Tapered sliding dovetails

[Wood Basher]

On my current project I will need to do some tapered sliding dovetails, and I will do this with hand tools only. Not having cut this type of joint before I decided to test on some scrap. On my first attempt I cut the male part "freehand" and it came out so poorly that I just threw it on the wood burner without even trying to cut a matching female part.

I decided I needed to create a saw guide so I made one by planing a 6:1 gradient on one edge of a piece of 2x4. I then cut my second attempt on some scrap, without making any effort to clean & square it up first. Here is how it turned out:

First the thin end of the taper. Not perfect, but better than I expected.

Now the thick end of the taper. Not so good.

Finally, a view from the side. This shows that the joint is not seating as well as it should. I guess I could make it seat better by clearing out the floor of the housing better, but then wouldn't the male part slide though further than I want?

So what can I learn from this, and what tips can anyone give to help me improve? OK, One thing I can learn is that the camera on my phone is crap, but other than that ...

As a general rule, is it better to have a gradual or pronounced taper? I think in my test the taper is too pronounced. I think a very slight taper would work just as well and be less error-prone.

I cut this joint with a saw, only using a chisel for clearing out the waste from the female part. Is this a good approach or should I use a chisel more?

Are there any techniques to scale this up to wider stock (longer sliding dovetails)? In my real project I am working with panels 300 - 400mm wide.

For my next test I will prepare the wood to be smooth, square and true rather than using something off the scrap pile with no preparation. Maybe this in itself will improve the result.

[Brendon_t]

Starting with square sure won't hurt. If you're not square, especially on your end cut your reference and cut lines will be difficult to get right.

Hollowing out the bottom would help it seat better and adding a very thin shim glued to each face will snug it back up.

[Tony Wilkins]

Have you watched the Woodwright Shop episode where he makes a modular book case (3-4 years ago I think).  It’s mostly about cutting a sliding dovetail.

 

Season 30 ep. 8 here: http://www.pbs.org/video/the-woodwrights-shop-the-case-for-books/

[wtnhighlander]

Obtaining a router plane, or even making the Paul Sellers "poor man's" version, will vastly improve your ability to make a clean, flat bottom in the housing groove.

[Barron]

Check the Renaissance Woodworker, Shannon may have covered this. 

[Immortan D]

There's a detailed article about this in Popular Woodworking Magazine: https://www.popularwoodworking.com/techniques/tapered-sliding-dovetails-3

[derekcohen]

It is more convenient to just make the dovetail on one side. Both sides is unnecessary. Here is an example - creating drawer blades in a chest of drawers ...

Creating the sliding dovetail can be done with a saw and chisel, or a saw and plane. Here is an exerpt from an article on my website:

 

Above – the 6mm wide line for the dovetail.

 

 

A rebate 6mm x 12mm is sawn.

 

 

A while back I began thinking of a simpler plane that could do both male and female joints. In part this was inspired by Terry Gordon converting one of his side rebate planes to cut sliding dovetails.

The weapon of choice for me was the Stanley #79, a double-ended side rebate plane. I liked this as it has a long depth stop and body, both which would provide more registration area than a singe-ended rebate plane.

The only modification needed was to add a wedge under the depth stop to alter the cutting angle from 90 degrees to (my preference) 1:7 – this is the same as the other planes I built, and works well with the hardwoods I use.

 

 

 

 

Set the lower edge depth stop flush against the edge of the board. This tilts the plane at the correct angle. Set the blade for a fine shaving. This is a low cutting angle and will pare away the wood quite quickly. The tip of the blade is left pointed and extends slightly below the body. This works in the same way as the blade of a rebate plane extended a fraction beyond the body to ensure that the corner is removed.

Note that this plane does not stop cutting when it reaches the desired depth (as the original dovetail plane does). An alternate method is described below.

 

 

First step is to scribble a contrasting colour on the surface to be removed. This makes it easier to see where- or where not the cut has been made.

Above: the yellow shows that there is a smidgeon at the edge left to be removed.

 Here is another example - Joining the end rail in this sofa table ...

 

 

 

 

All of the sockets were marked, sawn and chiselled.

 

The dovetails were planed with a modified Stanley #79 side rabbet plane. The modification involved an angled fence. The is an article here …

 

 

 

 

Hope this helps

Regards from Perth

Derek

 

 

 

 

 

[Wood Basher]

Thanks for the tips guys. Some useful information there. Derek, that must be the most thorough answer to any forum post, ever.

I have made a couple more test pieces. One was a disaster due to a stupid layout error, but the other was a big improvement. I am learning and I am close to trying it for real. Before that though my next task is to try a test on a wide board.

Derek, your point about only needing a one-sided dovetail will require less work to cut the joint. Also I suspect it will be easier to ensure the joint ends up square. I will do that on my real work, but for my tests I am sticking to double-sided dovetails to become more familiar with cutting them.

[derekcohen]

No problem, WB. Most of it was simply a cut-and-paste from my website. I have written so many articles on these topics.

This chest of drawers was largely entirely made with sliding dovetails ...

 

Regards from Perth

Derek