# Looking for Jig to create a radius



## medemt (Jul 3, 2008)

I am looking for ideas on a jig / fixture that I can route either a fixed radius or variable sizes of radius. Let me explain a bit further. I am building small animal caskets and I have come up with a way to take flat boards, cut the angles, and get a somewhat curved top. Now what I need is a way to smooth out the joint areas so it looks like a commercial casket top. 

If you have ideas, I sure would like to hear them.

Thanks. 

Dan


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## tvman44 (Jun 25, 2013)

Not sure I completely understand your needs, but would a circle cutting jig work?


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## timbertailor (Oct 4, 2009)

Woodpeckers makes a great set of corner radius and chamfer jigs. A little pricey but I think they can be bought individually.

You could also make your own custom ones to get the right arch for the top of the coffin lid. A flexible straight edge and some plywood material for a template.

OneTime Tool - Corner Jig


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## woodknots (Mar 7, 2012)

medemt said:


> I am looking for ideas on a jig / fixture that I can route either a fixed radius or variable sizes of radius. Let me explain a bit further. I am building small animal caskets and I have come up with a way to take flat boards, cut the angles, and get a somewhat curved top. Now what I need is a way to smooth out the joint areas so it looks like a commercial casket top.
> 
> If you have ideas, I sure would like to hear them.
> 
> ...


If I understand correctly, what you are trying to do is create joints on several flat boards and round the joints over to create a smooth curved top, similar to the staves on a wine barrel.

Not sure how large your caskets will be, but I would be more inclined to join the edges with a butt joint, with the appropriate angle depending on the number of boards you use, then use a plane to remove the sharp edge, slowly transitioning to a "rounded" top.

Hopefully I've understood your requirements correctly


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## Stick486 (Jan 4, 2013)

medemt said:


> I am looking for ideas on a jig / fixture that I can route either a fixed radius or variable sizes of radius. Let me explain a bit further. I am building small animal caskets and I have come up with a way to take flat boards, cut the angles, and get a somewhat curved top. Now what I need is a way to smooth out the joint areas so it looks like a commercial casket top.
> 
> If you have ideas, I sure would like to hear them.
> 
> ...


can you post an image of what you are after...
are making coffins or caskets??? both???
how large are they...
I googled images and there so many variations it's difficult to know where to begin...

https://duckduckgo.com/?q=coffin+images&t=ffsb&ia=images&iax=1
https://duckduckgo.com/?q=casket+images&t=ffsb&ia=images&iax=1


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## Quillman (Aug 16, 2010)

I have seen handmade/custom router fixturing that does clean up outside radii.
That is, a router on a carriage/support that has concave fixturing attached to its base plate. These sit on convex rails. Both created with a per-determined radius, not something that is adjustable. The one example I saw radiused a 16' long balance beam which had its upper surface radiused to ~12-14". A lot of work, big mess but clever indeed.
See Taunton's "More Proven Tips", 1990.


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## 163481 (Jul 8, 2015)

If I correctly interpreted your request, it seems you want the ability to vary the cut from an elliptical arc to a semi-circle. There are a couple Youtube videos on building ellipse cutters that you might be able to modify for your purpose. Good luck.


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## Cherryville Chuck (Sep 28, 2010)

I remember seeing an episode of the Router Workshop where Bob and Rick built a jig that would do what you want but I never made one and I don't remember the details clearly. Maybe one of our other members will.

You can make a sled that will do that though. The sled would need an arch between the runners that has the curvature for the width you need. Any size would need a different sled because of the arc/width differences. You need two sides that are tall enough to hold the router up with the curve cut onto the bottom edge and plywood glued to it that is thin and flexible enough to follow the curve. There would be a slot cut through the middle of the jig for the router bit to stick through. You would also need guides for the sled to run against to keep it in position relative to the board. You'll still need a little sanding at the end.

Another way if you have a large enough belt sander is to build a pendulum type jig to hold the boards and swing thing past the belt in an arc. This will give you a perfect arc and take care of the sanding at the same time.

Then there is the old, old fashioned way where you take a plane or planes and plane the surface curved by eye. A lot of people think that a curve like you want has to be perfect but the eye can't tell that close so it only has to look perfect which is something quite different.


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## The Hobbyist (Apr 25, 2015)

I'm not sure I understand what you are trying to do. Can you post photos of your work? Drawings? Google SketchUp images?


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## PhilBa (Sep 25, 2014)

It's hard to know exactly what you are looking for but I think you are asking for something like the top of this:









You might be able to make a carrier that moves a router sled through different angles. It might be easier to have a single track and rotate the work piece. Then adapting to different radii is simply a case of moving the pivot point. Might be worth the investment if you are turning out hundreds of them. Kind of like a giant router crafter.

Frankly, I'd make the bowed surface out of a number of segments and use a power sander (belt or 6" ROS) to get the rounded effect. 6 planks each with a 7.5 degree bevel will get you 90 degrees of bow - sanding that to smooth would be fairly easy. The smaller the angle, the more the segments but the less sanding need.

If the curve isn't too much, it might be easier to use 1/4 plywood and bend it to a frame. 

Take a look at boat and wooden bucket building techniques. They both produce smoothly curved wooden structures without specialized routing jigs.


