How do I make this cutting board curved joint?

[Alan Lightstone]

Been going crazy trying to make a cutting board for a friend. Should be a very easy task. I've done it a ton of times on straight cutting boards.

But for my friend I wanted to make one with a curvy connection between two of the boards in the middle. Not an inlay, but the two boards would be complimentary curves glued together.

Sounds simple enough, but I can't get the boards to match snugly. I cut the curve on the first board, sanded it smooth, then made a template of it out of 1/2" MDF with a pattern bit on the router table. OK. Good so far. It's making the complimentary board and then using a pattern bit on the 2nd piece of wood that I can't get it right.

What am I doing wrong, or how should I approach this differently? I've seen inlay techniques using a bushing and a handheld router. Is this a better approach?

Here's the present joint between the two boards:
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[Julie Moriarty]

After making it, did you use the pattern template on both boards?

[Jim Becker]

You need to make two templates by cutting on the line with the thinnest blade you can mange and then carefully working the two pieces until they mate cleanly...or have someone with a CNC make the matched templates for you. You need to do it this way so you can pattern route the mating edges and those routes have to be on each side of "the line" precisely.

[Alan Lightstone]

After making it, did you use the pattern template on both boards?

Yes. But strangely they didn't mate well. Perhaps need to play sexy music in the shop.

[Alan Lightstone]

Off the top of my head...make one pattern. Use it on one board, then flip it over for the mating board. It should come out the same, but opposite.

That doesn't quite work. You need to make a parallel template to the first one. Can't flip it.

[Christopher Giles]

Alan,
Bosch makes what they call a "router inlay kit" which is intended to use a smaller bit size to do exactly what you are after, but on a smaller scale. If you look at how it works, you can use the same technique to achieve what you are after, only on a larger scale. The trick is to remove the cutter diameter from the equation, which isn't going to be easy, but should be possible. Hope this helps.

[Bill Carey]

I have a pdf about cutting boards where a router with a 3/8" straight bit was used to create a curved dado maybe 1/4" deep, then that dado was split in the middle at the bandsaw, and the walls created by the router were used with a pattern bit to make mating curves. Haven't tried it myself but seems do-able. Alan, pm me your email and I'll send it to you. Might help.

[Bob Falk]

Can't you cut through both boards at the same time to get a tighter joint?

[Alan Lightstone]

Can't you cut through both boards at the same time to get a tighter joint?

If that was a straight joint, absolutely.

I could, I guess do one board under the other, with filler pieces diagonally. Thought about that originally. With a bandsaw that would make a perfectly mated joint, but a rough one.

[Alan Lightstone]

So I taped the boards next to each other, with filler pieces underneath with a gap and used a handheld router with a bushing and a 3/8" spiral downcut bit.
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This went great until the middle of the board on the big curve when the grain changed on the board. The router jumped, and ruined the board.
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So now I'll have to prep a new board (no big deal, I have one piece left), but still don't have a working approach.

[glenn bradley]

I think what you are missing is the radius difference between one side of the bit and the other -or- the bit offset if you are using a collar. If your templates fit fine and you use those edges independently to flush cut each blank specifically -AND- your flush bit is accurate (so many are not in this mixed imperial / metric world) things should fit. If you are not getting an exact flush cut I would look there. If you are using a collar you need to consider the offset. If you cut as shown in your previous post you have to account for the bit diameter.

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Example exaggerated for clarity.

When you use the one piece for a template you are offsetting the mating piece by the diameter of your bit. This is why two templates are required.

You can see here how the exact same arc used on opposing faces will not mate if one face is cut on one side of the bit and the other is cut on the opposite side. The diameter of the bit changes the radius by its size. A 12" radius on the "near" side of a 1/4" bit becomes a 12-1/4" radius on the far side.

459432
Here's another view of the same phenomena.

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If you filled the gap equal to the diameter of your bit with a third piece it would fit using your method.

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[Alan Lightstone]

Thanks, Glenn. Makes more sense now.

My first attempt was with two templates. I'll try that again, but using a 3rd piece to fill in is getting more tempting by the minute.

[Christopher Giles]

Alan,
I did a quick mock up to show how the Bosch "router inlay" system does it. It has a bearing which is removable from the router bushing after you have cut out pattern "A". After removing the bearing, you cut pattern "B" running on the router bushing. This beariing thickness is 1/8", so a 1/8" router bit is used for the cut. This leaves you with two patterns, one for each part to be joined.
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I used 1/4" MDF for the patterns which seems to work well for the 1/8" cutter to get through, and provide a good edge for the pattern bit. The mating is not perfect, but will match exceptionally well with light clamping. The wood shown is 3/4" thick walnut and white Oak.
I'm sure there must be other similar choices available if you do not have a Bosch router. Best of luck.

[Alan Lightstone]

Christopher, I'll have to seriously look at that. I don't have a Bosch router, and it may be specific to those. Infinity, amongst others has a similar piece. And I think I actually have that somewhere in a drawer. And thank you for doing that mock up. I am having trouble figuring out how to use that here. Basically the first template is made 1/8" larger than the wood size, and the second template is made the actual wood size? And could this be used with my first piece of wood already made?

What I'm having trouble getting my head around is how to make the second template.

Making the first is easy with a pattern router bit on my router table.
459461 You can't see it from the picture, but there is an MDF template underneath it that matches perfectly. The contour is traced in pencil on the Padauk piece, though it's hard to see.

The question is how to make the second template. You can clearly trace the cutout needed by putting the first piece of wood or first template a piece of MDF. But how do you cut it with a router? Clearly a bandsaw cut is way too rough. And the dimensions would be wrong using a bushing, per Glenn's post.

