The proper answer is 'buy or borrow a table saw with a dado blade'.
However, I don't want to.
I want to use my plunge router to place a 3-1/2" square lap joint about 3/4" deep on the ends of several pressure treated 2x4s. I will don a respirator first, no worries.
I've designed an machined jig to allow me to do this but I want to know how you pro's would approach this challenge before I search my junk pile for parts.
My Google-fu was not up to the challenge. Instead, it revealed some table saw adapters.
My band saw refuses to cut anywhere near straight so that's out.
First prize answer would be an inexpensive jig I could pick up at my local hardware store.
Typically what would be done on site by an experienced framing crew would be a circular saw to make multiple, close together shoulder cuts at the proper depth, and a chisel to finish chopping the residue of these cuts out.
Clamp the 2x4s side by side. Clamp a scrap across them an appropriate distance from the cut line as a fence. Clamp another 2x4 crosswise along the ends for the router to ride on at the ends of the cut. Route until done.
If this is difficult for you to set up you don't have enough clamps or don't have the right kind of clamps. And nobody _ever_ has enough clamps so go get some clamps if you need to.
It would be difficult to safely cut a lap joint on the end of an 8 foot 2x4 using a table saw with a dado blade. Far too easy for the long board to shift while cutting. Maybe with a proper jig, but I wouldn't try it.
A router would work fine, and it sounds like you're alerady set up for the task.
I don't know what kind of precision you need, but for rough carpentry I usually "dado" using my circular saw. For instance, if I want to "let-in" a 1x4 diagonal brace in a stud wall. Just mark the outside edges where you need to cut, then set your circular saw to the proper depth (3/4" in your case). Make a cut on each cut line, then a series of cuts in between. For construction work I usually just use the claw of my hammer to knock out the thin strips and clean up the joint. If you need a finer joint, you sould clean it up with a chisel.
Of course, it might be just as easy to make the cut with a handsaw. With a sharp saw, it shouldn't take more than a few minutes to cut a half lap joint.
It seems to me that a fairly simple jig, based on the size of your router base would make short work of this project.
I recently had to cut a number 3 1/2" x 1/2" deep recessed areas in the middle of some boards and a simple frame made of 1 x 2 stock clamped to the boards made quick work of them.
All you need is a square frame sized so that the router can only move enough to cut a 3 1/2" square and a way to mount the jig on top of a 2 x 4.
How about this:
Size up and build the square frame and set it aside.
Take some scrap 2 X material and make a "U" shaped jig so that your 2 x 4's can slip into the "U", essentially giving you a "flat board" just like I had. This will support your router as you rout the 2 x 4.
Mount the frame on top of this "U", positioned so the center of the area you need to cut out is in the center of the frame.
Slip a 2 x 4 under the frame into the "U" and rout out your lap joint. You can oversize the frame to allow the router to clean all of the material from the end of the 2 x 4 and then just clean up the other end of the joint with a chisel.
I don't know how this will come out, but I'll try a little ASCII art...
This morning, I followed the technique mentioned by you, Swingman and Anthony. (Thanks)
I have a confession to make. I am not Roy Underhill.
I'm an electronics tech with zero woodworking chops.
I placed the cuts at depth and chipped out the scrap between cuts. So I got the general idea. I see that if I spent say 10 min. with a rasp as suggested, I would eventually arrive at a surface flat enough to allow a halfway decent looking workpiece, though I am dubious about my ability to do that *twice*. :)
I've got 16 of these to do. Unlike you, my 'thrill of creation' happens with other hardware and not with wood so much.
So next, I will try J. Clarke's suggestion because that sounds like it would give me a good chance at a flat face surface, quickly. I can afford to 'notch' the material then slice off the end if necessary. Raw material is cheap. Time and talent are all but nonexistent here.
Ten minutes? Nah, 1 minute tops. Maybe you didn't cut the kerfs close enough together? Leave no more than about 1/8 between them, pop them out (I usually use a screw driver), if one breaks high, slick it off with a wide chisel (1" or better), use the rounded rasp side to smooth down. ___________
Yes, a fence and doing multiple pieces at one time is a lot faster with either saw or router. If you use a router, start at the outboard end so you don't leave the router base hanging over thin air. ____________
Skilsaw (or equivalent), cut across the 2x4 at the proper distance from the end, then use the Neander approach -- wide wood chisel and a hammer to 'split' in from the end.
*WAY* less dust than the router will throw up.
Of course, you've got to be able to chisel a flat surface. for the lap.
To reduce the effort of Neandering, do a -series- of parallel custs with the Skilsaw, then break the 'fingers' off, and clean up with the chisel.
You shouldn't really have to cut anything "straight".
The 2 x 4's for the base are already cut straight, you just have to cut them to length.
The same goes for anything that you'll be using for the upper frame. Any kind of scraps that can be laid out in a square will work, including more 2 x 4's.
I really believe that you are over thinking this fairly simple project.
Ah! I was leaving perhaps 3/8" between cuts. I knew I was doing *something* very wrong.
I tried J. Clarke's suggestion just now and it worked a treat. It was noisy, somewhat slow and messy but left a *very nice looking* step that required no further attention.
As you guys say, I will gang the planks and cut multiple at once. I will leave extra length and a step on the 'waste' side to support the router. Then I'll just flip them over and saw off the step.
I left too much material between cuts and it resulted in much more 'post processing' than I would have been comfortable with. I see now that leaving say, 1/8"-1/4" between cuts would have made that a whole lot easier.
Doubtlessly someone makes a 7-1/4" circular saw blade with a wide kerf (say 1/4"?) just perfect for this app.
Right now, I'm so pleased with the results of hogging out with the router that I will stick with that method.
It turned out that I only *really* needed to constrain one direction of one axis. So I clamped a piece of scrap aluminum square on top of my 2x4 as a fence and routed my step. It turned out much nicer than I thought it would and requires no cleanup. That'll do.
HomeOwnersHub website is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.