# Incra Double Dovetail Project



## SPHinTampa (Apr 23, 2008)

*Prep Work - creating the laminated stock*

I have gotten a few questions (actually 3) from folk about to how create the Incra Double Dovetails Joints such as the one in this project:










I will not be making a box in this blog. But a really good friend saw this box and asked if I could make a 14" x 19" serving tray in the same style. Maureen has been a huge help to my wife and I so I was happy to get a chance to make something for her.

Obviously, first place to start is to get an Incra Jig System. I have the old 16" LS positioning system with an upgraded Wonder Fence. The positioning system is awesome. The wonder fence is a "nice to have" and is expensive ($170 + an upgrade of original fence extrusion $40) and I still have mixed feelings about it being worth it. Mark, the incra tech support guy, was empowered to knock down the cost of the replacement extrusion $10 and was very helpful, so thumbs up for Incra support.










One important thing I have found with the Incra joints is make sure you have a zero clearance insert around bit or it tends to yank the workpiece sideways and downwards when the bit contacts which giives sloppy joints. I just use a piece of 1/8" masonite held in place by the router table.

Step 1 - Creating laminations for tray sides

Prepped the raw stock by face jointing the stock, then edge jointing it.










The planed it to a consistent thickness (7/8")










I used an incra marking gauge to mark the cut line carefully to ensure that the width of the maple + 2 paduak strips would result in neat 1/2 pins on each side. Ripped to width on table saw.

The incra system comes with a template book with full size drawing that lets you figure out precisely how to size the stock so that you can space joints properly.










It is important to have stock that is square and true. Jig gives accuracy to 1/1000" so stock that wobbles is not going to make nice, tight joints.










Cut strips to rough size for glue up










Glue up using bar clamps. Need to watch for strips wandering around a little when you clamp. For next project, I might make the paduak strips a little wider than the maple strips










Since I travel a lot, I use old hotel card keys as a glue spreader:










Then hand planed laminations down to the final size (3/32")



















I use my table saw fence and a clamped stop as an impromptu shooting board for final clean up.



















Again, the incra template guide will give you a suggested stock thickness for a given pattern, so in this case, they are suggesting I use 1/2" stock. So I used my bandsaw to cut resaw the laminations.










Used planer to take them down to final thickness.










Use Radial Arm Saw to cut to final length










This a lot of work for 4 sides:










Next Steps - Cutting the joints


----------



## Roger Clark aka Rex (Dec 30, 2008)

SPHinTampa said:


> *Prep Work - creating the laminated stock*
> 
> I have gotten a few questions (actually 3) from folk about to how create the Incra Double Dovetails Joints such as the one in this project:
> 
> ...


Very informative, thank you for sharing.


----------



## Howie (May 25, 2010)

SPHinTampa said:


> *Prep Work - creating the laminated stock*
> 
> I have gotten a few questions (actually 3) from folk about to how create the Incra Double Dovetails Joints such as the one in this project:
> 
> ...


Hard to beat Incra for accuracy.


----------



## lilredweldingrod (Nov 23, 2009)

SPHinTampa said:


> *Prep Work - creating the laminated stock*
> 
> I have gotten a few questions (actually 3) from folk about to how create the Incra Double Dovetails Joints such as the one in this project:
> 
> ...


I'm waiting for the rest of this. Wow!


----------



## Billp (Nov 25, 2006)

SPHinTampa said:


> *Prep Work - creating the laminated stock*
> 
> I have gotten a few questions (actually 3) from folk about to how create the Incra Double Dovetails Joints such as the one in this project:
> 
> ...


Thanks for doing the blog. I recently got an incra LS and will attempt these when the time is right. You are very through and I look forward to the rest of your blog.


----------



## SPHinTampa (Apr 23, 2008)

*Cutting the side joints*

First step of a double dovetail is to cut a through dovetail on each side piece and then attach a trim piece. This blog entry will cover that process.

So starting with the end pieces and a 6" piece of trim stock (same width as the side piece, thickness doesn't matter).










Install the two template strips into the positioning system (1 dovetail strip and 1 double dovetail strip).

The dovetail strip consists of an A side which lets you cut pins at 7/8" intervals and a B side that is offset by half that lets you cut the tails. The double dovetail side lets you use the same bit but you make double cuts that expand the slots to accommodate 3/32" trim outline. So you have a C/D cut for the pins the shrinks them slightly to accommodate the trim pieces.










