Ultralight Saws

[Delmar O’Donnell]

> I have Drill Doctor on the way to resharpen the bits frequently

Keep in mind the DD requires a diamond grinding wheel, which needs replacing more often than you'd think…ask me how I know…so factor that into the price!

On hardened steel, try to grind if possible, rather than drill (and keep the heat down).

[John Donewar]

Some hikers have adopted a method of starting campfires with the use of stove fuels such as Esbit tabs or alcohol.

When we did make a campfire my hiking partner and I used some of our alcohol stove fuel. The result was a campfire fueled by decently sized pieces of broken and un-split firewood. It was wet and rainy during the majority of our trip.

YMMV

Party On,

Newton ;-)

[David Gardner]

"On hardened steel, try to grind if possible, rather than drill"

But how do you grind a hole or slot in the middle of something? Wish I knew how to do it. All my grinding experience has been grinding around the edges of the piece being worked on.

I was thinking maybe a tungsten carbide drill bit might work. $30 for a single 5/16" bit. Ouch.

[James Marco]

Well, you covered most of the high-lights.

Thick bladed pruning saws don't work that well. Any saw needs a stiff blade to cut effectively. A single mounting point means a thick, stiff blade cutting away large amounts of wood. Generally wasteful of energy when cutting to make two pieces.

A bow saw is normally used to lengthen the metal in the blade 3-5 times with the bow providing a fair bit of tension on the blade to stiffen it. The body of wider blades can bind easily in rough cuts due to the wood fibers rubbing on it. So a thin blade is needed with a fairly wide kerf. But, more body is needed to keep tension on the thin blade and to provide clearance around the piece being cut (6-8".)

From an engineering standpoint, the a partial bow saw, a triangle shape as you have designed, is the best for form stability and strength. The pieces are not independent of each other, hence are locked in a bit better. This is the old SVEN saw design, too.

A full bow saw is three pieces plus the blade in a rectangular arrangement. However, it lacks any inherrant stability, but provides greater clearance.

The average cut stroke for an adult male is about 20". Some more, some less. So a blade of 21" (counting the dead area near the attachments) plus mounting points gives about 23". I think the Sven saw is a bit short at 21". A carpenters saw is a bit to long at 32". But, a lot is what you can get used to.

The tubular design is good, but it is too narrow to hold the pressures need for good strength. Idealy, both the pull, and push stroke should be used for more efficient cutting. The push will increass the tension needed on the blade to prevent blade flutter (and binding on the wood.) Pulling will increase the tension on the the other end. There is a LOT of pressure needed to remove the blade flutter and compensate for the dynamic stresses. I would guess around 200-300 pounds of static pressure to hold a blade to a few thousands of an inch of blade kerf while cutting a piece with a constant 15 pounds of force. This is where the smaller 1/2" diameter tubes fail. You will get a lot of blade flutter and binding, unless you drop the force to 4-5 pounds. You won't cut very fast with it.

Most blades today are electro tempered, meaning only the teeth, often only the tips, are hardened. This lets the body stay softer and they can be drilled for attachment pins. Of course, some tensioning mechanism is needed. The SVEN saw uses a wing nut and a longer bolt as a blade mount on one end.

The aluminum, frame can be made from 2, flat, 1/16" thick pieces of aluminum and one 1/8" piece with a couple rivets around the blade mount, all about an inch wide. A couple pieces of aluminum can be added above to allow the body pieses to lock against when tensioning the blade. Better is a hollow tube, flattened, like the SVEN saw, though the "u" shaped channel is functionally equivalent to two pieces… Since most of the strength is in the inside corners(compression) and outside corners(tension,) the handle/body pieces can be drilled out, reducing the weight by 25-30%.

You could make a bow saw. or, simply buy the SVEN saw and modify it. In colder months, I usually just bring a modded version of this saw. With mods, these weigh around 10oz.

