I have had the Reverse Glue Joint bit in my bit storage box for some time but have never used it. This week, I decided it was time to see if it would work. I wanted to use 1 X 4   mahogany decking stock for the Adirondack chair. Biscuits could be used but I wanted to test this bit out. If it worked, it would be better to use.    Bottom line: it worked, but there are some tricks to making it work perfectly.      Bit height is the key to success. Any error in height will double the error on the boards you join. It makes real sense to set it right at the beginning.    The art at the right is from CMT's catalog showing the center point of the bit. You can see in the photo above, the actual bit which has been centered on the center mark of the board I am going to route.    This all seems simple, doesn't it? It isn't. The pencil line may get you close, but not close enough. The goal is to set the height so exactly that the glued up panels will require no planing or sanding to make them flat.     Having tried several ways, here is the way that I found works best. Start by cutting two scraps from the exact same stock as you want to join.  Seven or eight inch pieces work fine.    Mark one "A" and the other "B".     Now set the router height to the mid-point as marked on a scrap board. You don't have to be accurate. This is a starting point only.    Note that I have clamped a hold down in position.       Next, I adjust the fence so that the inside edge of the cut is in line with the fence.    I route the "A" board with the "A" face up. Following that, I route the "B" board with the "B" face down.    Here is the first test fit. I am way off. I did this purposely so that you could see the error clearly in the photo.    Now, here is the clue: If the "B: side is lower, raise the bit.    I used the table saw to rip off the first try edges and then raised the router bit several turns (I use a screw adjustment on the router.)    As you can see, it looks like it is exactly right. It was so close that by eye, it seemed right, but I could feel a slight edge on the "B" side.    The "B" side was just a hair high, so I lowered the bit about 1/4 of a turn (1/64").    This time, it is right on. So remember, if the "B" side is low, raise the bit. If it is high, lower the bit. Literally, this setup should take no more than a minute or two and it will save you many minutes of planing uneven boards.    Now you can run all the stock you need, as long as it is the same thickness. This joint keeps the boards aligned as they are glued and provides good glue surfaces.    It is a good glue joint.   Main Menu Previous Page               To CMT Site    To Locking Miter First Page