First trick is to get the jig centered. That is done by roughly aligning the center of the bit with the center of the board with the jig locked on the centering mark on the template. You then cut a groove through the center of a scrap piece that is same width as your work piece. Reverse the piece and re cut the groove. Then adjust the jig, using the micro adjust feature, to the get bit evenly centered in the groove and move the template to re align the centering mark.










Then, as is required in all dovetail jigs, you must make test cuts to get the bit height set. This is done by making two cuts on the edge of two boards and then test fitting them.










If the fit is tight, you are done, otherwise - you raise the bit if the joint is loose or lower the bit if the bit is tight. The template will give you the initial setting for the height. First cut was a little tight.










With the height dialed in, I use the double dovetail template to cut the pins on the end pieces. This is done by taking a light scoring cut on the outside of the piece and then slowly advancing jig to first pin cut. Then you just move the jig forward on each cut and use the right angle jig to push the stock through the bit.










Reset the jig and use the trim marks to cut grooves in the trim piece.










I use the RAS to cut the trim pieces slightly over sized.










and then dry fit them










Ran into a problem when I put glue on, joints swelled and fit was too tight. Broken one of the pins. Lesson learned - make joints a little looser for glue up and/or cut extra trim pieces.










So glue up round two:



















Will sand down tails and trim to final length.

Next blog entry - cutting the tray front and back.


----------



## konaman (Jun 16, 2008)

SPHinTampa said:


> *Cutting the side joints*
> 
> First step of a double dovetail is to cut a through dovetail on each side piece and then attach a trim piece. This blog entry will cover that process.
> 
> ...


thanks for the blog on doing this.


----------



## ratchet (Jan 12, 2008)

SPHinTampa said:


> *Cutting the side joints*
> 
> First step of a double dovetail is to cut a through dovetail on each side piece and then attach a trim piece. This blog entry will cover that process.
> 
> ...


Excellent! Thanks for the tips.


----------



## SPHinTampa (Apr 23, 2008)

SPHinTampa said:


> *Cutting the side joints*
> 
> First step of a double dovetail is to cut a through dovetail on each side piece and then attach a trim piece. This blog entry will cover that process.
> 
> ...


I created some confusion with my description of the templates. If you are going to cut double dovetails, you only need the double dovetail template (A thru D cuts), not a single dovetail template (A-B cuts) as well.


----------



## SPHinTampa (Apr 23, 2008)

*Cutting double dovetails and making a few mistakes*

At the end of the last blog, I had glued up the trim to the tail sections of the R/L pieces:










I used my oscillating belt sander to sand the ends flush










Flush ends give me a flat surface for the next step










In my previous blog, I mentioned that you need a zero clearance insert to avoid having the bit pull the workpiece down. I forgot to mention the need to ensure that you hold the workpiece against the fence, particularly when you pull the sled back thru the bit (the climb cut) as it pulls the workpiece to the side. The result is a slightly out of square cut as you can see below. A little homemade wood putty (sanding dust and glue) will fix.










I then use a marking gauge to cut the trim back to 3/32" off the joint. Why 3/32"? Because almost all the incra double templates are designed to leave this much of a trim piece - the template book has the trim thickness listed.










Cross cut to the marked line on the Radial Arm Saw.



















Next step is to cut a rabbit. First of all, bury the bit in the fence to zero it out.










Then move one of the measurement gauges to sit under the marking line. In the picture, the top ruler shows where the measuring gauge sat originally (11" inches and change). The lower gauge has been moved to 10" even so I can easily sneak up on the 7/32" rabbit cut. Why 7/32", again rabbit depth is specified in template guide.










I then cut the rabbit with a very light scoring cut to start with (1/32") and then cut the rabbit in 3 more cuts, advancing to 10 7/32".










And this is what you get.










Now it is time for the big event. Time to cut the double dovetails.

First of all, clamp the tail sections to your right angle fixture and make sure there is no play in the movement. I forgot to mention previously but I will point out two important things now. First mark your pieces so that you are always putting the same edges against the fence. Even though I am sure that my centering was perfect, even a slight variation, coupled by cutting from the wrong edge, will leave gaps in your joints. Secondly, use a backer board (cut to same width as your work pieces) to avoid blow out. The book shows that you can cut two pieces at a time, which I am doing here. However, if I was working on a super fine project, I think I would cut each board individually. I find that the piece sandwiched between the backer and the front pieces always wants to move on me during cuts.










