Joint Advice

[Munroast]

Needing to make a 160° join out of 18mm sq profile that will be holding a piece of glass in a 5 sided frame. What is the best way to make such a joint strong. I don't have a suitable jig for a dowel

Was thinking of (as per the picture) routing a small grove then filling the recess with resin and a bent nail. Is their a better way ?

 

[Burnerman]

A shaped plywood ‘biscuit’ may be a little stronger......are you using rebated timber or beads to hold the glass in?
John

 

[Munroast]

inserted where ? remember the width is only 18mm and the routed recess you can see is only 6mm. I was thinking of cutting an inlay out of hardwood, but would need to be very skilful (so huge amonts of time) to get a good tight fit.

it will be grooved to hold the glass

 

[Burnerman]

A 6mm plywood biscuit could be inserted in place of your bent nail.....previously shaped of course but finished once the glue had set.
However if the glass is to be fitted into a groove, all of this would be redundant if the groove was in the centre of your timber.
John

 

[Burnerman]

Ah, sorry....the groove would be on the other timber face.....but not very deep!
Perils of a small screen.
John

 

[Deleted member 174758]

OP, do you have a router and a slot cutter with a bearing which is the same thickness as thin plywood, say 6mm?

If so rout a slot on the inside in each end of each piece:

I'd suggest doing this in a router table and NOT freehand which wouldn't be very safe.

Glue the pieces together with Mitre Mate (or similar), then cut a boomerang-shaped piece for each joint with a 160° angle, and radius the ends to match the radius of the slot cutter

Glue the boomerang-shaped fingers in place and when set trim the insides with a sharp chisel.

Alternative 1: Make-up the frame with Mitre Mate. Using a hand saw cut kerfs across the outsides of the joints. Glue-in slips of veneer and trim back when the glue has set. This is a technique once used by picture framers toi get extra strength (especially if the frame was to be painted, have gesso or plaster moulding applied or gilded afterwards

Personally I'd avoid trying to put metal into the joint or messing about with resin- just go for a woodworking solution for which you may already have the tools (or at least be able to get hold of them)

Edit: The cheapest bearing slot cutter I found on Amazon was this one:

which cuts a 3.2mm high slot. That slot would do for 1/8in plywood. I didn't recommend using biscuits as I feel that they would be too small, and the grain runs at about 30°. In addition standard biscuits are made from beech which rots very fast in external situations, meaning that any joint strengthened by beech biscuits wouldn't last very long at all

Alternative 2 might be to make-up a drilling jig and dowel the joints with a softwood or hardwood (NOT beech) dowel.

The more I ponder this, the more the alternatives...

Sorry for the crappy drawings, but all I have with me at the moment is my phone, a pad and a pen...

 

[Justin Passing]

That's too obtuse an angle for a pentagon? It would be 108°... 160° would be for an octadecagon
I'd use Dominos...
Else a routed slot in the outside face rather like J & K's but - but a simple router jig (just a 10° slope) so you could use a rectangular piece of ply.

If it IS 108º you could bridle-joint it - mitre the front so it looks more betterer.

Maybe your 5 sides are all at different angles??!

 

[Deleted member 174758]

That's too obtuse an angle for a pentagon? It would be 108°... 160° would be for an octadecagon
I'd use Dominos...
Else a routed slot in the outside face rather like J & K's but - but a simple router jig (just a 10° slope) so you could use a rectangular piece of ply.

If it IS 108º you could bridle-joint it - mitre the front so it looks more betterer.

Maybe your 5 sides are all at different angles??!

I took it that the OP is making a 160° joint - in which case a bridle joint would possibly be untenable. I also made the assumption that the OP ideally doesn't want the strengthening solution to be obvious. I agree that a Domino would do it (partly because I am a Domino user myself - brilliant piece of kit), but on the basis that the OP doesn't have a £700 machine just kicking about...

 

[Justin Passing]

green's the pocket, yellow's the 10°

 

[Justin Passing]

COcked that up!

Yes JK if it is 160 then it woud have to be a T & G cum bridle - a bit fiddly.

Regards it showing - I assumed it'll be painted or the resin option's going to show.
If it shows, I think a strip of dark wood would look fine?

 

[Munroast]

Ah, sorry....the groove would be on the other timber face.....but not very deep!
Perils of a small screen.
John

the inside face would be like this and I would put it all together around the glass, I'm thinking it would give it a bit more strength.

would like to make a better job in getting the grain to match

OP, do you have a router and a slot cutter with a bearing which is the same thickness as thin plywood, say 6mm?

If so rout a slot on the inside in each end of each piece:

View attachment 260825

I'd suggest doing this in a router table and NOT freehand.

