:help: Odd gaps with Porter Cable dovetail jig - Router Forums
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post #1 of 19 (permalink) Old 01-04-2012, 09:54 PM Thread Starter
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Default :help: Odd gaps with Porter Cable dovetail jig

I just purchased the Porter Cable dovetail jig. My first project involved half blind dovetails for a toy box for my kids. It is made of pine 1x12s. I checked and rechecked the setup but I kept getting weird gaps as shown in the pictures linked below (I tried uploading directly with no success) It was a Christmas present, (started too late) so I couldn't fully debug the joints before giving the pieces to the kids (it was a kit that we then assembled together) I am sure both boards in the jig were flush and against the stops and template.

I understand about lowering the bit for a tighter fit and raising it for a looser fit, but my problem is that with a tight fit, the pins and sockets did not match (as shown in the picture I hope)

Any suggestions on how to avoid this on future projects would be greatly appreciated.

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post #2 of 19 (permalink) Old 01-04-2012, 11:16 PM
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What bit are you using? If you are trying to make half-blind dovetails the bit that comes with the jig is a 17/32 - 7 #43776PC dovetail bit with a 3/4"od template guide. Both sides of the joint are machined at the same time in the jig. The picture looks more like a straight bit.

James
Whittier, CA.

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Last edited by jlord; 01-04-2012 at 11:24 PM.
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post #3 of 19 (permalink) Old 01-05-2012, 07:42 AM Thread Starter
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I was using the dovetail bit that came with the jig.
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post #4 of 19 (permalink) Old 01-05-2012, 07:44 AM Thread Starter
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I cut both sides of the joint at the same time too. They definitely locked together.
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post #5 of 19 (permalink) Old 01-05-2012, 10:59 AM
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Your problem looks odd to me. Usually if there is a gap you would need to lower the bit, but the gap is usually equal on both sides of the joint. How does the inside of the corner look? You shouldn't be able to see any gap at all. It doesn't look like it is cutting each part to equal depth. Any obstructions when clamped in jig? Boards narrower on ends where joint is? Planner snipe on ends?

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post #6 of 19 (permalink) Old 01-05-2012, 11:33 AM
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I have the same issue on my first attempts with the jig. I played around a bit with bit depth and the issue was minimized to some extent. My gap is approx 1/32". See below. I thought there was supposed to be a bit of a gap for glue. I also did notice that the wood I bought varied a bit in width and thickness. It was apparent when I locked the pieces down in the jig but I ran with it. You can see the width mismatch on the bottom left in the image below where the pin/tail joint on the edge don't match up. For the thickness mismatch I wonder if you're supposed to adjust the vertical piece to match heights rather than bumping it flat to the jig fingers?


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Last edited by Chris_L; 01-05-2012 at 11:36 AM.
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post #7 of 19 (permalink) Old 01-05-2012, 11:41 AM
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The template should be flat on top of material (fronts & backs). Then the front piece (sides) brought up flush to the template capping off the top piece. Parts should meet at line eched in top of template. Parts should be milled for equal thickness across material. You can join parts of different thicknesses but each board just needs to be flat & even.

Chris your parts look like they need to be adjusted as the joint looks uneven at the bottom. How wide did you cut your material?

James
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post #8 of 19 (permalink) Old 01-05-2012, 12:01 PM
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James,

I used boards off the shelf as bought and didn't cut them down. 7 1/4" nominal. For my next set I'm considering buying wider boards and ripping them down to 8 1/4" so that I know they are the same width across the given length.

Cary, NC
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post #9 of 19 (permalink) Old 01-05-2012, 12:07 PM
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Be careful that the boards are not cupped as this is common with wider material. Which means more machining would be needed.

James
Whittier, CA.

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post #10 of 19 (permalink) Old 01-06-2012, 09:31 AM
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Quote:
Originally Posted by jlord View Post
What bit are you using? If you are trying to make half-blind dovetails the bit that comes with the jig is a 17/32 - 7 #43776PC dovetail bit with a 3/4"od template guide. Both sides of the joint are machined at the same time in the jig. The picture looks more like a straight bit.
Look at the pic again. It looks to me like the top has the angle and the bottom is straight on both pieces. What would cause that is beyond me unless the guide didn't ride the template flush on both sides. To me it looks as if the guide didn't make contact on the right side of the template on either board.

When something is advertised as being foolproof there is always a better class of fool that comes along to prove them wrong.
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