I can now see why people put in inlays. Seems much easier, even though more parts.

[Todd Mason-Darnell]

This maybe a complete stupid suggestion, but this is the internet...could you overlay the boards and cut the curve on both at the same time with a band saw?

[Alan Lightstone]

This maybe a complete stupid suggestion, but this is the internet...could you overlay the boards and cut the curve on both at the same time with a band saw?

You can, but you get a rough cut, albeit both pieces matching well. Hard to get a smooth curve.

That's easier with the same species of wood. A little tougher this way.

[Bob Falk]

This maybe a complete stupid suggestion, but this is the internet...could you overlay the boards and cut the curve on both at the same time with a band saw?


That was my question. My father used to make cutting boards with curved elements (e.g.,wine bottle outlines) that way and they had tight joints.

[Bob Cooper]

I’ve built something like what Glenn shows where you take a single board and dado out say 1/4” or 1/2” of it. Then you use a bandsaw to cut down the moddle of the dado so that you have two pieces. Then use a straight bit with a collar to remove the left over part that was not cut out by the dado. Yes pictures would help. Now you cannot glue these two pieces directly together for the reason that Glenn shows but you can fill
it in with 1/4” or 1/2” of other material like he shows. This was a FWW article.

But for your case you could use one of those two pieces as a template for your other wood

You would need to keep the filler material between your two big pieces but it would solve your snug fit issue.

otherwise you need to do the router offset template idea

BTW the one issue I really struggled with was clamping. I found it very challenging to be able to apply pressure and not have the curves cause the pieces to shift as I applied pressure

[Bob Cooper]

Ok here’s a few pictures. Really only the first picture is important but figured the other might give you some ideas if you wanted to add some other woods

[Ed Mitchell]

https://www.youtube.com/watch?v=3mqrIGp-PQ8

[Malcolm McLeod]

I’ve built something like what Glenn shows where you take a single board and dado out say 1/4” or 1/2” of it. Then you use a bandsaw to cut down the moddle of the dado so that you have two pieces. Then use a straight bit with a collar to remove the left over part that was not cut out by the dado. Yes pictures would help. Now you cannot glue these two pieces directly together for the reason that Glenn shows but you can fill
it in with 1/4” or 1/2” of other material like he shows. This was a FWW article.

But for your case you could use one of those two pieces as a template for your other wood

You would need to keep the filler material between your two big pieces but it would solve your snug fit issue.

otherwise you need to do the router offset template idea

BTW the one issue I really struggled with was clamping. I found it very challenging to be able to apply pressure and not have the curves cause the pieces to shift as I applied pressure

If a pattern for each side is needed, then you could follow Mr. Bradley's and Mr. Cooper's process - just don't glue one side: Take the single board 'pattern', cut the (1/4") dado through it, bandsaw into two pattern pieces, flush trim the 2 sides, fill with proper (1/4") strip - only glued to one side of the patterns, and clamp them back together. ...With proper caution for clamping alignment, as per Mr. Cooper.

Now in theory at least, you have 2 properly sized (mating) compound curves in the resulting 2 piece pattern.

I think I would use as thin a dado & fill strip as reasonable? If you keep it thin, it might save steam bending, laminating, or at least the wrestling match of trying to get the filler strip glued/clamped in place.

[Jim Becker]

Can't you cut through both boards at the same time to get a tighter joint?

Straight, yes...but with curves, the "kerf" of the tooling you are using to cutting means the two sides will not match. That's why I indicated that two templates are required to get a perfect match; one for "each side of the line".

[Kevin Jenness]

You can make matching templates with a router by accounting for the bit diameter and offsetting the cut as shown in Chistopher Giles' post. Here is a similar technique with sturdier bits.

Make a template for one side of the joint by sawing and sanding. Clamp the initial template on blocks above the bench. Clamp another piece of template material roughly cut to mate with the first one, offset from the first less than 1/2" horizontally and 1/2" lower. Run a 1/2" diameter top bearing trim bit against the initial template, producing an offset cut 1/2" different in radius from the first. Now clamp the second template above a third piece and trace it with a 1/2" shank, 3/8"diameter bit with a 1 3/8" bearing. The third piece should match the first.

[Thomas Canfield]

This maybe a complete stupid suggestion, but this is the internet...could you overlay the boards and cut the curve on both at the same time with a band saw?

That will work and adding a thin strip in the joint helps to minimize any mismatch since the strip is the eye catcher.

[Bruce Wrenn]

Best I can remember, Bill Hylton's book "Router Magic" covers this. Been a few years (1996) since I bought it at American Wood Worker show in King of Prussia PA. Actually wife bought it for me as a birthday present.

[Wes Grass]

Patterns, a mating pair. And they have to be really good. Even milling these from a plate, they warp and have to be 'spring clamped' and given a finish pass.

I wound up doing 3 different patterns for this guy, and Lexan templates for the last 2. I did it 'cheap' for the experience ... but you'd have to be thinking real production to justify what it would cost in the real world.

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[Mark Hennebury]

I used to make a lot of complimentary curve items.
You need one template and router template guides that move the router bit from one side of the cut line to the other.

459501https://sawmillcreek.org/attachment.php?attachmentid=459502&stc=1&thumb=1&d=1623552390459506

[Rich Engelhardt]

So I taped the boards next to each other, with filler pieces underneath with a gap and used a handheld router with a bushing and a 3/8" spiral downcut bit.
https://sawmillcreek.org/attachment.php?attachmentid=459428&d=1623513674&thumb=1 (https://sawmillcreek.org/attachment.php?attachmentid=459428&d=1623513674)

This went great until the middle of the board on the big curve when the grain changed on the board. The router jumped, and ruined the board.It wasn't the change in grain that caused it. It's the fact that one side of that trench is being made by a climb cut. Secure the work - switch to an upcut bit that pulls debris out of the trench and take much shallower passes.
If you look carefully at the above post you can see how the template is shifted so it avoids using a climb cut.

