Frustrated with my Incra Ultra jig

[Charles Green]

Hi,

I'm needing some advice on what I'm doing wrong with my Incra jig.

I've had it for about a month. I've done some half blind dovetails and through dove tails with it.

I'm trying to do some double double cornerpost dovetails. My first attempt came out with a lot of gaps but I went ahead and went through the entire process just to get a feel for the joint.

I've adjusted the depth to what allows me to push the joints together but has no gap. And looser and I can see a little gap. Tighter and I have to give a little mallet tap to get them together.

When I install the trim piece which is the next step in the process, the trim piece cracks. I even lowered the bit a little more and I'm still cracking the trim piece. This happened with both my walnut and maple trim that I tried.
It is cracking with only hand pressure not even hammer whacks.


Any other ideas for me? I've got the dovetail video that Incra put out and can't find any other tips that I haven't seen.

Thanks in advance for the help.

[Terry Flowers]

If you got it from Woodpecker, the people there are very helpful. Assuming you don't get an answer from this forum, I would give them a call. I have watched them demo the joint at wood shows with no difficulty.

Terry

[Charles Green]

I'll try them in the morning. Everything is very easy on it except for this one step.

I guess I'll have my eureka moment with it when I lay down to sleep tonight.

Thanks for the response.

[John Keane]

Charles, you are not alone. I did a prototype attempt a few months ago and ran into the same problem. "Newbie". I intend to try again, and hope that I have better success. Watching the dbl dbl and other sexy joints at WW shows they always use a full board and then just match things up. I hope that you get the answer, so that I can save a forest.

[Ken Massingale]

I agree with giving Jason at WP a call. I've had the same problem with Walnut and Maple for the trim. There is not a lot of wood holding the recesses together. Now, I just try to be gentle with them. And yes, I have still cracked them after the dry fit and reassembling with glue. If it's a clean break with no wood break off, a little CA and a little hand pressure makes the crack disappear.
Also with very brittle wood I will make the trim pieces thicker then sand the excess off after assembling the joint.
Good luck with the Ultra, it is definitely a learning experience.
Ken

[Guy Germaine]

It almost sounds like you're cutting the trim pieces to final "thickness" before glueing them together. When you make the maple trim pieces, you should be making them out of the same thickness material as the other stock. That way, you should not have to change depth, once set. I always make a block of the trim stock bigger than I need and once the dovetails are cut in it, rip it into 3/4" wide sections. Glue the pieces together. You should now have a trim piece that is probably 1/2" or more too long. Once the glue dries, use a crosscut sled to trim to final length (usually 3/32")

Did that make sense?

[Tom Hintz]

It almost sounds like you're cutting the trim pieces to final "thickness" before glueing them together. When you make the maple trim pieces, you should be making them out of the same thickness material as the other stock. That way, you should not have to change depth, once set. I always make a block of the trim stock bigger than I need and once the dovetails are cut in it, rip it into 3/4" wide sections. Glue the pieces together. You should now have a trim piece that is probably 1/2" or more too long. Once the glue dries, use a crosscut sled to trim to final length (usually 3/32")

Did that make sense?

I'm with Guy. That's how I make doubles and have no trouble. I gtried cutting the trim piece to size before assembly and broke every one of them.

[Charles Green]

Thanks for the replies.

I did have the trim the same thickness as the others. I wasn't changing the depth of cut.

What I found out is you can put a lot more pressure on the test cut pieces than the small trim piece so that when I thought I had a good depth it was too tight for the trim piece.

I had to make at least a dozen sample cuts to get the depth close enough. It was very difficult to find a balance between no gap and not too tight.

I made three boxes with cornerpost dovetails to see if I could get that joint working first. I'm going to try some others today.