V4.12 - Setting those pesky knives, Part 2

Continuing our ongoing discussions about the Jointer, we were talking about setting the jointer knives. If I recall correctly, we last mentioned that the jointer knives need to be set dead-even with the outfeed table.

There’s a reason for that and here it is.

The way a jointer does what it does is because the knives remove material as the wood is passed over the spinning cutterhead, that has the knives installed in it. The amount of material that gets removed is determined by the depth setting of the infeed table. For example, if you set the depth at one-eighth of an inch, then one-eighth of an inch of material will be removed as the wood passes over the cutterhead. As that one-eighth inch of material is removed, the outfeed table must support the fresh surface of the wood. It can do that because the outfeed table is set dead-even with the peak of the knives.

So, how to get there from here? Some jointers have threaded screws that raise or lower the knives. Some jointers (I dare say ‘most jointers’) have small springs under the knife that push then up when they are loosened. The basic idea is that you would place a straight edge onto the surface of the outfeed table, let it hang over the cutterhead and raise the knife to touch the straight edge. This must take into account the rotation of the cutterhead, so the touching of the knife to the straight edge must be done at the very top of the cutterhead’s rotation. This is a very difficult thing for the inexperienced person to get the hang of. Fortunately, someone invented a ‘helper’ that makes this a much easier chore.

Let me introduce you to the “Jointer Pal”. This device consists of two magnetic bars that are held together and spaced appropriately with round rods. The unit is placed on the outfeed table and the magnetic bars pull the knife up to the bars, which are dead-even with the surface of the otufeed table. As the knife hangs there on the magnetic bars, you allow the cutterhead to rotate freely and center up, as you tighten the knife locking bar crews. No need for the springs, or the adjusting screws or any of the tricks of setting jointer knives that were learned with blood sweat and tears.

The Jointer Pal is one of the coolest ideas to ever make a dreaded chore sooo much easier than it was before.

If you have a jointer and don’t have a Jointer Pal, you owe it to yourself to get one and make your life a bit better.

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

V4.11 - Setting those pesky knives.

Let’s see…last week we talked about the cutterhead and how to loosen the knives. Now let’s talk about why to change them and how to properly set them.

First the why. Simply because using them makes them dull OR you might put a nick into the knife edge from hitting something harder than the knife. When a nick is there, they will not remove any material; therefore, it will leave a raised line on your workpiece. This also happens with nicks in planer knives. Now that I think of it, there is an old trick that you can do that will let you get more life out of your nicked blades before you need to sharpen them.

So, let’s say that you are jointing a piece and happen to hit a nail that was imbedded in the wood. (note: always check the wood over and look for nails or staples - anything that might nick a blade - BEFORE you run it thru the jointer) this puts a nick in all three blades.

Bad news, but all is not lost. For our lesson, let’s say the nick is one-sixteenth of an inch wide. So, here’s the deal, loosen one blade and move it one-sixteenth of an inch to the left and retighten. Then loosen the next blade and move it one-sixteenth of an inch to the right and retighten. The third blade stays the same. What you have just done is to introduce two un-nicked edges into the path of the original nick. Those two fresh edges will remove the nick line and your board will be nice and smooth.

The limit on moving the knives sideways is decided by the jointer itself. There will be a point at which you cannot move the knives far enough to remove the nick and then you will need to change the knives.

Now the how. Keep in mind a few things. 1) The tip of the knife edges MUST be dead level to the surface of the outfeed table at the topmost point of rotation of the cutterhead. This is a must. As your work passes over the blades, the freshly cut surface needs to lay on, and be supported by, the outfeed table. 2) Never remove more than one knife at a time. 3) Fresh knives are extremely sharp. Number 3 might sound like a no-brainer and it really is, but you would not believe how many people I have heard from that, just for that ONE moment, forgot how sharp they truly are. A few stiches later, they are reminded…over and over.

Ok, so you need to get the knives dead level to the outfeed table…but how?

Ah, that’s the hook to tune in next week.

See you then.
Send your questions or comments to:
Toolsmartz@bellsouth.net and we’ll see what we can do to help you.

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:
Toolsmartz@bellsouth.net and we’ll see what we can do to help you.

V4.9 - Make sure your Jointer is flat

So, we were talking about our little friend, the Jointer last week. We went over some of its basics and what it can do. Thinking maybe this week we’ll just outline some of the ‘care and feeding’ of it.

Like we said, the jointer is just “two flat tables, with a rotating cutterhead between them”. A simple and not very complicated machine, but oh so much it can do for you. In order for it to perform at its best, there are a few things that you need to pay close attention to. One thing is those tables I mentioned. They need to be nice and flat AND they need to be nice and flat. I know, that sounds weird, right? Here’s the thing: each table needs to be nice and flat… and the whole machine needs to be nice and flat also.

A couple of tools that are a must when making sure that your jointer is ‘nice and flat’, is a machined steel straight edge and a set of feeler gauges. The bigger your jointer is, the bigger your steel straight edge needs to be. A short straight edge can be used to check an individual table, but to check the whole table surface, the straight edge needs to be at least three-quarters as long as the whole jointer. In other words, if your jointer has an overall length of 6 feet, your straight edge ought to be 4 feet long. Here’s why. When checking an individual table, first you would use a ‘ladder pattern’. You’d lay the straight edge on the table surface-just inside the edge of the table-and use the feeler gauges to determine if the surface is within the manufacturer’s flatness tolerance. Do one edge and then the other edge (these are the rails of the ‘ladder’). Then take the straight edge and lay it across the table in several spaced out places (these are the steps of the ladder) and check the flatness there.

The last check for an individual table is an X pattern. This is done just as it sounds. Lay the straight edge from corner to corner on the table surface and then do the same from the other corner to other corner. If these flatness checks turn out good, each table is ok.

Then comes the fun part – checking the full machine. The checks are done the same way, but the straight edge is placed one the entire jointer surface, after you have raised the infeed table to be level with the outfeed table.

What this check will tell you is if both tables are in a proper ‘plane’ with each other. If they are not, your tables may be nice and flat, but you will never get a successful joint because your board will come out twisted.

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