The Knife Fantastic

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This article is from Issue 10 of Woodcraft Magazine.

The JJ-6CSDX long-bed 6" jointer from Jet has a timesaving new system for changing out knives — it’s as easy as one, two, three.

By Tim Rinehart

It’s tough to write a 6" jointer review that contains anything that hasn’t been written before, lots of times. There are only so many adjectives to describe big chunks of cast iron. When originally asked to review the Jet, my first reaction was, “Hey ... I had to do the last jointer.” But after I heard it had easy-to-change, double-sided knives, I had to see for myself.

I hate changing jointer knives. I have three sets of knives for my jointer: one dull set that needs to go to the sharpener, one sharp set ready to go in the jointer, and one set in the jointer that probably needs to be replaced. It’s not difficult — just time-consuming — to get them set up exactly right. Shop time is a precious commodity for me, usually coming late at night or very early on a weekend. The last thing I want to spend that shop time on is machinery maintenance and tune-up. I’m interested in anything that will shorten the maintenance time and increase the time I get to spend making sawdust. 

I’m still not really going to review the jointer. The 6" long-bed Jet jointer has been reviewed before, and I agree with all I’ve read from other testers. It is a good, solid machine for the money. It has acceptably flat and coplanar beds right out of the box, the fence is straight and adjusts easily, and there’s plenty of motor for facework. Bed height is adjusted with front-mounted hand wheels and the 56" bed length definitely helps work longer stock. 

The JJ-6CSDX arrived in two boxes. One contained the base cabinet with the motor, power cords and switch already installed. The second contained the base/beds assembly, fence assembly, and all the bits and pieces neatly packaged and mounted in Styrofoam. The manual covers assembly with simple instructions and plenty of illustrations. Jet even includes the necessary wrenches. 

Assembly time was about 45 minutes. The only fault I could find was with the fence tilt-lock handle and the outfeed table gib lock screws. The tilt-lock handle uses a sliding cross handle to give good leverage when locking the fence. When fully tightened on the machine I tested, the sliding cross handle slid down and hit the back of the bed casting when moving the fence toward the front of the machine. This stopped the fence about two-thirds of the way across the bed. Reaching over and lifting the handle allowed the fence to move the entire width, but it was an annoying glitch. I also had to remove the two outfeed table gib locking screws and run a thread chaser through the casting before they turned without brute force. 

Okay, that covers the cast iron part.

The JJ-6CSDX comes with a three-blade cutterhead featuring double-edged disposable knives, very similar to lunch box-style planer knives. Each knife is secured to the cutterhead with four screws and a flat gib. There are two knife adjustment cams about 1" in from the end of each knife. The gib has access holes to allow adjustment of the cams with the gib loosened, but in place.

REMOVING the knife gib. 
LOOSENING all four cam lock screws.

ADJUSTING THE KNIFE CAM is a very sensitive operation. A full rotation moves the knife a total of .015".

Adjusting the knife height

The manual gives straightforward instructions for checking the knife height to the outfeed table using the straightedge method. They forgot to tell you the only way to get to the pulley or the belt to rotate and hold the head is to remove the rear belt guard. You could just remove the fence to reach the pulley, but if you have a case of old eyes like myself and rely on a dial indicator to check your knives, you just lost your top dead-center mark. The first knife I checked was right on the money using the eyeball-the-straightedge test, so I checked the knife height all the way across using a dial indicator. It was perfect; life was good.

Checking the second knife showed it was low on the fence end. Not much — a little less than .008"— but more than I’m happy with. Piece of cake; I had actually read the manual. Rolling the cutterhead forward until the blade gib screws were visible, I used the supplied hex wrench and loosened all four screws, then switched to the smaller hex wrench to loosen the cam lock screws, then located the largest hex wrench to adjust the cams. Yes, it takes three hex wrenches to adjust the knives. Jet was kind enough to supply decent hex wrenches, but there is no place to store them. If I owned this jointer, the first thing I would do is make a holder for these three wrenches. In my shop, anything that gets used as infrequently as special hex wrenches for changing jointer knives will disappear unless tied to the machine.

A full rotation of an adjusting cam moves the knife a total of .015". Turning the cam more than one rotation starts the adjustment over again. Turning the cam is a very sensitive adjustment, and a trial-and-error affair. There is no way to tell exactly how much you have moved the knife, or what direction. “Kentucky windage” is the term that comes to mind. Take a guess which way the knife is going to travel, move the cam ever so slightly, hold down on the knife with a piece of wood to make sure it is seated, roll the cutterhead back and check the knife adjustment. Repeat as necessary. 

The good news is I soon got a feel for moving the cams, and within 30 minutes had the knives set to suit me. I would really like to have seen a mark on the cams showing the highest point. It would make a nice reference to help determine how much and which way for the first adjustment.

Reversing the double-sided blades

Although these knives are thinner than conventional knives, they performed great. We ran a lot of rough white oak, taking much larger cuts than I normally would, and could not tell which boards were done on my conventional cutterhead jointer and which came from the Jet.

After making a pile of chips, I decided to see how long reversing the double-sided blades would take. Having gotten a feel for the adjustment cams, I managed to get all three knives reversed, adjusted, and the jointer ready to use in a surprising 15 minutes. I’ve spent longer than that just looking at my jointer and considering whether or not to change knives. 

Overall opinion

There are still a few improvements I believe could be made to the system, but Jet has a winner with this knife arrangement. I’ve spent enough of my life fighting stuck jack screws and blades that move when you tighten the locking bar. Even though it requires three different hex wrenches, this cutterhead is far quicker to set up. Once you have a few minutes of hands-on time to get a feel for the adjusting cams, accurately setting these knives is just plain easy. There is no excuse for not having a jointer that is accurate and sharp with this cutterhead.

Other advantages include the fact that your spare set of knives are just a blade turn away, and that shifting knives if you get a nick can be accomplished in a just a few minutes. No cam adjusting is necessary since the cam holes in the knives are oblong; you just loosen the gib screws, slide the knife, and retighten.

For those of you who already own one of the Jet long-bed conventional head jointers, Jet offers a quick-change knife head kit to upgrade your jointer. Installation is simple. Remove the fence, belt guard, and head pulley for access. Then remove the two bolts from the bottom of the jointer that hold the knife head pulley housings in place (this can be done without removing the jointer from the stand). The complete knife head assembly then slides out the back of the jointer. Installing the new head is just the reverse. I would guess an hour at most to complete the upgrade.

I’m not ready to sell my jointer so I can run out and purchase the Jet JJ-6CSDX, but you can bet when I am ready to upgrade I’ll be looking for this cutterhead system. Don’t look at it as purchasing a jointer or head upgrade; look at it as buying more time to woodwork. 

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