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## Mike (Nov 22, 2004)

Dan, making some templates will handle what you are after. If you plan to build a lot of these then a custom made router bit will greatly simplify things.


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## Mike (Nov 22, 2004)

Chuck, is episode 1307 the one you were thinking about? Bob sculpted the legs for this table using the rolling jig and a pair of supports.


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## Stick486 (Jan 4, 2013)

look to the profile of thumb and finger nail router bits...


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## Ghidrah (Oct 21, 2008)

If I understand his request correctly, he wants to round his tops over. The pic below shows a faceted casket top I think he wants to make a jig to fit over the top so he can route it round.

If so, he would have to make a jig for every size coffin/casket he constructs and the only way I can see it working at all is if the casket is the same width and height head to toe. I'm thinking it would be easier to rough the top out with hand planes, rasps and scrapers then palm and hand sanding.


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## Semipro (Mar 22, 2013)

Marc Sommerfeld , Sommerfeld tools, has a router bit set for making round corners on cabinets ( if you're only building one probably wouldn't be worth the expense )
Link Woodworking DVD's


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## medemt (Jul 3, 2008)

Thanks to everyone that replied. Based on some of the answers, I have a few ideas. Just to answer some of the questions and give a bit more info, I have a jig that I will take 2" wide (3/4") boards, cut a 7 degree angle on both sides, and lay them side by side until I get the desire width and height (of the dome). I will them glue and pocket hole join the pieces. The cut the two end boards such that the dome will lay flat when turned over. Now comes the part that I was asking about. At each of the joints, there will be a "high spot". I was hoping to use my router to make all the high spots disappear and give a nice round surface as in some of the pictures of the casket. Once I get the round surface, I can make two 45 degree cuts on each end and fit the end rounded piece in. Just like what you see in "Ghidrah's picture.

From the comments I have some more ideas, and truthfully, maybe the best thing is to plane and sand. 

Thanks again everyone. Still open for more suggestions or pics of a fixture that may do this.

Dan


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## Cherryville Chuck (Sep 28, 2010)

Mike said:


> Chuck, is episode 1307 the one you were thinking about? Bob sculpted the legs for this table using the rolling jig and a pair of supports.


As best I remember Mike, it resembled a planter, the horizontal half round type.


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## Mike (Nov 22, 2004)

Dan, this can be done as long as the radius is the same on the ends as the sides. I figured out a jig that will make the cut but need the dimensions.


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## boogalee (Nov 24, 2010)

Check out part 2.


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## papasombre (Sep 22, 2011)

Hi, Al.

A lot if interesting videos. Thank you for share.


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## JFPNCM (Dec 13, 2009)

There was a thread on this topic earlier this year , started by bobditts under the title of Human Urns that might be worth checking out. The discussion focused on rounding lids and sides.


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## DaninVan (Jan 1, 2012)

"If the curve isn't too much, it might be easier to use 1/4 plywood and bend it to a frame"
-Phil

I agree. Making a cold mold jig for bending the plywood seems lika reasonable investment for multiple uses. The problem might be the wide variety of sizes.
On the 1/4" part, laminating two 1/4" sheets together might be another approach...but I think you might actually be referring to the hard corner where the top side and top end come together (see Phil's coffin picture above)?


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## medemt (Jul 3, 2008)

Thanks Al for the videos. There were a couple of great ideas from part #2. I had not thought of his top rounding method, but it 
looks simple enough.


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## medemt (Jul 3, 2008)

Mike,
I am sending my drawing of the casket that has the dimensions and my thought on a method for making the rough top. The jig can be modified for different radii and widths of the top, but that adds to the difficulty in coming up with a jig to do the round over of the finished top. Hope this comes through. I have never tried to attach a file.

Dan


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## rcp612 (Oct 22, 2008)

Personally, even though this IS a Router Forum, I think what you are wanting to do would be much simpler with a block plane.
There should not be much to remove after gluing up the slats for your top if you're cutting them at a 7* angle. That is 7* total as in 2 - 3 1/2* angles mated together?
I've done a similar top for a small treasure chest and amazed myself at how easy it actually was after fretting about it for a couple days.


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## tomp913 (Mar 7, 2014)

How about a ski setup? - not like Harry's but the kind that has the cradle that the router rides in. and sitting on tall fixed supports at each end. The supports would have to be tall enough to allow the fixture that holds the top to fit underneath. To hold the lid, cut two pieces of plywood with the finished radius at one end and a pivot at the center of the arc. You'd need a couple of pieces of all-thread running through the plywood ends to clamp on the ends of the lid, some type of support in the inside for the bottom edge of the lid to locate on and a method to clamp the fixture against rotation while taking a cut. I'm assuming that the amount of material to be removed is within the adjustment length of the router - adjust the depth of the bit to take an initial cut on the lid, starting at one edge. Loosen the clamp and rotate the fixture slightly before taking the next cut, etc. After completing the first pass, lower the bit a small amount and repeat - at this point, it should start looking like a smoother arc (after all, an arc in CAD is a series of small straight lines), plus you have the finished arc on the plywood fixture ends to judge how close you are to finished size. As stated above, and depending on how much material needs to be removed to get rid of the initial "flats", a sharp block plane may be quicker. I think you would have to be planning on multiples in order to justify the time to build the jig.


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