Tear-Out when Dovetailing Baltic Birch
Observations on router tear-out when dovetailing plywood, and advice on how to prevent it. July 5, 2006
Question
I am experiencing a lot of tear-out when dovetailing 12mm Baltic birch. We are using a Porter-Cable Omni jig. We first do a shoulder cut and are using a new bit. Any suggestion other than use a different material?
Forum Responses
(Cabinetmaking Forum)
From contributor D:
I usually use Baltic birch for drawers and do experience some tear-out as well. I've tried using laminate on front of Omni jig, but this was a pain and didn't work for me. Are you making a score cut first, then a plunge cut? Try to keep the router speed steady as you plunge. Also on this tearout, if it doesn't run down, the veneer will not matter anyway because it will be hidden in the pins when you assemble the drawers. Keep trying and you will find a way and a feel that works best for you. With my particular router, I will score across the face, then plunge. When I plunge, I will force it in there hard and this seems to work for me. I've tried several different ways.
From contributor J:
I've had the same problem in the past, and I agree that most of the tearout is covered when the joint goes together. It still drove me nuts, though, so now I try to sell the solid wood as much as possible.
From contributor B:
Get some Appleply form States Industries. I think it has a better core.
From contributor L:
I use a Leigh D-4 for my dovetailing. Apple ply will tear out as well. I don't notice a difference in machining from the Baltic. The tearout usually happens on the backs of the pins and is hidden. It seems that routing at a slower pace (don't race through the cut pattern) minimizes the problem. I occasionally get some tear along the front edge of the pins (blowout caused by worn backing?), but it's not much and so far, I've been able to putty it, making it all but unnoticeable. I am considering going to hardwood drawer boxes, also.
From contributor D:
If a customer wants hardwood drawers, I will usually order them, which I don't like to do. The reason for this is my hardwood supplier only sells a minimum of 4/4 lumber. I don't want to have to plane this down. If I could find another supplier, I would probably switch to hard rock maple or whatever species. But for now the Baltic birch works well and usually after I assemble the drawer box, I will run the box on my router table and round over all of the tops, then sand and spray. Also may occasionally stain the fronts and backs a darker color to accentuate the dovetails. This is all, of course, with an applied drawer front.
From contributor J:
Won't your supplier plane stock for you? I usually get mine 4/4 and mill it myself, but my supplier will mill to whatever thickness I need for a reasonable amount. If you're buying from a smaller outlet that doesn't offer this, you may want to shop around. Not so much just for the drawers, but you could probably get better pricing from a bigger supplier.
From contributor G:
We (Courmatt) manufacture a number of different angles, both in an upshear or a down shear solid carbide version. A TCT tool will break the edges, whereas these provide a smooth cut.
From contributor D:
Contributor J, do you mill down to 1/2"? If so, that seems like a lot of work. And no, my supplier does not mill lumber, but you got my wheels spinning and will look around. Thanks.
From contributor J:
Actually, I cheat a little bit. The slides I use will take up to a 5/8" side, so I make my drawers 3/4" thickness. (I prefer the thicker look.) Then, after I groove all the parts to receive the drawer bottoms, I just trim the drawer sides below the bottom to 5/8" thickness. I still have the grooving blade in the saw, so it only takes a couple minutes to do the whole stack. Quick and easy.
If you switch to solid wood, try out the thicker sides - you might like them. If you do stay with 1/2" sides, see if you can find a supplier who will sell you undersized stock. It's worth a shot.
From contributor F:
I have devised a method to dovetail 1/2" Baltic birch ply with the Porter Cable Omnijig and get almost 100% tearout free results. The trick is to climb cut as a first pass. I first run the router from right to left and I keep the rub collar firmly on the jig's fingers for the direction of the climb cut and I cut in each channel about 3/4 of the depth. On the second pass, going in the normal direction, I also keep the rub collar snug against the jig's fingers for that direction of feed. Keeping the rub collar snug is as important as climb cutting the first pass to 3/4 the full depth of the recesses between fingers in the jig.
Again, the trick is to hold the rub collar snug to the sides of the jig's fingers. Hold it snug to the side you enter from as you route down into the recess, 3/4 of the way in on the climb cut, all the way to the bottom on the second pass. When you change direction to come back out, keep the rub collar tight to the other side of the channel.
Use 1/2" shank bits only. 1/4" shank router bits will snap off at the head when they get a little dull.
From contributor M:
To avoid tear-out, I cut a piece of 1/2 inch MDF the same width as the drawer sides and clamped it in the dovetail jig on top of the Baltic birch. I run the router through a couple of times and tear-out is virtually eliminated.
