I'm building a bookcase with four fixed shelves (plus the top). It
will be a total of 50" high and 30" wide.

The shelves will be sliding "half-dovetails." I've _tried_ to
illustrate below what I mean, but basically think of a dovetail with
only one angle cut in. I got the idea out of a design plan I bought,
but the plan was more of a Craftsman-style bookcase with slatted sides,
and I want solid sides.

The bookcase is being built out of flatsawn cherry (YOU try finding
rift/quarter-sawn!), and the sides will be a total of 12" wide.

So here are my two questions:

1. Because the wood is flatsawn, the grain patterns are harder to
match-up, so I would like to glue-up two 6" boards, rather than three
4" boards. I am doing this for the sides and the shelves. Because
this is flatsawn, am I setting myself up for problems with cupping/etc?


2. The reason I'm doing the half-dovetails, instead of simply dadoes,
is that I want the sides of the bookcase to be held together by the
shelves themselves. I am NOT gluing the dovetails, but rather pinning
them in the front to allow them to expand freely toward the back of the
case. However, am I running the risk that, because I'm using flatsawn
boards, that this whole thing is literally going to pull itself apart
over time?

Thanks for any help you guys can give...illustration is below.


| |
| | Shelf
| _|_________
| |
| |/|_________
| |
| |

You should be fine. Cherry is pretty stable. You identified and fixed
the one big problem by pinning the dove tail, even though it is
actually not an opposed grain situiation so the side and shelf should
expand together.

One help for cuppng is to try and get boards that have the grain lines
running as close to perpendicular to the face as possible, ie close to
quarter sawn. Also, glue up the boards and let them settle for a few
days. If any of them cup, just rip them down and re-glue.

Another somewhat radical idea, but it could be a nice effect, would be
to bread board all of the pieces, sides and shelves. One advantage of
this would be on the shelves you would be cutting your modified
dovetail groove with the grain as opposed to cross grain. However, I
would use and extra deep tennon to ensure you get good structural
conformance from the shelf.

Sounds like a cool project.

BW

wrote:

2. The reason I'm doing the half-dovetails, instead of simply dadoes,
is that I want the sides of the bookcase to be held together by the
shelves themselves.

Why not use full sliding dovetails? Easier and double the grab
______________

I am NOT gluing the dovetails, but rather pinning
them in the front to allow them to expand freely toward the back of
the case. However, am I running the risk that, because I'm using
flatsawn boards, that this whole thing is literally going to pull
itself apart over time?

It will be fine. Would be too if you glued them (I would) as any
expansion in the shelves and ends is in the same direction. For that
matter, you could dump the dovetails - half or full - and just glue
shelf tenons into side dados...assuming the dados/tenons are a decent
fit the sides aren't going to pull out.

--
dadiOH
____________________________

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wrote:


1. Because the wood is flatsawn, the grain patterns are harder to
match-up, so I would like to glue-up two 6" boards, rather than three
4" boards. I am doing this for the sides and the shelves. Because
this is flatsawn, am I setting myself up for problems with cupping/etc?
I think you may be reducing your problems with that, if you glue one
board bark-side up and the other bark-side down. Result of any cupping
will then be a wave in the board rather than a deep cup or hump.


2. The reason I'm doing the half-dovetails, instead of simply dadoes,
is that I want the sides of the bookcase to be held together by the
shelves themselves. I am NOT gluing the dovetails, but rather pinning
them in the front to allow them to expand freely toward the back of the
case.

Why? isn't the grain on the sides vertical, and on the shelves along
the length of the shelf? If so, the sides and shelves should have the
same front-to-back expansion, so no reason not to clue the sliding
DTs.
--
Alex -- Replace "nospam" with "mail" to reply by email. Checked infrequently.

On 3 Oct 2005 08:01:56 -0700, wrote:

I'm building a bookcase with four fixed shelves (plus the top). It
will be a total of 50" high and 30" wide.

