Best method for gluing/assembly of long mitres.

[Hornbeam]

I am making a couple of carcases which will have basic mitres corners which are then reinforced with a number of keys in a contrasting colour.
What is the best method to ensure good alignment across a mitred construction up to 18 inches deep.
I dont want to use biscuits as I already have keys going across it
I have thought of making some thin ply outers with corner glue blocks so I can pull up with small g clamps.
Any thoughts

Ian

 

[Racers]

You will have to use splines as a long miter will pull apart due to shrinkage.
Thin ply will work.

Pete

 

[Phil Pascoe]

Are you putting in the keys after you've glued the mitres?

 

[Hornbeam]

The plan was to glue up as a basic mitre and then cut grooves through the corner at 45 degrees and then glue in splines. Once the splines dry they will then be planes flush leaving a contrasting line of splines along each corner
Ian

 

[MatthewRedStars]

I generally tape long mitres.

Lay them 'flat' side up in the orientation you want, stick plastic tape pulled tight across the mitre. Flip the whole lot. Bead of glue and then use clamping blocks or more tape to hold them square.

If the tape is nice and tight (not too tight though) you'll get a decent external corner.

 

[Eric The Viking]

+1.

Tape works really well, with the advantage that you get to double check easily that everything lines up as it should before committing.

 

[Phil Pascoe]

The plan was to glue up as a basic mitre and then cut grooves through the corner at 45 degrees and then glue in splines. Once the splines dry they will then be planes flush leaving a contrasting line of splines along each corner
Ian

How were you thinking to do this? With some sort of jig for the router? :?

 

[novocaine]

table saw I assume Phil. it's the method shown on about 100 million youtube videos by our darling american brothers who do everything from sheet work to bowl making with a table saw.

 

[Phil Pascoe]

Of course. Thanks, I've got dovetail keys in my mind.

 

[custard]

I am making a couple of carcases which will have basic mitres corners which are then reinforced with a number of keys in a contrasting colour.
What is the best method to ensure good alignment across a mitred construction up to 18 inches deep.

Depends on the material (solid timber, MDF, ply), the material thickness, and possibly even the project length. I might adjust my plans according to those variables. Also, does the project allow for internal glue blocks or brackets, are the keys decorative or for strength, and what glue are you planning on using? By alignment I'm assuming you mean a nice crisp mitre joint rather than alignment in the length?

 

[Mr T]

I have thought of making some thin ply outers with corner glue blocks so I can pull up with small g clamps.
Any thoughts

Ian

I use the system you suggest. About 9/12 mm outers the depth of the carcase with mitre blocks glued to the ends. Clamp these to the case then clamp across the mitres for give pressure at right angles to the mitre. This helps to get good closure of the mitre but may not help with alignemnt along the length, you would need splines, biscuits or something for this.

Chris

 

[Hornbeam]

Thanks for the replies. I think its a combination of tape and separate outers with clamp blocks.
Novocaine you are right probably on the saw with a jig. Can also be done on the router table with a jig.
One advantage of the saw is that you can cant the blade over so with a bit of planning you can create different effects rather than just plain splines

Ian

 

[LBCarpentry]

The tape method is by far the best. I have glued perfect mitres up to 2 meters long using the tape method. Just make sure that saw cut is perfectly flat. Lay them on a flat surface so the outside edges are facing up and the two 'points' of the mitre are just touching. slap yer tape on, spin her over. Nice bead of glue in there and softly squeeeeeeeeze.

 

[will1983]

The tape method is by far the best. I have glued perfect mitres up to 2 meters long using the tape method. Just make sure that saw cut is perfectly flat. Lay them on a flat surface so the outside edges are facing up and the two 'points' of the mitre are just touching. slap yer tape on, spin her over. Nice bead of glue in there and softly squeeeeeeeeze.

This has worked for me in the past also, one tip though, don't be shy with the tape!!! oh and use good quality tape with plenty of "stick."

Please post a picture when your done.

Will