Friday, March 8, 2013

V4.10 - The Jointer’s heart – the cutterhead

I hope everyone’s week is going good. We’re still learning things about our Jointer. This time we’ll be talking about the cutterhead and giving some hints about setting those knives.

Jointer cutterheads are essentially a round cylinder, made of either steel or aluminum – depending on whether the jointer is a professional style or a true hobbyist model. As you can guess, the aluminum cutterhead is the ‘cheaper’ of the two. Cut into that cylinder are some grooves that hold the knife locking bar and the knives themselves. I have seen everything from 2-knife cutterheads to 4-knife cutterheads. Again, it depends on if the jointer is a more expensive model or just a basic one.

For our lesson this week, we’ll just consider a standard, 3-knife, 6-inch wide jointer. This size of jointer is a fairly basic model and would do most jobs for most people. Obviously, if you are doing production work or using lumber over 6-inches wide, you’d need a larger jointer.

One of the first things to do if you need to get sharp knives in your jointer is buy another set of knives. If you want to have your dull knives re-sharpened, that’s fine, but one of the most basic ‘rules’ to follow: NEVER take all of the knives out of the cutterhead at the same time. Here’s why. While the cutterhead looks like a big block of steel from the top, take a mental look at it from the end. You will see a very small block of a center ‘core’ and three ‘wings’. When the lockbar and knives are put into the slots, they fill up – sure, but what can happen if you remove all knives at the same time, is that you will very likely distort the cutterhead when you put them back in. Yes, there is a way to do it without distorting the cutterhead but you have to be very careful and know the ‘trick’. It’s just easier if you don’t have to cross that bridge.

In each slot of the cutterhead, most jointers have a lockbar that has bolts in it and the knife sits alongside the face of the lockbar. On the backside of the lockbar, there are bolts that usually have a rounded head because they butt up against the side of the slot and they wedge the knife and lockbar into place to keep them from moving during adjustment and operation. Usually, under the knife, are a couple of springs. Those springs maintain tension and push the knife upward once the lock bolts are loosened. Another thing to remember: to LOOSEN the knife, you’ll need to screw the lock bolts INTO the lockbar. Holding the knife in place requires those bolts to act as a wedge, to loosen, you have to create some room for everything to be able to move.

More next week….

Send your questions or comments to: and we’ll see what we can do to help you.

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