Struggling with Leigh Dovetail Jig...Questions

Re: Struggling with Leigh Dovetail Jig...Questions

JL

I have used other brand bits on a D24 jig as well as other brand bits on PC jigs.

So long as the bit is the correct size - it shouldn't matter.

You do have to get the correct size bits though.

Re: Struggling with Leigh Dovetail Jig...Questions

John McGaw

Yep. Brand doesn't matter -- the size and angle are the key. And the sharp of course. I've never had any of the Leigh bits, using a set sold way back when by Jesada (anybody remember them?), and they've worked great. I'll have to say that test cuts have always seemed a necessity for me even though I keep samples on hand to use as jigs in the initial setup process. I've never done a DT in plywood so I don't know if that would be different in some subtle way I don't understand.

I've always had trouble with Baltic Birch

Dick Coers

I've made hundreds of drawers and always had trouble with veneer splintering with Baltic birch. Soft maple is my go to. Did some drawers for the kids in the late 80s when I was in a hurry. That's when I was running a woodworking business and making family things didn't buy groceries! Anyway, used 5 ply 1/2" plywood with biscuits and a false front. They are still using them to this day.

Re: I've always had trouble with Baltic Birch

Barry Irby

Dick, I understand. A friend and I worked our way through college building cabinets. Have made hundreds of drawers without dovetails. My friend has made at least a thousand. Never had a failure. I spoke to him the other day and after almost fifty years of kitchens he has never had a call back for a drawer failure.

My son just thought the drawers with 11 ply Baltic birch would look cool. This is one of those things I thought was going to be simple. Not so much. I was surprised at how badly the birch ply was splintering. I clearly completely misunderstood it's characteristics. It is pretty in it's own way but I may give up on the dovetails.

I may use some dominoes and leave them exposed. Or, I have some aluminum nails that are at least 1/8" in diameter. I may just butt the joints and drill some holes and install some aluminum "dowels".

When I get home I will check my stash of dovetail bits and if I have a nice sharp matching one I may give it one shot and then switch to another method if that fails. Was also considering coating the area with CA glue to cut down on splintering. We will See.

Tight fitting

David Yoho

My few experiences with machining dovetails in Baltic birch ply always ended up with very tight fitting joints. Too tight to go together. From then on I made drawer parts from solid stock. I have a different (newer) Leigh jig than you but haven't used it recent enough to begin to say how to adjust it. Seems like your owner's manual would explain it. Don't have one? See if it's available online. Even then, you'll probably experience tear-out.

Re: Tight fitting

Barry Irby

I do have the book. It's overwhelmingly detailed. It says raise the bit/looser joint. It gives no clue as to how much. If you raise the bit a 1/1000" does that do nothing or can you throw a cat in the joint?

What adds confusion for me is I am using Blum tandem under mount slides for the first time. Very strange. They apparently created the slides in Imperial and then converted everything to metric and back. For instance, If you want 15" slides, you buy the 381 version. Apparently to them, it's blindly obvious that 381 millimetres is 15 inches. So, the inside measurement of the drawer boxes needs to be 42 mm narrower than the opening, but the outside dimensions of the box length needs to be 381 mm. Now, if that dimension is not critical why wouldn't they use 380 mm?

They called for 16 mm (5/8") drawer sides, but I drove 20 miles to get 5/8" Baltic birch plywood but it's only 15 mm.

This too shall happen. Some how.

Re: Struggling with Leigh Dovetail Jig...Questions

Jerry Gibbs

Is ply suitable for dovetails?

Re: Struggling with Leigh Dovetail Jig...Questions

KenK

I've made quite a few drawer boxes using 1/2" Baltic Birch on a Leigh jig. I do it infrequently so I have to re-learn the process every time. I've found it imperative to use a sharp or new bit and to make a climb cut on the drawer surface face. Also use a backer board to prevent tear out when cutting the tails.

Jerry & KenK.....

Barry Irby

Is Plywood suitable....Not without a lot of effort. At least that is my experience.

I am building this for my son and he thought the Baltic Birch would be "cool". He also wanted Blum under mount runners. Blum seems to indicate plywood??? the call for 12 mm or 16 mm sides so I interpreted that to mean Baltic Birch. Now, having struggled through that I think they think everyone uses the prefinished "boards" that come with rounded edges and the groove for the bottom precut. The clue on this is they tell you to cut a notch in the back to allow for the runner. On a classic drawer the bottom would be cut off and the bottom would slide in under it and you would not need a notch.

It has been a real struggle. I thought the Leigh jig was already set up. Not so much. Took a lot of fiddling. The joints must be really loose in plywood or they won't go together.

The inner faces of the tails chipped away, but I am going to live with it. The front end will be covered by the false drawer front. The back may be hidden by a thin piece in the form of a half blind dovetail.

If the jig had not settled in, I was back to making old fashioned drawer boxes without dovetails. I am done with dovetails and am cutting the grooves for the bottoms. Then assembly.

Re: Struggling with Leigh Dovetail Jig...Questions

Larry Clinton At Frankfort, (Central) Indiana

Barry, I have an older Leigh jig, purchased in the box unused at a estate sale some years ago. I have a full set of Whiteside bits I use with the jig. The only issue I have had with the jig is that some boards "slipped" during machining. I applied a strip of fine adhesive backed sandpaper to the clamping bar and it solved the issue.

Ah Ha!  I needed that info....