Since there is a lot of pines up where I go, I usually open the kerf a bit and keep the blade sharp, though a grinder is needed for the hardened teeth.

[David Gardner]

James,

Thanks for your comments and insights.

Do you have any pictures of your modified Sven? I would be interested in seeing what you did to it.

I can get about 75 lbs. of tension with my bow saw. We'll see if it's enough.

I'm very interested in comparing cut speeds with modified pruning saw vs. bow saw. I'll need to make a 12" bow saw so I can compare it to the 12" pruning saw I am currently working on. Will try to get them both below 4 ounces.

FWIW the pruning saws can be sharpened on the back edge so they can be multi-used as a knife too. Some other advantages of the modified pruning saws are that no assembly is required, they are very compact, and they're virtually indestructible. But if you're cutting a lot of wood that may not be enough to favor them over bow or buck saws.

[Justin Baker]

David, have you considered making a traditional style buck saw (with the cross bar and tensioning line/stick)?

[James Marco]

Sorry, David. It never occured to me to take pictures of such a simple way to lighten the saw. I picked up the camera to get a couple, but it is dead…ahh well. I have a new battery on order for Christmas (it was going last fall.)

Anyway it is a series of 1/2" holes drilled in the handle and 3/8" holes drilled into the bar.

I just drilled another hole about a 1/4" closer in the end of the blade for more tension, almost warping the bar. I stripped the first wing nut, but got another at a hardware store. Takes about 5 minutes to sharpen it with a dremel tool, though. It cuts a 5" oak log in about a minute. An 6" pine long takes slighty longer. In a half hour I have more than enough for a night and mornings fire. 6-7 good logs and a good pile of smaller 2-4" stuff. Worth having in colder weather. I often set up the tarp near the fire to keep condensation down. Easy to do in most of the ADK's.

[Greg Mihalik]

Justin, you asked "…have you considered making a traditional style buck saw…"

You mean like this –

– The Little Buck, with a 15" blade, 4.5 ounces.

[Justin Baker]

Yeah I knew someone somewhere had made an ultralight bucksaw, that's what made me think of it. Thanks for reminding with the link.

By the way, while the difference between a bow saw and buck saw is well established when using traditional materials (wood), the difference seems to be obscured with modern materials and tightening systems. Is the sven saw a triangle saw? Is the sawvivor really a buck saw without a support rod and cord tightening system, how is the sawvivor different from a bowsaw other than the shape?

[Derrick White]

I understand Trailblazer, the manufacturer of the Sawvivor has ceased operations. Too bad as one of the rivets recently failed on mine and I wanted to replace it. It is guaranteed for life, which is now effectively the life of the company. Smiles.

Would still like to get my hands on one. Does anyone know where there any still for sale – preferably in Canada to avoid custom charges but would buy international if no other options.

Derrick

[David Gardner]

Justin, I'm considering a buck saw right now. Have some ideas I'd like to try out. It will have to wait until I finish the bow saw though.

[D S]

For you guys trying to drill holes in saw blades, there's a technique called "spot annealing". You soften the metal by heating it until it turns "blue" ONLY in the spot where the hole is to be drilled. There are several methods – pencil torch, drill press with nail or rod, soldering iron. Google it up and decide what works best for you. Saves a lot on drill bits, sharpening, and the whole gammut.

[peter vacco]

"spot annealing ", that's a good tip. if you are troll such as i, the drill bit sort of does that as it gets dull : )

i will try it when i get to drill'n 2" blades.

cheers,
v.

[Roger Caffin]

> The lightening holes are a PITA to drill, and dull even cobalt bits after just a
> few holes, but I have Drill Doctor on the way to resharpen the bits frequently.

Go down to hardware store and buy a carbide-tipped masonary drill. Using a diamond sharpening wheel in your Drill Doctor, sharpen the carbide tip as you would sharpen an ordinary HSS drill. Note that any other sort of grinding wheel is probably not going to work (except for what is called a 'green' wheel).

