Advice on a joint please...

[Steve]

Hi All,

I'm new here, and new to woodworking in general. My first real project is under way and I'll have a few questions as I go, so here's the first...

My project is a music stand for myself. Store bought ones just don't do it for me and I love natural wood anyway. For an idea of the kind of thing I'm making, I found an awesome website with quality that I won't even try to accomplish this first time out:

first question I have is how to join the bottom "music rest" portion to the back piece? The strongest joint that I can come up with is a sliding dovetail with the slot in the back piece and the tail making up the shelf, but I'm worried about how large of a bit to use. The wood itself is 3/4" thick (both pieces), so is the dovetail going to simply snap off when I put a heavy music book on it?

I guess the second question would be fitting it together with glue in the joint without it binding or cracking. I figure epoxy will give me the time to slide everything together (27" long), but I'm looking for any advice as I only want to do it once :)

If my description isn't clear, I'll post a quick rendering of what I have in mind.

TIA Steve

[pat]

Some tips on that operation at this link:

***************************** itself is 3/4" thick (both pieces), so is the dovetail going to simply

[Steve]

Here's a quick pic if it makes things clear(er).

[J T]

Wed, Aug 8, 2007, 9:46pm (EDT+4) [e-mail] (Steve) comes in, waves, and say, Hi All, I love natural wood so is the dovetail going to simply snap off when I put a heavy music book on it? I guess the second question would be fitting it together with glue in the joint without it binding or cracking. I figure epoxy will give me the time to slide everything together (27" long), but I'm looking for any advice as I only want to do it once :)

Yeah, unnatural wood gives me the creeps.

How 'heavy' do you consider a 'heavy' music book? Me, I'd glue 2-3 braces under if I was worried about it holding. But that's me. If you're worried, make a prototype, with cheap wood, and check how it does before you do it for real.

Just how long do you think it takes for glue to set anyway? I'd use Titebond II, I use it for about everything.

JOAT I do things I don't know how to do, so that I might learn how to do them. - Picasso

[tdup2]

A sliding dovetail is very strong. With the glue you apply it will do the trick. Regular Tite Bond is perfect, no need for expoxy.

Tim

[JeffB]

A sliding dovetail can indeed be a very strong joint.

Considerations - if the direction of the grain in both pieces is the same - like almost all the stands in the website you referenced - then a simple butt joint, long grain to long grain, will be stronger than the wood itself. This will easily hold up any music book you have. It takes hundreds or thousands of pounds of force to crack a well made glue joint.

You have to be careful that the dovetail socket is not too close to the edge of the board. Also, 27" is a fairly long joint, and making sliding dovetails is not terribly forgiving. How were you going to accomplish this? Router table? Special jig?

A well-fitted sliding dovetail has lots of inherent mechanical strength, glue is only necessary to keep the joint from sliding apart. You can slide the joint mostly together dry, and only need to put glue on the last couple inches.

-- JeffB remove no.spam. to email

Steve wrote:

[Leuf]

need to do anything other than butt the pieces together. A long grain to long grain glue joint is stronger than the wood itself.

-Leuf

[FoggyTown]

And if you really are nervous about the butt joint strength, several dowel pins (or screws covered by plugs) from the rear will reassure you. Although really unnecessary as others have allready attested.

FoggyTown

[George]

You're over-engineering, that's for sure. I'd use a simple rabbet/dado for extra glue surface and realize that the loading on the book ledge, trying to rotate the ledge into the bottom of the backing. Can't when the wood butts against it, as long as the glue's intact. The unrabbeted part of the ledge, fitted in the dado of the backing, should be at least 1/4" to provide shear resistance, that's all.

If you're using plywood the mechanical joint makes a bit more sense, but adds a degree of difficulty in cutting the joint without chipping the veneer. Score in advance.

If you get the show, try watching a few episodes of The Router Workshop. Stuff here at

that they use all the time. The joint's not difficult on a table, just remember to leave the bit height the same to cut both pieces, and sneak up on the thickness of the dovetail, ending up with what most would call a loose fit. The thing'll split for sure if you have to whack the glue-expanded piece into a glue-expanded opening.

If you're using plywood

[Father Haskell]

before you get the joint driven all the way home. Music equipment gets babied, so you won't need the extra strength or water resistance of exterior grade yellow glues. Sliding dovetails are tremendously strong anyway, by virtue of glue area.

Extending the back panel maybe 3/4" below the ledge will add strength against the back panel breaking at the joint. You've considered that, seeing how you've placed the dovetail high.

Do you need full 3/4" lumber? 1/2" or 5/8" might be sufficient, and will weigh less.

[Toller]

You are making way too much out of this. A plain butt joint with yellow glue is all you need. A sliding dovetail would be weaker. I would throw in some biscuits and a few screws wouldn't hurt, but neither are necessary.

[Phisherman]

I'd make a triangular (or pie-shaped) piece, 3/4" thick, with a hole in it. Dado the back (1/4" is fine) piece so that one side of the triangular piece fits. A little more complicated if you want adjustable tilt. A sliding dovetail is good too--the unglued sliding dovetail can be fragile but after the glue fully cures (overnight) it becomes very strong.

Fuss with the dry fit, snug but not tight. I'd use woodworker's glue and a small flux brush. Put glue on the deepest 10" of mortise and the last 10" of the tenon. You have 5-10 minutes of open time with the yellow woodworker's glue.

[Father Haskell]

Cured yellow glue is unbreakable in shear. Just glue the last 2" of each piece. Use a pipe clamp to drive the joint home instead of a hammer, and don't stop moving -- if the joint's cut tight, which it'll likely be for appearance, it'll lock up hard if you pause for even a second.

[Steve]

Wow,

I was away for about a week, right after my posting, just now reading the replies.

Thanks to everyone for replying, I'll read your notes, and sure to be asking a few more questions shortly.

Steve

[Steve]

Hi Leuf,

Ok, good to know. I've always enjoyed the look of a dovetail joint so in addition to the added strength, it had a bit of a "cool" factor too.

Thanks Steve

[Steve]

Hi Father Haskell,

I found this (to me) nice looking coffee table that I'll be using as my "source" lumber at a local pawn shop. It's 3/4" and made up of a lamination of a think centre piece of something (maple perhaps), and two thinner pieces of a rich darker wood that was exactly what I was looking for when I first designed it.

I'll be posting finishing suggestions soon, I'll upload a pic of the wood to see if anyone can identify it whilst helping me decide on a finish.

Steve

[Steve]

Hi,

Well, I typically have a 4" binder full of paper that I need to leaf through whilst playing, and there's often a hymnal that I have to throw on top if the music leader chooses something from there instead.

Good idea. I think I have some cheap 3/4" wood lying around, it will help me set up the router table for the passes as well.

Dunno, hence the request, thanks for the input. Steve

[Steve]

Hi Tim,

Thanks for the note. Steve

[Steve]

Hi Jeff,

Glad to hear it.

I guess part of my considerations is when kids play around the platform, they may knock it flying and it's the sudden G-force that would get applied to the corners might cause a span :(

Was planning on using a router table, as per one fo the websites mentioned by another poster.

Ah, good point, hadn't thought if that possibility. Steve

[Steve]

Hi George,

That was the plan :) As posted above, it's more to help with any "accidental" droppings this thing might take from the 3' box it'll be resting on.

I guess it'd be considered a plywood, but with only three "parts". The centre is a maple or maybe even nice pine, but the visible faces are a nice (but thin) dark wood veneer that has the color and grain I was looking for.

I'll take a pic tonight and post so that folks can see the wood I'll actually be working with.

Thanks for the input. Steve