How do I make this cutting board curved joint?

[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/...ass-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.
#1.jpg
1. Make a template.
#2.jpg
2. Route left hand side pattern using the first template guide.
Pattern Assem2b.jpg

Pattern Assem2c.jpg

3. Move the left hand pattern back out of the way. Route righthand pattern with the second template guide. Same template, same router bit.
Pattern Assem3b.jpg
Pattern Assem3c.jpg
Done.

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

Assem4a.jpg

[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.
#1.jpg
1. Make a template.
#2.jpg
2. Route left hand side pattern using the first template guide.
Pattern Assem2b.jpg

Pattern Assem2c.jpg

3. Move the left hand pattern back out of the way. Route righthand pattern with the second template guide. Same template, same router bit.
Pattern Assem3b.jpg
Pattern Assem3c.jpg
Done.

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

Assem4a.jpg

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.

Pattern line.jpg