[Alan Lightstone]

It wasn't the change in grain that caused it. It's the fact that one side of that trench is being made by a climb cut. Secure the work - switch to an upcut bit that pulls debris out of the trench and take much shallower passes.
If you look carefully at the above post you can see how the template is shifted so it avoids using a climb cut.

It's actually shifted here too. You just don't see it in the photo. The work is actually secured also. I should have taken a better picture.

[Rich Engelhardt]

Alan,
It's my fault - I know what I'm trying to get across but I can't seem to find the way to put it on paper (so to speak).

Anyhow,, Stumpy Nubs has a Youtube about it:
https://www.youtube.com/watch?v=fZmIMmdCTYA

[Mike King]

As Chris said, this is a job for a router inlay kit. I believe he was using the Bosch one, here is one from Whiteside.

https://www.whitesiderouterbits.com/collections/solid-brass-inlay-kits

[Alan Lightstone]

So, trying to get my head around this. All great suggestions, and thanks for your responses.

Putting things together. Two possible plans:

Plan A:

1.) I need to make a new router pass on a new piece of MDF where I have drawn a similar curved line. Please let me know if I can skip this step and use the pattern / purpleheart piece I already have made.
2.) Cut apart the MDF into 2 pieces and label them Initial board A and Initial Board B.
3.) Run the Bosch or Infinity 1/8" inlay bit with the bushing on the edge Initial Board A with a new piece of MDF under it to make pattern A.
4.) Run the Bosch or Infinity 1/8" inlay bit with the bushing removed on the edge Initial Board A with a new piece of MDF under it to make pattern B. These two patterns should now tightly mesh.
5.) Run a pattern bit on Pattern A to shape the Purpleheart, and Pattern B to shape the Padauk.
6.) Glue together, trim, and hopefully never have to think about this again.

or Plan B:

1.) Take the single Initial Board, cut the (1/4") dado through it with a 1/4" upcut spiral bit.
2.) Bandsaw into two pattern pieces
3.) Flush trim the 2 sides
4.) Fill with 1/4" strip - only glued to one side of the patterns
5.) Clamp them back together.
6.) Once glue has hardened, trim strips to be flush with top of pattern.
7.) Trace the final patterns on the Purpleheart and Paduak and bandsaw outside those lines for rough size of the two pieces.
6.) Run a pattern bit on Pattern A taped to the Purpleheart to flush trim it to final dimensions.
7.) Run a pattern bit on Pattern B taped to the Padauk to flush trim it to final dimensions.
8.) Glue together, trim, and hopefully never have to think about this again.

Do I have these correct? Not sure which I'm going to use. Still thinking about that.

[Michael W. Clark]

Use your existing curved piece and flush trim a matching template.

Then, use a rabbet bit to make a rabbet into the matching template you just made. The bearing rides your existing curve and the rabbet depth is equal to your pattern bit diameter. This makes a “smaller” template to your existing curve. You’ll need to flush trim off the edge where the bearing was riding.

Now, use a pattern bit, with diameter that matches your rabbet depth, and this “smaller” template to cut through another piece of template material. The offcut should be the matching template curve to your existing work piece.

[mreza Salav]

I have done this many times. The process Kevjn described is what gives you perfect fit. You need two templates. After making first you use that to make the second say using a 1/2" flush trim but it is offset by 1/2". You need to make a copy of the second with a proper bearing bit to bring back the 1/2" offset.

[Alan Lightstone]

OK. I used Michael Clarks suggestion and made a 1/2" rabbet in Template A. Then flush trimmed it (essentially no work) to make a new 1/2" smaller Template A.

I then used Template A with a 1/2" pattern top bearing bit, and have the offcut as Template B with 1/2" larger radius. That process is a little difficult, as you need to use the offcut, and any deviation from Pattern A while routing makes a defect that needs to be filled to make the template accurate. There are two such small defects, which I am now using wood filler to fix (hope it will stick to the side of MDF as I will have to sand it to shape.)

The templates do seem to match very well. I'll have to use them with my flush trim bit after getting them close with the bandsaw to get the Purpleheart (piece A) and the Padauk (piece B), to match, but that shouldn't be very difficult.

Boy, this really would have been much easier if I had chosen to just inlay a piece of contrasting wood instead of butting two curved pieces together. Hopefully tomorrow I can have this part done and the pieces glued together. I'll post some pictures when I'm at that stage.

[Patrick Morris IV]

i have made turning blanks out of two contrasting pieces of wood by overlaying one on top, cutting both at to same time on a band saw. swap the pieces for the contrast, use a piece of shop made veneer of a third wood (replaces the wood lost in the saw kerf) and glue together.

[johnny means]

The problem here is that, mathematically speaking, there is no way to use the one side of the pattern to create a perfectly mating piece. The opposing curves will always change in varying ways depending on what part of the curve your on. My technique is to get one side perfect cover it in packing tape, slather the other piece in Bondo,
then clamp the two together. I've never done a cutting board, but have used this for laminate and veneer seams like certain corporate "swoosh" shapes.

[Alan Lightstone]

i have made turning blanks out of two contrasting pieces of wood by overlaying one on top, cutting both at to same time on a band saw. swap the pieces for the contrast, use a piece of shop made veneer of a third wood (replaces the wood lost in the saw kerf) and glue together.

