I have had a request from one of our sons for a ‘piece of furniture’. “Be more specific.” I said. That was a mistake! His request follows:
An oval coffee table, 40″ long, 21″ wide, 16″ high; With a see-through glass top.
I can create ellipses on a solid top – but I cannot find any info on the construction of a rim which would have a rabbit to support the glass. When I solve that (with your help) I’ll wrestle with the joinery of the leg/support system.
I would love to laminate, with end-overlapped lams, to create a continuous ellipse, but question the feasibility at the small radius ends. The complexity of a brick construction (?) is daunting. Then, I could glue up a solid top and ‘waste’ the center – that’s expensive!
I await the accumulated wisdom of this forum. I’m stumped.
Frosty
“I sometimes think we consider the good fortune of the early bird and overlook the bad fortune of the early worm.” FDR – 1922
Replies
Waste the center and re-process the cutout for another project. Lay out two ovals, cut the inside oval out with a jigsaw. Fair the curve then rebate the inside oval with a piloted rabbet bit in a router.
Fair the outside oval and then finish building the rest of the table.
Edited 1/3/2008 9:42 am ET by UrbaneLegend
Sounds good. I came up with that idea as I typed the post. It has the advantage of solid wood for the outer edge-treatment and I have been considering "echoing" the top-rim shape with a floor pedastle connected to the top with angle/curved legs. That would make use of the center waste.Thanks for the input.Frosty"I sometimes think we consider the good fortune of the early bird and overlook the bad fortune of the early worm." FDR - 1922
With a little bit of help from heat and/or steam, you should be able to bend reasonably thin laminations (1/8" or so) to the required radius. I would pre-bend them to roughly the right shape without glue, then glue them up the normal way with clamps around a form, etc.
Since the table is going to have four legs (I assume), it would probably be a lot easier to laminate each of four apron sections as a separate piece, then connect the finished segments to the legs with mortise-and-tenon or bridle joints. At the very least, do the apron in two sections. Laminating an entire ellipse all at once requires too many simultaneous miracles....
Cutting a rabbet for the glass can be done easily on a router table after the aprons have been fabricated.
It's going to take some experimentation and probably a few missteps along the way, but it sounds completely doable. Full-size drawings are an absolute must.
-Steve
SIMULTANEOUS MIRACLES! Even one miracle is a rarity in my shop.You make a good point about doing the leg joinery on each quadrant. I haven't thought too much about that aspect yet. See my reply to UrbanLegend.Thanks for the prompt reply, Steve.Frosty"I sometimes think we consider the good fortune of the early bird and overlook the bad fortune of the early worm." FDR - 1922
Frosty,
I would suggest using a hexagonal or octagonal piece of MDF as the center which you will eventually waste. The oval frame could be glued up from 6 or 8 portions, well joined to each other with M&T or whatever joint suits you. After glue-up the outer and then the inner ovals can be cut using a router, straight bit and jigs. Then rabbet the inside edge for the glass.
David Ring
http://www.touchwood.co.il/?id=1&lang=e
Frosty ,
As Ring has said use a frame with solid joinery .
The solid glue up then cut out works good on paper but the movement across the grain in 21" could be hard to tame , especially with glass a frame is a more stable approach .
Sometimes you have to glue each section up to make the curve before joining and shaping .I try to make them with 4 joints which can require wider parts .
I've always drawn out the exact oval on a piece of 1/4" and take measurements off of the 1/4" .Cut the frame members out after you make the joints fit rout them after glue up or pre shape them .
You can pre shape the pieces before glue up and finish the inside with a drum sander on the drill press and the out side edge is easy to clean up and shape .
dusty
A solid wood top coffee table is going to be hard to tame? That's going to be news to the literally millions of them in existence and the tens of thousands that get built every year, not to mention dining room tables (and bigger) with solid tops.
How about cabinet maker's buttons to attach them to the rails?
Let's not get too scared of wood.
U L ,
A 21" X 40" oval frame with glass is not the same as a solid wood table top .
Typically a solid wood table top may have a frame under to help support and keep it flat , many times the top overhangs the frame like a countertop does .
Any movement and it does move , if designed properly will not cause problems seasonally .