Glue the pieces together with Mitre Mate (or similar), then cut a boomerang-shaped piece for each joint with a 160° angle, and radius the ends to match the radius of the slot cutter

View attachment 260826

Glue the boomerang-shaped fingers in place and when set trim the insides with a sharp chisel.

View attachment 260829

Alternative 1: Make-up the frame with Mitre Mate. Using a hand saw cut kerfs across the outsides of the joints. Glue-in slips of veneer and trim back when the glue has set. This is a technique once used by picture framers toi get extra strength (especially if the frame was to be painted, have gesso or plaster moulding applied or gilded afterwards

Personally I'd avoid trying to put metal into the joint or messing about with resin- just go for a woodworking solution for which you may already have the tools (or at least be able to get hold of them)

Edit: The cheapest bearing slot cutter I found on Amazon was this one:

View attachment 260827 View attachment 260828

which cuts a 3.2mm high slot. That slot would do for 1/8in plywood. I didn't recommend using biscuits as I feel that they would be too small, and the grain runs at about 30°. In addition standard biscuits are made from beech which rots very fast in external situations, meaning that any joint strengthened by beech biscuits wouldn't last very long at all

Alternative 2 might be to make-up a drilling jig and dowel the joints with a softwood or hardwood (NOT beech) dowel.

View attachment 260830

The more I ponder this, the more the alternatives...

Sorry for the crappy drawings, but all I have with me at the moment is my phone, a pad and a pen...

As always very interesting, and I think we do have some of those slot cutters, and I do have a table.

I want the top and the outside to be unmarked, so I can really just cut into the bottom of the frame.

Why do you not like inserting metal ? nails are often used to hold corners together. are tou thinking of expansion pulling the corner apart.
and this would be for indoor and I would be using sycamore (that is just pine I am experimenting with in the pic)
and I don't have a domino thingy.

That's too obtuse an angle for a pentagon? It would be 108°... 160° would be for an octadecagon
I'd use Dominos...
Else a routed slot in the outside face rather like J & K's but - but a simple router jig (just a 10° slope) so you could use a rectangular piece of ply.

If it IS 108º you could bridle-joint it - mitre the front so it looks more betterer.

Maybe your 5 sides are all at different angles??!

it will be 5 sides, think of house shape, bottom two angles at 90° next two at 100° and then the top one at 160° (don't know why that adds up to 540°)

I am very happy at making 4 of the 5 corners!

the whole thing (about 2' wide x 3' high) will form a hinged door with the hinges on the side.

 

[Justin Passing]

Ah that sort of 5 sides!.. (It's 540 because you can draw 3 x 180 triangles in a 5 sided thing... start at one corner...)

As it's only the one corner I wouldn't worry as much. Even a double ended screw all glued up would be OK I think. A bit of studding would grip your resin better than a nail perhaps. Or it wouldn't be too hard to set up a drill for a dowel hole normal to the end if you have a vertical drill?

One big sheet of glass - sounds a bit lightly framed - toughened glass I assume!


Just had a thought - you could use a dovetail bit to make a channel then make a dovetail section to slide in both ends... there's posh.

 

[Deleted member 174758]

I want the top and the outside to be unmarked, so I can really just cut into the bottom of the frame.

In that case I'd dowel, or simply strengthen a glued butt joint with corrugated fasteners

in the back/botttom of the joint (again another picture framing item). I didn't suggest them before as they are not suitable for exterior use. Remember that if you use Mitre Mate on the joints that is reasonably strong and a few beads of silicone to hold the glass in place will also add to the strength

Why do you not like inserting metal ? nails are often used to hold corners together. are tou thinking of expansion pulling the corner apart.

Nails are good for right angles - less good for obtuse angles as they lack holding power in that situation. I also think that there are better, more time-tested methods than trying to re-invent the wheel by messing about with resin (literally), so to speak. If metal is OK, then corrugated fasteners (essentially a locking "nail" which mechanically pulls the two sides of the joints together) will do as well and are cheap, readily available and are a proven technology providing the timber is soft enough. They were often installed with a push tool at one time (see below), but it isn't absolutely necessary providing the glass isn't in place (I'm assuming very thin glass). Your local ironmongeror even a stall on the market should be able to sell you a small box of them - look for a small blue/yellow box with the brand name "Challenge". The brand is long established and well known for doing a lot of different types of fasteners including tin tacks, upholstery nails, panel pins, etc in small quantities (so ideal for one iffs and DIY work)

BTW picture framers, who often work with very thin glass, tend to use a pneumatic tool (like a pinner) or a bench setting tool for the corrugated fasteners rather than a hammer, there are at least a couple of patterns of bench setting tool:

but I'm sure that a drill press could be suitably modified quite easily to fulfil the same function (I use my portable tool drill press with a socket to press on new bearings) and there are still hand tools available for the task as well:

although again a bit of ingenuity and a pair of parallel jaw pliers might well do the job