essentially the same if you vacuum bag or just use clamps. It will take about 45mins to bend one leg and then you will need to wait 24 hours for the glue to set. We are using Cascamite glue because the working time is significantly longer than PVA and because it doesn't creep. Creep is the way in which the parts you glued together can move slightly over time. This is a big no no for this project because of the spray finish and because we want a seamless look.
PVA working time is only about 20 minutes which is not long enough for us here. Cascamite is over an hour though.
Have your clamps and vacuum bag ready. Get some lengths of 2 stock to use as bars across the bag to pull it to the former so that the clamp heads don't damage the leg laminates and the pressure is evenly distributed. About the width of your former is the right length.
Mix up the glue as per the manufacturer's instructions. If you think you have enough glue, mix a little more incase because you wont have the time to go back to do this when you are in the process of laminating. Then if you have any leftover you can use it for cool casting projects!! Begin by laying your first laminate on the floor and covering it evenly with a layer of glue. Use a brush or roller to make sure it is even. Place the next laminate on top, line it up correctly (this can be fiddly and messy). Roll out a layer of glue. Repeat until you have all 5 laminates sandwiched together. Fast work is much better than slow here. Line up the laminates as best you can but don't be overly particular because they will be trimmed later anyway.
The process divides now depending on whether you are clamping or vacuum bagging. I will describe both.
If you are vacuum bagging you should now with your helper slide the glued up laminates into the bag and line it up as best you can so that the sides of the laminates are parallel to the sides of the former. Seal the bag, connect the vacuum pump and turn it on. If its anything like the one I used it could be a half hour pulling the air out of the bag. Put a bar across the middle and clamp it temporarily. I put the former in the bag too, but another method would be to just have the laminates in the bag and to lay the lot on top of the former. I don't remember the reason behind the way we did it. It may have been because the vacuum bag was too big. Anyway, next you wait and ensure that the bag doesn't get pulled in under the laminates. Pull it out quick if it does, you may have to stop the vacuum pump to do this. Even with all that vacuum pressure our pump couldn't pull the laminates to the former so we had to use clamps and bars to get the ends down. A super important point I forgot to mention is to have some sort of fabric in the bag at the hose connection and on top of your pieces to assist airflow. 24 hours later you can turn off the vacuum open the bag and pull out your first leg blank. Repeat the procedure to get your second.
If you are clamping then things are a bit simpler. Just put your laminate sandwich on the former, place bars across it and clamp. Starting in the middle is probably the best option. Trial run this and drill out holes in the former for the clamps if needs be. I think I used a 50mm hole saw to do this.
Step 6: Make the Top
Whilst you are waiting for the glue to dry on your leg blanks you have time to make the blank for the top and get some jigs made.
Glue up the two 18mm pieces to make a 36mm thickness for the top. There are many ways of doing this; I used a veneer press because I had one available to me. You could use concrete blocks or sand bags or a million clamps if you have them. I have in the past used concrete blocks and it turned out just fine. Again use cascamite glue to prevent creep.
Because I had the CNC available this time I used it to cut out the top and rout the rebate for the glass. You can do the same with a jigsaw and router though it will be a lot of work. I made the top sightly oversize but at the same radius to allow for the chamfer that I would have to later cut off of it.
Square up the ends of the rebates fro the glass with a hand chisel and a little patience. Then make some glass templates in 6mm MDF and send them out to get the glass made up. Because I was doing it on the cheap I got clear glass and planned to put car tint on the underside of it to give the blue finish. If you can afford coloured glass go ahead and get it instead becasue it will look far better IMO.
Step 7: Square Up the Legs
Now what I did worked in that there is no noticable twist in the finished table legs. I know it is there though.
To remove that possibility I recommend doing it the following way.
Simply put your formed pieces back on the former, rock slightly until it sits snugly. Push it to the side of the former making sure it does not go into twist along the curve. It should now over hang the former edge slightly. Clamp it in position and use a router and bearing bit against the edge of the former to square it up. Hopefully that makes sense.
Then get out your try square and mark perpendicular lines up the ends of the legs. Use a baton clamped to the leg to guide your circular saw/jig saw making the cut. Make sure you cut both legs the same length and at the same angle (I just left the saw at 90). I used a tailors tape to measure the length. Whilst you are at it mark a center line on the leg. You will need this later.
Step 8: Angle Jig 1
So you are wondering how the hell do I cut accurate repeatable angles on the top and bottom of these leg blanks. Jigs are the answer my friends. Where would anyone ever be without jigs....
Angle jig 1 is basicly what you see in the pictures and sketchup model. Simply a platform for the router to run on and an angled piece to clamp the leg to at the correct angle of 15 degrees. There are no critical measurements really except the angle. Just make sure the platform is parallel to the bench top or base of the jig.
Make a little base to raise up the router on that exposes the cutter at the edge. Then get routing...
I actually had to trim down the leg a little with an electric planer before I routed as I didn't mount my router high enough because my cutter was too short.
I also made a little pencil marking jig to work out how much height I was going to be able to get because I was a little unsure of my measurements.
Step 9: Angle Jig 2
This one is pretty simple too. You should be able to follow the pictures on this one.
Make up some sides about 500mm high and perpendicular to your bench or whatever you screw them to. Screw the already angled edge of the leg to a base and slide it in. Mount the router as shown. Rout away until you have the leg to the finished height.
