Sunday, November 29, 2009

Scraper or Sandpaper?

I grew up with the notion that sandpaper was the way to finish a wooden project, and later learned that steel wool was also the way to go.

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So there is a better alternative to the dust and fine particles from sanding.

The “cabinet scraper”, correctly sharpened can produce a better finish than even some Japanese finshing plane, especially in highly figured or gnarly and knotted woods.  The blade requires some special attention – firstly the width of the blade’s diagonal edge, needs to be approximately 1.5 to 1.7 x the thickness of the blade.  Knowing this, the angle is evident.

The blade is a Hoc scraper blade, which cost about $45 and really makes a difference.  The blade is 2” wide and best sharpened this way.

Firstly hold the blade on the edge of a table top, and use a bastard file to get the initial edge.  Do not use a wheel grinder, the bastard is a good tool to get a flat edge.  Once a nice bur is obtained move to the diamond stone.  Progress to bester, then to polishing stone, all the time paying attention to a flat back and a good flat forward angle.

The final part is to properly use a Jewler’s Burninshing rod tool with some 3in1 oil work the sharp edge into a curl of steel – this is the very secret to the tool taking off fine shavings regardless of grain direction.  Even the Japanese can’t do this.

So given that there are no sanding partilces only shavings and no noise and expensive sandpaper, give me a scraper any day!

Thursday, November 19, 2009

Bronze Casting – Sand Method

Last weekend we witnessed an actual bronze casting.  Bob Darr our teacher at the Arques Wooden Boat School set up the air blast propane forge.  Simply put it is the bottom third of a 55 gallon drum that is partially filled with a special cement, an inch and a half pipe is set at an angle and functions as the fuel input into the forge.

 

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For the bronze stock, Bob tried out an old propeller shaft, which Alex cut up into small three inch pieces.  When heated, to approximately 1800 – 2000 degrees Fahrenheit

Bronze Casting

The bronze melted in about 45 minutes, and by using a modified carpenters square, the ash and impurites are skimmed off the surface.  The alloy was also seen to be burned off, as seen by a green glow to the top of the forge. 

Bronze Casting

Two people then hold the crucible and pour the liquid bronze into the forms.

Bronze Casting

Flasks are only opened the next day, to ensure that the minimum amount of the expensive petrobond sand is not burned.  Here is Alex’s bronze dolly ( used for riveting and clinching boat nails and roves )

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Unfortunately the last flask was not a great success, as the bronze was cooling down by the forth pour ( each pore was about 2 minutes ), here one can see the bronze cooled before it reached the extent of the cavity in the form.

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Bronze Casting

Here is Alex’s finished dolly.  He opted not to patina it, but michael did, using phamarcy bought peroxide and wine vinegar heated with a blowtorch.

Here is some other items Bob wanted, a mast step’s support and a bow post cap.

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( Added later a link to a ‘safer’ version of Petrobond is something called K-Bond )