March 21, 2010

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Readying the drawboring pins, and applying finish to the dust cover

March 4, 2010 By Al Navas 4 Comments

As I stepped out of the shop, I noticed the temperature gauge in the shade, on the wall of the wooden shed:

The thermometer caught my eye.

I had to look. Confirmed! I might be able to get away with spraying some lacquer today. The temperature was just above 40°F:

The first time over 40°F in weeks!

In the shop, on the outer wall to the finishing room, the thermometer has held between 66°F and 68°F for the last several weeks:

Master thermo-hygrometer, on finishing room wall.

The remote unit, near the West wall, and on the lumber rack, showed a slightly lower temperature, but still acceptable to spray the finish:

Remote thermo-hygro, at lumber rack.

In the finishing room, with all the equipment set up and ready to go, I started adjustments on the spray pattern, and air and liquid flow – I like to use craft paper as the target to make the adjustments:

Adjusting air and liquid flow, for optimum spray pattern.

During the Winter months I use a small ceramic heater in the finishing room; I use it to keep the temperature at 73°-74°F. It is powerful enough to keep the temperature in the room at 73°F with the 2,200 CFM exhaust fan running. In Winter I am typically limited to about 12-15 minutes of spray time before the temperature in the open part of the shop drops several degrees as the make up air comes in through a window. I should have waited until tomorrow, or the day after, to spray, as the outdoor temperatures will be in the high 40s; but why not today? Aw, heck, just get it done!

Following a short session spraying the lacquer, I moved on to preparing the pins I will use in drawboring the joints. I found a huge amount of oak dowels at the local home center, and proceeded to select those with the straightest grain (I don’t own a plate, to make my own pins). To minimize measurement errors, I decided to use one piece of dowel, pre cut to 2-3/4 inches, to measure all the others:

Measuring drawbore pins.

I have been readying the band saw for a presentation on resawing lumber to our Guild next week; as a result, the guides and blade are off the 17-inch machine. Why not use the Kenyon replica dovetail saw (made by Mike Wenzloff) to cut the pins to size? Of course! That made sense:

Cutting pins, using dovetail saw.

Some people prefer to cut with the dowel vertical to the workbench:

Another way to cut the pins.

I had a great day in the shop. The outside temperatures and the sunshine have been a welcome addition to the time spent in the shop. Have you:

  • Been able to do much work in your shop, or is it too cold?
  • Applied any finishes during the cold Winter months, or are some projects waiting for warmer weather?

Drop me a note to let me know about your time in the shop during the last several cold weeks.

— Al Navas

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Filed Under Blog, Finishing, Joinery, Mortise, Tenon Tagged With dovetail saw, drawbore pin, finish, technique

The stand-up desk: drawboring the joints, and starting the finish

February 15, 2010 By Al Navas Leave a Comment

I finally reach the point at which all the preparation of the joinery leads to careful pre-assembly layout for drawboring the mortise and tenon (M&T) joints on the desk. For example, for the leg stretchers, I drill only one hole using an egg beater drill – the tape marks the depth for other holes, such as on the legs:

I find it important to keep track of which side will eventually be up, and which will be facing the floor:

I always make a spare of everything, including legs. This allows me to test the joinery; in this case I am able to test the offset for drawboring, to ensure truly tight assembly of the joint:

The pre-drilled joint:

And testing for offset of the holes, which will allow pulling together the joint truly tight – - the holes in the tenon are offset from the holes across the mortise by approximately 1/32″, and closer to the shoulder; it is this offset that allows pulling the joint tight:

The pegs I will use to pull together the joints on the legs will be 2-5/8″ long:

The front aprons also will be pulled tightly to the legs by drawboring. In the following photo I am marking the tenons from the already-drilled holes on the leg:

Once the drilling is finished, I turn my attention to sanding, in preparation to applying the finish. To avoid rounding corners unnecessarily, I place the two leg stretchers together on the bench, and sand them in tandem:

The larger pieces, such as the legs, are sanded first with the random orbital sander; then I sand the corners by hand, using one grit higher, and sand lightly to avoid leaving scratches:

In preparation for dark toning the dust cover that will also be the support for the drawers, I apply two coats of a wash coat of dewaxed shellac to the surface that will be under the desk, facing the floor:

I am getting close to being able to do the final assembly, followed by application of the finish.

Finishing tip/preview: Some of you will wonder why I apply the wash layers of dewaxed shellac. I do this to ease the process of applying the finish. I will also be applying a wash coat of dewaxed shellac to all the aprons and the drawer fronts, which are made of white oak. This is crucial, as the shellac will isolate the highly acidic (that is, low-pH)  white oak surfaces from the waterborne topcoat I will be using. Why is this necessary? Waterborne coatings are typically high pH, around 10, or even higher; if used directly on high-tannin woods, pin-holing of the topcoat is very likely to result, with ugly results, and ruining of the finish. Using dewaxed shellac isolates the wood surface, paving the way for a beautiful finish using a waterborne alkyd varnish. This makes it much easier to achieve proper leveling of the four topcoat layers I will apply.

Related posts:
Additional reading about the stand-up desk.

— Al Navas

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Filed Under Blog, Education, Joinery, Mortise, Tenon Tagged With drawboring, finish, Joinery, Mortise, Tenon

Preparing a hollow mortise chisel

February 4, 2010 By Al Navas Leave a Comment

One question from a reader prompts me to illustrate the process I use to prepare hollow mortise chisels before I even approach the benchtop mortiser.The process is called “tuning a hollow chisel”; it prepares the chisel for efficient cutting of the mortise, and eases penetration into the wood while minimizing burn marks. This results in smoother mortise walls, faster cutting, and better chip ejection while keeping the chisel cooler. So far I have not had to sharpen any of the drilling bits on any of the chisels.

In this photo you see the hollow chisel as received. The grinder marks are plainly visible:

Just like a bench chisel, the sides of the chisel should be lapped using either sandpaper or, as I show here, with sharpening stones. Following preliminary lapping on the 1,000-grit stone, I continue with the 6,000-grit or finer stone:

In this next photo you see how the steel begins to shine, and the tool marks have disappeared near the cutting edges – not quite ready for work, the chisel is getting close to being ready to cut:

Next I use a diamond-covered abrasive cone, to sharpen the inside surfaces of the tip of the chisel. The cone holder is part of a set available from various sources:

Careful inspection is a must, before using the chisel. Look carefully at the inside surfaces, to make sure the cone has left smooth, shiny surfaces:

Yup, that is the BenchCrafted tee shirt. And it is a shameless plug for the company that makes, along with 11 other winners, the Popular Woodworking magazine’s Best New Tools for 2009, the BenchCrafted Tail Vise. I was the lucky recipient of one tee shirt at the Valley Force conference:

To my friend Jameel Abraham, of BenchCrafted.com, and his brother Fr. John, congratulations for winning the award – it is well deserved!

Disclosure: I am a happy owner of one BenchCrafted tee shirt; I have no commercial or any other interests in BenchCrafted.com. And I love the vises they make.

— Al Navas

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Filed Under Blog, Education, Joinery, Mortise, Sharpening, Tenon, Tutorial Tagged With chisel, Education, hollow, Joinery, Mortise, Sharpening, Tenon, Tutorial