Monday, June 30, 2014

A Square Deal (10)

Back to the shop for some furniture work, after the past week's activities revolving around the Boston project.


After rough cutting the tenons by way of my portable grooving machine last time out, the table top had remained well behaved. Every time I am at the shop I check it with a straightedge and make any required minor adjustments to the clamps or the dunnage positions upon which the slab has been resting. So far so good, but every time I am faced with doing further cutting on the slab I tend to verge on a state of vigillance in regards to whether the top might move as a result of further material removal. As time goes on with this process, I have become more relaxed and confident about the outcome, but with solid wood there are always unknowns so one needs to remain somewhat alert to any changes as a result of cutting. I've got the sheep in the pen, so to speak, and hopefully we're at a point where the border collie need only raise an ear and the sheep will decide against further misbehavior.

Even when I'm working on other projects, I still keep this one in mind, and consider the details often, and revisit the drawing to explore new ideas that arise. I have made a slight revision to the breadboard end detailing, just a slight dimension change and have increased the number of tenons to three since last time I worked on this.

My plan for today was to complete the trimming of the end of the table top tenon shoulders, and then process the groove on each side which are engaged by tongues on the breadboard ends. My weapons of choice were two new router bits, a Whitesite 'Ultimate' pattern bit, on the left, and an Amana flat bottom dado cutter with bearing (center):

A Festool collet sits on the right. This is the second of these new bits from Whiteside I've acquired, which utilize developments in cutter geometry derived from CNC routing. They're good, but a bit pricey.

I had a couple of bits of aluminum plate left over from the jig I fabricated for the MFA project, and these turned out to be the perfect thing for aligning the top and bottom edge guides:

Here's the basic set up:

 After some careful mark out and triple-checking, I trimmed the tenon cheek and shoulder. The finish left by the Whiteside bit is excellent, with zero tearout:

Another view - these trims were accomplished using a climb cut:

The board is then flipped over  - taking pains not to disturb the metal guide rail positioning - and the opposing cheek and shoulder of the tenon are then trimmed. The target dimension for the tenon thickness is 0.5000":

Now onto the other end of the board. Here I was also working to achieve a target dimension after trimming for the entire top's length, so I was carefully checking as I set up. I have found that a lamp with magnifier is quite helpful for such tasks as spotting the marks on a ruler with 0.5mm graduations:

A look through the magnifier - I'm seeking to set a mark 71.5mm back from the cut line (this, the measured offset of the Whiteside cutter from the router base's edge), which will reference the metal guide jig:

Another check is made on the other end of the cut, again, looking to mark an offset of 71.5mm from the mark:

 Check the clamps were tight and everything in order, the completed the tenon trimming. I also took an extra minute and plowed out a few notches from the waste portion of the cut on each side as a means of reducing the wood grain's leverage to move the slab:

This step was probably not absolutely necessary, but it didn't hurt anything either. I wasn't sure at that point if I was going to remove the rest of the waste from the tenon cheeks or not on today's slate.

Next step was to plow out the grooves for the breadboard end tongues. Changed out to the Amana bit, set it up, and made the first cut:

At the far end of the cut I clamped a block in place to prevent any tear out as the cutter exited:

Flip the board over and repeated the process on the other side:

Then repeated the same two cuts on the other end of the board, to complete this stage.

After some mulling, I decided I could remove the waste from the tenon cheeks without affecting later cut out steps. The shaper seemed like a convenient way to accomplish that task, so I placed an Aigner auxiliary support table on the front, slid the sliding table forward a bit for extra support, and adjusted the cutter to position:

A closer look at the material removal nexus:

After a first cut had less than ideal quality, I decided to use a different cutter and reversed the feed direction. Here I'm halfway through the last tenon cheek:

The cutter was set to leave about 0.01" of waste proud, which I then removed with a hand plane:

After all was said and done, the tenon is now cut out on both ends of the slab, and the slab has remained doggedly flat throughout the process:

A final look at the joinery after today's work was complete:

Of course, I'm not planning to have one mega-tenon here, there is still a fair amount of cut out remaining to define the three tenons, the stub tenon, and the end joinery work after that. Things are rolling along well however, so I'm feeling pleased with the progress so far.

Thanks for coming by the Carpentry Way. On to post 11.

Wednesday, June 25, 2014

Gateway (XII)

Post 12 in a continuing series on the design and construction of a new gate for the Tenshin garden at the Museum of Fine Art in Boston.

Driving to Boston takes me 2 hours each way, in the best of traffic conditions, so I am careful to plan my trip as carefully as possible in advance so that when I get to site I have all the bits I need. Despite this, I find it quite difficult to execute this plan to perfection. It seems very hard to be perfectly prepared, and I often find I am short some little item. Sometimes my helper Matt comes through, either having the piece we need in his van, or making a trip to obtain something we need on his way to site.

