Dovetail help

[Phil Mueller]

I'm slowing climbing up the learning curve on dovetails. The one thing that's driving me nuts at the moment is trying to figure out exactly what's not fitting right when I go to put the two boards together.

Sometimes it's obvious to see "shiney" wood where it's too tight. But I'm working on one now that just won't seat to the baseline and I can't figure out why.

I'd show pictures, but who knows what angles to show and you all would likely really need to wiggle it yourself. Anyway, is there some trick to finding the problem (coat all surfaces with pencil, chalk, lipstick!)...?

Any advice appreciated.

[Robert Hazelwood]

I think the most likely culprit for that is a bump somewhere on the baseline surface. Check with a straightedge or square between the tails-at any location it should touch at the baseline on either side without rocking. If it rocks or if you can see any sort of gap at either edge, there's a bump you'll need to pare down with a chisel.

[Brian Holcombe]

Phil, if the baseline is clean, check the inside corners usually something can linger there. If they're clean check your pins to see if they're compressing at their tips.

If it contacts in one edge of the baseline (inside but not outside or vice versa) then you are out of square....either assembly or baseline. If your baseline is square but the tail board won't assemble square then check your tailboard for a square baseline.

If that doesn't fix the problems post photos. Don't open up anything with a chisel unless you know it for certain to the be culprit.

[Andrew Hughes]

Also could be the end of pin board was not square to the face.And when you run the marking gauge the chopping line is off.Same goes for the tail board.
Or the inside face isn't flat.
If your corners are clean then maybe check for square.

[Luke Dupont]

I have not done a whole lot of dovetails yet, so take my advise with a grain of salt, but, on the topic of establishing a good baseline:

Use a knifewall and stepdowns to give your chisel a place to rest and ensure perfect accuracy. Undercut ever so slightly when you remove the waste with a chisel. I prefer to chop the waste out completely with a chisel so that there is enough resistance on the bevel side of the chisel to keep it flush against the wall you're chopping; if you remove too much waste with a coping saw, I find it easier for the chisel to work itself out from the baseline and create a bulge in the middle. At the same time, also be careful of moving your knifewall with your chisel by driving too hard/too deep before you've made space for the bevel -- especially at the start. If you deliver heavy blows right on the baseline from the very start, you'll move (compress) the knifewall inwards, because the bevel will want to drive the chisel in that direction. Once you gently establish some depth, though, you needn't worry about this, as the wall will have a large enough surface to offer adequate resistance.

I have found that most of my problems when joints don't fit well have been from slight bulges in the cutaways. So, I've gone to chopping out more of my waste and undercutting slightly with much better results. So, if you haven't already, try chopping as opposed to cutting away and paring. You may find it easier to get a good fit.

I don't pre-drill my mortise holes for the very same reason. That resistance on the bevel side helps guide my chisel flush against the wall I'm creating. I find it much harder to establish the walls accurately by paring. It's just hard to be that accurate when paring endgrain -- at least for me!

This may or may not be your problem, but it's something to consider/try!

[Phil Mueller]

Thanks all for the quick input! i walked away from this on Friday and plan to have some time this evening for round two of this.

Yes, Brian, that's what I'm trying to avoid...paring something that isn't the problem and ending up with another problem. I'll take a look at everything suggested and see where I come out. There's five more dovetailed joints on this project...stay tuned. In the end it may be ugly...but it will be my ugly :eek:

[Phil Mueller]

Thanks all again. You do know your dovetails. It was, indeed, a hump at the baseline. I found another purpose for my titemark marking guage...I found if I set it on the ends of the tails/pins and moved it around, the "wheel" would let me know where the humps were.
The dovetails aren't pretty, but they do seat....another few hundred and I might have it!
Phil

[Simon MacGowen]

Thanks all again. You do know your dovetails. It was, indeed, a hump at the baseline. I found another purpose for my titemark marking guage...I found if I set it on the ends of the tails/pins and moved it around, the "wheel" would let me know where the humps were.
The dovetails aren't pretty, but they do seat....another few hundred and I might have it!
Phil

The gauge will only work for large/wide sockets; the proper tool to use is a simple square. The reasons why a fit could go wrong for dovetails are too many to list and diagnose without seeing the piece or a photo. Imagine reading a woodworking article on a furniture project without any pictures . . . that's how hard to understand what you might encounter.

Simom