So I did another, this time in walnut, for the friend whose idea it was.
As I mentioned in passing earlier I wanted to get fully bonded joints, the dovetail splines I used first time round were quite shallow and I found it hard to get decent clamping pressure on the mitre particulalrly on the inside of the corner (I've been using Titebond II for this project so clamping pressure is critical for a strong joint).
So I adapted my mitre spline jig to use it on the table saw as
@Inspector /Pete suggested and had no problem at all cutting fairly deep (~30mm) slots for plain splines (not dovetailed) and planing down some scraps to use as splines (planed down to interference fit).
To get good clamping I thought it would be a good idea to use a drawbore technique, so I cut a couple of 4mm holes either side of the mitre, and made corresponding holes in the splines, but these holes were a few millimetres closer together; putting a couple of 2/3mm oval nails partly or fully through closed up the gap between the mitres and indeed put the mitred faces into compression, spline in tension. I glued up six subassemblies this way and was pleased to see that the mitres were now absolutely in contact, and the joints seemed strong. I took out the nailes when the glue was dry, enlarged the holes to 6mm to get rid of any bruised wood where the nails had been pressing, popped in some dowels, and altogether felt things were going pretty well.
Having made the six subassemblies I was now ready to glue up the joints between the subassemblies; I left overnight for the glue to set, and after taking the nails out ther next day and inserting dowels instead I was ready to start sanding .... and that's when I dropped the workpiece accidentally on the floor. Since I have 19mm rubber flooring in the workshop and the workpiece weighs next to nothing I thought I would be ok, but I knew I wasn't when I heard a big cracking sound. It turned out no fewer than four joints had broken: the splines had snapped and the joints separated.
I realised what had happened: there was way too much tension in the splines, and the tension was still there wIth glue set; and once one spline snapped the resultat shockwave snapped more in a sort of chain reaction. I had once again snatched defeat from the jaws of victory!
I repaired the broken joints with epoxy, wishing I had used epoxy throughout (since thickened epoxy bonds well with light clamping.
I mention all this because the whole episode was typical of how woodworking goes for me, generally with me ending up having been too clever by half ...
Reading the forum I see that other members introduce themselves on joining and I feel embarrassed at my manners in not doing so. I'm 58, live in North Norfolk and started woodwork 2.5y ago when I retired. Having started off with hand tools only (other than electric drill), I bought machinery in 2019 (Wadkin AGS10 table saw, Startrite SD310 planer thicknesser, Meddings bench drill, Charnwood bandsaw B250 and Bosch GCM12GDL mitre saw). My main interests are making furniture for the house, and shipwrighting work for my boat (I have an Essex smack, built 1892) ....
