Peening dovetails in wood

[Derek Cohen]

I was planing and scraping the outside of the military chest carcases, happy with the joinery so far, when it occurred to me to show the underside of the cabinet - the part that will not be seen - and in particular the dovetails there.

Obtaining a tight fit for dovetails is not a big test if the wood combination used is sympathetic. For example, one hard and one soft wood. The soft wood will compress inside the harder wood and create a gap-free join. Well .. most times. :o

Joining a carcase that is built of medium hard wood is similar. As long as the woods involved have a little elasticity, they will compress. However, when one uses hard wood against hardwood, particularly woods that do not compress, such as the Jarrah of these carcases, then you had better take care to saw accurately. There is minimal compression with such woods.

For this reason I am extra careful with carcases in Jarrah. I saw to the line, but if I err I would rather that the fit is oversize - then test for fit and pare away any excess wood.

The result here was as good as I could have wished ...

http://i13.photobucket.com/albums/a262/Derek50/Joints/Peening%20dovetails/Scraping4.jpg

http://i13.photobucket.com/albums/a262/Derek50/Joints/Peening%20dovetails/Scraping7.jpg

Now the underside of both cabinets was another matter altogether. The dovetail fit was not bad, but I did not aim for a perfect fit, just a good join. If I needed to pare away a tad more than usual to make the sides fit easily, well so be it. As a result there were gaps. No one would know.

We all know about filling gaps with thin wood wedges or slivers of wood. This can make gaps disappear.

There is another method - peening - and this is particularly easy if the tails are slightly raised above the pins (in other words, the end grain is raised above the face grain).

Here is the underside of one end. There is one tail that split away as I pared it, and I did not both with a repair at the time ..

http://i13.photobucket.com/albums/a262/Derek50/Joints/Peening%20dovetails/Peening1.jpg

Peening is the process of working the surface - in this case wood - and moving excess into gaps. To do this we need a hammer with a domed head - the traditional Japanese gennou is perfect (these have a domed end on on side and a flat end on the other side).

http://i13.photobucket.com/albums/a262/Derek50/Joints/Peening%20dovetails/Peening3.jpg

Step one is to squeeze a little glue into the gaps. I place a little on my fingertip and then push it in ..

http://i13.photobucket.com/albums/a262/Derek50/Joints/Peening%20dovetails/Peening2.jpg

To peen one does not hammer downwards. Instead you need to hammer at an oblique angle and similtaneously drag the hammer head across the surface, as if you were pulling the wood into the gap. Several controled gentle taps are better a single heavy-handed slam.

You should achieve something like this ...

http://i13.photobucket.com/albums/a262/Derek50/Joints/Peening%20dovetails/Peening4.jpg

Now clean up the dovetail with a plane and see the result ...

http://i13.photobucket.com/albums/a262/Derek50/Joints/Peening%20dovetails/Peening5.jpg

Not perfect but not bad.

Update: http://i13.photobucket.com/albums/a262/Derek50/Furniture/Military%20Chests/Update1-1.jpg

Regards from Perth

Derek

[Tony Shea]

Certainly a method I would not have thought I could get away with in wood. I recently just joined a jewelry box with dovetails in some Honduras Rosewood. I know all too well the struggle with getting a tight fit between wood that is as hard as rocks. I'm not even sure that the rosewood I'm working with would even have enough give to peen well, although I may be wrong. Since all the joinery on this box is show I erred on the safe side and had to pare my way down to the tight fit I was after. But having this peening as a backup will be helpful in the future. Thanks Derek once again.

I would die a happy man if I didn't have to dovetail Honduras Rosewood to itself again, turned out to be nightmarishly slow.

[David Nelson1]

Interesting trick. Thanks for the heads up.

[David Keller NC]

Derek - You've a typo in your post - I think you meant pins slightly proud of the tails, not the other way around.

[Chris Schwarz]

This is a great, but old, technique.

As I tell all my students: Joiners have been hiding gaps from rich people for generations.

