A small bowsaw

[IanW]

I made myself a small bowsaw to take coping saw blades, about 20 years ago. Like so many of my projects it was meant to be a 'proof of concept' with the 'real' tool to follow. However, it worked ok from the start, & so the production model never quite got to the top of the priority list. Recently, I bought myself a small metal lathe (after MANY years of "will I, won't I" debates with myself) and what better way to give it a test run than making some small brass parts? The last set were turned on the wood lathe, which is not all that hard, but nowhere near as easy & controllable as the 'proper' machine!

Pic 1: I started with some 1/2" brass rod & turned two pieces down to a touch under 9mm, with a collar at one end to bear against the saw frame. The piece to take the handle was drilled to fit the shaft of a 12G brass screw, which was then soldered in place. One refinement was to add the brass turning pin on the un-handled end. My original was hard to move when twisting the blade left or right. The handle allows much easier twisting of the other end, so only one end needs a pin.

Pic 2: Handle fitted. The brass collar fits into a recess in the handle, but will bear against the frame to take the tension when tightened up.

Pic 3: The frame being prepared. I chose some Acacia, which happens to grow in my yard, & fall over when they get to about 100mm diameter, when there's a bit of wind & rain. Not sure of the actual species, but the wood is tough & not too dense & ideal for the purpose (when you can find straight, clean, pieces that aren't riddled by Acacia borer!). I went a bit silly & cut round-shoulderd tenons for the cross-bar. The idea seems good - it should allow a more smooth operation when the cord is tensioned. In practice, it doesn't seem to be all that much different from the standard square shoulders, & they are hard to make neatly & accurately, so I wouldn't advocate this 'refinement', at least not on your first try.

Pic 4: Frame roughed-out & test-fitting to get the bar length right - i.e. having the ends more or less parallel when tightened. This is where the rounded shoulders were a PITA - square shoulders are much easier to trim! I had marked them out with a knife, off a metal template, but once I started fiddling with them I lost the scribe line, so had to go by eye. The fit is close, but not perfect, though time & use will settle them in, I suppose.

Pic 5: Done. Much happier with the shape & balance compared with the original, which is ok, but a bit clunky by comparison. I was going to make a bobbin for the tensioning bar, so it can slip back & forth easily as the cord is twisted. However, it's another unnecessary refinement that can wait for some rainy afternoon when I'm bored & have nothing else to do - the piece of offcut in there is doing a perfectly good job as-is.

The verdict after a few test drives is that it's a keeper - I cut the frame down finer than the original, & it has a nicer heft & balance. A minor irritation is that the handle end twists a bit too easily for my liking, & so I will have to experiment with a thin neoprene washer or something to make it a little bit 'stickier'. I have fixed others by wrapping a rubber band around the shaft between handle & frame, but a more elegant solution is called for, this time! :U

Cheers,

[BobL]

Great job Ian. What sort of wood did you use?

I also had a lot of trouble with a wood screw on the original handle of my small bowsaw and gave up using it and epoxied the handle in place. Of course mine does not have a collar and the handle and blade can then twist more easily and not hold its position. I compensate for this by tweaking the blade tension up a bit more but understand this is not possible for coping saw blades. For my next one I am going to use a fine thread machine bolt and epoxy a nut into the handle.

Congrats on the metal working lathe. I just got an old (1965) Hercus but it hasn't made it past my drive way yet because I have no room in my shed. I can't wait to get it up and running, as you say it opens up a huge range of possibilities for tool making.

[IanW]

Great job Ian. What sort of wood did you use?


Hi Bob - Acacia sp.! I don't know what it is down to species - we have at least 4 different Acacias on our 2 acres, & I can only name 2 of them. The one I used has curly pods like Blackwood, but I'm pretty sure it isn't a Blackwood. Some day I'll get my Botanist mate to check it out for me. I've used Blackwood for a slightly larger frame & it worked very well. I guess there are a lot of suitable woods around. I would select a couple of straight-grained woods that appeal & cut a thin strips, being careful to avoid grain run-out then break them by bending between your thumbs. If it fractures with much splintering & only after a severe bend, good, & if it snaps like a carrot, try the next one......



I also had a lot of trouble with a wood screw on the original handle of my small bowsaw and gave up using it and epoxied the handle in place.


