Maintaining Grain Orientation with Box/Dovetail Jigs - Router Forums
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post #1 of 13 (permalink) Old 04-06-2019, 02:22 PM Thread Starter
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Default Maintaining Grain Orientation with Box/Dovetail Jigs

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Originally Posted by Marco View Post
...snip...
I am looking to keep my board orientation cut in the correct order so that the grain I choose for the outside of a box will be as planned/marked.
...snip... Dovetail Jigs for hand held routers
I am interested in the grain orientation aspect of the above thread.

I have the Incra LS Positioner, so the jig setup question is not strictly relevant to my question. I have used the LS once for a small box using box joints where I used 1/4" Baltic birch plywood (BBP). The BBP grain is relatively plain and uniform and I was focused on simply learning how to use the jig to make the joints, so all I needed to do was avoid the void patches.

However, as I use it more and begin being concerned about grain orientation, I am wondering how to go about maintaining grain orientation. Perhaps this will become self-evident with use, but I am wondering now. With the LS, you can cut boards individually, but typically two or more boards are stacked and cut at the same time. Also, the cuts are made with the boards against the fence and that side of the boards become the reference sides.

For box joints and possibly through dovetails, my first guess is that outside grain surfaces should be facing away from each other. Once the first sides are cut, the pieces are rotated 180 to put the ends that were up, down on the table. This places the "reference" edges on the outside, away from the fence, so it seems to me that the boards need to be rotated another 180 (in a different plane) to put the reference edge against the fence. As said, this seems like it works for box joints and through dovetails. For half-blind dovetails, it seems that does not work, unless the boards are so perfectly centered that the edges will match.

With the regular jigs (like the one in the referenced thread), there are what amount to two "reference" surfaces, the little "side fence" on the right and on the left so when the pair of boards are rotated 180, the reference surface (edge) of each board is maintained against one of the fences. With the LS system, the only way to accomplish this is if one of the two boards were to be fed into the cutter from the opposite direction, which I'm assuming is not a good idea. Short of doing it this way, my sense is one just has to deal with any mismatch of the reference edges by sanding or other means of making them even.

Rick

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post #2 of 13 (permalink) Old 04-06-2019, 11:55 PM
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I was watching this process the other day and the woodworker pre cut the lengths, then set up the box, selecting the inside, outside, top and bottom. Then he marked the inside in chalk, with an arrow pointing up to the top. Then he marked the front, agains with chalk. This allowed him to place the pieces properly for cutting whatever kind of joint you want. Box, dovetail, splined miters, etc.

The instruction book for the Porter Cable (pdf attached) has further information on laying out and marking your box pieces. I know the Sommerfeld instrutions for the Katey Jig also suggest how to mark up the jig itself as a memory aid while cutting.
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File Type: pdf Porter Cable dovetail jig instructions 1.pdf (1.46 MB, 25 views)
File Type: pdf Porter Cable dovetail jig instructions 2.pdf (2.13 MB, 20 views)
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post #3 of 13 (permalink) Old 04-07-2019, 10:15 AM
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I'd make a sample box, marking the orientation of the ends in the jig while cutting them.
Then assemble the box, and use it for reference.
When you build a new box, just refer to the sample to see how to machine it.

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post #4 of 13 (permalink) Old 04-07-2019, 10:33 AM Thread Starter
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Thanks, Tom. Some of the discussion in the manuals looks helpful. I saved the files for later reference. The part about labeling the boards looks particularly useful. I'm not sure about much of what is in the supplement, as it appears to be in reference to the PC jig itself. I'll have to ready it more carefully to see how much conveys to using the LS Positioner.

I was and still am hoping others with the LS Positioner or similar Incra jigs will speak to my question about rotating the boards to keep the reference edges against the fence, etc. It may come down to how well centered the boards. The process for centering appears as though it could be quite accurate, however the procedure described in the LS documentation appears to not take advantage of the precision capabilities of the LS leadscrew.

The procedure is to cut a full length slot "near" the center and then rotate the board and cut the slot again. The resultant slot width will be wider than the cutter, unless the bit is perfectly centered (extremely unlikely). The described procedure is to then "eye-ball" centering the cutter within that wider slot. It seems to me the missed opportunity is not measuring the slot width with calipers and subtracting the bit width from the slot width. Then dividing that difference in have and dialing the fence over by that one-half amount using the infinite adjustment knob. It seems to me that this would take advantage of the LS leadscrew, one of the features that Incra says sets their system apart from the other jigs. I'll have to try it to see how well it works. Maybe Incra has and found it doesn't make enough difference. I'll be surprised if that is the case.

