Archive for December, 2008

Resawing Boat Lumber – Fleam, Rake, and Set

Thursday, December 18th, 2008

resaw resultsThere’s been a lot more sawing since the last post, and a lot more learned about saw tooth shapes.

The first board resawn is four and a half feet long and will be used for decks. I tried three different saw blades while cutting this piece. I started with the blade shown in the previous two posts, the frame saw blade from Frog Tool Co. It worked well, but not as fast as I expected. I picked up that old Disston hand saw and used it for about six inches, and found it to be significantly faster. It was a bit harder to keep on the straight and narrow. Next, I whacked off a length of 4 TPI bandsaw blade and tried it. It cut pretty fast but was virtually uncontrollable, wandering wildly away from the line no matter how kindly I spoke to it. I abandoned it quickly and finished the job with the hand saw.

The photo on the right shows the sawn surface. Imagine the black line as the cutting edge of the saw blade. and the arrow as direction of movement. We’re looking at the board lying flat with a raking light shining across it. Those neat furrows on the right side were left by the Frog Tool blade. This is the first time I’ve seen anything like that surface. The smoother surface on the left is from the handsaw. Size reference: the board is 8 1/4 inches wide and 1/2 inch thick.

saw teeth patterns“What big teeth you have, Grandma.” It’s all in the teeth.

The “Fast cutting rip and cross-cut” blade from Frog Tool co. is actually a cross-cut blade. Note the drawing for cross-cut teeth. Each tooth has angles filed into the leading and trailing edges, making it behave like a chisel. These angles are called fleam. The leading edge of the teeth lean back from vertical about 15 degrees. This is the rake angle and is typical for cross-cut saws. Steeper is more aggressive; shallower is less aggressive.

The Frog Tool blade is filed cross-cut. That is, it has fleam. However the rake angle is quite a bit relaxed and is the same on both sides ot the tooth. This rake gives the blade the very interesting capability of being able to cut equally well in either direction. I’m guessing that the less aggressive rake is what yields those furrows, by letting teeth slip and slide more easily over the softer and harder parts of the wood’s grain.  Having fleam is what makes it slower than the Disston hand saw.

Now, let’s look at rip filed teeth. They have no fleam. Instead they have a flat edge that tears rather than slices. That works well when cutting along the grain. The typical rip has a rake of 8 degrees, quite a bit more aggressive than the typical cross-cut tooth. 

Lastly, we should understand set. Set is the angle a tooth’s tip is canted to one side or the other. Set alternates down the blade, one tooth left, the next right. It’s purpose is to widen the kerf the saw produces, to keep the blade from binding, and to ease waste extraction. Set isn’t a huge factor if there’s the right amount of it. Too little, the blade binds. Too much, the blade wanders. Imbalanced, the blade goes off line to one side or the other. Set was not a factor in the performance of any of the blades I tried.

Resawing is actually a ripping operation, so there’s little surprise that a saw optimized for ripping cuts faster. My next steps are to follow Harry Strasil’s advice and convert that old Disston rip saw into a frame saw. It is a 1900 era handsaw with 5 TPI. The blade saw a lot of pitting once upon a time but was refurbished. It’s been sharpened enough times to leave teeth a variety of sizes. It arrived here surprisingly sharp, but can be better. Cut down and cast into the frame it can do this resawing job and still be used for most ripping tasks.

I’m part way through reshaping and sharpening, following Pete Taran’s very well written guide at Vintage Saws. As an aside, Pete Taran is almost single handedly responsible for a revival in crafting high quality western hand saws.

Resawing Boat Lumber

Monday, December 15th, 2008
harry-strasil-avatar

Harry's self portrait

My question about resawing very long lumber was answered some time ago on the Sawmill Creek Forums with a very fine suggestion by Harry Strasil. He offered good suggestions about using a saw table and stool for holding the work, and described very precisely how to build a frame saw tuned for the job . One of his other entries has a couple of pictures of using such saws and benches. 

As shown in my previous entry, I built a frame saw somewhat similar to what Harry described. I varied from his suggestion by using a purchased blade instead of cutting down an old rip saw.  As an aside, I recently acquired an old Disston D-8 rip saw from fleabay. The blade had undergone enough pitting that the engraving has almost completely disappeared, so I can’t date it from the engraving. At some point there was a chemical restoration that stopped the rusting and left the blade in pretty good shape. The saw nut with the Disston medallion dates between 1896 and 1917. That saw cuts so well that I decided to keep it for ripping rather than cut it down as Harry suggested.

center marking toolcenter marking gaugeAlong the way, I took a short diversion to make a marking gauge. The usual marking gauge is used to mark a prescribed distance from an edge. For this work, the task is to mark the center line along the board’s edges. The tool doesn’t need to be very refined. Rough sawn cedar flitches are far from smooth, so anything that will rumble along those rough surfaces is fine. It’s a simple self-centering gauge made of two pieces of birch dowel, a scrap of oak, and a bit of six penny nail. It would work okay as a simple rectangular slug, but I like a little more shape, and this shape actually makes it easy to cant the gauge to hug the lumber. The shape is inspired by DaVinci.