Then drill the holes with the steel sitting on a hard base and using a carefully aggressive feed and a LOW spin speed. Drill press, not hand-held. Do NOT let the drill bit 'rub' – keep it cutting. Some light oil would help. The forces (and maybe noise) will be fairly high!

Trying to make the back edge of the blade into a knife is doomed to failure in most cases. Only the teeth are really hardened; the rest of the blade is relatively soft. This is deliberate and good blade design. So any edge you grind will die quickly.

Cheers

[Anonymous]

Roger, you should write a book of tips someday, both backpacking and not related.

[John Hillyer]

It's been a long time since I worked in a shop, but my first instinct would be to use a hydraulic punch. Drilling would be an expensive slow pia operation which would not be commercially viable.

[Delmar O’Donnell]

Roger, I know the DD says it's OK for sharpening carbide, but have you tried it? I'm imagining it would take a tremendous toll on the diamond grind wheel in the DD. Carbide is rough stuff! Not as tough as diamonds, but would likely give the binding material a run for its money.

I wouldn't do it just because I don't like purchasing diamond wheels frequently, but I guess it can be done. Your other advice on how to drill is good; I would add that the saw blade must be very firmly clamped. You don't want a bit catching the saw blade on breakthrough and whipping it around like a helicopter blade. I'm sure the OP know this already; just posting it for anyone who is going to try this in the home shop. The drill press is often cited as one of the "most dangerous" tools in the shop for that reason. I probably have more drill press injuries than any other shop injury (besides hammer-on-thumb dysfunction).

Honestly I like the spot-annealing tip the best so far, I'll have to try that sometime with my acetylene torch. Interested to see if I can keep the annealed spot reasonably small.

I wonder if a spot welder could anneal.

[David Gardner]

"Trying to make the back edge of the blade into a knife is doomed to failure in most cases. Only the teeth are really hardened; the rest of the blade is relatively soft. This is deliberate and good blade design. So any edge you grind will die quickly."

Roger, I already sharpened one, so we'll see I guess. I will say though, the non-teeth portion of the blades is the toughest steel I have ever dealt with and took a long time to sharpen. I once used a single cobalt bit, without resharpening, to drill 200 holes in a pair of disc brakes, which ate a HSS bit in a couple of seconds. I used the same bit on a pruning blade, with oil and pressure, and it only made it through 3 times. If that's not "hard" I can't even imagine how tough the teeth are. At any rate, when camping I usually just carry a small Victorinox and cut nothing tougher than a fish or tent cord.

John, right now I'm in R & D mode, so drilling makes sense because I can do it in my home shop. If I go into production, I will contract with a local machine shop that I have worked with before, and do the cutting by plasma, laser or water jet, depending on what they advise. At that point I probably won't even use round holes for lightening, but rather slots or triangles.

For now, I plan to try a combination of spot annealing (great tip Smoke!) and Roger's suggestion of using a masonry bit. If that doesn't fly, I'll plunk down the $30 for a solid carbide bit. Delmar, I made a small spot welder from a microwave oven transformer and will try that first. I will also try the pencil torch and nail/rod techniques for comparison.

I really appreciate all the responses and information from everyone on this thread.

[Roger Caffin]

> my first instinct would be to use a hydraulic punch.
I have this vision of punches shattering…

Cheers

[Roger Caffin]

Hi Delmar

> the DD says it's OK for sharpening carbide, but have you tried it?
Yes, lots.
I made my own 6-axis tool&cutter grinder. For steel (inc HSS) I use a Cubic Boron Nitride (CBN) wheel because steel can be a bit rough on the diamond wheels. Believe it or not, the carbon in the steel reacts with the diamond, eroding the diamond when hot. (I grind as cool as possible anyhow.)

But for carbide I use diamond wheels of various shapes. The resin-bonded ones are not all that expensive these days. I have to make my own tooling for the stove production you see: shaped miniature cutters. So yes, I have done a lot of diamond machining of carbide. It's the only way to go, and the finish is wonderful.