By twisting, I mean the whole thing rotates too easily - it just needs a bit more friction between collar & the saw frame. I haven't had any problems with handles unscrewing. No harm using epoxy, of course, but I have not needed it, so far. I use a 50mm screw, so it goes well into the handle, and drill it carefully with diminishing sizes of drill so that it fits nicely & tightens down very firmly on the last couple of turns. The wood could also have a bearing - a lot of woods simply will not hold on a screw thread along the grain. (I have tried a piece of that lovely Rock She-Oak you gave me, and it seemed to work very well. :;)

Not sure how much tension a coping-saw blade will cop, but it's more than I dare to apply! Must say, I have not been too impressed by the quality of the blades I've been getting lately, though. Anyone got a lead on really good ones??

A Hercus eh? My little toy is pretty puny compared with that 'real' machine. But it still opens up a lot of possibilities for toolmaking. I bought a milling attachment, so once I learn how to drive it, there's going to be some serious metalworking going on in my shed. A friend of mine is hoping to score a Hercus when his department closes its workshop in a couple of months. It needs some relatively minor repairs, & when they put it up for tender, the few people who came to look at it just sniffed & walked off, so he's hoping he can buy it for a very reasonable sum. I'm planning to be interstate on the day he brings it home, though.... :U

Cheers,

[IanW]

It worked!

As I mentioned, I was not totally happy with my bowsaws. There was not enough friction between the brass collar & frame on the handle end, & they had a tendency to twist when sawing. I was musing about the best way to make them stay put, & decided to try an O-ring. The ones for tap stems are just the right size, so I slipped a couple on each saw. Seems to be a perfect solution - the handle is now held firmly against the frame & stays where I twist it.

All well & good. :U

Cheers,

[RayG]

Hi Ian,

Nice work, I have a few turning saws in various stages of construction, waiting for the right moment to finish.

The problem of blade rotation is usually solved with a taper on the part that goes through the handle. So that it "locks up" when the blade is tensioned. Took a while to figure out, until I saw an old marples with the taper and suddenly it all clicked. The O-ring is a good solution as well.

Regards
Ray

[Woodwould]

Another beautiful tool Ian! :thyel:

I can attest to the quality of Ian's brass fittings and handle as I've got my grubby hands on a set. I'm not sure any saw I make with the fittings will bear comparrison to Ian's, but I'll give it a red hot go... erm... soon.

[artme]

:2tsup::2tsup::2tsup:

[IanW]

.....The problem of blade rotation is usually solved with a taper on the part that goes through the handle. So that it "locks up" when the blade is tensioned. Took a while to figure out, until I saw an old marples with the taper and suddenly it all clicked. The O-ring is a good solution as well.


Thanks Ray.
Now why didn't I think of that?! A tapered shaft would also take the tension, so you don't need a collar - clever. A much more elegant solution, but more challenging to make. Hmmm, looks like I'll have to revisit this down the track. I haven't tried taper turning on my little lathe yet, but it will do them, so that will be a good starter exercise.

However, it may be some time before I get the round tuit. The larger, 10" saw, has been in constant use for over 20 years without showing too many signs of wear. To stop that from turning too easily I just wrapped a rubber band arond the shaft, as I said. After a while, the rubber perished, leaving bits of rubber gunk stuck to frame & handle, which still did the job - crude but effective. The 0-ring is neoprene, & should last for years.

I find both my little saws really handy things to have on hand. The coping saw blades I get now are not great, but they're cheap & easy to replace regularly. However, the blades for the larger one are another matter. The originals came from Lee Valley, more years ago than I can remember. I broke my favourite 15 tpi one a few months ago, which was hardly surprising, since it had been resharpened quite a few times & was getting pathetically thin. LV seem to have dropped these from their inventory, so I don't know if you can still get them anywhere. I've got a slightly coarser one left, which may see me out, but if not, I reckon I can make a satisfactory replacement with a strip of the stuff we've been using for our backsaw-making binges. If I form the teeth on a larger piece before cutting the blade off, it should be a relatively straightforward job. Setting & sharpening teeth on a 1/4" wide blade is a bit of a challenge, but it can be managed...

Cheers,

[RayG]

Hi Ian,

I got some blades from TFWW, they are pretty good. For the coping saw blades, I can't find good ones anywhere, they are all stamped rubbish, so I buy the eclipse coping saw blades (the ones from bunnys) and re-sharpen the teeth. You would be amazed at how well they cut with even just a light cleanup.

As far as the taper goes, it doesn't take much.

Not sure if you've seen this method for making the handles.