Definitely seems like an easier approach in retrospect.

[Alan Lightstone]

The problem here is that, mathematically speaking, there is no way to use the one side of the pattern to create a perfectly mating piece. The opposing curves will always change in varying ways depending on what part of the curve your on. My technique is to get one side perfect cover it in packing tape, slather the other piece in Bondo,
then clamp the two together. I've never done a cutting board, but have used this for laminate and veneer seams like certain corporate "swoosh" shapes.

I really need to see how well the boards come together with clamping before actually gluing them. I might yet have to try this approach. Never heard of Bondo on a cutting board, though...

[johnny means]

I really need to see how well the boards come together with clamping before actually gluing them. I might yet have to try this approach. Never heard of Bondo on a cutting board, though...

The bondo is only to create the pattern, which I use to actually make the actual piece.

[George Yetka]

To salavage your current work I would glue what you have together and cut the curf or better yet route it 2/3 of the way through with a 1/4" bit then flush trim. You should end up with a perfect fit. if its too rough you could glue 2 sacrificial boards perpendicular and break them off after the routiing is done

[Mark Hennebury]

Its been a while since i have done any but I think this should work.

Matched pattern template routing. ( I have drawn a mirror image curve for the samples below, just because it was faster to draw, but It works with random curves, a mirror image can be done with one template and one guide, cut them both the same and just rotate one pattern to match)

One template, one router bit, two template guides.
459626
1. Make a template.
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2. Route left hand side pattern using the first template guide.
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3. Move the left hand pattern back out of the way. Route righthand pattern with the second template guide. Same template, same router bit.
459631
459632
Done.

Template guides move the router bit from one side of the cutline to the other.

459630

[johnny means]

Its been a while since i have done any but I think this should work.

Matched pattern template routing. ( I have drawn a mirror image curve for the samples below, just because it was faster to draw, but It works with random curves, a mirror image can be done with one template and one guide, cut them both the same and just rotate one pattern to match)

One template, one router bit, two template guides.
459626
1. Make a template.
459627
2. Route left hand side pattern using the first template guide.
459628

459629

3. Move the left hand pattern back out of the way. Route righthand pattern with the second template guide. Same template, same router bit.
459631
459632
Done.

Template guides move the router bit from one side of the cutline to the other.

459630

This can never work except for the gentlest of curves where the imperfect match just won't be noticable. My drawings not as pretty, but illustrates the problem with a more extreme curve. Line A simply can never be equal to line B.

[Mark Hennebury]

I think that you need to take another look at my drawings.


This can never work except for the gentlest of curves where the imperfect match just won't be noticable. My drawings not as pretty, but illustrates the problem with a more extreme curve. Line A simply can never be equal to line B.

[Mark Hennebury]

To route two patterns to fit perfectly you have to cut on each side of the cutline.
The small circles in the drawing below represent router bits.
The blue router bit cuts the blue pattern.
The brown router bit cuts the brown pattern.
The two template guides simply move the bit from one side of the cutline to the other.
The template guides router.
There is no loss due to kerf or radius.

459638

[Mark Hennebury]

Works the same on your curve Johnny.

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[mreza Salav]

The problem here is that, mathematically speaking, there is no way to use the one side of the pattern to create a perfectly mating piece. The opposing curves will always change in varying ways depending on what part of the curve your on.

That is actually not true, you can "mathematically make perfectly mating pieces (I am a mathematician btw and have done this).
Suppose you have an arbitrary curve A and you want to make a mating piece B. First you use a flush trim router bit of your choice, say 1/2", and following piece A create two pieces on a template piece (say MDF). You get a perfect copy of A on one side and a piece B' that is not a perfect fit of A as it is 1/2" off set.
Now use that piece B' with a bearing that is 1" on top of a 1/2" router bit and follow B' as a template and you create piece B. Now B will be a perfect fit of A.

[Andrew Hughes]

I would like to throw my hat in the ring. Sometimes I make complementary curve by stacking the parts on top each other and cutting them on the bandsaw.
I don’t need to part to fit perfectly like a cutting board does. Its a method I use to make tops for my boxes.
Thought I share to open up possibilities that haven’t been discussed.
Good Luck

[Jim Becker]

To route two patterns to fit perfectly you have to cut on each side of the cutline.
The small circles in the drawing below represent router bits.
The blue router bit cuts the blue pattern.
The brown router bit cuts the brown pattern.
The two template guides simply move the bit from one side of the cutline to the other.
The template guides router.
There is no loss due to kerf or radius.

459638

Exactly. This illustrates what I was describing earlier in this thread. Matched templates...one for each side of the end project material which are processed separately.

[Alan Lightstone]

Interestingly, (or frustratingly) the two templates I made with the 1/2" rabbet bit seem perfectly symmetrical, but have a tiny gap between them. I'm not sure if this will go away with clamping and gluing, or now I'm wondering about that Bondo trick on one of the patterns with the other one taped off. Another reason why this would have been SO much easier with inlay. The plan is for the final thickness of the cutting board to be 1-1/4".

Any thoughts?

Loving the discussion and the debate, BTW. Really shows the strength of the community here.

[Mark Hennebury]

Jim, There are no matched template.
There is only one template, in the sketches below the template is the pink piece.
The blue and brown are the finished pieces. they are the pieces that you are making.
This drawing shows the the two patterns that you are cutting, these are the finished pieces of wood, not templates.
The drawing shows where the router bits must be to cut on either side of the line for each pattern piece.
459648

The image below shows the template overlaid on the finished matched pieces for reference, to show the position of the router bits in relation to the template and the patterns cut .