This technique is mentioned in "The Joiner and Cabinet Maker" (1839). They call it: Hammering your dovetails.

Excellent technique. Take it too far and you'll get snake-bit.

[Chris Fournier]

Yes this is an old technique, likely as old as poor joinery (I am guilty of poor joinery too so please don't take this as condescension)!

Now metal and wood are two very different materials - crystaline vs. fibrous - and a peened metal dovetail is indeed a sound and strong joint. A peened wooden dovetail is however just as lame a joint as if it were left unpeened. Once you have glued and peened your sloppy wooden dovetail you have a sloppy mushy mess of disjointed and torn fibres kind of held together in a glue matrix. Of course the glue that you choose may improve matters somewhat.

Peening wood. An aesthetic solution? For sure. A good joint? A repair? Not at all.

[Don Dorn]

I've never tried it, but as much as I hate sanding, that is the approach I've taken because it essentially does the same thing. However, with this trick in mind, I'm going to try it. I purchased the Joiner and Cabinetmaker but not quite at the point of the school box yet so I assume the part Chris speaks of us upcoming.

[Chris Schwarz]

Dovetails are usually overkill anyway. So a peened (piened?) one wouldn't bother me one bit.

Chris

[Chris Fournier]

Dovetails are usually overkill anyway. So a peened (piened?) one wouldn't bother me one bit.

Chris

Please explain. I mean aside from the poor craftsmanship aspect, please explain. Poor craftsmanship should bother every craftsman.

[geoff wood]

sometimes in trim carpentry you gotta bash a tiny part of a miter, with a hammer, to close it.

[Sean Hughto]

I take him to mean that the joint is so strong that in a row of say five tails, if one is peened and therefore more cosmetic than joined, the overall joint is still plenty sound, and now looks pretty too.

[Rob Fisher]

Please explain. I mean aside from the poor craftsmanship aspect, please explain. Poor craftsmanship should bother every craftsman.I'm guessing, but I would bet that Chris is talking about the physical strength of the joint being overkill. The amount of gluing area as well as the one directional locking nature of the joint make it incredibly strong, even if it looks a little gap toothed. Peening the surface cannot change much of the structural integrity of that joint, IMO.The slightly gaped joints that Derek so graciously showed us are the bottom of the case. One could certainly argue that those joints should look as water tight as the top joints, but Derek has obviously decided to invest his time where it can be seen, leaving the bottom joints to be still functionally strong if a bit less aesthetically pleasing. Not unlike leaving plane tracks on the underside of a tabletop.

[Chris Schwarz]

Yup. I am a crappy craftsman. Sometimes I have small cosmetic gaps in my dovetails. I peen them to close them.

Does it bother me?

When I make the mistake, yes. When I fix it and it looks perfect, no.

[Chris Schwarz]

I can post photos of the dovetails I peened today if you would like to mock them.

[john brenton]

The OP isn't talking about a great trick to speed up dove tailing, but trying to hide one tiny gap on a project that he's devoted countless shop hours to. I can't speak as I generally play with soft to medium hard woods...I have some ziricote (I think) fretboards that I couldn't even imagine dovetailing. I'd be peining the bujeezus out of that thing...heck, I'd probably have to kerf the pins for a double wedge to hide all the gaps I'd have.

[Chris Fournier]

There's no point posting images of imperfect joinery to elicit mockery, the poor joinery is itself a mute but effective mockery of the failing skills of the craftsman. This is why I keep all of my dovetailed drawers closed.

I am no stranger to putting my best work in full view and the also rans to the back and bottom. It goes without saying that I start on the joints that won't be seen as a warm up for the ones that count. Ironically I tend to do a good job on the hidden joints, and in a fit of hubris I botch the visable ones.

Smashing wood to effect a fit makes me feel dirty nonetheless - even when doing trim carpentry. I take the hgh road using wax sticks, caulking and lumpy paint.

