Wednesday, June 30, 2010

Building A Gramercy Bow Saw

Wow, summer's here and the time is right for ... everything! Too many things competing for too little time. I'm a little behind on posting projects here.

Back when I ordered the Gramercy holdfasts for my Roubo workbench, I also ordered the parts to build one of their bow saws. This consists of the blades and brass pins. Joel has all the plans and instructions posted on the website.

Let's get one little faux pas out of the way right off. Joel uses hickory for the frame. Great, a couple years ago I bought one board each of a bunch of different domestic and exotic species from The Woodery, so I had a piece of hickory buried in my stack. I dug it out, thinking I had gotten a bigger piece.

After a few different steps working it, I started to think this was more like a tropical hardwood, especially on the glass-like end grain. This wood was darker than the wood in the Gramercy photos, but it was clearly not rosewood or padauk or bubinga or cocobolo. Finally I checked a little deeper in my stack, and I found that 8' piece of hickory. So what was this stuff? It had a wonderful scent when I cut it, peppery with a strong cinnamon.

Checking the Woodery website, I finally identified it as Honduras rosewood. I was used to seeing darker rosewood. No problem, Honduras rosewood is a good choice for tools. The only issue is that it has at least a 20% higher specific gravity than hickory according to the figures I've seen, making the saw a little heavier. Part of the charm of this saw is its light weight for easy handling.


Rough-cutting the pieces to length.


Planing to proper thickness. This wood is like planing a piece of glass; it requires a very sharp iron.


Notching the end for starting the saw to rip an arm to width. This is especially helpful in this hard wood to keep the saw from jumping when starting the cut.


Initial rip cut.


After flipping the piece over, ripping from the other end to complete the cut. And hopefully the twain shall meet.


Jointing the cut edge of the remainder so I can gauge it for the width of the second arm. Not really necessary, but this wood is fun to work, it's so crisp.


Using a bow saw to make a bow saw: cutting the curved outline of an arm.


Using a coping saw for the tighter curves.


For best match, I used the first arm as the template for the second.


How do you make a bow saw if you don't have a bow saw? The kerf-n-chisel method: cutting a series of kerfs down to the outline.


Chiseling off the waste between the kerfs. Be sure to stop the kerfs well before the line in case the chisel chips too much out.


Cleaning up the rough-chiseled edge with a spokeshave.


Forming the curved mortise shoulder for the stretcher with an in-cannel gouge.


Refining the shape with a rasp.


Final shaping with the scraper.

Using the scraper on this wood was a revelation, the second big lesson on this project (after learning to tell the difference between hickory and rosewood). It took wonderful curls, acting more like some kind of carving tool. The surface it left was like polished glass. While this wood is hard and dense, it's a bit brittle across the grain, and I think it's that brittleness that makes it work so nicely with the scraper.

Next step will be tapering the arms.

(Continue to part 2)

2 comments:

  1. Be careful with the grain direction for the arms. I did my first one with some Texas Ebony and couldn't see a twist in the grain. As soon as I tightened it up, the saw self destructed. I remade it with some plain old boring oak and it came together fairly nicely. (But not as pretty)

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  2. Nice web site. Very informative techniques.

    Bob

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