The first thing any workshop needs is a good sturdy worktable. The Adhikaris had an old broken down ironing board at their home in the village. The ironing board was in terrible condition, but the wood was sound and the joints were repairable. Disassembly was a process of pulling out a few dowels which had become loose and also unscrewing some 6" long lag bolts with very nifty washers.
Back at the workshop, I proceeded to show Sachin how to strengthen a section at a time. We attacked one complete square. First, the joints were loose, we drilled out the dowel, expanded the hole a tiny bit and drove in a larger dowel. We did this for all 4 corners and then we cut a long diagonal brace from 12mm ply and cross braced the square.
This was the essence of the rebuild. At some corners we found that the mortise tenon joints were very badly made and were 4mm short of being snug. Here we cut and glued additional pieces of wood, veneer or laminate and built up the tenon so it was a snug fit.
The resultant frame was extremely sturdy and I really wish I'd taken images. We cut up a 18mm ply leaving about 15 cms of overlap on all sides. I still don't quite know how we screwed up the markings on where to place the screws, but we did and securing the table top took way long than it should have. But that's the build and all's well that ends well.
As usual the verbose post follows.
Here at 'Mohraan'; the Adhikari's farm; as has been mentioned in the speedy description above, we set out to make or arrange for a worktable. As the first table, neither they nor I wished to go in for some heavy duty scratch build which would take both time, effort and money. But ofcourse the first table needs to be sturdy. The very last thing I want is to teach someone on a rickety table. Anyway, Sachin conviced Adhikari senior to part with a beloved sheesham ironing table which was at their home in the village. When i first laid eyes on the table I was downright despondent. First off, the table was out in the garden of course under a roof, but essentially exposed to the elements. And the elements had not been kind. The table was listing terribly, and at least 3 members had fallen off. My 'conservator' training kicked in. Visual inspection showed white rot, and spongy wood (another type of rot) was in play here. There was no termite infestation or even evidence of a small attack. The wood itself felt intact and even the spongy wood didn't run deep into the sections. This old sheesham was clearly some good quality stuff.
First up; disassemble, To disassemble something, one must ascertain how it was assembled. In a museum, I'm told, they use scanners and stuff, here we went with a more affordable option. Instinct! The table was simply constructed of mortise and tenon joints. These are the old and proper type of mortise and tenon joints with 4 shoulders and not the new fangled dressed up tongue in groove sort of rubbish that is used today. This gave me hope. The tenons were too short, but more than that, they seemed to be cut with varying precision. It was the dowels that were holding them together. Anyway, as I said, the build was simple. Essentially 2 squares help parallel and connected by 4 sections to make a box frame. The squares were held together with doweled MTs. But the connecting 4 lengths of wood had a long lag bolt through the joint.
This lag bolt was one of the reasons why the corresponding tenon on the other side was so short. A small niche had been chopped into the section through which the lag bolt ran and the bolt had been anchored there. This would pull tight the remaining 4 sections. These builds piss me off. Why would the carpenter not just trust the mortise and tenon. At their level of expertise, they should. Why go in for a meal fastener. grrrr. Disassembly didn't take long and we were soon back to the farm.
Under the tarpaulin we examined what we had, the mortise and tenon joints were of 2 types, doweled and lag bolt jointed. On closer examination we began to see the problems with the doweled joints. As is expected, over time and constant rocking, the dowel had caused the hole to expand and we were able to simply pull out the dowels. As I mentioned earlier, we found the tenons themselves were too short, but more importantly, the tenons were not snug. In places the misalignment was about 4mm. Typically, rot and fungus get into these crevasses and deteriorate the lignin, causing the wood here to slowly fall apart. Further enlarging the mortise. The effect then becomes cyclic. The solution is actually quite simple; rebuild the tenon. This is done by chopping out the rot and soft wood from within the tenon and then adding bits of wood taking care of the grain direction, to build up the joint to the size that is required for a snug fit. Finally, the dowel. Understand that in nearly all situations, the hole in the tenon has enlarged more than the ones in the mortise, which means that simply pushing in a dowel will not help. The hole itself has to be enlarged to match the hole in the tenon and then a corresponding, square dowel has to be inserted. Locking everything in place. We did this for all the corners of the 2 parallel squares. Additionally we put in one more smaller dowel at each mortise and tenon, further impeding any rocking motion of the members.
The fit was snug, but there is only so much strength a 1/2" rebuilt tenon is going to give. We needed this table to withstand work shop forces. I cannot begin to explain the racking force that a bluntish plane can generate when being pushed through ain wood. (OK now I'm just showing off, hehe). But yah we needed something more sturdy. Every engineer, we hope, knows that the triangle is the stablest form and hence we decided to cross brace all the squares. But before this I felt from experience that we needed a little more support at the corners.
These simple triangles did the trick. As long as 2 screws are put in on either arm, these serve well to stop the corners from jiggling. And here is the cross bracing. You'll notice that all the bracings are plywood. Ply is pretty stable and good ply doesn't split easily.
Finally we chopped up some 3/4" ply and screwed that into the the frame as the top. As I said ply is stable and doesn't expand very much; so screwing it directly into the frame isn't as much an issue as with solid wood.
And lastly the mandatory quality test. We did a little jig on the table. Perfectly solid.