Thread: There's something about bowsaws

Very nice. Think I'll have to have a go at one of those.
Did you put blade storage in the stretcher?

Ian another great read.
I've been toying with the idea of making a bow saw for well ages to long really.
I hope you have pushed me a long far enough that I get on with it.
The glass cutting drill bit you mentioned, it's next to what looks like an old nail .
Did you use the old blunt nail tip to local heat and and soften the area before using the glass cutting drill bit?
Secondly the glass cutting drill bit ,is that the same one as you would use for tiles especially glassed tiles that all the big sheds sell? in a few different sizes.

Matt

Originally Posted by hiroller

... Did you put blade storage in the stretcher?

Nope. I managed to drill a hole through the beam of a 10" saw without breaking through, but I reckon my chances of repeating that, particularly with an extra 2 inches to negotiate, are vanishingly-small!

But perhaps the major reason for not doing it is that I'd really need a hole bigger than the beam, for it to be useful with this saw - I intend to use only relatively wide blades in this one...

Cheers,

Originally Posted by Simplicity

....The glass cutting drill bit you mentioned, it's next to what looks like an old nail...
Did you use the old blunt nail tip to local heat and and soften the area before using the glass cutting drill bit?
Secondly the glass cutting drill bit ,is that the same one as you would use for tiles especially glassed tiles that all the big sheds sell? in a few different sizes...

Well, it is just a nail, Matt, but with a sharp, triangular piece of very tough carbide brazed on the end.

No need to soften the steel, the bit goes through it like butter. You only need to soften if you are trying to use an ordinary HSS bit.

And yes, the bit came from the big shed - it's labelled as a tile/glass bit. You will need to be careful with it or you may end up with a much bigger hole than you want, because it will go through the steel very easily. I find it isn't too hard to control in a drill press, but it might be a bit of a delicate operation in a hand-held drill...

Cheers,

Sorry Ian
What I was revering to was that in the fifth pic I think.
Layed next to the tile/glass cutting bit looks like an old nail ??
As for the glass bits I have several that I use in my day job cutting holes in tiles(very boring no pun intended lol)
So now I'm itching to try them on some saw plate when I get a chance a lot more exciting
( sorry out of edit checks tonight)

Originally Posted by Simplicity

.....Layed next to the tile/glass cutting bit looks like an old nail ?? ....

You're quite right, it is a nail, Matt. I use 1.6mm nails for pins, & it was there because I was testing that I'd got the hole the right size.

If you ever want to try the local-softening trick, you'll probably need a heftier nail than that though, it takes a fair bit of pressure and speed to get the spot to annealing temperature. I used that technique a few times early on, but it seemed to be a bit hit & miss. Then I tried those 'builders' drills' for drilling the holes for saw bolts. They work ok, though they don't have a very sharp point & need a good-sized depression to prevent them from wandering when you are starting the hole. And they don't come in tiny sizes, so there seemed to be nothing easily-available to make small holes for bowsaw pins. You can 'persuade' a 1/16" HSS drill to go through thin plate without annealing it, but after one or two holes at best, it's cactus.

So I was always looking for some easy way of making small holes in spring steel and one day it occurred to me to try a tile drill. The sharp point was easy to start in a small centre-punch hole & it went through the steel like butter. So I went out & bought the smallest I could find, & that's what I've been using these last couple of years. It's not like making holes for backsaws where you want them as close to spot-on as possible. It doesn't matter if the pin-hole isn't exact, in fact a bit over-size makes it more convenient, if anything, & easier to get the pin through when you are assembling the saw. That can be a struggle sometimes, when you are trying to re-assemble it with the blade in a small starting-hole, and the frame wants to fall apart, or the cord comes off while you are conceentrating on getting that pin through the right spot - one of those situations where you wish we came with 3 or 4 hands instead of just two! Once the blade is tensioned up, it's fine.

So if you've been planning a bowsaw, go for it. They take a bit of getting used to if you've not had one before, but once you get the hang of them, I reckon it's an extremely handy tool to have. My little 10" saw comes out for some job or other just about every day. It's mostly used for cutting irregular shapes (like saw handles), which involves some pretty tight turns, so it normally wears a 15tpi, 4-5mm wide blade, but I'll keep a wider blade with either 10 or 12 tpi in this bigger saw. The exact width & tooth pitch will be decided after I use it for a few months, to find out what's most handy for me...

Cheers,

I meant to mention, that after much casting about & tying different materials for tensioning cord, I've settled on 3mm venetian blind cord as the best alternative for these small saws. It takes a fair amount of tension make a blade work nicely, though not as much as I first thought! My earliest saws were heavy, awkward things and I tensioned them with a 3/16" bolt attached to twisted wire - clumsy & ugly!.

The blind cord is cheap ($5 buys 20 metres, enough for more saws than one person needs!), though not perfect. It stretches a bit more than I'd like, but seems to settle down after a bit of use, & as long as I slacken it off after each session, it tensions up nicely with the same number of turns next time.

So, if anyone has any suggestions of something that might be better, I'd be happy to give it a try. I've read that the old-timers used rawhide. I tried using cured leather, but it won't take the strain & soon gives up.

Cheers,

Ian

Most interesting. I haven't really had any time to experiment with the blades, but I did want to try them out. I twigged that they fit a standard size hacksaw frame. The only modification is to slightly enlarge the existing hole for the pin.

Bow saw blades 002.jpgBow saw blades 001.jpg


I only tried with the widest blade which cut roughly. Too few teeth combined with a lot of set.

I think I measured that blade at .032".

Regards
Paul

Originally Posted by IanW

So, if anyone has any suggestions of something that might be better, I'd be happy to give it a try. I've read that the old-timers used rawhide. I tried using cured leather, but it won't take the strain & soon gives up.

I think braided fishing line would work well.
A small roll of 1mm line should do a bow saw or 50.

I was thinking about the synthetic strings they use for bows, those bows that are used for arrows.

Olive Drab with Black Fleck Paracord

One of the properties of paracord is that it is quite elastic up to about 30%.
It is made of nylon and designed to absorb shockloads like parachutes and saftey lines.
This would mean a lot of winding to get your saw tight.

Modern braided fishing line is made of Dyneema, same stuff as bow strings, trawler lines and maxi yacht lines.
It's about 10 times stronger than steel of the same weight.
It does creep a little over time, so you might have to occasionally take an extra wind.

The maximum strain you are going to draw with a bow saw is around 20 - 30kg (turning saw would be a more apt description of what Ian is making).

Olive Drab with Black Fleck Paracord

I have used an old bow string on a very rough bow saw I made. I had to cut large tenons and my two backsaws at the time did not have the depth of cut. Just happened to be hanging in the shed at the time so on it went and worked fine. I dont think it matters a lot what string you use.
Regards
John