Dovetail help! (Leigh super 18)

[ivwshane]

I'm trying to do single pass half blind dovetails just to keep things easy and so far all I'm doing is making a ton of saw dust.

I watched the DVD and I've managed to get the joint tight but I cannot get it flush. In the video the scale they show is not the same one used for hb dovetails but using logic I know that if the tails protrude I need to push the jug back towards the clamp. I do this and it's either too much or worse! How can it get worse? I make very small adjustments and the results don't correspond.

So either my routing technique is either bad or I don't have the bushing facing the right way (I have it set to 10 pointed away from me).

What am I doing? Does the setup always take forever?

[Dal300]

In my opinion, no matter what jig you use, or if you do it by hand, the joint shold protrude a bit so you can use a block plane, sand paper or card scraper to make it perfectly flush, otherwise you will always be chasing a perfection it may not be possible to achieve.

This is just my opinion, YMMV, and objects under the Tee shirt may be larger than they appear!

[ivwshane]

I'm ok with a little protrusion but an 1/8 to a 1/4 of an inch?

It's just frustrating and I was really looking forward to using this jig

[Dal300]

1/8 -3/16" is usually acceptable, although it's block plane time or time for a Japanese pull saw.

[mpc]

I don't know any details about the Leigh jig... but a common problem with dovetail jigs is the router bushing itself not being centered or not being tight to the router base or the router base itself not being tight to the router body. Ergo the bushing-to-cutting-edge distance is NOT consistent, fighting every attempt you make to adjust the jig.

For whatever guide bushing you are using do you have a "centering" router bit? It's basically a router shank that ends in a widening cone shape. For plunge routers you compress the plunge pretty much all the way and insert this bit into the collet, then slowly raise the plunge mechanism until the cone intersects the guide bushing. With the bushing lock nut loose, this should center the bushing. Tighten the locking nut/ring. Make sure your router base is tight too. For regular routers the process is the same - just start with the router height adjustment screwed down most of the way so the bit collet is close to the router's bottom plate.

Even with a well-centered bushing, it's still a good idea to try to keep the router position consistent on the jig - i.e. with the router sitting on the jig, keep the same point of the router facing you. (imagine grabbing the handles and turning the router 180 degrees so you're now looking at the other side - this is exactly what you do NOT want to do.)

I don't know what your "10" setting means; if your bushing is eccentric and you can adjust it then my centering idea is out the window. But you still want to make sure the router angular position never changes - keep the same side of the router facing you at all times.

Also, your workpieces have to be consistent on thickness. It's pointless to adjust the jig with a workpiece half an inch thick... and then make another test cut on a workpiece only 3/8ths of an inch thick. For practice and setup, consider making two scrap pieces a few inches wide (they don't have to be as wide as the pieces that'll eventually be the drawers, they just need to be wide enough for 3 or 4 or more dovetails to be made) that are exactly the same thickness as your workpieces. Use these to adjust the jig. If a trial set of dovetails sucks, run the trial workpieces through the table saw, slicing off an inch or so to cut off the bad dovetails. Keep shortening the trial workpieces this way until the jig is adjusted correctly, then bring in your real workpieces.

mpc

[ivwshane]

Yeah my bushing is concentric and I already made rhe mistake of using one thickness to test and then using the real peice that's a different thickness:| I found out all my hard work was for nothing (there goes half the day).

I try to keep the router level and always facing one direction too.

I guess dovetails really are a pain in the ass I'll keep at it, I refuse to do a butt joint.

[Black wallnut]

Dovetails are a challenge no matter the jig. There is also a learning curve so don't be too hard on yourself. I wish I could help you with that jig but I've not had the privilege of owning one yet. mpc gave great advice, it took me a bunch of test cuts with my PorterCable jig to get good results. I've not tried using a jig for full dovetails and I think they are easier to do by hand anyway. Keep at it though because I think the jig you have is the best out there. You'll get it, if you go through enough scrap.

[cwsmith]

I have no experience with the Leigh, other than to wish for one.

I just purchased a very inexpensive HF jig. The description of your challenge, at least as it applies to my jig, would be handled by adjusting the router fence forward, by the "overhang" distance that you describe.

On my jig, that "fence" is an angle-iron which is secured on top of the jig, just to the rear of the comb where it limits the deph of movement into the comb by the router. You move the fence back to lessen "shortness" and forward to decrease any extension.

I hope this helps,

CWS