bow saw blades

[geordief]

could I ask for advice regarding bow saw blades?

As I do a fair bit of cutting branches and medium sized trunks I have invested in what I understand was a fairly top of the range (Bahco 24 inch) bow saw.I was fairly chuffed that it was displaying a replacement blade at just under 10 euro (new!!).
I have used this equipment for the past 10 days or so , on and off and was surprised when the job seemed to be getting harder (more sticking etc) over the past short while.I had not cut into anything other than wood (mostly green).

Returning to my old bow saw with its cheap oldish blade that I had nevertheless shapened as best I could (with a chainsaw file) and derusted with wet and dry enery paper I am a bit disappointed (well should I be pleased?) that it was noticeably better.

The expensive Bahco blade is ,I can see . the kind you are supposed to be unable to resharpen (it has the rainbow coloration at the tip and I think that means it has been heat hardened )
Do I draw the conclusion that these unsharpenable bow saw blades will not last for a very long time at their initial sharpness and that they can be outdone by a cheap blade that I am prepared to sharpen from time to time?

ps is it possible to over tension the blade?
Obviously not from the point of view of possibly breaking the blade or bending the frame.
But is it enough for it too be reasonably taut without obsessing over it?

 

[Dave Budd]

the bacho frames (like most good frames) keep the blade quite tight, so the blade doesn't buckle or come off in use, but the set is pulled out. The blades are fine and stay sharp plenty long enough as long as you take the tension off when not in use

You can, with care, re-set the teeth. Though with the hardpoint ones there is a very good chance of snapping them off, but if you are going to bin it anyways... try to bend the teeth a touch below the colouring (you may need to make an old fashioned saw set froma bar of steel with a slot cut into it).

 

[brancho]

The usual problem my Scouts have is that they pinch the blade in the cut and take the rake out of the teeth making the blade stick a lot and almost useless.

Are you using blades for green wood?

 

[geordief]

. The blades are fine and stay sharp plenty long enough as long as you take the tension off when not in use

.

thanks for your help.I don't understand the need to take the tension off between uses.Is it to keep the set? Is set another name for kerf?

 

[geordief]

Are you using blades for green wood?

hi ,yes nearly always green but if there are old , dry branches I am also cutting them.Is that a mistake?

 

[brancho]

hi ,yes nearly always green but if there are old , dry branches I am also cutting them.Is that a mistake?

No problem really just wondering which you are using and byt what you have written you seem to understand plent about saw blades anyhow. I find the blades without raker teeth bind more easily and you lose the kerf.

Is the blade actually blunt or is the blades losing its kerf thats what happens to my scouts usually I have seen a blade ruined after one cut.

Blade quality definetely varies but scouts ruin them at an alarming rate

 

[geordief]

No problem really just wondering which you are using and byt what you have written you seem to understand plent about saw blades anyhow. I find the blades without raker teeth bind more easily and you lose the kerf.

Is the blade actually blunt or is the blades losing its kerf thats what happens to my scouts usually I have seen a blade ruined after one cut.

Blade quality definetely varies but scouts ruin them at an alarming rate

well it could be the kerf as it does seem more or less as sharp as it was at first.
I am not quite sure what raker teeth are but I am guessing they are those different shaped teeth you see on the blade sometimes - they look a bit like a crown.This blade just seems to have the one kind of tooth which seems to repeat every 2nd or 4th tooth.
If I have damaged the kerf how do I go about not repeating the mistake?
Do I detension the blade between uses?
Is it important not to twist or force the blade?

 

[brancho]

The kerf can be checked by looking along the blade to see if the teeth have flattened out instead of being splayed.

If it is this this you are either twisting the blade or pinching it in the cut and this is deforing the teeth this causes the saw to jam more and more and become impossible to use efficiently.

To avoid this keep the saw straight avoid too much pressure and speed, dont force it let the saw do the work. Ensure the cut does not close up and trap the blade.

 

[mr dazzler]

The kerf is what the saw teeth make in the wood, the line of the cut that results from the waste being removed by the action of the teeth. The saw's set is the tiny amount that the teeth stick out either side so as to give clearance in creating the kerf and (theoretically) so that the blade doesnt bind. But if there is any set on the teeth when they are made, it is extremely minimal. If stretching the blade under tension ruins what set there might of been, then the bahco blades are crapper than I thought. All too often wet wood acts like brake shoes on the blade and the kerf develps a mind of its own, the cut becomes impossible to control etc.....Personally I dont rate bahco blades any way. I much prefer a 28 inch Disston crosscut to cros cut green logs. It is just as efficient at cutting as a bahco and has a much more comfortable user friendly handle as well....with a 3 or 5 point blade it only takes 10 minutes or so to set the blade, another 10 to sharpen it.