Barry Irby

I too have had a piece or two slip. I crank down on the handles so hard I wonder if I am damaging them. I was thinking about a piece of rubber or cork glued onto the bars. People making Moxon vices use Crubber, a combination of cork and rubber. Andy Klein sells it if I am not mistaken. Now I am trying to think if I have any PSA sand paper. Thanks for the idea.

I sharpened the bit with a diamond plate and got through the four drawers. They are glued up now and I am waiting for the glue to set. Suffered a few minor blowouts on the Baltic Bitch plywood. Seems to be difficult to avoid. Repairs were easy enough. I tend to doubt I will be making any more drawers with dovetails out of the rest of the stuff.

Re: Fine in ply.

TomD

Ply is suitable, though you are not going to get the structure you get with hardwood, and the 90 layers will be cut away from support and will not glue as well. But the end result is still really good. Nobody doubts it when ply has dinger joints, that is used a lot. Same issue there. I used to use dovetailed ply neck blocks in guitars. Worked great. I cut them with hand tools, and sometimes used a router as well.

Re: Struggling with Leigh Dovetail Jig...Questions

TomD

Brand of bit is irrelevant, you adjust the fit on half blinds by raising the dovetail bit for tighter, or lowering for looser.

On through dovetails, you adjust fit by moving the pattern in and out. And it is the act of cutting the pins with the straight bit that does the fitting.

The biggest difference is if you follow the settings for the through DTs, and you hedge to a fatter fit (further to the back with the guide), you can move the guide forward and make the result looser until it is perfect. Then you can run the rest without further adjustment. But with the HBs, you have to run test cuts. if you have to raise or lower the bits, you don't get a second chance, if I remember correctly. It has been probably 25 years.

With the HBs, I once did a very delicate project where I had cut the drawer fronts very carefully out of a larger piece so that they had only a very tight crack all the way around them. This way I got great grain continuity. But the problem with that was I had to get the first shot perfect. I forget how I did it, but I do remember the adjustment is in the vertical exposure of the dovetail bit. These days I would cut the HBs by hand. I still like the leigh for production through dovetails.

Re: And the pro techniques are...

TomD

At least the original old units with the knobs were designed to be tightened by putting the piece to be cut on one side, if it was under full width. You learn by experience how much to tighten the side on the tight side. It is easy to tighten because there is no force on the long side. So if you have a 24" and you are doing an 8 inch drawer, you have the piece on the left side, tighten the left knob, then you use the remaining 16 inches as a leaver and crush it down, till you can just spin the second knob down to the compressed jaw/bar. No difficult turning of knobs required. This was how it was intended to be used. I remember calling for the fancy lever retrofit kit, and the owner was surprised he had had to make it because as far as he was concerned the actual technique was better than the levers.

As far a blowout is concerned here are your 3 pro tips

1) sharp bits, which you already know.

2) Dovetail joints actually look better with a marking gauge line to stop the eye wandering. So if you are OK with that idea, real joints almost always have a gauge line, you can spare some of the blowout with a light cut line.

3) You start the cut on throughs from the right and move to the left. This makes most of the cut a climb cut, so the blowout is controlled. There is a crumb on the right end that will be cut by the half of the cutter that can't climb cut, so you want to use the smallest bit you can get away with as it has the least unsupported width in the cut. You could also get in there and nick it with a chisel before the router pass

Next you remove the cutter after this heavy scoring, and you move it to the far right and plunge straight through to the other side, but then mover hard left, and score from left to right. At this point you have as much of the grain prepared as you can get, and you remove the remaining material as efficiently as possible.

With HBs, you do the first part, basically the right to left, and then get the rest out.

Re: Struggling with Leigh Dovetail Jig...Questions

Barry Irby

Thanks Tom,

You are correct on what you say. Part of my problem was that I already had the jig and a dedicated router set up to do HB dovetails. I had just done the cabinet with four corners 18" long and figured I could use the same set up. The plywood for the drawers was thinner and the drawers would turn out to be through DT's but the font gets an overlay front and the rear seldom if ever shows, so I was OK with that. This was a poor assumption. I would have been better to go to the method for Through DT's and use two routers.

As it was, I had just put some wear on the DT bit with the trial and error of getting the depth just right for the cabinet. White Oak is tough. I was hoping I could just use the existing setting and move on. Nope. Took a lot of fiddling to get the fit right.

Apparently the plywood just cuts differently than the oak. The trial and error dulled the bit further. An even slightly dull bit is a bad thing in plywood.

And there are a LOT of adjustments on the Leigh Jig. The rack of finger guides moved on me one time. For some reason the right knurled knob on my jig will lock up really tight if you just snug it, requiring pliers to loosen it. So I try to tighten it "just right". Apparently I failed to snug up the left one, which normally works just fine. Threw that drawer part away and made another.

My jig has the older style fingers that are in two pieces. Pictures of the newer ones seem to indicate Leigh has combined them in to single pieces that aw wider and have two screws. On the 18" ones on the cabinet I spread them apart. Somewhere along the way one of them moved about a 1/32", making one DT loose. (I shimmed it, don't tell my son.) I was ritualistic about checking those screws in the fingers when I got tot he drawers and I put the fingers back to back to have the effect of two screws together. Triple check the screws for tightness. In cutting the sockets (four drawers, 16 sets of sockets) they gradually separated by maybe a hundredth. Just enough to see, but only after it's over. This loosened the fit, but that is what epoxy is for.

Of course my stubbornness did not help. Or maybe it did.