Machinery: Sharp around the edges

Bruce Lett

Though an essential piece of equipment for many farmers across the country for everything from fencing to cutting firewood, little is understood about the chainsaw and how it is often poorly maintained.

Many, including myself, believe they know how to put a good edge on the chain in preparation of some serious wood work -- but that is not so.

So, the Farming Independent spoke to a man who actually knows what he is talking about to see if he could cast a little bit of light on this subject.

I was surprised by how little I knew and understood about the design and function of a chainsaw.

Andy Walsh, a service manager at Dublin-based Liffey Distribution Ltd, is the man in the know. Liffey are importers and distributors for the Husqvarna, Jonsered, Partner, Flymo and McCulloch brands, all well-known and synonymous with chainsaws in Ireland.

Andy's knowledge of the chainsaw is extensive and hopefully his knowledge here will help educate on the proper use and maintenance of the working end of the saw, the chain.

"First off, most chains operate between 20 and 24 metres/second (roughly 45-55mph), so that gives you an idea of the demands placed on the chain and chainsaw," Andy says.

"Secondly, recent technology in chainsaw chains means that all new chains are now low profile, which means they are lower and narrower.

Get the latest news from the Farming Independent team 3 times a week.

"This makes them easier to use because they are lighter, there is less vibration created and transferred to the user, and there is less kickback.

"The entire chain is equipped with alternate left and right handed cutters," says Andy. There are three aspects to each cutter that will affect how each individual one, and ultimately the saw, will perform -- or not.

"There are two angles that you need to get right when filing or sharpening a chain: the top plate angle of the cutter and the side plate angle of the cutter. One other piece of information is critical: the depth gauge height."

Before you sharpen, though, Andy says it is essential to get the correct file for the size of chain you are sharpening. For example a 0.325in pitch chain requires a 3/16in file. If you take the wrong file, things can go wrong.

"Use too big a file and the angle becomes too obtuse, too small and the angle becomes too acute, hooking the cutter.

"The latter will cut well, but not for very long. It's very important to get the file size right," Andy says.

To my untrained eye the file that looks right for sharpening the cutter is the file that is too small. Andy demonstrated that the correct file fits snugly between the cutter and the depth gauge/raker at the front, without touching the depth gauge. He recommends that you ask your chainsaw dealer if you are unsure about the file size.

A chainsaw is one of the few saws that require the cutting mechanism to be sharpened. How often this is required depends on many things, from hitting nails or clay to cutting hard or soft timbers.

"As a guide, the golden rule to working a chainsaw is if you find yourself leaning on the chainsaw at all to make it cut then you need to sharpen it."


To sharpen the chain Andy advises to do the left-hand cutters first.

"Lock the nose of the chain guide bar in the vice and put the chain brake on. Ideally what you want is to have both hands free."

A mark on the top of each cutter is what he refers to as a 'witness mark'.

"The witness mark serves two functions. Firstly, it indicates the sharpening angle and, secondly, it marks the end of the life of the chain when filed to this point."

Sharpening beyond the mark is dangerous as the cutters could possibly break off, risking injury to the user or others close by.

"If you see the witness mark, it usually denotes the new 25° top cutter angle of the new-type chain.

"If you don't see the witness mark, you can take it that the angle of the face of the top cutter is 30°.

"Really, only the old 0.404"in-pitch chain is sharpened at 35°. The majority of top cutters usually slope 10° down to the open side, which requires the handle end of the file to be dropped by that amount to align the file with the cutter," says Andy.

For the purposes of sharpening, all of the mentioned angles are indicated on the file holder to guide the user when sharpening.

"Only sharpen in one direction with the file, inside to out, or the cutter will develop burrs on the outside and lose its edge very quickly again," Andy warns. "Basically how quickly you have stopped determines how much you take off.

"Give each cutter two or three wipes of the file and you will get the full life out of the chain," Andy continues.

He explains that the chains are made of steel but coated in chrome. If there is damage to the chrome at the cutting front edges, the cutter needs to be sharpened to what is required to remove the damaged area.

"If there is damage to a cutter or a number of cutters from hitting a nail or obstacle

, then you find the worst one and count the number of wipes required to clean up the damage," says Andy.

"You have to give all the other cutters the same amount of wipes otherwise the saw will end up cutting crooked.

"The same goes for damaged chrome on the cutters."

The top plate cutter is sloped backwards so it runs smoothly through the timber. When it is filed and sharpened, the top plate goes back and reduces in height. As a result, the depth gauge, or raker, also needs to be adjusted with a file to compensate.

"When sharpened, you need to check the depth gauge/raker height at the front of each cutter with a depth gauge tool. If the raker appears above the tool then you need to file it down."

Andy demonstrates that the desired height from the top of the cutter to the top of the raker/guide is stamped on the side of the cutter, though very small.

"After that, it is how you want to sharpen it," says Andy. "This, to me, is the best way, with the file in a file holder with the angles shown on the file holder.

"One thing to remember is to turn the file holder as you are filing; you will feel the teeth of the file disappearing or filling up with material.

"A quick tap on the vice will clean out the file.

"Other methods of sharpening are with a special bench grinder and filing guide," Andy says. For those who want a way of sharpening without investing in a bench grinder, there is also a battery-operated Oregon grinder. This is an incredibly handy tool because farmers can work it off the tractor's battery out in the field. It's obviously Andy's favourite outside the conventional file and holder.

Irish Independent

For Stories Like This and More
Download the Free Farming Independent App