Sunday, November 2, 2014

A Square Deal (35)

Post 35 in an on-going series - previous installments can be found in the 'Blog archive' to the right side of the page, and each post links to the next at the bottom of the entry.


It's time to button up many loose ends on the side table as we move towards finish...

Planing the perimeter of the table top assembly:

Checking as we go with a square to keep things where they should be along the edge:

I also mortised the central tenons on the slab for the rectangular pegs to be fitted through the breadboard ends. The peg mortises have been marked out on the hammerhead keys, but that mortising has not been tackled yet.

I trimmed the table corners back with a facet so nothing potentially sharp is in the way of the lower thigh, and put a concave bead around the underside of the top:

The outer corner of the hammerhead keys will be shaped to follow around the blunted/faceted corner. The top edge will have either a rounded over treatment, or a chamfer - likely a chamfer.

Chamfering is one of those project tasks that can seem like an afterthought, however it really is not. Failure to anticipate how surfaces will intersect after chamfering has been done can lead to disasters. So, I'm most careful about this part of the job.

Also ran a concave bead down the outer arris of the legs, creating this form of intersection with the mitered apron pieces at the junction:

Preliminary stage yet with this detail. The proud corners of the apron miters are yet be relieved also with a concave bead - wait for it - and I'll slightly deepen the concave bead on the apron outer upper arris.

Also re-did the arris treatment on the stretchers, previously a simple chamfer, as a concave bead - here's a detail:

The bronze leveler feet have been an ongoing puzzle. I initially looked to the idea of sand casting them myself, or possibly lost wax casting. I have a book on how to do that and it looked interesting, but, ah, time to spare is not something I feel I have right now. Then I looked to have the parts sand cast by a foundry near Boston, and while the price per unit was reasonable, all the parts would have to have a pattern made with a draft and compensation for the material shrinking as it cools. So, a bunch of machining work on the front end, followed by more after the casting is completed. Time, money.

Thinking about it from a machining perspective, I then looked into getting the leveler feet CNC machined. I sent some drawings to a company and they came back with a price - more than $2000 for the feet for both tables. So that was out.

Then I had a third idea, where I considered how the feet could be made from two pieces of bronze instead of one. The stem of the leveler could come from some bar stock, while the foot pad could come from plate stock. The two parts could be mortised and tenoned together, either by press fit, or soldered fit. So, I looked into that, and found a supplier of aluminum bronze with just the sort of pieces I needed, and a willingness to sell in small quantities. The bronze stock cost about $220, and arrived yesterday. I took the material to a local machine shop, along with some detailed drawings, like this one:

The stem material I bought is already 0.75" square (and 1.0" square for the coffee table), and the plate is 0.375" thick (0.5" in case of the coffee table), so there is only a modest amount of machining required compared to cleaning up castings. At least it looks modest to me. The interference fit issue is no problem for the machinist anyhow. So that ball is rolling.

I'm going to patinate the feet a color to match the bubinga fairly closely, and from my book Patinas for Silicon Bronze I selected one called Red Marble. I had to buy some stuff called liver of sulfur (sulphurated potash) and some silver nitrate, which are a world of unknown to me, but the 'recipe' looks simple enough to follow. I need to pick up some red oxide as well. The patination process doesn't take too long to do, and I will try it on some test pieces first to see what happens.

I've started working on the wrought iron pull for the drawer. I'm planning to do some chemical etching on that, so more new stuff to explore.

Back to the wood.

I trimmed the apron miter arrises down to meet the corner double miter:

As seen above, the left side apron miter is still about 1/64" off the surface, but that will be no problem to feather down.

Next corner, where the surfaces we a lot closer to a match:

Number 3:

Above, the right side apron miter surface is slightly proud and will need to be feathered down.

Another one:

Somehow took two pictures of corner 3 and omitted to take a picture of corner 4. Oops!

A round of final tuning still required on those connections. I will peg the apron frame together after I finish plane the under surface and front surface of those parts, and then see if further tweaks to the miters will be needed. I post also locks to the apron with a wedge through the tenon, for which I have yet to cut the mortise, but it is marked out.

A look at the stretcher with concave beads on the arrises, and the peg mortises for connecting the stretchers, a tiny size of 5mmx6mm, are also complete now on the posts:

Gradually ticking off items on the punch list. Hoping to have finish on the piece later this week.

All for now - thanks for dropping by the Carpentry Way. Onward to #36.

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