Dovetail Jig Question

[PJC]

I was playing around with the PC 4212 DTJ today. I was tried doing a through dovetail, but the pins came out way too big. The pins are way too thick. I only did one test piece, so adjustments will be needed. My main question is, why do you use a dovetail bit for the tails and a straight bit for the pins? I always figured that a dovetail bit would be used for both tails and pins (or a straight bit for both tails and pins if doing a box joint).

I am not sure how to fit the "strait" pins into the "dovetail" tails.

Thanks,
Pete

[RayintheUK]

..... why do you use a dovetail bit for the tails and a straight bit for the pins?

As the boards are joined at right angles, one part of the joint is angled (the dovetail bit) whereas the other part, although cut at an angle, has straight sides (cut with the straight bit), like this:



HTH.

Ray.

[LCHIEN]

I was playing around with the PC 4212 DTJ today. I was tried doing a through dovetail, but the pins came out way too big. The pins are way too thick. I only did one test piece, so adjustments will be needed. My main question is, why do you use a dovetail bit for the tails and a straight bit for the pins? I always figured that a dovetail bit would be used for both tails and pins (or a straight bit for both tails and pins if doing a box joint).

I am not sure how to fit the "strait" pins into the "dovetail" tails.

Thanks,
Pete

If you hold up each part of a through dovetail, with the joint up and looking at the side (not the edge),
imagine that the router is on top with the bit down.
One part will have the cuts in a dovetail shape (e.g. sides angled from vertical at the dovetail angle) as the router passes through the side.
The other part will have vertical edges (hence a straight bit used to cut)
even though the path through the wood is at the dovetail angle, its guided by a template to achieve that angle.

[Stormbringer]

Maybe this will help

Here's an image I scanned a while back. Hope it helps

http://www.bt3central.com/attachment...7&d=1142988270

[Tom Hintz]

Pete,
Have faith that the dovetail/straight bit sequence works. After you do them a little while it becomes clear, though I admit sounds a little weird at first.
The fitting part is a little harder to understand, again until you get some experience with a jig.
The important parts of fitting through dovetails is to use the stock that will fit in the part of the joint being cut to set bit depth. Hold a sample of that stock against the bottom of the jigs fingers and draw a line on the piece being cut. Set the bit depth so that the bottom of the cutting edge splits that line. That should produce pins that are slightly proud of the surface when assembled to allow sanding them flush rather than having to sand the side down to meet them.
The actual fit between the pins and sockets is usually controlled by the position of the template when cutting with the straight bit. Moving that template forward or to towards the rear changes the size of the joint being cut and thereby the fit of the pieces. (SMALL changes are all that is needed usually) Here is where following the instructions very closely, step by step, is crucial. I've not used the PC jig, but on my Leigh, those instructions were clear and sticking with them a few times drilled the sequence into my head.

[Ken Massingale]

What they said, unless you use an Incra jig. Then all cuts are made with a dovetail bit. Just adding to the confusion.
ken

[PJC]

Thanks for the posts everyone. It makes a lot more sense. Especially after cutting a proper set of tails and pins.