Dovetails - someone remind me to...

[Mike Goetzke]

...check the concentricity of the bit to the bushing. I've had the newer 16" Porter-Cable Omnijig for a few years now. I don't use it all the time so need a refresher every time I use it. It is really a nice jig and simpler than most but twice now I've messed with the depth of cut several times only to find the bit wasn't concentric to the bushing. I don't know how it moved since last time I used it. Oh well maybe someone can benefit from this.

Mike

[Charles Lent]

You can avoid router bit/bushing concentricity problems if you always orient your router in the same direction while cutting the dovetails. I drew an arrow on the top of my router bases and always point this arrow toward the jig. A concentricity offset, that's always in the same direction, will not show up in your dovetail cuts. I always try to adjust my router bases for concentricity, but orienting the router so it always points in the same direction guarantees that there won't be an error from a concentricity offset so long as the bushing remains tight in the router base and you don't change the bit height half way through the cuts.

Charley

[Mike Goetzke]

You can avoid router bit/bushing concentricity problems if you always orient your router in the same direction while cutting the dovetails. I drew an arrow on the top of my router bases and always point this arrow toward the jig. A concentricity offset, that's always in the same direction, will not show up in your dovetail cuts. I always try to adjust my router bases for concentricity, but orienting the router so it always points in the same direction guarantees that there won't be an error from a concentricity offset so long as the bushing remains tight in the router base and you don't change the bit height half way through the cuts.

Charley

I usually have the router in the same position, but, I do find it easier to roll the router a bit between the fingers.

Mike

[Charles Lent]

And when you roll the router you are entering whatever concentricity error you may have between the bit and the bushing into your dovetail joint. Keeping the router always oriented in the same direction throughout the cut will apply this concentricity error exactly the same to the whole dovetail cut, so the end result will be a good dovetail joint, but offset slightly by whatever the bit to bushing error is. If you turn the router while making the cut this error will create varying amounts of error in your dovetail cut, depending on how the router is oriented. It will be at it's worse if you rotate the router 180 deg while making the cut.

Put an arrow, or just a piece of masking tape on the top of the base of your router and point this mark in the same direction during your whole dovetail cut. You will be pleasantly surprised how much better your dovetail joint fits together.

Charley