10 tuning up your jointer

Replacing dull knives in your jointer is one of the trickiest machine setup operations you'll have to do in the workshop

And the reason has to do with the way the blades are held in

I want to show you a specific way for getting the blades installed correctly

It's fast, but more importantly, it's also very accurate, which is vital when it comes to this job

The challenge springs from the design of most jointer knives. They're just a rectangular piece of steel with a bevel sharpened on one edge

There's no groove or hole or anything to register this blade in the revolving cutter head

The adjustment of the height on all three knives is entirely up to you

And it's got to be within several thousandths of an inch in order for this machine to work right

I can show you how to get that kind of accuracy with nothing fancier than an ordinary piece of wood

The first step, of course, is to shut off any power to the machine. Either unplug it, or in the case of this jointer, which is hardwired into the circuitry, shut off the breaker

In either case, try the switch. Turn the thing on. Make sure it's not going to come on before you get involved with this

because you're going to be touching all the knives, and you definitely don't want the machine to start up

Next, retract the guard and put some wedges under it, just to hold it back

When you look at the cutter head, you'll find that it probably has three blades. This one does

And there are four bolts that hold that blade in. The first step is just to loosen them

And it doesn't take very long. They're small. They're not hard to turn

And you need to loosen them all enough so that the knife and its holder actually comes out

With the knife and its anchor strip removed, it's a good time to clean all the sawdust out from the cutter head

You'll also find that different places will have resin buildup. It's a good chance to remove that now

The trick is getting the knives so that they're all exactly the same distance from the center of the cutter head

Now, you can use a dial gauge or other fancy machinist's tools to get this job done

Or, as I said, just an ordinary piece of wood. Start by putting the blade and its holder back in the cutter head

And then snug up the anchor bolts. Not too tight, but just tight enough to hold the knife wherever you put it

Now you have to lower the outfeed table of the jointer just a little bit

Maybe a thirty-second or a sixteenth of an inch at the most, below the top of the arc of the blade as the cutter head rotates

With your new blade snugged up in the holder, and the outfeed table lowered a little bit

and a fairly narrow piece of wood laying on top, turn the cutter head so that the knife just contacts the wood

Mark where the edge of the outfeed table is with a sharp pencil

and then rotate the cutter head, pulling the piece of wood until the blade leaves

Mark again. That distance is critical because it's a magnified view, in a sense, of the height of the knife

You now repeat the same process at the other end of the knife

adjusting the blade so it's a consistent level all the way along, and repeat the process for the other blades

Snug everything up, raise the outfeed table so that it's just level with the top of the arc of the blade, and you're good to go