Friday, August 11, 2017

The Roubo Frame Saw - Part 1

For a long time I've thought about purchasing a band saw.  Mind you, I don't have the space for one, but that doesn't stop me from thinking about it.  Band saws can do a lot of things, from cutting curves to resawing thick boards into thinner boards.  My interest was in the latter.  After some research and reading, I decided to make something that would fit in my shop and allow me some resawing capability.  I ordered a Roubo frame saw kit from Blackburn Tools.  When the kit arrived last week I was giddy with excitement, but a little worried about the condition of the package.
Bent package
Turned out not to be a problem at all.  The parts were well wrapped and the package was stuffed with wadded-up brown paper.
Kit components
I got the 36" saw kit.  Isaac Smith, the proprietor of Blackburn Tools, will sell these with the blade unsharpened and the teeth unset or with the blade sharpened and the teeth set.  I chose sharp and set.  The saw plate is 0.042" thick and the total set is somewhere around 0.052-0.055 (difficult to measure).

The brackets are heavy 1/8" thick steel with a slot cut on one end to accept the blade.
One of two brackets

Slot for the blade
Slot on other side.  Guessing this was the "exit" side of the tool that cut it.
Note: that roughness was only at the surface - it was perfect on the inside surface.
The brackets apparently are welded at a seam that can be seen on the inside.
See the weld?
Closer view
This took only a minute or two to file away with a coarse file.
Hump filed away
A heavy eye bolt provides the mechanism to tighten the blade.  The small end of the eye bolt is tapered to fit into a conical hole in a bearing plate that is housed in a mortise in the handle.

Speaking of the handles, let's get into the making of the frame.  I had a big chunk of 2" thick poplar and got all four parts from it.  The final thickness of the frame members is 1 5/8" and I took a couple days to get it to final size, allowing some movement overnight (twice) before planing to final dimensions.
Wood parts ready to go
Initially, the shorter handle pieces were cut over long, 25" to be exact.  The plan provided by Blackburn had a 24" handle.  I'm a fairly slim guy and fretted for a long time about how wide I was going to make my handles.  I wanted the saw to be comfortable.
25" long handle stock in back, ~23" piece in middle and 20 1/2" piece in front
So I found some scrap pieces of different lengths and held them as if I was holding the frame saw handle to see how it felt.  In the end I went with 22" length.
Made an 11" template to mark half a handle
While things were still square and easy to work with, I chopped a mortise for the bearing plate, which was exactly 1" x 2" x 1/4".  The mortise was long enough to even out the bottom with a router plane, but unfortunately the grain was diving to the right (in the picture below) and that side was not nearly as smooth on the bottom.
Mortise for bearing plate
At first I kept the mortise depth not quite the thickness of the bearing plate so that it would sit a little proud of the surface.  I was thinking that some wood compression might sink the plate more fully.
About 1/16" proud
Turned out this didn't work, as the dimensions of the blade and stretchers were such that the blade couldn't reach the keepers.  So I had to fully sink the plate.
Bearing plate flush with surface
I didn't get pictures of the mortising and tenoning of the frame members, but here she is dry-fitted.
Well, I was zinging with anticipation, so I made a small test cut even before shaping the handles.
First test cut - oh, man this felt good
Back to the shaping.
After marking the shapes (including the round-over areas) ...
... made a bunch of stop cuts
Then chiseled out the waste, chiseled close to the lines, rasped and filed smooth and got handles I was happy with.  No in progress pics, but here are the parts after applying a couple coats of BLO.
Soaking up some BLO
And here she is assembled.
The handles are comfortable and I like the way it looks
I shaped the handles a little differently from the way the plan laid them out.  In the plan, the rounded ends extend all the way to the bottom edge of the board (yellow arrow).
Red arrow shows bottom location of my handle
Yellow arrow shows the plan location
But I was a little worried that with poplar I might get more flex than I wanted.  In the plan, almost 7/8" of material is removed from the top edge, making the final width of the handle about 2 1/8" just inside the stretcher mortises.  By moving the handle ends up away from that lower edge (to the red arrow), I got more like 2 1/2" thickness just inside the mortises.  So far I haven't noticed any flex at all.

I've made a few practice runs at cutting up some stock.  And HOLY CRAP!  This thing can go through some wood in a hurry!  I'll post on that experience next time.  But suffice it to say, there is a learning curve involved in getting a straight cut.