The only reason I would advise against cutting an oval frame from solid stock with the grain all running in the same direction is I tried once and learned first hand , it was ugly .
regards dusty
This discussion has revealed new elements for consideration:Glue up of segments has the advantage of the elimination of end grain at the head of the oval; however, the reult is some short grain glueing, plus the challenges of M & T joining of the segments.One solid piece, glued up, then routed on an ellipse jig, will result in end grain at the head of the ellipse, however, all glue joints are long grain. If any of you saw a post of mine from a while back, I had a 1/16" off-cut from a round table that, even with 4 glue joints, would not fail.I think the seasonal dimensional changes across 21" can be accomdated by the width of the glass-rabbit; I believe any tendency to warp will be controlled by the weight of the (probably) 3/8" glass insert. I plan on 4 curved legs descending from "quarter points" to the ring cut from the center of the primary glue-up.At any rate I will do a full-scale mockup in poplar.Comments?Frosty"I sometimes think we consider the good fortune of the early bird and overlook the bad fortune of the early worm." FDR - 1922
Frosty ,
The solid glue up does consist of long grain joints as opposed to the frame section joints , but remember you will be cutting away all but the width of the frame . So while it may be very stable on each end the larger center part would be my concern.
I would go with the same basic way Dave has offered up , either splines or loose tenons .
If you do make a frame one thing you can do to make glue up a bit easier is actually leave some material shaped to help with clamping around the outside to act as clamp blocks , you could rout or bandsaw and edge sand the shape after glue up to final dimension .
dusty
1) Plant four seedling trees of an appropriate species in four pots. (Use large pots--see below).
2) Over the next several years, gradually tilt the pots to cause the trunks to bend into the appropriate curve to form 1/4 of the table apron.
3) Wait an additional 80 years, then harvest the wood, dry it, and build your table.
-Steve
What are you drinking?I want some!Frosty"I sometimes think we consider the good fortune of the early bird and overlook the bad fortune of the early worm." FDR - 1922
Does the glass have to be "framed" with wood? A rectangular base (legs, aprons, and stretchers) with a piece of oval glass sitting on it might work just fine - and be much easier to build. - lol
Yes - that would be a soltuion. However, I try to push myself on each new project. The "intellectual stretch" is what makes woodworking so rewarding.Thanks for the suggestion.Frosty"I sometimes think we consider the good fortune of the early bird and overlook the bad fortune of the early worm." FDR - 1922
I threw that out there as an alternative that might have worked. Sometimes, folks get caught up in an idea and overlook other (simplier?) solutions. Not me, of course! (Yeah, right!! - lol)
If I were doing this, I would use my CAD program to draw a full scale pattern which I could use to make a template. The pattern would be drawn at full scale and glued to a piece of MDF or plywood which would be oh so carefully cut and shaped to make a template for my router. Many drafting supply businesses will do the printing for a small fee.
Then, I would design my frame for the glass top. The oval shape will probably require that the frame be made in segments mitered together to get the desired shape. The biggest headache with this would be getting strong miters. I would probably use biscuits or loose tenons and position them so they don't show up when the oval is cut.
When I had the frame ready, I would rough cut the inner and outer ovals, attach the template, and finish the ovals with a router and flush cutting bit. A rabbetting bit would cut the recess for the glass.
When the frame had been cut, I would take it to the glass shop. Hopefully, you will have talked to them in advance so you don't have a heart attack when they give you the price to fabricate this thing. - lol (Around here, rectangular pieces of tempered safety glass run ~$20/sq ft - and fancy shapes are more expensive.)
This job will require some careful planning and meticulous work, but it really isn't all that difficult. I've done similar things although they were smaller and involved circles and arcs instead of ovals. Doing a prototype - or more than one prototype - is a very good idea so you can work out the "bugs" in your process. Ideally, when you do the "real" one, you'll be asking yourself "So, what's the big deal with this?" - lol
Frosty; I would go with a lminated frame. All long grain wood 3/8 or 1/2-inch thick, layed up in 4 or 6 layers, with the glue lines horizontal, and the butt joints overlapped at least six inches.
I salute you, Jigs. Your idea of building up a laminated piece for the oval blank is way better than my mitered segments. As I was writing up that post, I was worried about getting enough strength in the miters - as well as positioning the biscuits or loose tenons so they didn't show up when the ovals were cut.
Using laminations would also allow a smaller frame since there will be lots of glue surfaces to maintain strength.
I could probably make one with my method, but would always be paranoid about someone sitting on the table and having a joint fail.
I like it! Let me work on it.Frosty"I sometimes think we consider the good fortune of the early bird and overlook the bad fortune of the early worm." FDR - 1922
Frosty, I thought about it a bit more. I've been down with the flu for a few days, so hopefully this makes sense. If it doesn't, let me know and I will see if I can do a better job in a day or so, with a clearer head.
