Cutting my first rabbet into hardwood, any tips for success?

[Chris Lukowski]

I'm working on a small project (41"x17" changing pad tray for nursery) that will call for my first-ever use of a router and need some pointers so I don't mess it up. The sides of this tray will be made with maple 1x4s and I need to cut out a 3/8" rabbet on the bottom to insert a plywood bottom. The plan is to assemble the sides to form a rectangle and route the rabbet on the inside of this assembled piece with a 2.5HP router (either with a fixed base or a plunge base. One tip that I had heard was to not remove more than 1/8" of wood at a time or else the cut might get choppy or burned, especially in hardwood. That seems to suggest that I either adjust the width to 1/8" (with bearings or some other means) and cut at full depth (1/2" to match the plywood), OR cut at full 3/8" width and use the plunge base to start with a shallow depth and work my way up (if rabbet bits even play nice with that strategy). I believe for both options I would be using the router at max speed since it's a sub-1" cut, correct? After the rabbet is cut I was going to glue in the plywood and hold it in place with a few hand hammered brad nails as I don't have a nail gun at the moment. Any advice would be greatly appreciated!

[Robert Engel]

You should be able to do that in one pass is you go slow. Wobbling will be an issue better to do this in a router table with a straight cut bit. (I cut most of my rabbets on the table saw.)

I think the trick is learn to do climb cutting to minimize blow out.

You might also consider just cutting a 1/4" wide groove and put the rabbet on the bottom.

[Chris Lukowski]

Thanks Robert! I -do- have a dado stack for my table saw and haven't yet bought the router or bits, and I initially didn't consider cutting the rabbet using the dado method because I didn't want the rabbet to go from end-to-end on the boards. Seems like it would be tricky to get the groove to start and stop at particular points and also to deal with the rounded edges from the dado blade. I unfortunately don't have enough cash at the moment to get a router table set up so if I routed it would have to be freehand.

[Prashun Patel]

If you cut a rabbet on the bottom then nail in the plywood bottom from the bottom, it is only supported by glue and nails.

If strength is a concern for you, a stronger design would be to make a small rabbet on the bottom of your plywood bottom so that you create a tongue on your bottom. Then you route a small groove 1/2" or so from the bottom in the sides of your tray. The bottom then slides into that groove. Add glue if the base is plywood so that it improves the ability of the sides to resist shifting and racking.

If you are set on doing as you plan (not saying it's uncommon!) then I would take care to pre-drill holes for the brads. You'd hate to blow out your sides.

[Charles Lent]

Only climb cut as a second pass to smooth the cut. Trying to climb cut on the first pass will be a disaster. you will damage the project, probably the router and the bit, and possibly even you. Only climb cut when taking very very light cuts and you probably will not need to do this for this project. 3/8" is NOT a very light cut. I would use either a table saw with a 3/8 or wider DADO blade with the excess width buried in a sacrificial fence, or a 3/8 rabbeting bit with a bearing in a router for this 3/8 rabbet. To avoid blow out, use a larger diameter bit of a diameter at least 2X if the width of the rabbet. If a bit is used with no bearing, a router fence is required, but a large diameter bit is even more important when using the router fence, to avoid blow out. Using a router table is best to avoid wobbling, but an offset base with a handle attached can help you keep the router from wobbling.

Charley

[Chris Lukowski]

Hi Prashun,

The bottom won't be load bearing during use so the 3/8" rabbet into the side walls of the tray from the bottom seemed like the simplest solution. This tray will sit on top of a dresser full time to hold a foam baby changing pad and accessories, as depicted in the following image:

do-i-really-need-a-changing-table-in-my-child-L-OFbuDw.jpeg

[Ellen Benkin]

Whatever method you use (table saw or router) practice on some scrap material to get the "feel". This is not a difficult cut but it does take practice. I would rout each piece before assembly and use a router table for safety but I know woodworkers who do it after assembly with excellent results.

[Prashun Patel]

In this case, I suggest you route the rabbets before assembly.

Depending on how the sides are joined, you will have to make 'stopped' rabbets on two of the sides, but if that's beyond your ability, you can cut little plugs and nobody will be able to tell once assembled and stained and finished.