Saws Seen - Saw Scene - Saws I've Seen - Making Bow Saw Handles/Step 1. Tapping the Handle for 3/8" (http://www.backsaw.net/cpg/displayimage.php?album=13&pos=0)

Regards
Ray

[IanW]

....
Not sure if you've seen this method for making the handles.


Hi Ray - no, I hadn't seen your method before. But it's interesting how many times you & I have found similar solutions for our projects! Your method is an excellent way to do it if you don't have access to a metal lathe.

For the first saw I made, I used a long coach screw & self-tapped it into a pre-drilled handle, with a dash of epoxy as insurance. The head was then cut off & the end slotted & drilled for the pin. It workd perfectly ok, but I was a bit worried it would give, over time (it probably wouldn't have), and I thought brass fittings would look sooo much better. So I decided to make a shaft with a collar to take the strain when the saw is tensioned. A friend lent me his mini lathe, & that's how I made the first set of brass fittings. Later, I found you can turn brass on a woodlathe, so a couple of sets were made that way. It's not too difficult (a slow speed, & keep the cutting point at centre, or you'll experience much more dramatic dig-ins than wood can produce!). It takes practice to be as controlled & accurate as you can with a metal lathe, but you can sneak up on final dimensions with a file & emery paper.

All good fun. :U
Cheers,

[Mike Wingate]

Nice idea. I have a rubber washer between the handle and frame on mine to stop the slip when " sawing sideways" on mine. I do like your rounded shoulders. A bit dissapointing that they do not improve thesaw in use.

[IanW]

...... I do like your rounded shoulders. A bit dissapointing that they do not improve thesaw in use.

Hi Mike. Interesting how we find similar solutions to these little 'problems'. :U

WRT the rounded shoulders for the beam, I expected I would notice a smoother & easier action when tensioning the saw, but it doesn't seem any different from the standard square-shouldered saws I'd made previously. Thinking about it after the fact, I concluded that with square shoulders, the arms pivot on a fulcrum formed by the upper corners of the tenon shoulders, which works perfectly well. The radiused shoulders distribute the load over a wider area, but this doesn't alter the tensioning force significantly, so it doesn't make a detectable difference in use. Still, as you say, it looks the part. I mentioned it originally because it takes a bit of mucking about to get a really good fit, so it's probably not worth the extra effort on your first saw, if function is your main aim.

Cheers,

[chook]

I actually get a good long holiday soon and apart from finishing a few tables which have been sitting idle for too long I have been hoping to make a some brass inlayed cutting gauges and a bowsaw. Your saw is beautiful to look at and if I can get even close to making something as nice I will be both amazed and pleased, I have often toyed with the idea of learning about making saw blades and you posts have inspired me to have a go at this part of the saw too.

Where do I get suitable steel and what type of steel do I get?
What sorts of files do you use to file the teeth and do you use a specific tool to put a set on the teeth?

[Brobdingnagian]

Saint Roy and Bill Anderson making the Howarth Bowsaw (http://www.pbs.org/woodwrightsshop/video/3100/3102.html)

Bill, X-rayed the the handle and taper arrangement's.

[IanW]

........Where do I get suitable steel and what type of steel do I get?

Chook - old bandsaw blade is a good source of material for making bowsaw blades. Blades between 0.5mm up to 0.8mm thick are about right for small saws with 250-300mm long blades. Depending on the type of bandsaw blade, you may need to cut off the impulse-hardened teeth before making new ones. This is easiest done in the home workshop by clamping the bit of blade you wish to use between two bits of straight steel & using a 1mm cutoff wheel in a small angle grinder.

Some blades have a useful tpi and if the teeth are not hardened, are soft enough to file, but the rake will be too aggressive, so they would need backing off.


What sorts of files do you use to file the teeth and do you use a specific tool to put a set on the teeth?

Take a look at the file size chart on the Lie Nielsen web page. You can buy your files there, or, once you know what size you need, get them from a local supplier that carries a decent range of files. Note that smaller sizes like 4" DEST, which you need for fine teeth, are not carried by many tool suppliers any more.

I use an ordinary Eclipse saw-set to set my blades. They seem to work fine on blades as narrow as 5mm wide.

Which side of the city are you? If you are anywhere near me, a shed visit might be helpful to get you started...

Cheers,

[Pac man]

4 Inch DEST (http://www.jimdavey-planes-sharpening.com/EShop/Product.aspx?EshopID=8607ccbf-fea8-48e0-a1d5-90600a129f1a&CategoryID=00000000-0000-0000-0000-000000000000&ProductID=cc5721aa-2412-4890-8462-21054077ae82)