459649

The sketch below shows the relative positions of the template, the template guides ( bushing/ bearings) and the router bits to the cutline.
You can see that changing the template guides bushings changes the position of the router bit. with the small template guide bushing the router bit is moved close to the template and cuts on one side of the cutline. When you use the large template guide bushing the router bit is moved to the other side of the cutline.

459650

In the drawings below, you will see that the cut line in each operation is exactly the same distance from the template reference edge, and the you are cutting one pattern from one side of the cutline and the other pattern from the other side of the cutline.


459651






Exactly. This illustrates what I was describing earlier in this thread. Matched templates...one for each side of the end project material which are processed separately.

[Edwin Santos]

Jim, There are no matched template.
There is only one template, in the sketches below the template is the pink piece.
The blue and brown are the finished pieces. they are the pieces that you are making.
This drawing shows the the two patterns that you are cutting, these are the finished pieces of wood, not templates.
The drawing shows where the router bits must be to cut on either side of the line for each pattern piece.
459648

The image below shows the template overlaid on the finished matched pieces for reference, to show the position of the router bits in relation to the template and the patterns cut .

459649

The sketch below shows the relative positions of the template, the template guides ( bushing/ bearings) and the router bits to the cutline.
You can see that changing the template guides bushings changes the position of the router bit. with the small template guide bushing the router bit is moved close to the template and cuts on one side of the cutline. When you use the large template guide bushing the router bit is moved to the other side of the cutline.

459650

In the drawings below, you will see that the cut line in each operation is exactly the same distance from the template reference edge, and the you are cutting one pattern from one side of the cutline and the other pattern from the other side of the cutline.


459651

Hi, I'd like to thank you for posting the illustrations and details on your single template process.
As I understand what I'm seeing here, the difference in guide bushings is compensating for the router bit diameter and thus resulting in coincident cut lines.
In fact, it doesn't have to be the same router bit. Any combination of router bit/bushing that cuts to the same line will do. Clever

[Mark Hennebury]

Hi Edwin, Thank you.
Yes you are correct, any combination of bit and template guide that give you the correct position will work.

If you wish to multiple pieces you can of course use the finished pieces as templates and a flushcut bit, but for a single job this is a simple, quick and accurate setup.



Hi, I'd like to thank you for posting the illustrations and details on your single template process.
As I understand what I'm seeing here, the difference in guide bushings is compensating for the router bit diameter and thus resulting in coincident cut lines.
In fact, it doesn't have to be the same router bit. Any combination of router bit/bushing that cuts to the same line will do. Clever

[Alan Lightstone]

Mark. I get it, looking at your pictures, then I don't get the order of doing things. In particular, how do you make the right-hand piece? Making the left-hand piece seems straightforward with a router and the appropriate matched bearing size.

Do you put both the template and the righthand rough wood piece on another piece of wood then rout it?

[Mark Hennebury]

Hi Alan,

You can do either piece first, but it probable makes sense to cut the lefthand (Blue) first, then use that for supporting the template (Pink)

To make the righthand cut;

Support the template (Pink) on a piece of wood (Blue) the same thickness as the piece that you want to cut ( Brown)
Move the brown piece into the cut path of the router bit and clamp it in place.
The router bit will be cutting on the edge away from the template.
When you route following the template the bit will trim off any material that is in its path left of the cutline.

I will see if i can do a video to demonstrate.

459754


Mark. I get it, looking at your pictures, then I don't get the order of doing things. In particular, how do you make the right-hand piece? Making the left-hand piece seems straightforward with a router and the appropriate matched bearing size.

Do you put both the template and the righthand rough wood piece on another piece of wood then rout it?

[Mark Hennebury]

So I went in the shop and made a quick template setup and did a sample.
I made one of the template guides as i didn't have one the correct size.
This setup was done with 1/4" router bit. Patterns are 1/4" hardboard.
This is super easy to do, minimum amount of steps and as accurate as you want to make it.

I have to go into town this afternoon and I will try to do a video this evening when i get back in the shop.


A couple of points to keep in mind.

1. Template guides are not as concentrically accurate as shaft mounted bearings.
2. Router bases are not accurately mounted concentric to the shaft.
3. Router bases are not precision fitted the the router body and move when tightened.

So there are lots of places to lose accuracy with templates.
So it's best is to use a bearing setup.
It's best whatever setup you use to leave it setup until you are finished.
Setup two router and leave them setup, or a system that you can rely on to maintain accuracy.

One more point is that off center template guides can be used to advantage, as you can vary the cut offset by referencing a different part of the bushing.
It's all quite fascinating stuff!


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[Alan Lightstone]

I was almost tempted to start a contest as to each person's methods, and comparing the results. Hmmm.....

I glued up mine today, after using Bondo Fast Dry Filler to fill in the gap between the Final piece A and the Template B to make Template B more accurate size (note to self - never use that type of Bondo again. 3-4 minutes of working time is way too short). I then used a bearing trim router bit to trim Piece B (the Paduak) and it is being glued to the Purpleheart Final Piece A now. Tomorrow morning I'll take it out of the clamps, joint/plane/sand it again, and see how well I did.

I'd love to see your video, Mark. As would, I'm sure, all of us. It will be very instructive.

[Mark Hennebury]

Hi Alan,

I didn't get the video done tonight but will do it tomorrow.

Lets do it!.
When the flag drops the BS stops, as they say at the race track.



I was almost tempted to start a contest as to each person's methods, and comparing the results. Hmmm.....