[Brian Tymchak]

I know you didn't ask for this kind of feedback but I'll offer it anyway. IME, plywood is not uniformly flat. If the plywood bottom is to be flush with the bottom of the side rails, the tray will likely end up wobbling or able to spin on a high spot in the plywood. I would hold the plywood bottom up a bit from the bottom of the rails so that the rails are what supports the tray. So, in this case, you would end up cutting a groove vs a rabbet.

[Pat Barry]

Only climb cut as a second pass to smooth the cut. Trying to climb cut on the first pass will be a disaster. you will damage the project, probably the router and the bit, and possibly even you. Only climb cut when taking very very light cuts and you probably will not need to do this for this project. 3/8" is NOT a very light cut. I would use either a table saw with a 3/8 or wider DADO blade with the excess width buried in a sacrificial fence, or a 3/8 rabbeting bit with a bearing in a router for this 3/8 rabbet. To avoid blow out, use a larger diameter bit of a diameter at least 2X if the width of the rabbet. If a bit is used with no bearing, a router fence is required, but a large diameter bit is even more important when using the router fence, to avoid blow out. Using a router table is best to avoid wobbling, but an offset base with a handle attached can help you keep the router from wobbling.

Charley

He means, if using a hand held router, to make your cuts from left to right, not right to left. Right to left cutting will make the router bit want to pull the router into the work and effectively the bit will want to climb up the wood. Generally you don't want to cut right to left when removing material as this can become dangerous / exciting depending on your point of view. If using a router table (recommended) then feed right to left, not left to right

[Chris Lukowski]

I know you didn't ask for this kind of feedback but I'll offer it anyway. IME, plywood is not uniformly flat. If the plywood bottom is to be flush with the bottom of the side rails, the tray will likely end up wobbling or able to spin on a high spot in the plywood. I would hold the plywood bottom up a bit from the bottom of the rails so that the rails are what supports the tray. So, in this case, you would end up cutting a groove vs a rabbet.

OR could I alternately cut the rabbet 1/16" or so deeper than the plywood so that it's in a slightly raised position? Or would the ever so slightly raised position cause a problem with the weight of a baby on top of it, even if the glue-up is reinforced with a dozen or so brad nails?

[Chris Lukowski]

So just so I'm clear, is the consensus that assembling the rails and routing out the rabbet in a single circular motion on the bottom edges of the boards a bad idea?

[Prashun Patel]

I don't think it's a bad idea. You just have to be careful of your direction, and you have to be careful not to tip. That gets tricky as the bit depth protrudes further from the base with each pass.

Also, you'll still require chiseling out the corners or truncating your plywood bottom.

[Pat Barry]

So just so I'm clear, is the consensus that assembling the rails and routing out the rabbet in a single circular motion on the bottom edges of the boards a bad idea?

Lets say you do the rabbet as you described. As Prashun noted you will need to chisel out the rounded corners to accommodate your rectangular panel. I'd much rather see the panel then captured with a full perimeter support (not just nails). For example another set of added on retainer pieces. I'd want to maximize the bottom side support with screwed and glued on supports. Who's to say someone doesn't try to carry the baby in this nice little basket? It would be a sad day indeed when the bottom let go.

[Jerry Miner]

You don't say how you intend to join the corners of this tray.

If you miter the corners, you can pre-cut the rabbets (or grooves) in the sides before assembly--and use the table saw/dado set.

If you use dovetails, or box joints, or butt joints, you have the choice of pre-cutting then filling small spaces with wood plugs, or cutting the rabbet after assembly with the router (as in your original proposal).

If you rout the rabbet after box assembly, yes, light cuts, several passes (easier, IMHO to keep one bearing on and sneak up on final depth in small increments.) You will get an idea of chip-out issues with the first pass, and can consider climb-cutting for subsequent passes. I don't generally recommend climb-cutting for beginners---and it sounds like you don't even have a router yet--- so be very careful here, as climb-cutting can be surprising and dangerous.

Be sure to clamp the box firmly to a stable surface while you rout. Do NOT try to hold the work in one hand and the router in the other! Balancing the router on the edge of a 3/4" thick board can be tricky--and even trickier as that board gets reduced to 3/8 after the first pass. Consider an "outrigger" or a spacer or a wide sub-base to help keep the router vertical