Hint for anyone making one of these: If you use an aggressive auger (in a brace) to bore the holes for the pins, it is a very good thing to bore those holes in the oak stock before cutting it to length or making any decorative shapes. Don’t ask how I know.

resaw benchresaw with bobThe bigger puzzle was how to hold the workpiece. I have a pair of great saw benches that are exactly the right height. One of them now has a simple modification, two vertical rails added between an end stretcher and the top of the bench. They are mortised into the bottom of the bench top and screw attached to the stretcher. The space between them is about 1 and 1/2 inches. The space from stretcher to bench top is 10 and 1/2 inches. Most any board I want to resaw can be stood on edge within that space. Then, wedges are used to center the board vertically and to push it up against the bench top. The fit snugs up nicely enough to not need any other clamps.  This ended up being a very simple solution which seems to work well. I haven’t yet discovered the saw blade’s optimum attack angle, but will soon. The ergonomics feel right with the saw just wide enough to be evenly guided by knobby knee bones.

resaw 16 footerThe test piece shown in the first pictures is about four feet long. When I get to resawing a sixteen foot piece, I was expecting that I would need another pair of vertical rails installed on the second saw bench. Not needed. A quick set up finds that a simple pair of wedges on that other bench will be enough. Time to find some good music and get to sawing.

New Frame Saw

Saturday, December 13th, 2008

frame sawA few new cedar flitches are acclimating themselves to the shop. In the meantime, I’ve been busy preparing a saw that will be used to get planking out of that cedar. This saw’s main work will be resawing, slicing thickness from roughly 4 quarters to pairs of roughly 2 quarters boards. Getting two boards from each flitch is the goal. Most people would use the bandsaw for this job, but mine is good for only 6 inches of resaw capacity, and some of these boards will be from 8 to 10 and 1/2 inches wide. I would rather have a good hand tool method than invest yet more in the band saw.

This frame saw derives from Josh Clark’s “Making a Frame Saw” article. I used red oak, 1 and 1/2 inch square, for the stretchers. The arms were gotten from a piece of the same oak, resawn to half thickness. The blade is also 1 and 1/2 inches wide. I found it at Frog Tool Company in Dixon Illinois. Frog Tool Co is interesting. While they have a simple web presence, stuff can’t be ordered online. Their online catalog looks like scans of a newsprint catalog. To order something, call the proprietor, get up to date prices, and send a check. Yep, old fashioned, but it appears to keep the prices low. I dropped the check in the mail on Thanksgiving Thursday and had the blade in hand the following Thursday. Good service!

frame sawAs Josh suggested, I used half-blind dovetail joints. saw fasteningWhile I’m skeptical that the forces on the saw actually need this kind of joint, I saw it as opportunity to learn to do them. First time doing dovetails. I cut the tails on the arms first and did a couple of practice pockets on scrap wood. Then, did the real ones. Each one gets better, and yes, that’s the last one thats shown in the picture. All are snug enough to require gentle tapping to assemble. No glue used so far.

All edges are chamfered, because I imagine I’ll spend quite a few hours using this saw. I’m an Art Deco fan, so the upper arm has a series of stop chamfers in an Art Deco motif, and a wing nut to match. The wing nut is simply a wooden shell covering a 3/4 inch metal nut.

The first cut, on a 7 inch wide board, shows the saw will indeed do the job well. Planing will be needed to smooth the cut surfaces, but that was expected. Now, all I need to do is figure out how to hold a workpiece that’s 16 feet long.

New Bow Saw

Saturday, December 6th, 2008

A few weeks ago, I cursed a wretched coping saw as I cut the oval hatches in the Fiddlehead’s bulkheads. A week or so later, I needed a turning saw to cut the long gradual curves on the Fiddlehead’s bottom, and actually hacked together a temporary saw from a hacksaw frame and part of a used bandsaw blade. It worked, but it’s a good thing the curved line wasn’t too far from the edge of the board.

Those incidents led me to make a bow saw. Of the available designs, I found the Gramercy Tools design most appealing. The design is classic, yet uses a moderm pair of brass pins to hold the blade. The pins can accommodate blades that already have pins pressed in, or blades that have open eyelets. The Gramercy bow saw is available from Tools for Working Wood as a completed saw for $139.95, or as individual parts. Gramercy offers a very complete set of drawings for people who want to make their own. I chose to buy only the pins and blades and make all the wooden parts myself. While they use Hickory, I used Oak because that’s what I had on hand.

Features that appealed to me are: the classic style, the curved faces of the mortise joints on the stretcher (fun cutting them, allows for slightly varying blade lengths), and the subtle sculpting of the various curves and edges, including a finger rest near the base of the cheeks.

The pins are glued into the handles with epoxy. I used a couple of coats of boiled linseed oil for finish. It still needs a good cord for tensioning. The fuzzy hemp is temporary, enough to try it out. The blade is 12 inches long. This blade is the coarsest of a set of three, 10 tpi.

That little squiggly block of wood represents the first cut, an S shape about an inch long, through 4/4 cedar. The saw ends up being very light and pleasing to use. While I thought the handle a bit small when I was turning it, I find that it falls very naturally into the hand. Gramercy did a fine job on the design. This one is a keeper!

For Luke and Dan: Yes, I used electrons while building this saw. I used a bandsaw to resaw the oak to useful dimensions, and I used an ancient miniature lathe to turn the handle, toe, and toggle. The lathe was only moderately easier than hacking them out with a pocket knife. Oh yes, there are also electric lights in the shop. The remainder of the making used hand tools, rasps and the eggbeater drill.

So now, we’ll have many fewer colorful words while sawing.

Update (12/13): Those brass pins from Gramercy are so smooth that the saw frame wants to rotate around them a little too easily. More tension? The blade already sings a high C when plinked. A small sliver of 320 grit sandpaper inserted along with the pin provides exactly the right friction. For long time coping saw users, this saw is a great upgrade. Break the habit of taking short stokes, Use the entire length of the blade and be amazed at how easily the saw works.

Setup Complete

Monday, December 1st, 2008

The outside temps are up for a couple of days, making it easier to get the shop to 60 degrees. The bottom is now glued and screwed in place.