Lap Joints

I'm looking for a easier, faster way to cut half lap joints in heavy timber on site. The application is fitting vertical posts to horizontal joists when building decks.
Posts vary from 3 x 3, 3.5 x3.5, 4 x 4 (inches) Joists are mainly 6 x 2. Joint has to be square or getting the post plumb is a problem.
No trouble in the workshop with my RAS, but it's not really practical to do it off site.
Tried various things, L10 135mm blades in my Makita jigsaw, but whatever I do the blade wanders, surprising that Makita make 135mm blades that don't cut straight even in such a superb machine. Don't think its me!
El cheapo reciprocating saw is slightly better, probably because the blade is wider..
Currently cutting by hand & cleaning up with a chisel. Dead accurate with care but slow & bloody hard work! 6" long cuts along the grain in 3" timber are no fun!
The answer seems to be some kind of jig & a circular saw to cut multiple notches, but it needs to be safe - no damage to posts - or me!
Tried Google & found this very useful site http://www.woodworkingtips.com/etips/index.html but nothing for my problem.
Any thoughts?
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Dave
The Medway Handyman
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timber
do
timber
problem.
You take two pieces of 3x3 about 4' long, about 2" inwards you drill a hole right through at each end, you then get 2 wing bolts and feed these through the holes. You make another one as described above,what you have now is two 4' long clamps and you clamp as many pieces of poles lined up into these clamps and then run the Circular across the post where the lapjoints cutout will be adjusting circular for the required depth.
A chisle will be far more easier to knock out the waste wood as the depth is equal and should give you a smooth flat.
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timber
do
timber
problem.
Set CS blade to correct depth and lock. Make carful measured cuts for the start and end of the joint and then rough cuts in between at about 5mm spacing. Insert the widest chisel you have in the first cut and lever to crack off the waste and remove odd remains with the chisel.
Very quick once you get going. Only potential problem is when the timber stock is not all the same size. so worth a check on this first.
I've just been doing lots of this sort of joint but in the workshop recently. Dado head in the table saw (big cast iron 3HP beastie - Xcalibur 806) makes very light work but no good on site for you sadly.
hth
Bob
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On 2007-04-09 10:44:18 +0100, "The Medway Handyman"

Sliding compound mitre saw.
Mine (Makita LS1013) has a depth stop on it which can be adjusted and swung into place to prevent the blade dropping all of the way. It's a pretty simple thing and I would have thought that something similar could be improvised for almost any SCMS.
Presumably if you are doing a lot of deck work, you have an SCMS anyway?
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Andy Hall wrote:

I do. An Axminster jobby, but it doesn't have a depth stop that I can find.
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find.
My cheapo ebay 80 jobby has, so your axy must have?
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George wrote:

Alas not all of them have this capability.
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Cheers,

John.

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On 2007-04-09 11:42:57 +0100, "The Medway Handyman"

Probably not - I don't think many do. I just mentioned it as a possibility because it might be possible to improvise one. In effect it would create a smaller version of something along the RAS albeit without dado cutter.
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Don't make a joint at all - just bolt them together.
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who know little, not those who know much, who so positively assert that this
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Huge wrote:

Not strong enough - you need the half lap (on the post only) to make the post rigid. I use polyurethane waterproof glue & 90mm coach bolts as well as the lap - that makes the post rigid.
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Cutting the post makes them weaker. Bolts should do the job if they are big enough. If you really want the notches then a good radial arm saw with a dado head is the best bet.
BTW my 30 SCMS has a depth stop on the rear right hand side. It stops the swinging bit from going the full depth so you use the slide to cut the slot. Are you sure the Axminster doesn't have one?
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The Medway Handyman used his keyboard to write :

Depending upon how deep, have you thought of an heavy duty router? Though it sounds to be outside the range of a router.
I can do a good accurate job with a circular saw. Just set the saw to the depth of cut you need, mark out the edge of the cut(s) then run the saw through to the mark(s). Then use the saw to make repeated cuts between to take out most of the waste material - clean up the last bits with a chisel - Bob's your auntie.
Maybe pin a bit of wood on to act as a cutting guide.
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Regards,
Harry (M1BYT) (L)
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Harry Bloomfield wrote:

Essential to have both hands on the saw for this. I'd do them on the floor and just rig up a couple of battens or something to stop the post moving. Using your foot to hold it is not a good idea as your weight needs to be behind and over the saw. I don't generally regard kickback as an issue but these are essentially deep, "blind" cuts where the blade may not be clearing itself fully and the cut may not be dead straight. That said, a piece of cake if the timber is properly secured and you have both hands free.
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AIUI your problem is the face cut ripping up the length of the post (rather than the shoulder cut across the post).
In the workshop the obvious way to do this would be on the bandsaw (i.e. just like making tenons).
Assuming you don't have a portable bandsaw, one way would be to make a trench cut with the circular saw on the opposite faces of the post (and cut the shoulder the same way).
Now either your CS will have enough depth of cut to make a cut just over halfway from each side, or it won't quite make it and you have to remove the remaining portion to make it a through cut with the jigsaw.
Either way there will also be a remaining portion at the end of the face cut as you come up to the shoulder line (due to the shape of the CS blade), this again is easily removed with the jigsaw.
The rips are relatively easy as you can use the CS fence (although you will be guided by a different face when you roll the post over for the second face cut). A homemade crosscut jig that clamps in place on the post makes nice straight shoulder cuts much easier
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The Medway Handyman wrote:

Assuming you don't have a SCMS with trenching cut capability, then I usually do the same sort of trick using a hand-held circular saw. Set the depth, cut both ends of the cut, then make more passes relatively closely spaced. Break out the remaining fingers of wood and clean up with a wide chisel.

I think 135mm is pushing it for a jigsaw blade, no matter how well the saw supports the fixed end there is very little it can do about the other end flopping about.

I have never felt particularly at risk making a non through cut with a hand held CS. Having the wood well supported obviously helps though.
--
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John.

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A jig and router. Jig is 2 pieces of timber fixed at 90 degrees forming the 'hand piece'. The top surface forming a guide for the router. and the jig is clamped to your timber.
The lap joint will be cut by multiple passes of the router starting at the end. You would need a wide cutter set to the depth of the joint.
The Hand Piece will be moved back after each cut until you reach length of the lap joint cut.
Arthur
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Arthur wrote:

Sounds labour intensive and OTT for garden work
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On Mon, 9 Apr 2007 10:44:18 +0100, "The Medway Handyman"

Mostly you need a set of trestles to work on. Can't do big framing carpentry without lots of trestles! Make them nest in 3's, just by tweaking their length.
Handheld circular saw (a real, proper one, not the POS you mentioned the other day), a stringline for layout and a big square. If you can find it, the _big_ Stanley adjustable roofing square was good. This was cast aluminium and thick enough to use as a guide for a saw. Some people just weld up their own, with a T-edge to hold it in place on the timber.
The technique is to saw the two faces, slice the remainder into short grain wafers, then bonk them out with a bronze Thor hammer. Clean the face with a slick, if you have to.
I freehand with a handheld circular saw, but only so long as it has a couple of horsepower. It's far too dangerous with a little one that's going to bind and stall unpredictably.
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Router
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The Medway Handyman wrote:

Why can't the posts simply be alongside the joists, and continue down so that they are sat on the existing ground, or even into it a small amount, then bolted to the joists? - I mean proper 10mm bolts with washers through pre-drilled holes....a ratchet and socket will be required IME, they never move again

It's not you - jigsaws are fine for what they were intended for - cutting holes in boards....I've also tried, and failed miserably.
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