I glued up mine today, after using Bondo Fast Dry Filler to fill in the gap between the Final piece A and the Template B to make Template B more accurate size (note to self - never use that type of Bondo again. 3-4 minutes of working time is way too short). I then used a bearing trim router bit to trim Piece B (the Paduak) and it is being glued to the Purpleheart Final Piece A now. Tomorrow morning I'll take it out of the clamps, joint/plane/sand it again, and see how well I did.

I'd love to see your video, Mark. As would, I'm sure, all of us. It will be very instructive.

[Rich Engelhardt]

A couple of points to keep in mind.

1. Template guides are not as concentrically accurate as shaft mounted bearings.
2. Router bases are not accurately mounted concentric to the shaft.
3. Router bases are not precision fitted the the router body and move when tightened.
This is why the sell a centering cone/pin. They do a tremendous job of eliminating (or significantly reducing) all those issues.

[Alan Lightstone]

Lets do it!.
When the flag drops the BS stops, as they say at the race track.

OK. I'm in. Hopefully will finish up the cutting board this week, if I don't get too busy. So mine will be the rabbet / Bondo technique.

Any other takers? Let's see some great skills and learn new techniques along the way.

[mreza Salav]

sorry, can't see the photos posted (I know, have to renew my membership but can't do right now).
The method I have described is tested and works perfectly. No need for bushing or guide, does not depend on the shape of the curve (as long as it's not too tight so the router can follow it). You just need a 1/2" top bearing bit and that's it! you need a couple of different bearing sizes as well to change.
It gives you perfect fit, guaranteed.

[Michael W. Clark]

Hi Alan,
One thing you might do to improve the fit, is when making the mating template, do a first rough pass cutting all the way through. Then, cut it again but this time secure the rough mating template so you are only removing a small amount along the router bit's path.

Your situation is different than most. Most of the published methods have you make a set of templates first, then use those to make both workpieces. You already had one workpiece that you wanted to match, so you had to use your workpiece to make the first template that was offset the correct amount so it could be used to make the mating template. This was an extra step for you that you may not have to repeat on the next job if you make the templates first.

[Alan Lightstone]

Your situation is different than most. Most of the published methods have you make a set of templates first, then use those to make both workpieces. You already had one workpiece that you wanted to match, so you had to use your workpiece to make the first template that was offset the correct amount so it could be used to make the mating template. This was an extra step for you that you may not have to repeat on the next job if you make the templates first.
No question I headed down the wrong path in the beginning. I didn't realize that the two pieces wouldn't match due to the thickness of the bit changing the radius of the "matching" piece.

I was surprised that making the second piece using a suggested technique didn't provide a great fit. And using Bondo to fill in the gap did make the joint much tighter, and I was able to glue it successfully together yesterday. Ignore the glue stains - I haven't sanded it yet, or cut it to size.

A better / easier technique, as several have suggested above would have been better from the start.

I would love to see some samples to see which of the above techniques really work, and which ... not so much.

Man your routers. On you mark. Get set. Rout...

[Malcolm McLeod]

Interestingly, (or frustratingly) the two templates I made with the 1/2" rabbet bit seem perfectly symmetrical, but have a tiny gap between them. I'm not sure if this will go away with clamping and gluing, or now I'm wondering about that Bondo trick on one of the patterns with the other one taped off. Another reason why this would have been SO much easier with inlay. The plan is for the final thickness of the cutting board to be 1-1/4".

Any thoughts?

Loving the discussion and the debate, BTW. Really shows the strength of the community here.


Don't recall anyone mentioning this so far, and not exactly fitting with your initial proposition, but.... If you wanted an inlay to show on both sides:

make the field board at 1-1/2" thick initially,
route the (curved?) inlay dado at 1-3/8" deep,
add glue & fill dado with your contrasting wood of choice (leave it a little proud),
plane infilled 'front' flat,
then plane the 'back' down to final 1-1/4" thickness, and so expose the inlay..??


In theory, you could repeat steps 1-4 several times, then step 5 as final - exposing all the infill on back side. I recall the FWW article on similar method, but don't have it in front of me. Seems like the first 4 steps match their method. I just can't remember if they proposed step 5?

[Alan Lightstone]

Don't recall anyone mentioning this so far, and not exactly fitting with your initial proposition, but.... If you wanted an inlay to show on both sides:

make the field board at 1-1/2" thick initially,
route the (curved?) inlay dado at 1-3/8" deep,
add glue & fill dado with your contrasting wood of choice (leave it a little proud),
plane infilled 'front' flat,
then plane the 'back' down to final 1-1/4" thickness, and so expose the inlay..??


In theory, you could repeat steps 1-4 several times, then step 5 as final - exposing all the infill on back side. I recall the FWW article on similar method, but don't have it in front of me. Seems like the first 4 steps match their method. I just can't remember if they proposed step 5?

I just looked at the Article (FWW, May/June 2013 - "A Unique Cutting Board").

They did not propose step 5. Interesting method, Malcolm.

[Mark Hennebury]

Got a video done, let me know if its okay. If you have any questions or suggestions, i would very much appreciate hearing them.
I took some overhead shots also, and may insert some of those later.


https://www.youtube.com/watch?v=noA5nij2ubA

[Mark Hennebury]

Hi Alan,

You could have used your one good piece to make a template and used the single template method that i showed to trim the bad fitting piece. There are lots of different ways to do this stuff, It's all good to see a few different ways, food for thought for the future.



No question I headed down the wrong path in the beginning. I didn't realize that the two pieces wouldn't match due to the thickness of the bit changing the radius of the "matching" piece.

I was surprised that making the second piece using a suggested technique didn't provide a great fit. And using Bondo to fill in the gap did make the joint much tighter, and I was able to glue it successfully together yesterday. Ignore the glue stains - I haven't sanded it yet, or cut it to size.

