Sunday, April 19, 2015

Table Progress - part III

This week has been a busy one; back to work on the table. As mentioned in the last posting on this project, a few weeks ago I got the needed timber, but wanted it to acclimatise to my workshop before proceeding further. That process has been accomplished, and this week I was hard at work cutting, planing, and joining parts to begin the top. This week's posting will be a "slide show" type of story showing (most of) the steps in that process.


The planks which will become the top
I forgot to add the two needed for the leaves though


The first step was to choose the best pieces for grain and straightness. Some were straighter than others, however.


Let the sawing begin.

After the pieces were chosen, the lengths were marked out and cut off. Some smart guys often try to tell me that God invented an electric saw some hundred years ago, and it goes much faster using one. I agree, but it is not about how fast I get it done; for me, the joy is in doing it. Using a hand saw takes skill, and I enjoy the challenge of mastering that skill. It also means that I do not need a gym membership.


All the pieces laid out on the template


Once the cutting was finished, it was time to start planing. Most of the timber was fairly flat, but a couple of them had a nasty bow; time for the scrub plane.



The line shows the amount of bow in this piece of timber


I have several scrub planes, but my favourite is this German one from the middle of the 19th century. (no chip breaker, just a solid iron) The small size, deep curve, and the horn on the front make it a very aggressive plane. It made quick work out of the curve.



Checking for straightness 


One down, 17 more to go. Fortunately most of them were much flatter. The whole process took most of a day however. Planing elm is a bit tricky, because it tends to tear in long ropey strands if you go counter to the grain. Therefore, many of the pieces had to be worked from multiple angles. One thing I do to help minimise the tear-out is to go diagonally across the grain with the courser planes, then do the final smoothing with the grain.




Nearly finished



 Once all the pieces were planed, they had to have the taper marked and cut. Each narrow end is approximately 0.4666% of its wider end. The pieces must be cut on both sides, however, to keep the grain running straight and to keep the ends oriented squarely to the radius.



Some of the parts with one side cut.
the off-cuts are in the box


I hate dust and messes, so I try to collect the sawdust in a box instead of letting it fall on the floor, but that does not work for ripping, so I just have to sweep it all up afterwards.


Checking the sawing for squareness


I cannot rip a perfectly square edge very often, but I usually get pretty close. I have a much better success rate on cross-cuts. A long time ago, (cannot remember when) I discovered that adding wax to the blade from time to time, greatly eases the effort of sawing. Some time after making that discovery, I read in the Dictionary of Woodworking Tools, by R. A. Salaman, that cabinet makers used to have a box filled with oil soaked rags which they used to draw their saw through as a way of lubricating it. I keep intending to make some such box, but have yet to do it so I just wipe it on with a cloth.

Once all the tapers were cut on one side, and the first cut on the second side of the first piece, it was time to start joining them. The nice thing about joining by hand, is that it does not matter if you keep the edge perfectly square to the sides, so long as you match them face to face before you begin. As a way of demonstrating this, I made an exaggerated diagonal line across both pieces. When they are fit together, these two lines will be parallel each other. Of course, the down side of doing this is, that any curve you get in the length will be doubled once you fit them together, so one still has to be very careful when joining by hand.




these lines are at the same angle




Nice and smooth, and hopefully straight...




It looks like it worked. Here are those two lines, parallel as
I said they would be.





Out of sequence picture, cutting the second tapered edge


Each piece must be marked and joined to its neighbour in a custom fit sort of way. Though in theory, one should be able to cut all the parts with the same percentage of width to the wide end, in reality, even one degree of variance would put the whole thing out of round very quickly. The solution is to join two pieces together, mark where they fall on the template, put down the next piece and mark it to fit the preceding one. I used a giant compass to draw the template in the first place, so using that template in its original position, and a long straight edge, I am able to keep the angles accurately.




Straight edge and center point


Each new piece is laid over the line of the preceding piece and marked for cutting. Once the joining has been done, however, it will no longer be exactly in the correct place, and each subsequent part gets 'corrected for'.

The arrow points to the leading edge of the
preceding piece.




Showing the correction which must be made in the next
segment after joining the two pieces. (actually the
two arrows are backwards, but you can get the idea.)




FINALLY - SPRING!!!!


Here all the pieces have been joined and laid out, including the four pieces which will make up the two leaves.




The next step involves making all those part into one whole table top. I could just glue them all up, but I do not like relying on glue alone; I much prefer a mechanical means of attaching parts to one another. I first encountered the method used here whilst studying 13th century altar panels, but have subsequently learned that this method was still in use into the 17th century. It involves inserting a loose tenon into both pieces and then inserting dowels through the timber and the tenon.



Drill and then chisel. The drill is a brace from the early
part of the 20th century. One of these days I will
find an antique one.





The floating tenon; the off-set boring is clearly visible.
The tenons are oak.



In order for the tenon to do its work properly, the holes must be drilled in the table top first, then the tenon is inserted, marked, removed and bored separately; slightly offset to the holes in the table top. Once the pin is driven through the holes, it will, on account of the offset, pull the parts more tightly to one another. This method is called "draw boring" and is an ancient method of keeping mortise and tenon joinery tight. When you drive the pins in, you will be able to feel them following the hole, as they tend to lean one way, then back the other slightly, on passing through. I have restored dozens of pieces of 17th and 18th century Continental furniture which are joined in this way and the joints are usually still tight.



Cutting a tenon on the end


One more thing that needs to happen before the pieces are permanently affixed is that they need to have a tenon on their ends which will fit into the edge rail. The end of each segment of the top needs to have a slight arc to it, in accordance with its portion of the circle, but that will not be done until the whole unit is joined up. It would be much more difficult to cut the tenons after the whole thing has been fit together, so I initially cut them a bit short. Once the centre section of the top is all complete I will then mark out the radius and trim the tenons back to the final shape. 

Speaking of the pins; they are made from some of the scraps which came off the edges. I cut them long enough to get four pins from each piece. I pound one into the hole, cut it off, point the end, then drive it into the next and so on.


cutting dowel pins


Finally, the pieces are glued together and the dowels driven home, then cut and trimmed flush. The final stage in this part of the process is to use a cabinet scraper and level out any slight variance where each segment meets in order to have a smooth surface. In addition to being functional, the pins will add a bit of a decorative element to the top.



Four pins which secure one of the
floating tenons; several more pins
await the saw.


I will join small sections of the top together in this way, then plane the backs of them even with the scrub plane before joining them all together. At this point, all the timbers are still rough on the back and of varying thicknesses. I will not worry about making them smooth, they just need to have more or less, the same thickness. The critical part will be the edge which is yet to be made, this will be slightly thicker than the centre panel. It is this edge which will have a uniform thickness throughout, establishing the visual dimension of the top.

That border and the parts which will make the skirt will be the topic of the next posting on this table; they have to be steam bent. This week I will be making my steam box for that purpose.  Before I bend the parts though, I have to do the carving to the skirt pieces; it will be easier to carve them whilst they are still straight than after they have been curved.

This blog is about, and for, many things, but one of the goals which I hope to accomplish is showing those who do not know, the time and effort making something actually entails. We live in a world where everyone wants everything instantly, and most things are made in a matter of seconds on machines or by robots, I feel it is important to share with people the process that goes into actually making something. I hope, by doing this, that at least some people will gain a greater appreciation for non disposable craftsmanship.





Videre Scire



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Cheers





2 comments:

  1. Johann, love the progress on the table. Amazing workmanship!! Looking forward to seeing the finished piece.

    ReplyDelete