I just found out there is a building supply store a few miles from site, but this didn't help yesterday - as far as I knew there was nothing nearby. This entire process (working out on site) would be a bit different if it was something I did all the time - I guess I would set up some sort of trailer with supplies well stocked for unforeseen eventualities - however this is the first job away from my shop in years so I am not totally set up for off-site work. I'm doing the best I can, but I do find it a bit stressful at times trying to anticipate every eventuality.

Yesterday was the day to pour concrete for the new foundation. I awoke in Greenfield to find overcast skies, and I thought conditions couldn't be more perfect, however when I reached Boston, the skies were clear and the temperature over 80˚F, so conditions were a bit more challenging for concrete work. I arrived at site, with my helper a few minutes behind, and we spent the first while shlepping bags of concrete out to the garden and getting the mixer set up, etc.. Then we set up a string line between the two concrete walls where the main gatepost centers are to be located. The string line was affixed to a wooden cleat on the end of each wall, and the cleats were fastened to each wall using concrete screws.

Now, one of the walls was forgiving of placing Tapcon concrete screws, while the other was not, and we snapped a few screws off. I thought I had packed a box of Tapcons, however it was not to be found. Turns out it was in the trunk of my car, and I brought the truck to site, so there you go. Fortunately we managed to get the cleats attached to the wall, but it came down to the very last scrounged screw dug out of my helper's van.

Here's the set up, which is the same on the end of each concrete wall:

The cleat below fixes the threaded rod for the wall post at a precise offset from the wall, while the cleat above is for the string line anchor. You can see the inked centerline on the concrete that was used to align both cleats, checked with a spirit level before the fasteners were fully tightened.

With the string line in place, I could place an aluminum positioning jig, starting with the front rail alone, and later connecting up the rear rail. Here's the jig completely set up:

I spent the weekend constructing the jig after having traveled down to Yarde Metals in Southington Connecticut to obtain the raw materials. The jig uses 2"x3" box section extrusions, connected to one another with doubled 0.250"x2" flat bar links. The jig employs a pair of cables to tension the works together - measuring the diagonals on the cables until they are identical ensures that the rear extrusion is centered to the front extrusion:

In the above photo, close to view is the main threaded rod which will be used to fasten the main post to the foundation. It's a 1.125" diameter high-strength stainless threaded rod. The rear post rods are 0.75" stainless. A wooden 'fork' is screwed to the side of the forms on each side to firmly hold the extrusions in position. Many checks were made to obtain the correct alignment of the four threaded rods and the position of the rods relative to the opening in the wall, and getting everything level and plumb as required. You really can't be fastidious enough in setting this sort of thing up prior to pouring concrete.

Another view:

Not readily seen here are that the bolts holding the cables had been turned in a lathe by a local machine shop so as to leave a raised nubbin on the center of the bolts, making it much easier to check the diagonals with a measuring tape, bolt center to bolt center. So, how about a close up?:

Next, a view down the line - this gate will be precisely centered in the wall opening, which also means it will be centered to the stone paving:

The target depth for the threaded rods was that they be buried 11.5" deep into the concrete, however existing concrete made this not possible at each location. At worst though, the rods are buried 10" or more and I'll have to trim a little off the top of the rods later on to bring them to target height. That's plenty of depth into the concrete  so the anchoring will be robust. The above photo also clearly shows one of the details about the flagstone paving, which is that it crests in height right in the middle of the opening for the gate.

Then came time to dance with the concrete. Anyone who has poured much concrete will know that it waits for no man and this went doubly so given the midday temperatures over 80˚F (27˚C). In order to keep the waste concrete from hardening inside the mixer barrel or just setting up too fast generally, we had to keep going pretty much continuously for three and a half hours and keep the mix slightly wetter than I might have liked. There was absolutely no time to breathe really. Trying to keep the mix on the dryer side seemed to lead to the mixer producing a bunch of rounded concrete balls inside the mixer so more water went in. It would have been good to have had some concrete retarder on hand but I hadn't thought to obtain any. Trowels, shovels and buckets had to be continuously washed and rewashed to keep concrete residue from hardening and making a mess of things.

Adding to the excitement was the performance of the mixer itself. At the rentals yard, the fellow told me that though the mixer was supposedly rated for two bags worth of concrete, in reality it could apparently handle 1.5 bags. This turned out to be an exaggeration. The mixer could only really handle about half a bag of concrete at a time. Add more concrete, and the motor would bog down, which meant that the barrel had to be physically assisted to keep turning. Possibly the drive belt started to slip but I really didn't have time to futz with it given the demands of the rapidly setting concrete. The drive gear on the mixer's motor was partially stripped as well, and mounted in a carrier assembly which allowed it to the gear shaft to slip down too low, allowing the gear to have about a 1/3 engagement with the planetary gear on the back of the mixing barrel. So, periodically one had to push the back of the shaft with a block of wood to get the gear to mesh properly. Oh joy.