Other really important thing is to always perform a scoring cut and use 3-4 small cuts on the outside pin cuts. I am cutting 20C to start with. As you can see, I start far away from 20C, cutting 1/32" on my first pass and then advancing to 20C in 3-4 cuts. Similarly for the last cut, I will advance past the last cut, perform a scoring cut and then back into the cut slowly. In theory, give bit rotating into the piece, you don't need to do this … my experience is that it is less wear and tear on bit and seems to give me better results.










Second pass after scoring cut.










Now you just have to advance the cutter to each individual cut. Pushing thru and pulling back smoothly (wax the table top) and make sure you keep the piece pushed laterally against the fence for the climb cut.



















These look great when they are done.










Life sucks when the trim blows out.










When you cut the trim piece, you might be tempted to make it 4" and try to squeeze you end cuts out of a smaller piece of wood. Don't do it. Make at least 2-3 extra trim pieces because you may need to fix a mistake or two (or in my case 3). I chiseled out the trim










And recut the entire sequence from rabbiting onward.










Next blog … cutting the other ends … way faster now.


----------



## ratchet (Jan 12, 2008)

SPHinTampa said:


> *Cutting double dovetails and making a few mistakes*
> 
> At the end of the last blog, I had glued up the trim to the tail sections of the R/L pieces:
> 
> ...


This project is going to look great!
Makes me wonder if using a fronter and a backer board might help stop the trim piece from chipping out. Also , I've noticed that wooden screw clamps seem to work better at holding the material for me than quick clamps.
Please keep going.


----------



## Kindlingmaker (Sep 29, 2008)

SPHinTampa said:


> *Cutting double dovetails and making a few mistakes*
> 
> At the end of the last blog, I had glued up the trim to the tail sections of the R/L pieces:
> 
> ...


I found your "how I did it" really cool. Thanks!


----------



## JackMakesSawdust (Nov 26, 2014)

SPHinTampa said:


> *Cutting double dovetails and making a few mistakes*
> 
> At the end of the last blog, I had glued up the trim to the tail sections of the R/L pieces:
> 
> ...


You talked about the pieces moving. I'm just starting with my Incra LS and had the same problem. I, also, was using the Irwin clamp. I noticed that in the demo videos they use parallel jaw wood clamps. So I tried that and no more movement.


----------



## SPHinTampa (Apr 23, 2008)

*Cutting the Pins*

In the last blog, I completed the tails for the project (after a few mistakes). The next steps are a lot faster and less error prone.










Line up to the A cuts and then first step in cutting the tails is to set the stop block so it just barely misses the bit.










Making sure to keep you fence mark side aligned against fence (easy to forget for this step), cut one full set of pins, advancing to each A cut.










Then check the fit.  As you can see, I am shallow by 1/16". So I need to push the stop block back by 1/16".










I then recut the pins, check the fit and then cut all four sides.










And then we are done … quick, easy and no mistakes.










Given that I have done all the cool stuff, not sure how many people will read the rest of this blog but I will finalize the project by completing base, cutting hand holds and finishing it up.

Thanks for reading.


----------



## ratchet (Jan 12, 2008)

SPHinTampa said:


> *Cutting the Pins*
> 
> In the last blog, I completed the tails for the project (after a few mistakes). The next steps are a lot faster and less error prone.
> 
> ...


Not wasted on me. I appreciate your effort. Thanks for sharing your knowledge with us.


----------



## abie (Jan 28, 2008)

SPHinTampa said:


> *Cutting the Pins*
> 
> In the last blog, I completed the tails for the project (after a few mistakes). The next steps are a lot faster and less error prone.
> 
> ...


Thanks
Great Blog and nicely done
I've an incra setup and still have to return to the instructions since I don't make this stuff often
'when I do…
it is awsome.


----------



## SPHinTampa (Apr 23, 2008)

*The Tray Bottom*

In my last post, I finished cutting the double dovetails … sorry for the passive aggressive parting line. It was late and I was tired.

Now I will put the finishing details on the tray.










The only 1/4" plywood that I have in the shop is a piece 13"x72". My tray is 14 1/4" wide. So this is an opportunity to create a composite panel as a tray bottom. It will look like this:










First I cut the center panel on the table saw.