A better / easier technique, as several have suggested above would have been better from the start.

I would love to see some samples to see which of the above techniques really work, and which ... not so much.

Man your routers. On you mark. Get set. Rout...

[Mark Hennebury]

Here is the video from overhead if you want to see things a bit closer up.

If anyone can sit through both, your opinion would be much appreciated.
I am hoping to do some more demonstration videos, I have a lot to learn and appreciate any help, advice or constructive criticism in that regard.


https://www.youtube.com/watch?v=l792uX7Yiag&t=15s

[ChrisA Edwards]

Thank you, I found that video helpful.

For those that do not have the ability to make their own bushings, I believe this kit, from Whiteside, https://www.amazon.com/gp/product/B076DP6LGJ/ref=ox_sc_saved_title_1?smid=A1WO0LWTFI0BL8&psc=1 would achieve the desired results.

My only suggestion, not that this video really needed it, for the cut, I would have zoomed the camera down more on the actual cut.

[Mark Hennebury]

Hi Chris,
Thanks for the reply,
I will work on this video to make it shorter , cleaner and better, I will see if I can add some cad drawings etc.

Thanks, Mark


Thank you, I found that video helpful.

For those that do not have the ability to make their own bushings, I believe this kit, from Whiteside, https://www.amazon.com/gp/product/B076DP6LGJ/ref=ox_sc_saved_title_1?smid=A1WO0LWTFI0BL8&psc=1 would achieve the desired results.

My only suggestion, not that this video really needed it, for the cut, I would have zoomed the camera down more on the actual cut.

[Alan Lightstone]

Thanks for the video, Mark.

What I see as the most difficult step (and the one I had some issues with) is making the second template and making sure that the router doesn't deviate at all from the pattern. If it does, you decrease the size of the template as it routs into that, and that piece gets thrown out. It's certainly easier, and more forgiving to rout away waste and have the template you are making protected, like routing the first piece. I found it took a decent amount of force to keep the router hugging the pattern, and you can't let up as you go around the curve. I must have a little bit around the line as I made my second pattern as I had a small gap. And I fixed that with the Bondo and clamps.

[Mark Hennebury]

Hi Alan,

On the single template method that i have shown.

Trim the righthand part to rough size on the bandsaw, leave a small amount 1/16" to trim with the router. then climb cut the part on the template, it will push the router tight to the template. If you do standard upcut on the righthand part the router will tend to pull away from the template and into the cut. And you will have to fight it to keep it tight to the template. Climbcut it and you wont have that problem.



Thanks for the video, Mark.

What I see as the most difficult step (and the one I had some issues with) is making the second template and making sure that the router doesn't deviate at all from the pattern. If it does, you decrease the size of the template as it routs into that, and that piece gets thrown out. It's certainly easier, and more forgiving to rout away waste and have the template you are making protected, like routing the first piece. I found it took a decent amount of force to keep the router hugging the pattern, and you can't let up as you go around the curve. I must have a little bit around the line as I made my second pattern as I had a small gap. And I fixed that with the Bondo and clamps.

[Edwin Santos]

This has been an interesting technique thread. I'd like to contribute another alternative, neither better nor worse than the others but just another option.

Some years ago I was impressed with an approach to cutting perfectly mated curves that was showcased in a FWW article. The article "Cut Matching Curves" appears in Issue #179.

What the author did was cut a single template edged with a flexible 1/4" MDF strip secured with glue blocks. Then she made a perfectly mated template by clamping a second MDF strip to the first which conformed to the first curve and while clamped, she then secured this second strip to a mating template using glue blocks. Ultimately the final workpieces are rough cut at the bandsaw and then final cut with bottom a mounted bearing guided flush trim bit using the templates.

It's a little difficult to explain, but here is a link: https://www.finewoodworking.com/2005/09/01/cut-matching-curves.

This is yet another option for cutting perfectly mated curves.

[Alan Lightstone]

Wow, her technique is a lot more work than anyone here has suggested. It looks like it should work, but our crew here has better suggestions.

[Mark Hennebury]

Here is a video of a guy making cutting boards with complimentary curves straight off the bandsaw.


https://www.youtube.com/watch?v=jcvSK4kBE9A&t=404s

[Alan Lightstone]

Desafortunadamente, mi español no es muy bueno, así que no pude entender lo que estaba diciendo. Pena.

But basically, he used an inlay to solve the geometry problem with the two pieces, as well as the rough cut from a bandsaw. Interesting other steps, all with a handheld router. I used a router table. Did not want to risk tilting the router and ruining the board. I did use a handheld router to round the corners, although with a corner jig.

I wonder what woods he used. The darker word was quite pretty. Quite nice work.

[Alan Schaffter]

Matching curves for cutting boards- The reason the pieces won't mate and you can't successfully use almost all of the techniques suggested in this thread is simple geometry. You especially can't use the technique where you route curved kerf partially through the boards, bandsaw down the middle of the keft, and flush trim the waste. It just won't work. Likewise you can't use the cut piece and router with bearing bit- the same thing happens.

Let's see if I can do this- I don't have privileges any more so can't see other's pics, but hopefully you can see mine.

In the following SketchUp drawings I used an exaggerated curve and simulated a 3/8" wide kerf to make a near triangular shaped piece and mating piece- not quite the worst case but close! As expected, the perpendicular distance between all points on opposite sides of the kerf is 3/8" and as the pieces are brought together at the apex they meet after moving 3/8." However you are not moving the other angled surfaces perpendicular to t tje surface of the angle, you are moving them obliquely so the angled segments will never both meet. Remember this a a worst case scenario. The shallower the curve the closer the curves will get, but unless both surfaces are flat and parallel (horizontal in my drawing) they will never mate perfectly.

