Lap joint on end of 2x4?

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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.
What would SuperWoodworker do?
Thanks!
--Winston
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On 4/26/2010 9:09 AM, Winston wrote:

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.
Just one of many options ...
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On 4/26/2010 7:27 AM, Swingman wrote:

I will give that a try.
Thanks!
--Winston
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Winston wrote:

After popping the uncut parts with a chisel, use a shoemaker's rasp (AKA 4 in hand rasp) to smooth the bottoms.
http://www.dick.biz/medias/sys_master/711049_01_P_WE_8.jpg
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On 4/26/2010 8:02 AM, dadiOH wrote:

Hokay.
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.
Thank you for your help, guys.
--Winston
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Winston wrote:

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. ____________

After you do a couple you'll be an expert :)
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On 4/26/2010 1:06 PM, dadiOH wrote:

(...)
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 can't believe how nicely that worked! Thanks!

Heh!
--Winston
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Depending on the number of cuts through the half lap depends on how easy it is to clean up.
In mathematical terms.
One cut between the two cuts determining the with of the lap = a lot of time with the file or chisel.
An infinite number of cuts = very clean lap.
Something in between will make it easy to remove the excess wood, but still make it quite easy to clean up the bottom surface. Usually if you make the cuts in <quarter inches slices they come out pretty clean with very little chisel of file work. Also a sharp chisel I find works better the the file.
On 4/26/2010 1:03 PM, Winston wrote:

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On 4/26/2010 1:23 PM, keith Nuttle wrote:

Yup, you and dadiOH got to the key issue.
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.
Thanks!
--Winston
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Winston wrote:

Put on more than one blade.
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On 4/27/2010 5:07 AM, dadiOH wrote:

(...)
Oh! You guys weren't kidding?
I shall try that.
Thanks!
--Winston
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Winston wrote:

Just adjust them so the centers (hub) are touching. You may have to rotate them so teeth of one are next to the gullets of the other, maybe not.
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On 4/27/2010 8:38 AM, dadiOH wrote:

Soon as the rain lets up I'll head to the hardware store and pick up a couple blades.
This should be good. :)
--Winston
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<snipped>

That is what I'd do in your shoes... a flatter bottom and if your routing guide is clamped square to the pieces, a nice fit. Make a couple practice cuts to achieve the proper depth to wind up with both pieces (joined) on the same plane. Be aware cross grain joints don't do well with glue alone over time... peg, dowel, or screw them as well. Tom
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On 4/28/2010 8:11 AM, Tom B wrote:

Copy that, Tom.
I've tried lateral cuts with the skilsaw, chipping and chiseling. My second attempt looked a *lot* better than my first attempt.
Neither gave me the great looking step provided by the router. Each attempt took about the same amount of time so it's an easy decision even though the router approach is noisier and messier.
I will have at least two wood screws through each glued lap in the corners so I'm pretty confident that will be sufficient.
As Larry says, I would be well advised to provide some kind of enhanced diagonal support, like aircraft wire to address sag. I am still pondering how to make that brace look a little less clumsy than they normally do. Perhaps I will epoxy a couple 1/4-20 standoffs inside some 1/2" steel tube and then paint it thoroughly.
Hmm.
Thanks!
--Winston
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On 4/26/2010 10:09 AM, Winston wrote:

Machined jig?!?!?!?!
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.

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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.
Take care,
Anthony
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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...
The Frame:
|-------------------| | | | | | | | | |-------------------|
The "U" (=) with 2 x 4 (x) inserted, obviouslY not to scale.
====================== =O==========O======O== ====================== xxxxxxxxxxxxxx ========= xxxxxxxxxxxxxx ======O=== xxxxxxxxxxxxxx========== ====================== =O==========O======O== ======================
Center the Frame over the "U", screw it where indicated (O) and rout to your heart's content.
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On 4/26/2010 8:04 AM, DerbyDad03 wrote:

(...)
Two Great Minds, DerbyDad!
That is almost exactly what my machined jig looks like!
If I can't make any headway using J. Clarke's suggestion, I'll go ahead and hog one of these out of some scrap aluminum.
Thanks!
--Winston
--

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re: I'll go ahead and hog one of these out of some scrap aluminum.
What? Why are you using aluminum?
Grab some scrap wood and drywall screws and throw this thing together in 10 minutes.
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