 

[Peter_t]

iv got an oldschool 30 inch bowsaw with the sharpenable blade. the blade is much wider but at leest half as thin. i imagen this would not get pinched. problem is i have no idea how to set the teeth lol.

are the old style blades any good? mite have to lern to to use them if they are

pete

 

[brancho]

Mr Dazzler
You are right I did mean the set of the teeth.

 

[Dave Budd]

the problem with the set being taken out isn't to do with the quality of the blade, just how much tension it is under and better made frames tend to hold the blade more taught. I've seen saws that have been used once and then put away for 6 months. When they are next used they bind in the wood simply because the set is taken out!

I have a few bowsaws, two of which see regular use. One is an old skip diving job (30" metal frame) with a bacho blade that has raker teeth (the rakers are not set or sharp, they just rake the damp saw dust out of the kerf). That one has a slightly bent frame that has opened up to about 30 1/2", so the blade is stretched quite tight. I reset the teeth on that blade after about a week! When I did so, I set them too much and the kerf is about twice as wide as it should be (and the cut is never as straight through thick branches), but I leave it under tension and it is gradually stretching to the sort of set that it once had; at which point I will take it out of tension. That way the £4.50 blade will have lasted me a few of years instead of that one week!

The other saw is a new 24" Bacho and the blade is the origial V-pointed with no rakers. Not as fast on green wood as the other one, but a cleaner cut due to the corectly set teeth. I take the tension off this one to keep it good, but I also have a coarse toothed blade with rakers that I tend to use in it if I I don't want to use the chainsaw for some reason (it weighs more and I'm basically quite lazy).

In preference a silky or large crosscut saw (a normal woodworking crosscut will work great on dry or part seasoned wood, but just try cutting a tree down with them) that has teeth designed for greenwood are more efficient, but bowsaws are cheap and work.

 

[mr dazzler]

I should of added, a quality old Disston saw has a taper ground blade, which means it is considerably thinner at the top of the blade, than it is at the bottom of the blade where the teeth are. Its not just stamped out of a sheet of uniform thickness. So as the saw progresses through the wood, you greatly reduce friction, and it is much less likely to bind. The thinner area at the top doesnt touch the sides of the kerf. This combined with the proper amount of set, and you have very precise control of the cut. LOL I would rather buy a saw file and do my own sharpening than keep buying bahco blades...I do have a modified euro style wooden bow saw with a blade fashioned from a disston blade (which had been sharpened so often over the preceeding 50 or 60 years that the toe was only about 1 1/4 inches wide). I just made a parallel strip 1 1/14 inches wide, and added rivetted tabs at either end to fit into the saw handles with pins.

 

[Toadflax]

In my ignorance o), I gave my Bahco bowsaw blade a really good tightening a couple of weeks ago, not realising that this isn't a good idea, and since then it has been binding up really badly.

I was resigned to buying a new blade, but stumbled on this thread after a bit of googling yesterday and the set of the teeth has, indeed, relaxed, though the blade was still very sharp.

I had a rummage through the Pandora's Box (tool chest) that has been passed down from my wife's great grandfather and, among the Victorian moulding planes, I found a fairly modern Draper saw set. The Bahco blade has teeth at 4-5 per inch, so I set the dial on the saw set to 6, set all of the teeth and the saw now cuts through wood like butter.

I know I've only saved myself a fiver or so on a new blade, but I was really pleased with myself for rescuing the blade.

The saw is now back in the toolshed, with the tension released.

Moral for those like me: don't over tighten your bowsaw blade, and relax the tension when you've finished.


Geoff

 

[ged]

Are you oiling it before putting it away? If it sits in the shed wet for a couple of weeks that won't do it any good. I give them a spray with WD40 after each day's use. I don't use one every day, mostly let the cutting pile up for a while then do a job lot at once in a few hours.

I often find with green wood (try not to do it) that bits of bark and stuff can stick to the blade quite firmly, and make it a bit thicker than it should be. Cleaning it off makes quite a difference.