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Someone mentioned the Bondo method to make complementary templates- I concur. I used that technique to quickly make templates before, e.g. use that to a template to cut the opening in the top of my router table that matched the radius of the corners of the router mounting plate. It is quick and easy and doesn't require a lot of precision: Draw the desired pattern on template #1. Bandsaw, file, and sand for a smooth, pleasing profile. Trace the profile onto stock for template #2 and cut it out with a bandsaw- it just has to be close, not precise. Remove any high spots so they roughly mate. Then cover the edge of template #1 with thin plastic tape. Mix and spread Bondo onto the mating edge of template #2. Force and clamp the templates together. Once the Bondo has hardened, clean excess Bondo from the top and bottom faces of template #2 and you will have two templates that mate perfectly and can be used with a flush trim router bit to make mating pieces of cutting board.

Can everyone see the drawings? I can't. My apologies to Glenn if his post demonstrated the same principles.

[Mike King]

Matching curves for cutting boards- The reason the pieces won't mate and you can't successfully use almost all of the techniques suggested in this thread is simple geometry. You especially can't use the technique where you route curved kerf partially through the boards, bandsaw down the middle of the keft, and flush trim the waste. It just won't work. Likewise you can't use the cut piece and router with bearing bit- the same thing happens.

Let's see if I can do this- I don't have privileges any more so can't see other's pics, but hopefully you can see mine.

In the following SketchUp drawings I used an exaggerated curve and simulated a 3/8" wide kerf to make a near triangular shaped piece and mating piece- not quite the worst case but close! As expected, the perpendicular distance between all points on opposite sides of the kerf is 3/8" and as the pieces are brought together at the apex they meet after moving 3/8." However you are not moving the other angled surfaces perpendicular to t tje surface of the angle, you are moving them obliquely so the angled segments will never both meet. Remember this a a worst case scenario. The shallower the curve the closer the curves will get, but unless both surfaces are flat and parallel (horizontal in my drawing) they will never mate perfectly.

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Someone mentioned the Bondo method to make complementary templates- I concur. I used that technique to quickly make templates before, e.g. use that to a template to cut the opening in the top of my router table that matched the radius of the corners of the router mounting plate. It is quick and easy and doesn't require a lot of precision: Draw the desired pattern on template #1. Bandsaw, file, and sand for a smooth, pleasing profile. Trace the profile onto stock for template #2 and cut it out with a bandsaw- it just has to be close, not precise. Remove any high spots so they roughly mate. Then cover the edge of template #1 with thin plastic tape. Mix and spread Bondo onto the mating edge of template #2. Force and clamp the templates together. Once the Bondo has hardened, clean excess Bondo from the top and bottom faces of template #2 and you will have two templates that mate perfectly and can be used with a flush trim router bit to make mating pieces of cutting board.

Can everyone see the drawings? I can't. My apologies to Glenn if his post demonstrated the same principles.

thats the issue. And that issue is solved exactly with the bushing method Mark showed above (challenging requiring a metal lathe) or the simpler process of buying the Whiteside guide and bushing I referenced far earlier in this thread or, for that matter, using the concepts Mark showed and different sized bearings on pattern routing bits.

[mreza Salav]

Looks like some people still don't believe (or think) there is a simple way to get "perfect" fitting curves using the method I described. No bushing is needed, just two different bearing sizes (e.g. if you are using a 1/2" router bit you'd need a 1" bearing). People do these things all the time. how do you make matching rail/stile pieces on curved rails then?

[Alan Lightstone]

Looks like some people still don't believe (or think) there is a simple way to get "perfect" fitting curves using the method I described. No bushing is needed, just two different bearing sizes (e.g. if you are using a 1/2" router bit you'd need a 1" bearing). People do these things all the time. how do you make matching rail/stile pieces on curved rails then?

Mreza:

This is one of the reasons I suggested that people put their methods to a test. By making a board using their technique and posting pictures of it. And videos of those would be better still. I can't be the only one who tried to make curved matching pieces. And yes, an inlay looks so much simpler to accomplish.

I used Michael Clark's methods, which should have worked perfectly, but I still had a bit of a gap. Then using the Bondo method to create a perfectly matching pattern, I was able to make perfectly mated pieces and a nice cutting board.

[mreza Salav]

Perhaps you didn't read my earlier posts. I have used this method I described several times and it does give perfect matching pieces. So I speak from experience.
I think even the bed whose picture is in my avatar and a few other beds I made had curved rails that needed to be mated with the Stiles.
I am out camping for several days and can't take pictures or videos but am willing to explain the method in more details.

[Rod Sheridan]

Hi, make a pattern then use a 1/4” straight bit to cut maybe 1/4” deep. In something to use as template.

Now saw the board in half, then trim flush on the router or shaper.
Now you have 2 templates that will fit….Rod.

[mreza Salav]

Hi, make a pattern then use a 1/4” straight bit to cut maybe 1/4” deep. In something to use as template.

Now saw the board in half, then trim flush on the router or shaper.
Now you have 2 templates that will fit….Rod.

That won't fit tight Rod. The two curves have a radius difference of 1/4".
You need to compensate that on one of them with a bearing 1/4" bigger.

[Mark Hennebury]

If it's the way that i read it, it wont fit, but then i am only guessing at what you mean. why not do a sketch so we know what you are talking about.


Hi, make a pattern then use a 1/4” straight bit to cut maybe 1/4” deep. In something to use as template.

Now saw the board in half, then trim flush on the router or shaper.
Now you have 2 templates that will fit….Rod.