Saw Shop Tech, questions and answers: Sickle bar mowing machine knives.


Vern Burke, SwiftWater Edge Tool Works

Skowhegan, ME

I’ve had a number of questions come in recently via both the blog and the website about sickle bar mowing machine knives so I’m going to dedicate this post entirely to them.

Farmall sickle bar mowing machine
Farmall Sickle Bar Mowing Machine

The first picture that usually comes to mind when thinking of sickle bar mowing machines is the standard old tractor pulled or carried (via the hitch) machine for mowing hay fields. There also were a number of small walk behind machines that used basically the same mechanism, just in a smaller size (I don’t know if anyone is still making these). In this post, I’ll be specifically referring to the tractor powered sickle bar mowing machine.

The mowing machine consists of a row of stationary fingers or “points” and a “knife” that slides back and forth above the points. The knife consists of a long bar with a series of triangular “knife sections” riveted to it. As the hay comes between the points, it’s held by the stationary point until the knife comes by and shears it off. Sounds simple, doesn’t it? :)

Excluding the mechanicals, the first item of repair on a mowing machine is the points. Points get damaged or broken outright fairly commonly, usually by hitting obstructions in the field (rocks, small trees or stumps, etc), things too hard or too large for the machine to cut. Broken or damaged points can usually be replaced one at a time.

Back in my younger days, down on the old family farm in Washington County, Maine, I watched my great uncle sharpen the sickle bar knife on an old fashioned hand cranked wet grindstone. As much as I like and still use the old grindstone for certain sharpening jobs, it’s really interesting trying to handle a 6+ foot bar of razor sharp edges on a grindstone.

sickle bar mowing machine grinder
Mowing Machine Grinder

Fortunately, there are easier options. I rescued this vintage General belt driven grinder (probably 1950s) from the old farm. The “V” shaped stone on the left is the stone for grinding sickle bar mowing machine knives. Definitely a lot easier and safer to use. There are also antique/vintage hand cranked sharpeners that use the same grindstone but clamp to the tractor or mowing machine.

sickle bar mowing machine knife sections
Mowing Machine Knife Sections

The last common maintenance on these is section replacement. Knife sections can be damaged or broken by hitting things too hard or too large to cut. They also eventually wear out due to use and repeated sharpenings. Replacement of the knife sections is accomplished by drilling out the rivets that attach the section to the bar, removing the bad section, installing the new section, and replacing the rivets (I use the big shop anvil for this purpose).

This is just a brief primer on the basics of the sickle bar mowing machine. I provide complete repair and sharpening services for these machines here at the shop, call or email for a quote today!

Visit me at any of the following locations:

Elm Plaza, Waterville, ME (Mondays)
Tractor Supply, Skowhegan, ME (Tuesdays)
Arundel Flea Market, Rt 1 & Log Cabin Rd, Arundel, ME (Fridays)
298 W Front St, Skowhegan, ME (all other days)

If you’re looking for a special tool, please drop me an
email and let me know and I’ll restore one just for you!

SwiftWater Edge Tool Works provides mobile sharpening services across Maine and mail in services around the world for handsaws, carbide blades, planer knives, hand planes, chain saws, knives, scissors, hair clippers, router bits, and almost any blade!

Tales from the saw sharpening shop: Inverters, bent backsaw blades, and more!


Vern Burke SwiftWater Edge Tool Works

Here are a few questions I’ve seen show up in search engine hits on the blog and web site and the answers to them.

1. What type of inverter do I need for mobile sharpening?

The real question is not type (most inverter types will run small sharpening equipment just fine) but size. Remember, there’s a LOT of inertia in large grinding stones and it takes a LOT of current to get the machine started.

On my small machine that I use for knives, plane irons, planer knives, etc, I had to remove the coarser aluminum oxide wheel and just leave the wet horizontal fine wheel because I couldn’t start the machine consistently without overloading the biggest inverter I could get, due to the inertia.

2. How do you straighten a backsaw blade?

It takes a special talent to bend a backsaw blade, since the spine holds them super rigid. The only credible sources I’ve seen recommend removing and reinstalling the spine after straightening but I think this is liable to produce sub-optimal results. I straighten a lot of handsaws here, but I wouldn’t attempt a backsaw.

3. How can I tell if a handsaw is combination tooth?

Combination teeth have the same slope on the front and back rather than being raked toward the front like a normal crosscut or rip specific handsaw. If you find one of these monstrosities, which crosscut and rip but do both poorly, I recommend running over it a number of times with heavy equipment so that nobody else makes the mistake of attempting to use it.

4. How do I sharpen sickle bar mower knives?

The best tool I know of for sharpening mowing machine knives is the same on the old timers always used, the hand cranked or foot treadle cut stone grinding wheel.