> the saw blade must be very firmly clamped
Oh my god yes! Fingers …

> Spot annealing with a torch: messy. Not at all enthused. The affected area would be much larger than you think. But with a spot welder – for sure. Been there, done that – in various guises. It's a neat way to do micro-brazing of a joint too.

Cheers

[Roger Caffin]

For what it is worth, I used a sharpened carbide masonary drill to drill through molded glass. Very slow revs, gentle pressure, a pool of cold water around the tip (plasticene is your friend), and a firm backing. Made two neat holes for my neighbour in a glass thing he wanted to hang up.

Cheers

[D S]

>For now, I plan to try a combination of spot annealing (great tip Smoke!) and Roger's suggestion of using a masonry bit. If that doesn't fly, I'll plunk down the $30 for a solid carbide bit. Delmar, I made a small spot welder from a microwave oven transformer and will try that first. I will also try the pencil torch and nail/rod techniques for comparison.<

I would not use a solid carbide bit in a drill press, unless it was a mill/drill. They are meant to be used in milling machines. They cannot stand the chatter generated by most drill presses and will shatter. Flying chunks of sharp heavy carbide is not something to play with.

[James Marco]

Delmar,
A lot of what happens with the diamond grinding wheels is they just wear finer. Think of a new extra-fine diamond stone used for honing a chisel. At first it has a few scratches in it where the higher/larger diamonds are. After a few uses, the stone will actually loose these letting you put a smoother finish on the edge. I prefer my older stones to brand new ones for this very reason. They also cut slower.

My DD has done several hundred drill bits, including carbide. I have never even considered changing the wheel because it gives a smoother/sharper edge, used as it is. The jig is a pain in the back side, though. Light pressure, multiple rotations…

A small troth, cut into the carbide before sharpening with a diamond stone/Dremmel tool, can help a LOT trying to drill alloyed steel. This will supply a cut angle of about 5-10 degrees. Some, with high quantities of chromium (some stainless,) can get quite sticky and build up on a 0 degree cutter. This helps clear the edge, though you loose in longevity.

[Delmar O’Donnell]

Well I'll be darned, Roger. You taught me something new about carbide & carbide tipped bits. Very interesting. I'll try it!

James, thanks for the DD tips.

One additional note on the difficulty of drilling: the two holy grails of a good steel are hardness, and toughness. They stand somewhat in opposition, more of one usually means less of the other, but you can get a steel that's high in both, as you'd find on a survival knife or, probably, a saw blade. A tough steel can be just as difficult to drill as a hard one. So even if you're drilling saw backs that aren't hardened, they're still probably punishingly tough.

[peter vacco]

will a small punch shatter ?

ohh ya ! like gangbusters.n if you stop a moment and ponder how a punch works (is like a shear, but round), you will see that as a punch gets smaller, there is ever less and less of it to deal with the substantial forces involved. all the while, the smaller piunch is not getting a ot shorter, so it's rather sticking up there looking weak and wobbly. it helps if smaller piunches are shorter of course, but there is often a limit to that trick.
bottom line, is that punching does not scale down as nicely as we hope it would.
keep in mind that punching is indeed shearing, and consider how well your material is going to cut with a set of shears.
sometimes a small punch will fail , and just wad up when it hits the plate. pieces of it fly out with vigor.

carbide drill bits.
carbide is not magic. it must be held (and the work) extremely rigidly. no wobbles. no hand held drilling. not anything of that sort.
drill press at least, preferably a vert mill. clamp as well as possible.

that spot annealing trick was still the best tip.

more : the drill doctor. peter not a big fan of that pos. good for sharpening screwdrivers .. you betcha. a crude joke of a tool for real drill work though. worth having one for sure. just not be expecting much in the way of great drill bits out of it.

cheers,
v.

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