Hello. I’m making a couple of hallway benches for a local school and now that my design has been approved, I have to figure out how to make them! Specifically, how do I make the cove (?) in the seat plank? See attached sketch.
I thought about the tablesaw method running the board at angle of the blade, inching it upward bit by bit. But I think that would give me too small a radius.
Another idea would be to have the seat plank be an edge glue-up of two boards, each of which would be planed thinner along the glued edges and thicker along the outside edges. I envision some sort of carriage sled to hold the board at an angle through the planer. Not sure how I would go about shaping the curve from there. Scrape? Sand? Other (likely)?
Anyway, there you have it. Hope that what I’ve described makes some sense. Any ideas would be much appreciated! Thanks.
Joe Murphy
Annapolis, MD
Replies
Hi Joe,
I am going to take a stab at answering this and then go do some research for you. The first idea that comes to mind is to use a router milling jig similar to those used to flatten the surface of a thick plank. See my sketch below.
View Image
How it works:
1. Secure the workpiece to a flat surface.
2. Create two support rails that extend the length of the board. Both must be the same height.
3. Create a router base that is attached to two long boards that extend over the support rails. This allows you to move the router back and forth and side to side and always remain on the same plane.
4. Your task is to figure out the combination of passes to make, and what bits to use, to remove the desired material.
5. Do the final fairing of your curves with a handplane or scraper.
After drawing this and writing down the steps, I suppose you could do a similar thing on a router table...
Anyone else care to chime in?
Matt Berger
Fine Woodworking
Matt - Thanks for your suggestion. That's a good idea. I've been trying to think of a way to add a pivot feature to this approach as well. See attached images for what I mean.I haven't thought it through completely but I could possibly have some kind of curved carriage/jig that is narrower than the width of my router base and this carriage would ride along rails the length of the board. The router would not be attached to the carriage/jig - it would be free to follow the curved edges of the jig, side to side. The whole jig would then be moved down the length of the board. Make sense? Another suggestion I received outside the forum was to try the tablesaw cove technique but doing a series of two off center cuts - each centered on a line that is outside the actual center line of the board. These would be followed by a cove cut down the center of the board, slightly deeper. Of course I'd have to play around with the angles etc.I'm making two of these benches - which of these ideas do you think would be the fastest?? Again, thanks for your help.JoeBy the way, how do you have an image show up in the body of the text as opposed to an attachment?
Edited 10/27/2006 9:40 am ET by JHMurphy
Here is the other image I had intented to include in the last post.
I'd do this differently, with my approach you will have the seats roughed out long before you have gotten a router jig half built.
I'd use a table saw. Set the saw up with a dado set with all of the cutters in it so you are taking a wide cut. Now, by changing the blade height, the blade angle, and the fence position, you can work your way across the seat in a dozen or so passes that will remove 95% of the wood. You'll have to do some cleanup but the router wouldn't leave that much better of a finish.
To quickly set the blade for each pass, make a template of plywood cut out with the shape of the seat section. Place the template on the saw table and then adjust the settings so that the blade just touches the shaped surface of the template. Mark the blade's position on the template before you put it aside so you will know where to move on the template for the next pass.
If you set up a stop system you could begin and end the dado cuts short of the ends of the seat blank creating a more elegant bowl shape in the seat.
John White, Shop Manager, Fine Woodworking Magazine
Ahhh. That sounds great. I love the simplicity of it. What would you recommend for fairing the curve after that? Go straight to planes and scraping? Thanks,
Joe
Flat soled bench planes won't work on the inside curves so they will have to be cleaned up with scrapers, sandpaper, or possibly a spoke shave with a curved sole if you have one-whatever works basically.
When you are shaping the seat on the saw, you will have to turn the blank around when you reach the center to get the saw blade angle to match the slope of the curve on the second half. You probably would have figured that out, but it gave me pause for a few minutes. If the seat blank is heavy, use infeed and outfeed support to keep control of the wood.
John W.
Edited 10/27/2006 12:00 pm ET by JohnWW
Thanks again for your help. This is a great resource.If the curve is centered in the seat plank and symetrical, I could probably flip the plank around with each pass, right? I have an outfeed table next to my saw but nothing but me arms for infeed support. I have to admit I haven't used a dado set much at all - only briefly in a class several years ago. Should I use a featherboard or any kind of splitter that is modified for a dado set? This indeed will be a heavy seat blank.Joe
Seats contours are usually not symmetrical, the deepest part is typically toward the back edge. If you do make the seat symmetrical then flipping the blank between passes would speed up the job.
A splitter won't serve any purpose for this operation and the weight of the blank should hold it down firmly, so a feather board on the top won't be needed. A feather board on the side wouldn't do any harm but it isn't a necessity. I would set up a simple saw horse or some other type of support in front of the saw so that you can easily get the blank against the fence and level before feeding it into the blade.
A safety concern with this operation is that you might push the blank from its back edge and have your fingers in line with the blade when it comes out through the back edge of the blank. I would screw two short lengths of 2x4's crosswise onto the upper face of blank, just a couple of inches in from each end, so you will have a safe place to push against. The screw holes will be on the underside of the finished seat so they won't be visible. Be sure the screws don't end up projecting into the area you are cutting away.
If your saw doesn't have a lot of power, you may have to make the deepest cuts in two or three steps, raising the blade higher for each pass. Waxing the table and the fence will make moving the blank far easier.
John W.
John -Excellent. With all this good info, I think I'm set to go. Thanks.Joe Murphy
Wow. I think we really got to the bottom of this question!
As for embedding an image in a post, here's how to do it:
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3. Once the image is hosted on the Web, right click on the image and choose "copy" from the list of options.
4. Then "paste" the image into the Knots text edit window, choose and it will appear.
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