Novice question re: mortising box walls for dividers

Hi all,
I'm a novice (though not a newbie), and I'm struggling to find a solution to what ought to be a pretty simple problem. Here's the deal:
I'm creating a box that will have multiple dividers in it. Rather than gluing the dividers to the bottom and sides of the box, I'd prefer that they be slightly mortised into the sides of the box. Not a lot, maybe an eighth-inch in to each wall (the walls will be about 7/16" thick). This way the dividers aren't going anywhere at all, and to my mind this is better than butting the dividers up against the wall and hoping there's enough glue surface to hold 'em. Ideally I'd like the dividers to be 5/16" thick. 1/4" would be okay too but 5/16" seems about right for the proportions.
Now, the dividers aren't as tall as the box walls. So the mortise has to go -partly- up the side of each box wall - we're not talking about a simple dado. The rub is, I can't figure out a good (read: relatively painless) way to accurately put the mortises in. The two basic requirements are that they all have to be the same height, and from one wall to the opposite wall the mortises have to be a perfect mirror image, otherwise the dividers won't line up. I've done this once successfully using a router table, 5/16" straight bit and very, very, very careful measuring, marking, remeasuring, copious use of stop blocks, pausing to pray, etc. But this took me several hours (!) to install two shallow mortises - enough for one single divider. This can't be the most efficient solution.
I already have the problem of rounded mortise edges solved - simply using a roundover bit on both sides of the dividers themselves makes the profile a good fit for the rounded end of the mortise. No problem there.
But - for my current project I need a lot of dividers, so I'm trying to figure out how this can be done efficiently. I'm sure there's a slap-your-forhead-simple way, but I haven't come across it yet. Here's what I -have- thought of:
Route by hand using a straight edge as a guide. This is okay as far as it goes, but my router is pretty bulky (DeWalt 621) and not terribly easy to use this way. Plus, you'd have to change your setup for each mortise, so I'm not sure it would be all that much faster than the method I described above. It also introduces a lot of potential for each mortise being ever so slightly off. That's enough to convince me it's not a good approach.
Now, a template should be a good way to go, since it's repeatable and if it were routed all the way through it could be flipped over to create the reverse image - thereby making an instant setup for the opposite wall. But:
Template on a router table. This seemed at first to be a viable approach, but then I realized that it would be impossible to route a shallow mortise from below, using a guide. If I were routing all the way through the piece, this would work. But it's physically impossible to route a shallow mortise this way.
Template on a bench, router on top. Okay, this makes sense at first too. But this would require a templating bit 5/16" in diameter, and so far as I can tell there's no such thing (templating bit meaning the guide bearing is at the shank end). Half inch, no problem. Bigger than half inch, no problem. Less than half inch, forget it (from what I can find, anyway).
Now then, all of this has lead me to conclude that using some sort of bushing setup on the router is the only way to do this. Fine, I can go get some bushings (assuming anyone makes some that can adapt to the 621...?) and I imagine this would work, using the through template idea mentioned above.
But before I go do that, is there some flaw in my thinking? Where's the slap-my-forehead-simple solution? I can't be the only person who wants to make boxes with accurate mortised dividers....
PQ
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Pet Quality wrote:

I would think the easiest way would be to slide a bearing off a 1/4" bit onto the 5/16 bit and use a template.
How tall are the boxes? If they are tall enough make the sides out of thin strips glued together and leave the last strip off of the top until the slots are cut then glue it on.
If the dividers come close to the top made the sides the same height and then glue a different piece on top or cover the top with some sort of trim to hide the slots cut all the way up.
Make the dividers the whole height and then cut them lower in the center, sort of a wide U shape or a nice ( on its side shape for the top of the dividers.
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Pet Quality wrote:
<snip>

<snip more>
PQ...
Leon's dado jig would seem to fill the bill for this job - just add a stop so that you produce a stopped dado instead of a full width dado.
I grabbed his photos from ABPW, added a CAD drawing, and put the works on a web page at http://www.iedu.com/DeSoto/dado.html - the jig consists of four slotted boards and a pair of bolt/washer/nut sets. Check it out...
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DeSoto, Iowa USA
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Thanks - this is a very handy resource. But here's the thing - this does solve the problem of how to make a single, straight stopped dado. What it doesn't address (as far as I can see) is the issue of creating a set of dados on one wall, then another set mirror-imaged for the opposite wall. So using this jig you could definitely save time and get the height of the dado perfect for each one, but it wouldn't help get the placement right from one side of the wall to the other.
... or am I missing something?
PQ
p.s. - the walls of this particular box are about 6" in height. That previous suggestion about adding a strip to the top of the wall is very clever - I definitely wouldn't have thought of that!
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Pet Quality wrote:

I don't think you are. You could add an arm that'll allow stops for positioning the jig appropriately. Build the arm so that it works equally well right/left-handed so that the mirror-image solution is built right in...
Or you could extend one of the bottom boards and use a sharpie to mark where the end of the board to be dado'd should be for each of the cuts...
Your template idea is perhaps the best. I'd suggest using a guide bushing instead of a bit with a bearing. Without looking, I'd guess that 1/4" bits without bearings are less expensive. This would allow positioning the template once and making all cuts exactly where you want them.
<gloat> I cheat. I'd write a Q&D part program and batch cut 'em on a CNC router - probably take less than 30 sec/drawer. </gloat>
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Morris Dovey
DeSoto, Iowa USA
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Yes, this is the direction I'm leaning. Now, does anyone know if there even -is- a guide bushing setup for a DW621? I haven't found anything so far, but I've ony checked a few sources.

Yes but with that method there's no cursing involved - and where's the fun in that? :-)
PQ
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On 6 May 2004 16:30:07 -0700, snipped-for-privacy@yahoo.com (Pet Quality) wrote:

Yes - the PC bushings work with the included adaptor plate.
Alan Bierbaum
web site: http://www.calanb.com
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Pet Quality wrote:

I have an ongoing monologue with the Planetary Architect concerning the decision to create Iowa as prairie/cornpatch rather than hardwood forest. I seem unable to present adequately persuasive arguments for changing the current arrangement...
Perhaps the intent is that I develop a greater appreciation for the hardwoods that grow so abundantly elsewhere. If so, it's working. (-:
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Morris Dovey
DeSoto, Iowa USA
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Stopped housing joints (dadoes) are what you want. If the divisions are "pigeon-holes", then use a cross - halving joint at the intersections.
Cheers
Frank

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Pet Quality wrote:

Rather than "mortised", I think you mean for the dividers to sit in "stopped dadoes" on the sides of the box and "through dadoes" on the bottom of the box

I'm going to make the assumption that the bottom of the box will sit in a rabbet/rebate in the bottom of the sides of the box. That means that the bottom of the box is narrower than the front and back of the box and shorter than the left and right side of the box. The differences in the bottoms dimensions being because of the difference between the thickness of the sides and the width of the rabbets/rebates in their bottoms (whew!) So You can't line up one end of the bottom with one end of the sides of the box and cut the dadoes in the sides AND the bottom with the same router table fence setting UNLESS you start with the bottom exactly the length of the front and back of the box and exactly the width of the left and right sides. After routing all the dadoes and stopped dadoes you could then symetrically trim the dadoed bottom to fit using a hand plane.
The other approach is to use a guide for routing the stopped dadoes and through dadoes together at the same time. Here's a not so good ASCII illustration. Note that the ends of the Bottom are aligned with the ends of the stopped rabbets/rebates in the bottom of the SIDES and NOT with one end of the SIDES
Also note the scrap on both ends of the boards to be dadoed. The DW621 has a fairly small base and can get tippy on the ends of the cut. The scraps just give the base some support at the beginning and end of the cut.
+--------------------------+ | scrap | +-------------------------- + | ++ ++ | Back of Box | | | | | | |(1) | | | | (2) | note stopped | +------++---------- ++---+ | <-- rabbetrebate in ++====== ++==========+++==++ bottom of SIDE | | | | | | | | | | | | Bottom of Box | | | | | | | | | | | | ++======++===========++== ++ | +------++---------- ++-- + | | | | | | | | | | | | | | ++ ++ | Front of Box +--------------------------+ | scrap | +--------------------------+
Hope this helps some
charlie b
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Thank you for the correction. I had a feeling I was tossing around the wrong terminology...
I actually wasn't planning seating the dividers in dadoes on the bottom - only on the side. But admittedly, that does make sense. I might have to use a thicker bottom than I had in mind though.

Hm, if I understand you correctly, then no - that's not what I had in mind. The bottom will sit in a separate dado that runs the entire inside of the box. Like a typically drawer assembly. -That- dado is easy, thankfully.

This is interesting... if I understand it, it's conceptually similar to the template idea.

Yes, that's an excellent point. I use the 621 on a router table about 95% of the time (I know, everyone says the 621 is wasted as a table-mounted router. What can I say, it was a gift, the table came afterwards). So I'm not terribly good at working it "top-down" - and that's a very important point to keep in mind. Thanks.
Now, does anyone know (as per my other post) if there are bushing guides for a 621? Or do I have to go get one of those more "standard" PC routers? (not that I mind a good excuse to buy more tools, heh heh).
PQ
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