See image.
What would be the best way to join these 2 pieces (part of an octogon) The rebate is approx 3/4 x 3/4 inch. My thoughts are 2 screws + exterior wood glue at each joint as per the red line.
Glue, clamp well and these:
They are sold as decking screws, I've been using them for floorboarding and my mate (who's a carpenter) used them to do ad-hoc joins.
Treat them like removable nails (ie use the angle to do the holding , rather than relying on them pulling together, because they don't do that so well).
In message , ss writes
Depends on your tackle:-)
If you have a table saw and can make up a suitable jig/sledge, slotting the corners and inserting a thin plywood section makes a very strong joint. I have done picture frame corners with 1mm perforated galvanised steel sheet:-)
Otherwise a variant of the *corner halving* joint for the thicker section and ignore the rebate.
As you suggest, but add screws from the opposite side, mirroring your red line. Also consider dowel(s) right through the joint, i.e. horizontally on your diagram.
There isn't a single 'best' way, it depends on things like strength required, if there will be weather and movement, what the purpose is etc. A few options:
surely other ways too.
Tim W
Need more info ... is it to be treated, painted ? is it external or internal? Does it take much in way of external forces?
If not much loading simply glue it with a good glue .. mitre gives good surface area.
If it does take loading and you are painting ... drive a nail in where you have RED line, easy if you have a nailer ... if not drill a pilot hole and hand drive in a nail (lost head would be best)
Screws can be problematic as they often cause joint to slide as you screw them in. Any nailing should be done while glue is wet.
forgot to add if the inside below the mitre can't be seen .. then add a matching angle fillet and glue it across the joint. A good 2" overlap each side would give a lot of strength
The other point is that if this is a frame for your slats, then they are potentially providing some more strength holding the octagon together, reducing the need for cleverness at at least four of the bevels (and maybe at the other four, if you have structural elements joining the two bits that are parallel to the slats).
Thanks to all for input, been helpful. To answer to some points.
The wood has already been cut so I wont go for various joints as this would reduce the circumference + trying to keep it simple.
The plan now is screw and glue plus I have some metal so I could strengthen the joint underneath by bridging the joint.
The slats for the table will be screwed in so should add more strength.
If you have one of the basic pocket hole jigs[1], this would be an ideal time to use it. You could also just glue a bit of thin ply over the join for added strength. (rebate it in, if you are feeling fancy!)
[1]Some, although since they are not joined to each other, it will only be a limited gain.
a trick we used to use for joint strengthening when I worked in historic buildings -
Cut a piece of threaded inox bar and cut a slot in the end to make a stainless screw-in dowel to join the sound parts of an otherwise knackered piece of joinery. Supplement with resins or adhesive and embellish with plugs over the holes as appropriate
Tim W
I usually avoid cheapy silverline tools, but I have one of these, and there's not much to go wrong with it, has sleeves for different dowel sizes
Something I dont have but should now consider, previously I have just done them by hand, but can see the benefit.
Yup should be ok (in fact the one I linked to gets some poor reviews for the drill bit quality).
Note to the OP that having the right drill bit and a suitable clamp are also pretty much essential, as is a long square drive bit for the special screws.
Ease and speed are often cited as the advantages, however the jigs give a much stronger joint than just driving in a screw at an angle, since the screws are pan head, and the head engages positively on the shoulder left by the stepped bit. Much less likely to pull though than a normal countersunk screw.
Not the prettiest of joint techniques, but fine when out of sight.
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