Chain Tension...

If ever there was a subject about which produced lots of differing views, this has to be it. I've been told so many ways of how I should set the tension of a saw chain that I could write a book blog article about it.

Most of these ways are street-myth, complete rubbish or somewhere in between. Some have a certain amount of truth in them, whilst others belong in a Hans Christian Anderson tale.

So, for this post, we'll take a look at some of the ways of setting chain tension.

It should be easy really, just set the chain so that it's not too loose, and not too tight; somewhere between those two extremes is the correct tension. But where? Let's examine a few of the more popular methods of checking chain tension...

1. "You should be able to lift the top of the chain and see 1 / 2 / 3* drive links." *Delete as necessary.

Nope. This just does not hold true - there are too many variables at play here to make this worth listening to. Your strength will have an obvious bearing on how much you can pull up on the chain; in fact, just how much force should you use when pulling up the chain? The length of the guide bar will have a huge bearing on how much you can pull up anyway.

2. "You should be able to fit a penny between the chain and bar."

No - complete rubbish! See above.

3. "You should be able to push the saw over the worktop and the chain should move round as the saw moves across the flat surface."

There's some truth in this one - but I have a major problem with it... how many nice flat surfaces are there out in the woods? However, this is one that I used to use to set the tension up in the workshop, and is similar to the next one...

4. "Grip the chain on the topside and underside of the bar; the chain should move round reasonably easily... now hold the chain on the topside of the bar and pull it towards you. The saw should move across the flat surface, but the chain should remain still."

This suffers from the same problem as the previous option - but for setting the tension in the workshop, it's pretty accurate. But no use in the field where flat, smooth surfaces are hard to come by.

So where does this leave us? Four different methods, two of which I would give some credence too (options 3 & 4), and two that don't deserve the time of day (options 1 & 2).

The simple answer is to set it in the workshop, get a feel for how tight it is and use that as your basis for future tensioning. It's a bit of a 'feel-thing' that you get with experience, but let's try to give you a better answer than "let your experience be your guide", as that's not particularly helpful if you are new to chainsaws!

First things first... take the chain brake off so the chain is free to move! You'd be amazed how many people forget that bit.

There are two very basic rules...

  1. If you can see daylight between the underside of the guide bar and the chain, it's too loose.

  2. If you can't move the chain around the bar, it's too tight.

Between these two extremes of tension is what we are after, so here's how to do it - in fact I might just make a video of this and post it up later...

  1. Make sure the chain brake is off and that you are wearing suitable work gloves.

  2. If necessary, slacken the nuts that are clamping the guide bar in place (or whatever system your saw uses to hold the side plate and bar on with). We don't need these really loose - just finger tight will do.

  3. Slacken off the tension until the chain is obviously too loose.

  4. Using one hand, hold the nose of the bar up.

  5. Now, whilst the bar nose up, adjust the tension so that the chain just touches the underside of the bar. Adjust the tension just a little bit more, so that the chain fits snugly against the guide bar - no need to overdo it.

  6. Whilst still holding the nose of the bar up, tighten up the side plate nuts / bolts / quick-release system.

That's it - you're done! There are a couple more points to note when tensioning your chain, but those will be mentioned in the next post.

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