The shelves will be sliding "half-dovetails." I've _tried_ to
illustrate below what I mean, but basically think of a dovetail with
only one angle cut in. I got the idea out of a design plan I bought,
but the plan was more of a Craftsman-style bookcase with slatted sides,
and I want solid sides.

The bookcase is being built out of flatsawn cherry (YOU try finding
rift/quarter-sawn!), and the sides will be a total of 12" wide.

So here are my two questions:

1. Because the wood is flatsawn, the grain patterns are harder to
match-up, so I would like to glue-up two 6" boards, rather than three
4" boards. I am doing this for the sides and the shelves. Because
this is flatsawn, am I setting myself up for problems with cupping/etc?


2. The reason I'm doing the half-dovetails, instead of simply dadoes,
is that I want the sides of the bookcase to be held together by the
shelves themselves. I am NOT gluing the dovetails, but rather pinning
them in the front to allow them to expand freely toward the back of the
case. However, am I running the risk that, because I'm using flatsawn
boards, that this whole thing is literally going to pull itself apart
over time?

Thanks for any help you guys can give...illustration is below.


| |
| | Shelf
| _|_________
| |
| |/|_________
| |
| |

There should be problem with your plan. Traditionally, these would be
dadoed and glued without any problem of expanding/contracting as there
is NO cross-grain at these joints! It may be helpful to study grain
directions so that you know exactly where to be concerned.

wrote:
I'm building a bookcase with four fixed shelves (plus the top). It
will be a total of 50" high and 30" wide.

Go play with the Sagulator (google) before building any bookshelves
more than 2' wide.

The shelves will be sliding "half-dovetails."

Even simple dados would be adequate. If you're routing these dovetails,
then a full dovetail is probably easier to cut. Don't be afraid of
getting an accurate fitting joint here - it's one of the easier parts
to get right.

The bookcase is being built out of flatsawn cherry (YOU try finding
rift/quarter-sawn!),

Actually I have no trouble (although cherry is itself scarce in the
UK). It's a high-end timber, so it's one of the few where there is an
obvious trade in quarter-sawn.

and the sides will be a total of 12" wide.

Now this starts to worry me. I think your shelf plan is sound, but a
big slab side like this might need some care in design and
construction.

1. Because the wood is flatsawn, the grain patterns are harder to
match-up,

Actually figure, rather than grain. Grain's the little stuff, figure's
the big "cathedral" patterns you see on a flat sawn board.

so I would like to glue-up two 6" boards, rather than three
4" boards.

For the shelves, then stop worrying. Assemble 4" boards because they're
easier. On a loaded bookshelf you'll never see the difference. 6"
boards sound quite reasonable for the sides though.

am I setting myself up for problems with cupping/etc?

Depends more on the quality of your timber than on the size difference
to 6". Personally I'd already have had this board in stack for a year
or two before I got round to using it. I'd certainly store it at
ambinet use humidity for a few months before planing it (you do have
some $5 air hygrometers, don't you?)

I am NOT gluing the dovetails,

Up to you. It's no problem to glue them because it's not a
cross-grained joint. Personally I wouldn't even pin them - friction is
plenty adequate. Just pinning at the front would be the right thing to
do though, if you did pin them.

Any relative movement in the timber is going to be cupping, not
shrinkage (if these boards are all the same timber from the same
batch). I'd worry about cupping in the sides, but not the shelves.

Personally I'd be concerned about the sides in this design. I'd want
something to support the sides against cupping, particulary if they're
6" wide and relatively thin. This could be framing top and bottom,
full-blown frame and panel, or a sliding dovetailed batten on the
inside. Most of all though I'd just want those sides to be well-dried
before I planed them, and not too thin.

wrote:


Personally I'd be concerned about the sides in this design. I'd want
something to support the sides against cupping, particulary if they're
6" wide and relatively thin. This could be framing top and bottom,
full-blown frame and panel, or a sliding dovetailed batten on the
inside.

wouldn't his sliding dovetail shelves serve this purpose?
--
Alex -- Replace "nospam" with "mail" to reply by email. Checked infrequently.