Panel Jig Straightness

[anikun07]

I built my first panel jig last night using 3/4 Araucoply because it was what I had available to me at the hardware store when I bought my 1/2 plywood for a THT. I used 3/8" ripped pieces for the rails to fit into the miter tracks and at first they didn't slide freely because they naturally bowed after being cut. The pinch was only in the center. I realized my mistake was putting screws at each end of the rail when it was in the track but screwing the rest in out of the track to get the runner and panel flush since the rail is just a little shallower than the track. Even though I pre drilled with the rails in the track so the screws should have straightened the rails but it didn't. I fixed that by taking the middle screws out and putting them in new spots while in the tracks. The final cut-through also helped relieve the rail pinching too.

So I got that all set. With the rails being the same length as the panel jig I noticed the first few inches don't cut straight because there's some wiggle room until the rails become better seated in the track. Would it be better to add new rails that are longer than the panel so they can be seated before the saw blade start cutting the stock? And the 3/4 Arauco has some bend in it, will this go away over time?

Thank you for all help and suggestions.

[Bruce Weldy]

Yes, extend the rails out a few inches. I made mine from red oak.

[anikun07]

Thank you. I was thinking about using the extra oak I have from the 8' piece I got for the back boad of the jig. I will trim the depth to fit the tracks. Thanks again for confirming my suspicion. Would you recommend a smaller jig for smaller pieces or is it okay to regularly start the saw with the blade in the middle of the jig?

[Bruce Weldy]

Thank you. I was thinking about using the extra oak I have from the 8' piece I got for the back boad of the jig. I will trim the depth to fit the tracks. Thanks again for confirming my suspicion. Would you recommend a smaller jig for smaller pieces or is it okay to regularly start the saw with the blade in the middle of the jig?

For smaller pieces (under 8 inches), I use a 12 in. miter saw.

[Tom Smit]

Try putting the rails in the slots, put carpet tape/double-faced tape on the rails, lower the panel jig over the raised blade and onto the rails. Then you can pull out the jig and install screws from the bottom.

[anikun07]

I replaced the plywood rails with oak and re-squared the jig, it seems to be cutting straight. I made sure each side of the blade was square before putting screws into the rails. Boy, it sure works nice. Thank you for all the suggestions.

[anikun07]

Does anyone have any tips for bow? The 3/4" plywood is bowed upward in the middle, front to back. It cuts straight but I didn't know if I could get rid of the bow?

[Bruce Weldy]

Does anyone have any tips for bow? The 3/4" plywood is bowed upward in the middle, front to back. It cuts straight but I didn't know if I could get rid of the bow?

I assume you are talking about your panel jig being bowed. That's why I built mine out of MDF for the base and oak for the rails and fences. It's several years old and hasn't moved a lick.

If you are going to build jigs out of ply, it's best to use BB as it is less apt to warp....especially any jig that has large panels involved.

[anikun07]

I will probably switch to MDF after this project and I find a use for this plywood. I can't justify wasting $40 in lumber just yet and I'm pretty sure it cuts straight or close to it. It's just a bit of a nuisance not having it flat. The oak rails extending 6 inches past the front of the jig certainly helped. I've got all my THT panels cut so I hope it finishes up well enough despite the few mistakes I've made.

[koturban]

It's important that the backer is stiff enough to resist any bowing by the plywood.

I used 3/4" BB and laminated two pieces of 3/4 X 4 inch laminated oak. Any bow that was in the plywood disappeared when I screwed it to the backer.

[anikun07]

I used 3/4" x 4" oak for the backer but the. Bow is perpendicular so it wuld have to the the rails that straightened out the jig. I expect MDF is cheaper than plywood, so perhaps my next project i'll replace the jig panel.

[koturban]

I used 3/4" x 4" oak for the backer but the. Bow is perpendicular so it wuld have to the the rails that straightened out the jig. I expect MDF is cheaper than plywood, so perhaps my next project i'll replace the jig panel.

Depending on how much you plan to use the jig afterwards, consider a set of Incra Miter Sliders. They will straighten most any bow and are durable.

[anikun07]

I will consider that. I also clamped.the edges of the jig to the table si.ce I wont be using it for a while and hopefully that can help bend it flat.

[koturban]

I will consider that. I also clamped.the edges of the jig to the table si.ce I wont be using it for a while and hopefully that can help bend it flat.

Hate to dash your hopes, but it'll most likely spring back when you remove the clamps, even after an extended period.

[anikun07]

Yeah, I sort of expect It but I.figured it.couldnt hurt. i've read of people setting damp towels in the sun to warm up and then place them over the plywood to help straighten it.