You can resharpen the heat-treated parts of a blade but you probably shouldn't ever need to do it unless you hit a nail or something. A blade lasts me several years and then I buy a new one. Can't remember last time I bought one, must be around five years, but the one I'm using is still fine. I leave it in the saw under tension all the time and it doesn't seem to give it any trouble although it's an old saw (was my grandfather's) and the tension isn't huge. I think it's a Sandvik blade.

 

[mawdsk]

Hi, just had to join up to add a bit to this old post.

I bought a new bow saw, albeit a cheap one, and couldn't cut anything thicker then the depth of the blade. Examining the teeth showed there was no set at all on them so it was just binding up. My dad being an old tradesman has a lot of tools and as he used to sharpen his old saws had a tool for the job. Set the teeth and now it cuts much better. He went into a few shops and also looked at the new blades he has and none exhibit much if any set on them. Have modern designers forgotten how to make a saw blade! Check yours otherwise your just wasting energy and getting frustrated.

 

[geordief]

I do this all the time .I reset the teeth. What I do is to sit the bow saw on my lap and clamp a large vice grip onto the blade itself. Then ,using a pliers or a second small vice grip I "open up" the teeth so that every second one points outward in opposite directions.

This can take about 5 minutes but it is very rough and ready and the result is never as good as a new blade-even though I do also emery cloth any rust along the main body of the blade (also ,since I do this by sight the bow sow tend to cut "crooked" -which I get around by reversing the sawing action as required)

I used to sharpen the individual teeth also but these seem to be sharp anyway for the most part and it is only when the teeth loose their width along the length of the blade that I really notice that the performance dives.

It seems to me obvious that whenever I do this operation that the teeth must loose their firmness and I sometimes wonder about heating the metal and quenching it but have yet to try that.

Could there be blades that keep their shape better than other? Are there any really top quality bow saw blades to be had anywhere?

I doubt it as I remember when I used to work with knives for a living and the basic idea used to be that soft metal was better since you could resharpen it easily....

 

[Dave Budd]

the bacho blades are about as good as they get I think. Some saws have stiffer frames or tighter tension when clamped up, so they will pull the set out of the blades more quickly.

If you go heating and then quenching the blade, then you will either harden it and it will snap (if you heat to red/orange); or soften the whole thing so it will not hold an edge and the set will pull out really quickly (if heating above about 250C). Either way, heating won't undo the damage of work hardening caused by constantly resetting the teeth.

Best solution is to take the tension off when not in use and oil the blades when stored so that rust doesn't dull them (and create more friction on th blade surface

 

[geordief]

the bacho blades are about as good as they get I think. Some saws have stiffer frames or tighter tension when clamped up, so they will pull the set out of the blades more quickly.

If you go heating and then quenching the blade, then you will either harden it and it will snap (if you heat to red/orange); or soften the whole thing so it will not hold an edge and the set will pull out really quickly (if heating above about 250C). Either way, heating won't undo the damage of work hardening caused by constantly resetting the teeth.

Best solution is to take the tension off when not in use and oil the blades when stored so that rust doesn't dull them (and create more friction on th blade surface

Interesting. I tend to tighten the blades as much as I possibly can when actually working with them as I assume (wrongly?) that this makes them cut better.

Could it be that I am (over) tightening them unnecessarily?

Actually I have never ,ever bothered to take the tension off when the saws are not in use (well I never really came across that advice before) .I can't say I have ever noticed that effect of the set being lost after "storage" . Would that perhaps apply to powered saws more so than to saws that are not powered?

 

[Dave Budd]

it's the case with all normal bowsaws. A lot of folk think that they are blunt and they jam in the cut, but it's normally because they have been pulled straight

In use, a tight blade should cut straighter than a loose one but will have a narrower kerf so if the wood is wet then binding is a real possibility. The same principle works with powered bandsaws; but in that case the blades also stretch in use and cost a lot more when the do go! I sometimes find that a cheaper non-adjustable saw frame won't get the blade very tight at all and it wobbles a bit in use, so I have buckled and bent blades when it binds or I get a bit too vigorous with the motion.

Making it tight enough to keep taught in use and then loosening it a bit (just so there is no tension) for storage would seem to be best.

On the point of resetting the teeth. I've deliberately over set them in the past (just for the experiment) and the blade will cut a kerf twice the width that it should. It was slower going through dryish wood (due to removing so much extra wood) but was much easier on very wet or rotten wood because the kerf didn't clog or close up behind the blade. That saw I keep under tension in the cupboard just to take a little of the over-set out a bit. I don't think I would do this again but it was an interesting experiment