I would make up a pattern out of mdf the size of the perimeter frame you want, and then use it as a pattern to make two more ovals.
Then I would cut them into sections with the overlap laid out into the three sets of templates you will end up with. Remember that the kerf will eat some of your length and width so either compensate for it in you initial layout, or use the thinnest blade you have and be willing to live with the loss.
From that point it is just a process of planing the stock to thickness, rough cutting to size, and finish trimming with a router using the templates.
And, lots of gluing. But with lots of long grain surface getting glued together, it will be quite strong.
Personally, I would use a contrasting wood, and put little dovetail key "dutchman" on every joint to make them into a design feature rather than try to hide them.
edit to add: Frosty, after a little more thought, I would keep one template intact, and trim the pieces a little oversize (about and 1/8th or so, it depends on how much bigger diameter guide bearing you have for your flush trim bit), with the router. Then after I had everything glued up, I would use the intact master template to trim the frame to final size.
Edited 1/5/2008 7:25 pm ET by Jigs-n-fixtures
I have done several dozen elliptical glass top tables without doing anything around the edge of the glass. I like the cleaner look, however, if you want more detail, have them do a bevel on the glass. Then you can concentrate on doing something more sculptural with the freedom of not having to deal with legs and apron.
Also, if you have not ordered your glass. I think you should know that you will be told that whatever measures you give for the long and short radius, or for even square cuts, you will likely be told that they will only work to something like + or - 1/4". So don't cut a rabbet then expect them to cut a nice matching fit.
Good advice. Thanks.On my previous glass topped tables I've taken the table to the shop and told them to "cut-to-fit". I don't give them dimensions.Frosty"I sometimes think we consider the good fortune of the early bird and overlook the bad fortune of the early worm." FDR - 1922
I have been reading the discussions with interest,and have built similar wood tables, with a marble top insert. Interestingly the insert does not have to be oval. Making a square frame mitered reinforce corners and wide enough accomodate you outside oval , tnen cutting the inside with simply complimenting curves brings on a new design picture,(the curves do not have to be oval but simply meet at or near the miter mark) and can be very attractive. It then is celebrating the beauty of the wood and the glass.. Also have you thought as the previous post suggests bevel edge and simply setting the glass on top with some small silicon pads
interesting stuff good luck
Ed
Sounds interesting but I don't really 'get the picture'. Can you post a photo?As I told another 'poster', I could simply place the glass on top of a support structure but the challenge of the inset is too good to bypass. As I told my wife last night, "Sometimes the journey is more interesting than the destination."Frosty"I sometimes think we consider the good fortune of the early bird and overlook the bad fortune of the early worm." FDR - 1922
Frosty As an old woodworker there is no doubt that the journey is the joy and then th process takes over
I am not sure if I can send a photo. My wife is the photog and the computer savey with pics. I could mail a small sketch in reg snail mail. Maybe I can get her to take a pic tomorrow and send it to you.
Lets see if I can do a better description. Make a frame say 4 or 6 in stock Draw your oval on the frame then meas in say 3" from the center of the long edge make a mark then draw a flatter complimentary curve thru the center mark from the corner of the miter to the corner of the other miter Repeat on the short ends and the other long side The shape of the inside like a rectangle with curved sides. then rabbet the inside and cut the glass for inset and make any base you would like
It really is a nice look.
its a pleasure to talk to other woodworkers. By the the way my other passion is my 1950 Chevy pickup Just finished a new white oak bed but she's put up for the winter. Too much salt on the roads Ed Lenz
Ed,Many thanks. The drawing and letter arrived yesterday.That IS an interesting shape. I have already embarked on the path of ####conventional ellipse (as this is what my son requested) however, I am
intrigued by your suggestion and will pursue it in the future. You epitomize
what is good about the Knots family!FYI - I elected to glue-up 7/4 boards, eliminating the joinery, and am
cutting the ovals from the solid board. I will laminate the 'arching legs'
to support the top on a smaller, floor-sitting oval I will 'rescue' from the
center of the top rim.I figure with the glass inserted in the rim, there will not be any bending
stress on the solid wood rim which could cause short grain failure.Thanks again,JerryFrosty"I sometimes think we consider the good fortune of the early bird and overlook the bad fortune of the early worm." FDR - 1922
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