Working Edges: Part One.

Post number three in this quick look at common sharpening problems takes a closer look at the working edge of the cutter. This is the crucial bit that slices through the wood and so it must be sharpened correctly. I've seen a number of common errors when filing the cutters and getting the working edge correct is probably the most difficult. Click on the jump to find out a bit more...

There are a number of things that need to come together to end up with a good sharp chain that's capable of cutting effectively and efficiently. When we sharpen a chain we need to know:

  1. the file size;

  2. the filing angle;

  3. the depth gauge setting.

We've already seen in the previous post that selecting the wrong file size will affect the side plate angle, or the amount of hook, given to the cutter; and this time we'll have a look at the issues surrounding the filing angle.

The filing angle, given by the manufacturers, lets you know the best angle for the type of work that the chain is to be put to. For example, a crosscut chain will have a filing angle between 25o and 35o, whereas a ripping chain is much shallower - the ideal is 0o but values in the range of 5o to 15o is more common. This is because of the different way the cutter has to remove the wood when cutting across, or with, the grain. Cutting across the grain (cross-cut) the cutters must be set up to sever the fibres, when cutting along the grain (rip-cut) the cutter must essentially chip the wood away. We'll take a closer look at rip cutting and cross-cutting in a later post and see how it actually works.

Back to our filing angle; there are several ways of filing the cutter - from using just the file on its own, to using a Dremel with an attachment, through to the professional grinding wheels for accurate setting. Each has it's own merits and drawbacks (perhaps that could form another post in the future!). Here, we'll stick to using the good ol' file with a file guide.

The potential problem with using just the file is that you have no control over the height that you are filing at, making it all too easy to set the incorrect side plate angle. The file guide, used properly, should reduce the chance of this - notice that it doesn't completely alleviate it as you can still place it incorrectly or put too much pressure down on it. But it helps, and it's also got the lines etched in to it to make lining it up to the correct angle a simple task.

Stihl recommend a filing angle of 30o with their Rapid-Micro and Rapid-Super chains which makes it easy to remember, but you need to be a bit more careful with Oregon chains, even those with the same identifier on them. An Oregon #21 or #22 chain could have it's filing angle set to either 25o or 30o depending on whether it's a 'round ground chisel' chain or a 'micro chisel' chain.

Once you know the angle, the problem then is that it can be hard to achieve if your filing stroke is not even. The picture at the top of this post shows what happens if you change the angle right at the end of the stroke; you can see that the working edge of the cutter is no longer straight. To correct this, make sure that you keep your filing stroke completely straight from the beginning to the end, and maintain an even pressure.

In the next post we'll continue with the working edge and the difference in shape between a chisel cutter and a semi-chisel cutter. Chisel cutters tend to be very easy to file with a straight edge all the way across, but time and again I see semi-chisel cutters not done to their best, so we'll pick up on this and have a look why...

Cutter Lengths.

Continuing our look at common problems encountered when sharpening the chain, in this post we'll take a look at the effects of variable cutter lengths.

When you first start sharpening your chain, it's natural to wonder where to start, i.e. which cutter do you choose to begin the process? Does it even matter? Well, yes it does! Find out more after the jump.

Many of those coming to the chainsaw maintenance and cross-cutting courses don't realise that it's important to start filing the correct cutter when sharpening as you must end up with all the cutters filed to the same angle and the same length. And the clue is in those last few words - they should all be the same length.

This means that you have to base the length of all the cutters on the shortest cutter; but why does it matter? Surely as long as the filing angles are correct, the length of the cutters is irrelevant? Errr, no.

The main problem with having the lengths all different is that it will cause the chainsaw to cut in a curve rather than a straight line. There is a very noticeable drift from the cutting line, and I've seen it referred to as a 'banana cut' on the ArbTalk forum just recently. This is a good description!

So, when we start to sharpen we must find the shortest cutter - but what if there's a longer cutter that has lots of damage? What if they're all the same length? What if you don't have a set of vernier calipers to hand to check? Let's deal with each of these in turn...