Then I cut the outer border strips










I then remove my excalibur splitter so I can use the thin ripping set up on my GRR Ripers. I have another zero clearance insert with the MJ Splitter in it that I use with the GRR Riper because its short height will allow the GRR Riper to pass over. I dont use the small splitter all the time because it does not have anti kick back pawls.










For those of you that don't have a GRR Riper system, they are just an expensive pushblock that lets you keep great pressure downward and towards the fence while keeping your hand safe. And they will never wreck a saw blade (sorry, mini sawstop rant).

I use this set up to cut 1/4" by 1/4" trim pieces.



















Lower the blade and take second pass.










Time to glue the trim strips to the border strips.










I use tape to clamp them on










Then I cut 45 deg on the RAS. I find it helpful to attach a sacrificial fence to the table top:










Cut the ends to size









Check with a square:










True up with a block plane










I then temporarily clamp the long sides in place. With the long sides in place, I can play with the end pieces to much sure everything is square. Then I glue the long side in place.










With long side in place and clamped and I glue the short sides and put them in place. Once they are clamped, I can check for square and the loosen and re tighten clamps as needed to adjust the final assembly to square. If you over tighten, you will bow the assembly (which is ++ bad). Just bring it together enough to get a fine, even line of glue squeeze out.










Although I wipe away the initial squeeze out on the top, the assembly can not be lift so I will need scrape the glue squeeze out off the bottom to get my final panel. I then cycle through sand paper 120, 150, 180 to get the final surface. I don't start at 80, 100 because they are a little too aggressive for the plywood.










Next blog entry …. cutting the panel grooves and finger slots.

Thank you for reading.


----------



## Roger Clark aka Rex (Dec 30, 2008)

SPHinTampa said:


> *The Tray Bottom*
> 
> In my last post, I finished cutting the double dovetails … sorry for the passive aggressive parting line. It was late and I was tired.
> 
> ...


Super series Shawn, I saved the set as my favorites.
Especially many thanks for making this very informative series, which must have taken you time to plan and execute. Bravo


----------



## ratchet (Jan 12, 2008)

SPHinTampa said:


> *The Tray Bottom*
> 
> In my last post, I finished cutting the double dovetails … sorry for the passive aggressive parting line. It was late and I was tired.
> 
> ...


I am going to have to try this one. Thanks.


----------



## AugieCoe (Jan 13, 2011)

SPHinTampa said:


> *The Tray Bottom*
> 
> In my last post, I finished cutting the double dovetails … sorry for the passive aggressive parting line. It was late and I was tired.
> 
> ...


First off, thank you for a great blog. I just bought my incra system and will be attempting double dovetails over my vacation this week. Second, what is that wood in the background with so much figure? Love it. Thanks again!!


----------



## SPHinTampa (Apr 23, 2008)

SPHinTampa said:


> *The Tray Bottom*
> 
> In my last post, I finished cutting the double dovetails … sorry for the passive aggressive parting line. It was late and I was tired.
> 
> ...


Thank you for the kind comments. The figured wood is rotary cut bubinga. That piece is the start of a sofa table that you can see on another blog entry - click on this link- if you want to see how it finishes.


----------



## SPHinTampa (Apr 23, 2008)

*Putting it together*

In my last blog, I created the tray bottom.










In this blog, I will cut the grooves for the tray bottom, rout finger holds and put the tray together.

First step is to cut grooves in the tail section. I use the MCLS 13/64" plywood bit (because 1/4" plywood is smaller than it's nominal size). As a rule of thumb, I like to cut the groove 2x the groove width (so 1/2" in this case) from the bottom in order to leave enough material for a strong assembly.

I mark the cut location in chalk as well as make a note of which edge to run against the router fence as I have a bad habit of cutting the wrong side of my work pieces. At this stage, you would have an irreparable mistake.










I set the bit height to the 1/4" depth I want for the groove (groove = with the grain, dado = cross grain) using the Rockler brass set up bar. Start with the bar behind the bit and below it. Raise the bit using the router height adjustment until you can see the bit and then lower it again to run even with the bar.










I use blue tape to show where I should start and stop the cuts on the router table. I mark a start location that is 1/4" past the outer edge of the bit. I also mark a stop location 1/4" before the outer edge of the bit.










With the edge of the workpiece lined up on this mark, I can tilt the work piece down onto the bit to start the groove.