The fact that the mixer could only do half a bag at a time, or 2/3rds of a bag with physical assistance from yours truly, meant that the processing of the twenty bags of 80lb concrete - 1600 lbs of material, plus water -  went fairly slowly. We added to the mix a bit of plasticizing agent, and some Portland cement. The existing concrete was primed using a mix of concrete bonding compound and Portland cement, applied as a slurry, followed by immediate application of fresh concrete. The only conveniently available size of Portland cement is a 94 lb bag, so I supplemented the ready-mix concrete with a half shovel of extra Portland cement with each bag so as to make use of the material.

Here's one half done:

The other half at the end of the day:

I had made careful estimation of the concrete required, and had brought 2 extra bags, however it turned out that we were short by two bags, so the left side rear post was left unfilled at the end of the day.

I returned the mixer to the rentals yard this morning and explained the scintillating level of performance achieved by this fine precision unit, and they were kind enough not to charge me for the rental. Sometimes things you get from the rental yard work well, and other times...not so much. If I mixed concrete more frequently I would get my own mixer, but usually I'm hacking away at wood so....

Back to site today to finish up. I mixed the remaining two and a half bags using a trough and shovel:

This was four hours of driving and one hour of work, but that's how it goes sometimes. Squishing the mix into the form, and starting to trowel it off:


Today it was over 90˚ in Boston. I sprayed the concrete down to cool it off a bit and then put a few layers of burlap on top which was further soaked:

Then I laid a layer of plastic on top of the burlap. This should keep the concrete moisture from evaporating too quickly. You want to keep it wet and cool for the first few days. Weather forecast calls for heavy rain tonight and tomorrow so that is a help.

The site as I left it:

It's satisfying to be complete through this phase of the project. Whew! It was a bit of a slog. It's kind of funny to hop from furniture making one moment to concrete work the next. I think I'll take up lumberjack sports soon, or possibly mining.

Next up, in a couple of weeks, will be the stripping of the forms and back-filling, followed by placement of the granite footings a couple of weeks after that. I will be sending drawings of the various granite components required to the company in New Hampshire that will be fabricating the parts in a couple of days, so the ball will be rolling soon. I also need to cut the metal shoes off of the kiosk footings as these will be modified so as to raise the posts further away from the soil.

All for now, over and out. Thanks for visiting the Carpentry Way, and comments most welcome. On to post 13.

Friday, June 20, 2014

Gateway (XI)

Back to site today for a few hours to set up the concrete forms for the other side of the gate. We used a builder's transit to set the forms to within 1/32" of the height of the forms already set in place on the other side:

Did you spot the chipmunk?

A few cross-straps are yet to be installed on the tops of the forms, which will only take a few minutes to complete. The rebar is epoxied in at all locations, and I brought 10x80-lb. bags of ready-mix concrete to site, which is a bit more than half of what will be required altogether. So, things are looking all ready for concrete pour next week, weather-permitting, save for the threaded rod setting jig I need to fabricate next. I'm planning to work on that on Monday and have already acquired the necessary materials. The six threaded hold down rods are all high strength stainless steel of various diameters, depending upon location.

A view of the scene - wish I had that wide-angle lens:

The above photo is of course from the inside of the garden looking out to the parking lot.

One more, showing the side we just installed the forms in, now viewing from the entry side of the gate:

Also took the opportunity to remove all the metal shoes and brackets from site, which I took to a metal recycling place back near my home - a total of 1100 pounds of steel.

The MFA has agreed as well to my proposal to move the rear posts back slightly - about 5" - from the original locations. In the original configuration, the gate doors did not clear the rear posts when fully opened, and thus banged against the rear posts. The repositioned posts, already accommodated in the concrete forms now installed, allow the doors to tuck in as they should and will also require that the gate paving be adjusted - a situation mentioned in an earlier posting in this thread. The paving work is outside the scope of my contract, though I did bid on it. I'm kind of glad not to be doing that work though as setting irregular-thickness pavers on a gravel bed seems like a hassle to me, at least in terms of trying to achieve a surface that tens to stay even over time.

All for now. Have a good weekend, and I'll be back to site early next week, Tuesday is scheduled, to pour all the concrete. It will be satisfying to reach that stage of the job, and i hope you'll tune back in to see what unfolds. On to post 12.

Tuesday, June 17, 2014

Gateway (X)

Back to site yesterday with another fairly long day to move the foundation prep work along. Over the past few days I had put together some plywood forms based on measurements taken at site. The forms turned out to be a good fit:

After a bit of searching, I obtained some epoxy coated 1/2" rebar. The epoxy coating makes them far more rust resistant. I had the 90˚ end bends done by the rebar company, and then completed the rest of the bending on site. These three rods reinforce the 6" wide concrete beam which spans between the posts:

As you can see, these forms resemble a dog bone in shape.