Damaged Cutters

In theory, as long as you only cut wood with your chain the cutters shouldn't get damaged. But life being what it is, sooner or later you'll cut through some timber only to see sparks coming out of it - then there's the sinking feeling that you've just found a nail, or part of a wire fence, in the middle of the wood. Maybe you touched the chain on the ground as you exited a cut, or maybe there was just lots of small bits of flint in the rough bark of an old Birch tree. Whatever it is, one day you'll end up with the leading edge (or working edge) of the cutter getting damaged.

The main thing is to file away all the signs of damage. Now in our example where there is a longer cutter which is damaged, it makes more sense to file this first of all and then check it's length against the [previously] shorter one. If it's still longer, then it'll need to be filed more; if it's now the shortest one, then this is the one you'll base the rest on.

Same Length

If all the cutters are the same length, and none are more damaged than any others, then you've got no worries - start anywhere!

No Vernier Gauges

For the utmost accuracy you can use vernier calipers - but there really is no need, unless you pride yourself on engineering tolerances that NASA would be proud of. Use the simple nut and bolt trick - one bolt, fitted with two nuts is all you need. Fit the head of the bolt between the working edge and loosely tighten the first nut up against the trailing edge of the cutter (use the second one to lock it in place). For more information, check out this post...The Nuts And Bolts Of Meaasuring.

Setting The Lengths

Once you have sorted out any damaged cutters, and you know which one is the shortest, make sure that it's sharpened correctly and then measure along where the side plate and top plate meet. Set your measuring apparatus to the required length and don't forget to mark it!!. I just use a permanent marker to colour in the top plate so I know when I've gone round the whole chain.

Try to get the cutters all the same - if you don't you'll find it more difficult to get accurate felling cuts, particularly when using the medium fell technique as the saw will drift of course as you cut around the back of the tree. You might also find that you suffer from more vibration when you use the chainsaw, as the chain reacts to the odd lengths.

In the next post we'll take a look at filing angles and the working edge.

Left Hook

There's a lot of criticism within the industry surrounding the ability of chainsaw operators to correctly sharpen their chains. It's not helped by those in the industry who persist in setting out the same old myths that have been around for years. If you want the best performance from your chain then it needs to sharpened correctly.

Incorrect sharpening of the chain can lead to varied problems, from slow cutting performance to a greatly increased chance of kickback. Knowing how your chain should be maintained is extremely important - yes, it's a drudge but it needs to be done.

Here on DriveLink, sharpening the chain was covered in the following posts:

So, let's try and take a closer look at some of the problems encountered when sharpening. Find out more after the jump...

First off, it's important then when using the file that we keep it flat and straight whilst filing. We also need to maintain the correct pressure to ensure that the correct side plate angle is maintained. Now, it's difficult to measure the side plate angle correctly, although Stihl have attempted to make things a little easier with the various markings on their depth gauge tool; instead, when I teach sharpening I tell the students to use the angle specified in the manufacturers literature as a guide to how much 'hook' their should be on the side plate. An angle of 85o would suggest little hook, whereas an angle of 60o would show a definite hook in the side plate of the cutter.

The picture here shows a chain where this hook is completely wrong - the cutter actually appears to lean backwards and there's no hook at all. There's two major reasons for this:

  • the file used to sharpen the chain was too large;

  • too little pressure on the file whilst sharpening caused the file to ride up.

If you suspect the file you used was too large, check it against the filing table for your particular chain. If you use Oregon chain, check out their maintenance and safety manual at the manual - it's full of really useful information.

But what if you used the correct file size? It's likely that the lack of hook on the cutter was due to the file riding up as you sharpened - you'll be able to see this if you look at the shape of the gullet (between the cutter and depth gauge). If there's a ridge starting to form then it's a sign that you should have used a little more pressure - get rid of this ridge before you continue sharpening.

There is another possibility, and that is that you did not hold the file correctly - if you used a file guide, it should rest on the cutter and the depth gauge.