Angles all done, both legs should be the same height because you didn't change your router plunge depth between cuts.
Again with this one I had to get the electric planer at it a little to get it down to size. I should say that you could probably mark and cut that off witrh the jig saw, but I am lazy and didn't think of it until I had everything set up.
Step 10: End Curve
Your legs just need their end curve now. This is achieved using the template pictured.
I projected the radius in 3D CAD to a work plane and measured it. Will add this radius when I find it.
Anyways, projected radius is marked on 6mm MDF which when bent around the leg gives the true radius. Neat, eh? Cut this with the jig saw and smooth with a rasp and file.
Remember that center line we marked earlier, well this is where you need it. It helps you align the template.
Put the template exactly at the legs end. Mark a line. Use the jigsaw to trim off the excess on the waste side of the line.
I had planned to use the bush guide against the template but when I set it up I realised cutter length was was going to be too short. So I did something dangerous I in no way endorse. I ran the shaft of the cutter against the template by having less of it in the collet than is safe. This worked because my cutter diameter is the same as shaft diameter.
Take care and take light cuts. You don't want to drop a router cutter spinning at 20,000 RPM on your foot.
Step 11: Join Legs to Top
I did this the wrong way. I used wooden dowels and screws through my table top. This meant I had to use filler. But no matter how hard you try filler and lacquer finish just never works out.
You should do it a better way. Epoxy and steel dowels. It is what I originally had intended doing. Definitely no screws and no filler.
To mark out your dowel locations first set your top upside down and put the legs on it. Line them up where they are supposed to go and trace your pencil around the outline so that where the leg goes can be clearly seen on the top when you take away the leg. Then offset from the inside line by 12mm to get a line for your 10mm dowels. Mark their locations. If you have dowel markers you can use them now. If like me you haven't you just drive some panel pins into the locations to about half their length. Cut the tops off the panel pins. This should give you a nice sharp edge.
Get your leg and place it down on the top again so that the cut panel pins stick into the top edge and mark the dowel locations in it. Remove the nails and drill everything carefully with a 10mm bit. You just kinda have to eye it really. I must say the little bubble on my drill that I always thought was gimicky was pretty handy for this.
Clean out the holes and test fit. If everything is good then mix your epoxy and get it assembled. Clamp down the legs lightly so as to add some pressure but not enough to open up the joint. Epoxy the joint as well, or wood glue, whichever is handiest.
Step 12: Fit the Glass
My glass arrived at this stage so I test fitted it and trimmed a little to make it fit.
I used the router with a rebate bit and my trusty hand chisels.
Because it was hand cut both of the bigger pieces were slightly different.
Step 13: End Curve on Underside of Top
I dont know that I have found a good way of doing this step. Suggestions are welcome.
What I did was to create a sort of platform for the router to sit on so that when the platform rode the ends of the legs the router bit would follow the same path. Hopefully the pictures and sketchup model explain this better than I have.
This worked ok, but I still had to do a lot of cleaning up work with the belt sander as it wasnt perfect. It was heavy and awkward to hold which led to me dropping the cutter down on the work a few times and those "imperfections" needed to be filled.
This jig cut the table top to a fragile point so I clamped a batten across it and squared it up. This gave about a 5mm thick edge at the end point.
Step 14: Chamfer Top
As with the rest of the project I had a simple router jig for this process. The little platform from angle jig 1 was used. It rode on the outside face of the leg. I think I clamped the table top to the side of my bench to allow me to do this easily but its so long ago I dont remember.
Sorry I didnt take any pictures at this stage but I was in a rush to get it done and had no one helping me.
Step 15: Sanding and Finishing
I have no pictures of these steps because I was in too much of a rush.
Filled all the holes with P38 Isopon (car filler). If you are in the States Bondo is a good alternative.
Sanded progressively with 80 grit, 120 grit and 180 grit paying special attention to the MDF 'end grain'.
Used sanding sealer on all the MDF 'end grain'. You should put it on heavy and let it soak in a while. I think I did two coats.
Then I took it to the college spray shop and got it sprayed. 2 base coats and 2 top coats. Cutting back with 320 grit silicone carbide paper in between coats. Then I gave it a quick polish with a cloth by hand.
Step 16: Review
I wouldnt change the design except to scale it down slightly for more efficent usage.
Hard to say what I would do differently making wise. I couldnt come up with a better process really given the resources available.
The finish has held up well, though i would have preferred to use AC instead of PC lacquer because it is higher build and gives a better finish when using high gloss. I might perhaps change the colour to an off white or a cream.
I think I read something on instructables one time about sealing MDF 'end grain' with epoxy. Maybe someone could enlighten me on this because I am sure it would be better than sanding sealer which did only an ok job.
The leg to table top joint has opened slightly (from me strapping it down in my van) and cracked the lacquer along the joint which kind of ruins the smooth look I was going for. If I was to do it again I would master that face in 3mm MDF so that it would be all one piece and couldn't crack.
I will get the window tint eventually even though I haven't gotten it so far.
If there are any mistakes or things you think need to be explained more clearly (I tend to over complicate at times) let me know via comments and I will put them right.
Enjoy, and get building!!!
For more pictures of the (nearly) finished coffee table see the slideshow: https://www.instructables.com/id/Coffee-Table-Mackintosh-Inspired/