A fair bit of time was consumed by chipping out loose concrete debris from last weeks cutting and jack-hammering session, followed by cleaning. Then I bored holes to accept the rebar:

I used Simpson Strong-Tie anchoring epoxy to fasten the rebar into the concrete:

My plan to to attach new concrete to old using a combination of mechanical and chemical means. The epoxied-in rebar forms the mechanical portion of the connection.

The form pictured above was leveled carefully and then fastened to the existing concrete using Tapcon concrete screws. I placed the top of the forms 2.5" lower than the top of the existing flagstones, though the stones themselves turned out to be of irregular thicknesses. Some flagstones were 2.125" thick, others 1.75" and some only 1.25" thick. By keeping the forms 2.5" below the top of the existing flagstone height, I can accommodate the placement of flagstones of any of the thicknesses around the concrete. Better to expect worst case scenario sometimes, and since I won't be laying the flagstones, I want to forestall any potential problems.

At the end of the day I elected to do more jack-hammering, knocking off the remaining concrete from the metal shoes so that the metal can be recycled:

That was two hours of my life I'll not be getting back, if you know what I mean. Those shoes are heavy suckers too - the biggest ones are, I would guess, 150lbs each.

The remaining forms were left at site and I have done the preliminary work to fit them, however I won't fasten them in place until later this week when I can bring a builder's level to site and set them relative to the height of the one already placed. That will require my helper Matt, who has kindly agreed to come to site later this week to keep me on the straight and narrow.

Today I went to the drying facility to check up on the Port Orford Cedar, which has been sitting in dehumidification for a couple of months. To my surprise, quite a bit of the material was already dry, down to between 8% and 14%:

All the material in the above stack is now dry and has been removed from the kiln. Again, I was surprised so much of it was ready so soon. The degrade was minimal, though the stock was not totally devoid of checks.  Even though all the stock is free from heart center, I still had a little bit of checking here and there on the 8"x9" rear posts, so I am wishing I had put relief kerfs in those sticks. I didn't think that their rift grain orientation would precipitate checks, but this was not 100% true.

View of the end of the stack:

The stock marked '10' on the ends isn't for this project. It's sugar pine, and has ZERO checking.

The biggest timbers, those for the main posts and main crossbeam, will remain in dehumidification for a few months yet - they are down to 20% M.C. or thereabouts, so they are definitely getting closer than when they stated. It's looking like I won't need to do any vacuum kilning after all, so that saves a bit of money. It's nice to be able to bring the wood down in moisture content by a slower and gentler means, though vacuum kilning does work incredibly well for larger sections.

The relief kerfs on the chunkier stock have been doing their job by and large:

On this one though, the kerf didn't open up too much at all, at least not so far:

Some of the bonus 'mistake' pieces, where I received several 48" long chunks of beam instead of a 17' long beam, were drying well:

Not sure what there are going to grow up to be.

Well, a little end checking here and there, and little face checking here and there, but overall the material is looking good. Now I'll have to make room in my shop somehow for this material. I expect to move it over to the shop over the next couple of days.

All for now, over and out. On to post 11

Saturday, June 14, 2014

A Square Deal (9)

Post 9 in a series describing the design and build of a coffee table, end table and maybe more, all in solid bubinga.

Feeling confident that the table top slab would remain reasonably docile, I decided it was time to trim the slab to length and rough cut the tenon ends.

I referenced the layout off of the stress relief grooves on the underside of the table. Here are some of the layout tools I, ah, brought to the table:

Once I had determined the end cut lines, and triple-checked everything, I set up a long ruler against a machined straightedge to act as a circular saw guide:

The off cut is a fairly unique sorta piece really, but it went into the firewood pile all the same:

Ends trimmed to length, I then set up a second straightedge underneath, and use a double square to bring both straightedges into alignment with one another:

A closer look:

Once the straightedges were set up accurately, I used them to guide the knife lines defining the ends for the table top surface. These lines define the abutments for the breadboard ends to be fitted later on:


 Both sides then complete through this stage:

With a cleanly cut edge to reference against, I brought my groover into play to hog out most of the waste for the breadboard end tenons:

Both ends done on both faces:

A closer look - some anchor seal was applied to the end grain for the time being:

I still have to do some final trimming of the abutments, but I'll let the table sit for a few days more yet and see how any possible changes in board stresses as a result of the material removal might resolve.  I expect that the material removed will further weaken the ability of the board to mechanically cup across its width.

A commenter in an earlier post asked for a picture of the top with some alcohol on it to show the figure a bit better, so here goes:

It'll be dang pretty with some oil on it later.

Thanks for stopping by the Carpentry way. On to post 10.