Try to maintain an even pressure on the file - not too much and not too little. Too much pressure results in the opposite problem; i.e. too much hook as the side plate is being filed by a different part of the file, resulting in what is sometimes referred to as a 'birds-mouth'.

Next post we'll take a look at cutter lengths.

Calling Out Around The World.

I've just been taking a look to see where the readership of this blog is located, and I was pretty surprised! Find out more after the jump...

It seems we have a truly international readership; from the good ol' US of A to Japan, and all points in between.

So, if you are one of those readers from Norway, Canada, Croatia, Chile, Laos, New Zealand - or indeed from anywhere other than the UK - do please get in touch, even if it's just to say "Hi!".

But, even better, let me know something about how the forestry or arboriculture business in your neck of the woods. Felling and logging must be quite different in Norway, when compared to New Zealand. The trees that you work on are probably somewhat different from here - the huge Eucalyptus trees of Australia to the Baltic Pines of Scandanavia.

Just drop me a line via the comments...

Give Me A Hand...

How much attention do you give your personal protective equipment? Do you just throw it in the back of the wagon once you've finished the job? How do you dry out your gear once it's been soaked in the latest summer downpour? In this post, I'll take a look at chainsaw gloves - and hopefully they don't look like the pair in the photo. Find out more after the jump...

As you can guess from the picture at the top, these chainsaw gloves were not in a condition to provide any protection - if you're gloves look like that, do yourself a favour and replace them. New chainsaw gloves are not really that cheap - not like a pair of work gloves at £1.99, and so you should look after them. But how?

Ever read those little paper booklets that come with new gloves / jackets / helmets / boots / etc.? Stihl recently sent us a new pair of gloves and I thought I'd take a moment to browse through the leaflet and report my findings.

During the course of normal tree work, chainsaw gloves live a hard life, dragging brash, using a chainsaw, winching and so on. They get pretty grubby, pretty quickly and if they then get wet as well they'll set rock hard - making them difficult to put on and uncomfortable to wear. Improper care will also accelerate the demise of the stitching caused by fuel, oil and maybe stump protection fluids - all things that are not recommended to come in to contact with the gloves.

I've never read the leaflet that comes with gloves and I'm as guilty as the next person of just abusing them until they fall apart and then getting another pair - but what I found was interesting. For instance, were you aware that you can wash those gloves? I wasn't, but it turns out that these Stihl gloves can be washed gently in warm, soapy water when they get dirty. Or contaminated with petrol. Or oil. Or indeed, anything else. Of course, they need to be dried, in just the same way they should be if they get thoroughly soaked during inclement weather.

Drying gloves should be done without unnatural sources of heat, i.e. don't go putting them directly on a radiator, or use a hairdryer to drive off the moisture. Put them somewhere where they can dry out slowly over time and once dry, they should be treated with a leather feed - I'm thinking something like NikWax should do.

So, it seems that looking after your gloves might just save you some money - but there's obviously a 'fiddle-factor' involved in maintaining them. Having said that, I've got an oldish pair of Husqvarna gloves that could do with a good clean, I might just try it and see what happens...

Back from holiday!

Well it's back to work after a couple of weeks holiday, and straight back in to running a couple of chainsaw maintenance (CS30) courses. It's always great to meet new faces on these courses and watch beginners tackle chainsaw sharpening, or listen to the more experienced users views on how they have carried out certain tasks. This got me thinking if there was a way to bring the questions, answers and information to a wider audience. There is, it's obvious and you can find out more after the jump...

Naturally, I get asked many of the same questions on the various courses and quite often also get those 'off-the-wall' questions, that often start with "This may sound stupid, but...". Well as we all know, there's [generally] no such thing as a stupid question - if you need an answer then you've got to ask the question!

So, I thought that as I'm about to start another year of chainsaw maintenance, felling and climbing courses that I would put some of these questions up here - along with answers, or put the question out to you lot to answer. This way, if you've got a 'stupid question' you won't have to ask it as someone else will have hopefully asked it already!

So, when it comes to questions about chainsaws, just remember not to hold the pointy end.