[Ed Looney]

I for one don't think that Derek was showing poor craftsmanship. I admire the quality of his work and it is refreshing for a craftsman to show the real and prevalent human factor that we all deal with. All of us would love to do goof proof work but in reality we all must learn the methods necessary to fix our goofs. Thanks for the tip Derek I will add that method to shimming or wedging those errant gaps.

Ed Looney

[Zahid Naqvi]

Interesting idea Derek, I could have used this "trick" a few years ago. If the likes of Chris and Derek can live with it I don't see why I would loose sleep over it.

[Derek Cohen]

This is a great, but old, technique.

As I tell all my students: Joiners have been hiding gaps from rich people for generations.

This technique is mentioned in "The Joiner and Cabinet Maker" (1839). They call it: Hammering your dovetails.

Excellent technique. Take it too far and you'll get snake-bit.

Hi Chris

Now I would have known about this being in "The Joiner and Cabinet Maker" ...however your company does not sell internationally. Rats .. when will you reconsider sending lonely books to a welcome party (me) in Western Australia? :)

Another name for peening is bishoping. I tried to add that in later, but the Edit facility wouldn't oblige (must have thought the article perfect as it was .. unlike the dovetails underside of that cabinet!).

Regards from Perth

Derek

[Derek Cohen]

Yes this is an old technique, likely as old as poor joinery (I am guilty of poor joinery too so please don't take this as condescension)!

Now metal and wood are two very different materials - crystaline vs. fibrous - and a peened metal dovetail is indeed a sound and strong joint. A peened wooden dovetail is however just as lame a joint as if it were left unpeened. Once you have glued and peened your sloppy wooden dovetail you have a sloppy mushy mess of disjointed and torn fibres kind of held together in a glue matrix. Of course the glue that you choose may improve matters somewhat.

Peening wood. An aesthetic solution? For sure. A good joint? A repair? Not at all.

Hi Chris

Please note that this method is not intended to strengthen joinery, but to effect an aesthetic improvement only. If it was a single dovetail that was "fixed", peening would not add to the strength more than about 5% because the gap-closing is at the top and not all the way through the joint. If you want to strengthen a poor joint, then you must saw out the kerf and add a veneer of wood to fill the gap along its length (much as you would do to a loosely fitting tenon). Peening is simply to "make nice", and it bothers me not a whit to do this to the dovetails I show off. We are not talking about peening large gaps, but hairlines. The fact is, later (once the ends are planed down) I cannot tell which dovetails were peened and which were not.


Regards from Perth


Derek (with 12 drawers now to make)

[Chris Schwarz]

Derek,

Last I heard, Lie-Nielsen Australia had taken some copies of our books to sell. If not, the best, fastest and cheapest way is to get our books from Lee Valley, Tools for Working Wood or Lie-Nielsen. They are set up to handle international orders. It's very expensive an unreliable for us to do it (which is why we have the retailers do it).

[Chris Fournier]

Hi Chris

Please note that this method is not intended to strengthen joinery, but to effect an aesthetic improvement only. If it was a single dovetail that was "fixed", peening would not add to the strength more than about 5% because the gap-closing is at the top and not all the way through the joint. If you want to strengthen a poor joint, then you must saw out the kerf and add a veneer of wood to fill the gap along its length (much as you would do to a loosely fitting tenon). Peening is simply to "make nice", and it bothers me not a whit to do this to the dovetails I show off. We are not talking about peening large gaps, but hairlines. The fact is, later (once the ends are planed down) I cannot tell which dovetails were peened and which were not.


Regards from Perth


Derek (with 12 drawers now to make)

There's no doubt that this technique (as long as you have a proud enough pin that is) is tougher to detect than the good 'ol kerf and shim fix. Thankfully an oil based finish or first coat anyways tends to darken the endgrain and obscure any jiggery and pokery that has gone on in the name of aesthetics. Dovetailing in two unyielding hardwoods is a tough gig for sure - a cabinet carcass even more so.