Then run the workpiece along the bit until back of piece is even with the stop mark.










I also find it helpful to run the groove for 2" and then pull back a little to let the vacuum clean out the saw dust and then keep running. Just be careful that the bit does not grab the piece when you pull back (Note to other LJs … is this bad advice? please comment).










Run a test piece to check your set up and the run all four workpieces, remembering to use your marks to ensure cuts are on the right side and location on the work pieces.










Fit is dead on with no slack or play.










I then swap the plywood bit out for a 1/2" core box bit (could use a bowl bit or a sign makers bit as well - anything that will cut a profile without a bearing guide).










I want to cut another stopped groove. This time, my old homemade fence is better than my incra set up - mostly because it is longer. First I center the bit against the workpiece by eye.










Since the work piece is 14" and I want a 4" long finger hold, I measure 5" back from the outer edge of the bit, place the workpiece against the fence and place the stop to mark the end of the cut.










I then measure back and set the start block.










With the blocks set, I can lower the piece onto the running bit pushing it forwards and backwards between the stops.










I usually do 1-2 passes to cut the depth and then raise the bit by 1/64" for a final finishing cut. Final cut gets rid of fuzzy edges and burn marks. I cut finger holds on both sides of piece.










Now I use the oscillating sander to finish the sides before assembly (120 grit, 180 grit, 220 grit). The second version of this machine that Rigid sent me is awesome and really speeds stuff up. You just need to stay from rounding off the ends so you don't affect the fit of the joints.










I then glue together the tray. Beginning with the pin sides, glue only a 1" or so at the center of the long sides.










And then fit the tail pieces.










I am such a pack rat that I wont even throw out my saw dust. Instead I bottle it to make custom filler.










I mix small amounts of glue with very fine saw dust to make filler to hide my mistakes in the joints.



















Smear the filler in place, and let it dry for an hour or two. Padauk really makes a mess.










I use the sander to clean up the end joints, being careful not to round off the edges.

I then sign the back of the tray.










I first vacuum the dust and then use mineral spirits and rags to get the last bits. Note, if you miss any significant amount of the padauk dust, it will turn into red paint if it gets wet, so be careful.

And the project is ready to be finished.


----------



## Blake (Oct 17, 2007)

SPHinTampa said:


> *Putting it together*
> 
> In my last blog, I created the tray bottom.
> 
> ...


This is great. Thanks for the progress photos.


----------



## ratchet (Jan 12, 2008)

SPHinTampa said:


> *Putting it together*
> 
> In my last blog, I created the tray bottom.
> 
> ...


Excellent blog! Thanks for detailing it for us!


----------



## konaman (Jun 16, 2008)

SPHinTampa said:


> *Putting it together*
> 
> In my last blog, I created the tray bottom.
> 
> ...


very nice blog. I have wanted to see someone making incra dovetails for a while. I'm looking forward to seeing more of your work. Thanks


----------



## SPHinTampa (Apr 23, 2008)

*Finishing and Finished!*

I have been sanding as the project progressed so I am able to hand sand 180 grit and then 220 grit.










I then finish with three coats of rub on poly. Let the piece sit for a couple of weeks to wait for the finish to fully cure and then rub out any dust nubs with 0000 steel wool.










Finally, I use my Beall Buffing system to buff out the finish. Use the red tripoli finish first, followed by white diamond compound and finally wax. To be honest, I should have sanded to 320 to really see the difference. However, I can definitely feel the difference. People can not resist rubbing a wax finish once they touch it.










I then take it outside to view in the sunlight to look for any final defects that I missed.










Now I am off to the beach to give this to my friend Maureen.


----------



## JL7 (Apr 13, 2010)

SPHinTampa said:


> *Finishing and Finished!*
> 
> I have been sanding as the project progressed so I am able to hand sand 180 grit and then 220 grit.
> 
> ...


Nicely done - really looks good.

Now I'm off to the garage to tune up the snowblower, casue I know it's coming…...

Jeff


----------



## empeg9000 (Oct 5, 2011)

SPHinTampa said:


> *Finishing and Finished!*
> 
> I have been sanding as the project progressed so I am able to hand sand 180 grit and then 220 grit.
> 
> ...


Great project. Really nice work. Seeing this made me decide to go ahead and get the incra ts-ls with joinery system. My awesome fiance is getting it for me for Christmas.

Thanks for the inspiration!


----------

