Backer boards with a Leigh Jig

[Harley Lewis]

When dovetailing with the D4 jig, I see lots of references to backer boards to reduce tear out. What material do you use for the backer board, and how thick should it be? I tried poplar that was 5/8 thick and it did not work very well in my novice opinion. If a person uses a backer and a fronter board to prevent tear out on both sides of the dovetail -- it gets awful thick. So, what does a person use to get those fantastic cuts shown by our craftsmen posting on the creek?

[Al Navas]

...I tried poplar that was 5/8 thick and it did not work very well in my novice opinion. If a person uses a backer and a fronter board to prevent tear out on both sides of the dovetail -- it gets awful thick. So, what does a person use to get those fantastic cuts shown by our craftsmen posting on the creek?

I don't use backer boards on most wood. Sometimes I need to, but most of the time I don't. I use mostly native woods; red oak was the worst for me (early on in my WW career) - I used 1/2" white oak ad the backer board, behind the work piece ONLY. Walnut also tends to tear to a certain extent; I just baby it as much as needed :) .

Three suggestions, when using the dovetail cutters at maximum router speed for the smaller bits:

For the first cut, take a VERY light cut right-to-left.
From then on, take deeper cuts left-to-right, until you go through the board. On 5/8" poplar it takes me about 5-6 cuts to cut each tail with the dovetail cutter.
Patience, patience... The results ARE worth it!You should have zero or minimal tear-out when using the straight bits to cut the tails.

Let us know how this works for you.

Are your router bits in good shape, and sharp? If they are not sharp and in good shape, you are likely to experience problems.


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[J D Thomas]

Over the past 2 summers I built 2 large workshop projects with about 40 drawers of various sizes. I felt it would give my Leigh jig a good workout. All the drawer boxes were 1/2" BB plywood, and I had NO tearout. I used 3/4" MDF as the backer board and 1/8" hardboard on the front to eliminate the tearout there. It is possible.

Pics on request.

[Tom Jones III]

I used 3/4" MDF as the backer board and 1/8" hardboard on the front to eliminate the tearout there. It is possible.

Didn't you have to keep putting in fresh backer boards? I stopped using BB ply for my cheaper drawers because it seemed like too much work to keep putting in new backers. I switched to poplar for almost all my drawers, but that just shifts the work to milling.

[Daniel Rabinovitz]

Wait a minute - time out
The backer board is horizontal and fits in from the back and butts up against the "back" of the "project board" that you are cutting.
From what I understand from your post - you think that the backer board should sandwich the board that you are cutting - hence making the thickness 1-3/8 inches for two boards; one being 3/4 (the project board) and one 5/8 the backer board.
Then you are suggesting adding a fronter board to the sandwich?:eek:
Please clarify? :rolleyes: :confused:

[Alan Schaffter]

Along with a backer board if needed, sharp bits and good technique are also important. Take it slow, start with climbing cuts on the sides, don't try to hot out too much material at one time, remember the bit rotation direction when cutting and take it easy on that side of the cut.

[Harley Lewis]

Yep, fronter and backer boards. If you read the Leigh manual they suggest both for difficult woods to prevent tear out. I have done a fair amount of dovetailing and use the climb cutting techniques but still get some tear out on oak and other brittle, grainy, hardwoods. So, using two boards (fronter and backer) is the question. I am wondering if a 1/4 inch softwood like pine, or perhaps 1/4 inch mdf or similar stuff would work better than those thick pieces of poplar (which did not work very well). Really, I guess I am wondering what is the best material for fronter and backer boards, and what would be the minimum thickness you could use.

Harley

[J D Thomas]

Didn't you have to keep putting in fresh backer boards?

Someone has already mentioned that the backer board is the one inserted and clamped horizontally in the back of the jig. That's the one I'm referring to. And I only change the backer when I change the finger setup on the jig. There's no reason to otherwise. Same goes for the 1/8" hardboard in front for the most part. On the back, I just rotate the 3/4" MDF to get a fresh edge. Simple.

[Mark Conde]

I just made 7 drawers to go under my work bench. Made of oak and walnut. Walnut for the fronts and oak for the sides and back. I had significant tear-out on both the oak and walnut. I did not use a backer board, but wished I did. I am glad that these drawers were for a shop proj.

I have used maple and had little to no tear out. I think I will try to use maple in the future for drawer boxes.

[Fred Voorhees]

Didn't you have to keep putting in fresh backer boards? I stopped using BB ply for my cheaper drawers because it seemed like too much work to keep putting in new backers. I switched to poplar for almost all my drawers, but that just shifts the work to milling.

Tom, you wouldn't need a fresh backer board for each cut if they are all the same size and use the same finger layout. The previous cuts would repeatedly line up with your newer cuts.