Incra Jig

[Joe]

Hi,

I'm just starting to use an incra jig and I have a question on making doube dovetail joints.

I have cut the first dovetails and slid the second set into the first. But when I try to make the net set of dovetails I keep having the wood split on me. I know these are delicate pieces ( the wood is 1/2 inch thick) and I am trying to make small cuts where possible. I have made three attempts and all have had the same results, the pieces of the second dovetail are broken off.

Is the a trick to makeing these joints? I'm thinking that the first set of dovetails is too tight and I'm starving the joint of glue. Does any one have any experience with this?

[GerryG]

Unsure how close your spacing is (which template?), or what type of wood it is. Will assume you have the grain oriented correctly, else that's your problem.

In general, you need to calibrate your bits with scrap, adjusting for enough play to slide the dovetails together with only light pressure. Any tighter than that, and they'll jam when you add the glue.

Have made many dovetails with the Incra, and haven't had that problem even with thinner stock, IOW you will get past this issue.

GerryG

[Joe]

Thanks for the response. Here is what I've done so far.

I've used scrap pieces to set the bit height and the joint can put together by hand even after adding glue but you do need some force to slide the pieces and when the pieces slide together a good amount of glue seems to be pushed out of the joint. Is this normal?

The joint I am making is IDDD using a 1/2 inch bit at 14 degrees. The wood type that keeps breaking is maple.

The grain direction is an interesting question as I was going to play with this anyway. From the drawings in the book it appears that I make the openings in the wood by running the board through in the direction of the grain. That is to say, the grain and the fence are parallel with each other and when the joint is made you would see end grain showing. In the picture below, when the mating piece is installed, you would see end grain when looking at it.

__ __ \ / \ /

---------------- | | | |

I was thinking of changing the direction of the cut so that the grain of the mating piece would run along the length of the board. i.e. in the picture above the grain would run in the direction indicated by the arrow below.

---->

I would do this by running the piece through with the grain perpendicular to the fence. (the end grain would be butted against the fence)

Am I on the right track??