Rick

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post #5 of 13 (permalink) Old 04-07-2019, 10:55 AM
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@RickKr I couldn't recall which document had the pictures in it so I posted both. The longer one had the drawings, not sure the second one will be useful. The PorterCable dovetail jig is really tricky to set up and even a slight error will ruin the fit. Went to a demo once and the "expert" didn't get it right. Not exactly intuitive.

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post #6 of 13 (permalink) Old 04-07-2019, 11:07 AM Thread Starter
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Quote:
Originally Posted by DesertRatTom View Post
...snip...
The PorterCable dovetail jig is really tricky to set up and even a slight error will ruin the fit. Went to a demo once and the "expert" didn't get it right. Not exactly intuitive.
That does not sound appealing. I'm glad I have the LS, which is very intuitive to me. Given that I have not used it but once, we'll see if that holds.

Rick

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post #7 of 13 (permalink) Old 04-07-2019, 02:20 PM
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Quote:
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That does not sound appealing. I'm glad I have the LS, which is very intuitive to me. Given that I have not used it but once, we'll see if that holds.

Rick
The best way for me is to just fool around with it until I get the hang of it. There are some good tips here and if a person sifts through them and chooses the ones that look like they will work, then try them out and you will soon develop the technique that works for you. Everyone has to figure out what works for them.
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post #8 of 13 (permalink) Old 04-08-2019, 11:53 AM
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A triangle on the face side written with chalk or on a piece of blue tape is how I do it. Inside the triangle I put a number indication, 1 being the front and then going counter clockwise from there. The top point of the triangle indicates "up". This keeps all of the pieces orientated and sequenced correctly, the odd numbers are always the front and back and the even numbers are always the sides. I begin cutting each piece in sequence for the grain to follow counter clockwise around the box and mark each piece on the face side with the number and triangle pointing toward the top edge. From then on I depend on these markings to keep the pieces oriented and sequenced correctly.

When making a box using box joints I always cut both ends the same, so the bottom always begins with a pin. The front and back then always begin with the space, and both ends of each pair are cut the same. The odd panel numbers are the front and back and the even numbered panels are the ends. You face the marked side out during assembly and always decide which way is "Up" by the point on the triangle marking.

I use a similar method when doing dovetails. The tails get cut on the even numbers and the pins get cut on the odd numbers. Since I have a Leigh D4R jig with variable pin and tail spacing, I always put the pin on the bottom of the odd numbered and the first tail on the bottom of the even numbered sides.

Keeping everything labeled the same way and always working with this same marking sequence keeps me from making mistakes and all 4 sides of the box that I'm making have continuous grain around their corners, of course, with the grain not matching in the left rear corner where the two ends of the original board come together, but all of the other three sides will have the matching grain around the corners.

The trick is to develop a marking and sequencing method that works for you, and then stick with this method every time you will build a box. Use my method or something similar every time and you will have great results.

Charley
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Last edited by CharleyL; 04-08-2019 at 11:59 AM.
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Excellent, Charley! That is an impressive process. I like it, a lot. It is exactly the kind of process that appeals to me. Your method of having the grain travel all the way around through at least three corners is beyond what I was thinking, but is beautiful. Your marking system is sophisticated but practical. Thank you for providing such detail. I'll bet the casual observer never catches on. Have you experimented with selecting the boards so that last joint matches more than randomly?

I've seen references to using chalk elsewhere. How is chalk for disappearing with sanding, etc.? I've used light pencil marks and they erase and sand away, mostly, but sometimes it is more difficult to get the last remnants out.

Rick

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post #10 of 13 (permalink) Old 04-08-2019, 03:49 PM
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Chalk comes off easily, almost too easily. If doing any other marking I don't use it because it's too easy to wipe it off. I then use a large round pencil with very soft lead frequently, because it doesn't dent even when marking pine, if you are careful. I bought a bunch of these pencils at a flea market many years ago when I discovered this. I've still got a few left. These look like the round carpenter's pencils that are available today, but I haven't tried these to see if they are the same. For what I have, the soft lead dulls quickly, so frequent sharpening is necessary.

Did you know that DNA will remove pencil marks without a trace, as long as you don't leave a pencil line dent? Lead pencils no longer use lead for the writing material, and what is used now removes quickly with alcohol.

Charley

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