I think i'd be more inclined to use a table saw for that if you have access. If you could find an 1/8" straight bit with that deep of a cut you'd still really have to nibble at it. Slot cutting router bit would hold up better that a straight bit, but i don't think you'll find a slot cutter that can get you the depth you're looking for.

earl

 

I agree with Earl but also add the option of a Thin bladed handheld circular saw and a Kregg "Rip Cut" sliding square (option). This makes multiple passes accurate & easy.

Hope this helps - Baker

 

A slot cutter in the router table would be my choice, it wouldn't have to be 1/8" thick, a thinner one would be fine by taking several cuts, each time adjusting the height of the router.

 

George, if you make this type of cut with a table saw you will need a high fence to guide it safely. This is easy to make. If you want to do this on a router table then a slot cutting bit as Harry suggested will give the best results.

 

George: I have done this with a 1/8 inch Rotozip bit and a 1/8 inch reducer in my small Dewalt. Not the best solution but got it done where I didn't have room to run in a blade.

 

A standard slot cutting bit will only get you to maybe 3/4" depth. Like Mike I would go with a TS and tall fence if possible. You didn't say how large a piece of ply you were going to working with or why you need a slot that deep. If you try Scott's suggestion I would clamp a straight edge on either side of the ply so you have a wider, stable base to work on.

 

1/8" bits are not generally made in that length (1 1/4"). If you can find one, you want an up-cutting spiral that will bring the chips (swarf) to the surface, and unless you have machine feed you will very likely break the bit. It is unlikely that you will find an off-the-shelf slot cutter that will cut 1 1/4" but you can have one made but you may not get a guarantee with it. A table saw can be used if the workpiece is not so wide that supporting it vertically is a major problem. I have made similar (but wider) cuts to in situ materials using a hand-held circular saw by clamping a support piece and a guide rail to the edge of the workpiece (you'll want to practice a bit before you start on the critical piece and may require to make that cut in several passes).

Let us know how you go !

 

It really depends on how long the slot is to be and if is a blind slot (fixed ends of stopped slots).

Being that plywood is not consistently dense and being you want to go down 1-1/4" deep-- Even if you did find an 1/8" bit that long, an 1/8" diameter bit doesn't have the lateral strength to create a slot 1-1/4" deep. A slot cutter would have to be 3" in diameter to get that deep...

Depending on the dimensions perpendicular to the edge, a table saw with a tall fence or a TS raised panel jig might work... But if longer than that...

Then you are either looking at something like a biscuit joiner... although the slot created may be too wide for your application. Biscuit joiner blades measure out at 0.165". If that width is okay by you, then that would be the tool to use. But if not, then a Better Idea...

Build a jig for a circular saw.

Just as people here say, as a rule of thumb, that if it's somewhat small, use a router table, it's it's too large to comfortably manuever and control on a table... then build a jig and use a hand router. Same goes with saws. You can only stand up "so big" a workpiece on edge on a table to a certain size before you would have to call Leonardo DaVince in to figure out a hellacious jig to keep it under control. Better to build a jig for a circular saw's base to bisect your 3/4" edge, to keep it steady and perpendicular to the sides... as it moves along that edge and makes the cut.

That sound simpler now?

 

Thanks to all who responded. I appreciate all the experienced responses. I'm new at this. The plywood will hang vertically supported by an aluminum T-Bar, inserted into the slot, and will be weight bearing, (not too much weight). I've considered using the table saw and may end up doing so. It would be nice to make a square notch in the upper end. I'll let you know how it goes.

 

Couldn't you just rabbet the back edge and put some screws through the aluminum into the wood? That's a really easy operation and size doesn't matter. You'll have to run screws into the aluminum or through the aluminum either way and with a rabbet on the back side you can use a 1 1/4"D straight bit and do it in one pass.

 

Do you have access to a radial arm saw? You could set the blade to the horizontal position, adjust the setting for the depth of cut, and slide the plywood along the table. You probably will have to construct an auxiliary table and fence that sets on the saw table; also some sort of outboard support.

 

Radial Arm Saw Slot Cut DANGEROUS



PLEASE use EXTREME caution using radial Arm Saw for such a purpose. I have learned many years ago that is NOT the intended use for a R A S, especially with fir or pine, soft woods. I have seen wood explode (twice) durring such attempts. Luckily my friend was not injured. NEVER stand in line with any cuts on R A S or Table saw. You might try a thin-kerf saw blade on Table Saw or a 1/8th spiral bit in your router, making several passes to gain the depth needed.

 

Here's another idea. The Dremel 561 general purpose cutter is 1/8 in dia and has a cutting depth of about 1 1/2 in. It is rated to about 30,000 rpm. A 1/8 in collet adapter allows it to be used in a router. I have used it with my Makita 3612c. It does loosen after several minutes of use. I would first cut the plywood groove with a 1/8 in slot cutter to the maximum depth allowed by the slot cutter (9/16 in is the max. I can find) then cut to the complete depth with the Dremel cutter in the router.

 

If it is a full 4x8 sheet of plywood I would definitely use my circular saw with a simple sled. If it small enough pieces or strips I would go to the table saw. Also depends on how exact the slot size has to be.

 

Thanks, the result of the effort

Thanks to all who responded, I read and considered every response. I changed the design a little and decided the slot not only needed to be 1-1/8" deep, but one end needed to be a repeatable 45 degrees. After a couple of failed attempts, a sled was made to hold a Rotozip tool. It was constructed such that it could incrementally and easily let the depth of cut be adjusted. The sled itself sits and slides in a jig that attaches to the edge of the 3/4 inch plywood. A couple of pictures are attached. There are probably better approaches, and there are certainly better designs. Using this tool set up was easy, but tedious. The 2" x 1/8" spiral cut bit tended to flex sufficiently as to ruin the first practice slot. Success and repeat ability was obtained by starting with a very shallow cut, and by sliding the tool backwards (in the direction of the 135 degree angle).

So, did it work? - we'll, the slot was perfect, but the aluminum piece deflected slightly. under a load. Ultimately a different, more conventional design was chosen. But, I learned a lot from the effort, and really enjoyed the work. My new favorite router is a small 1-1/2 hp trim router. It is very easy to use, and quick to set up and adjust.

 

Another picture of the setup

Just another view of the rig.

 

That jig is a good, practical solution, George.

Thanks for showing.