Getting to Know the Jointer

A beginner has trouble his first time out with a new jointer, and learns a few things from the experience. April 27, 2007

I recently purchased my first joiner, a 6" Jet. I have never had so many troubles with a tool. After about four hours getting the knives dialed in, I was still having trouble, so I bought a dial indicator accurate down to .01". So I figure it's set - here we go. I am milling down cherry to 2.5" x 2.5" for custom newel posts and then putting a taper at the top. All I am trying to do is take this rough cut 3"x4"x4' long material and make it straight and square on all four sides - then I can cut the tapers. Out of 5 or 6 tries, I've been successful 3 times.

Do I have to take a two decade course until I understand this wacky machine!? I have almost given up on the joiner and made a carriage jig that I put these rough posts into and send them through the planer this works! It gives me at least one flat side with no twist so that I can turn it around and send the other side through. Now I have two parallel sides and need to get my one square side on the joiner - wham! Everything goes down the tube. I don't get it. I understand the way the machine works with the level of knives in relation to the infeed and outfeed tables, but I don't understand how I can work on a board and have it come out worse than it was before I started. I also don't understand why three times it worked like a charm. I feel like I wasted my money with this thing. Any advice?

Forum Responses
(Furniture Making Forum)
From contributor C:
I can sympathize. Back in 1989, when I was setting up my home workshop, I bought a good grade (Delta DJ 6) jointer. I never got it to work right, from day one. It kept tapering my boards. I have had a couple of woodworking friends look at it, and they can make it work better than I can, but still, they don't have complete satisfaction, and point out that there must be some error in the blade settings. So I spent $1000 back then, and it was the worst tool purchase I ever made. I wish you better luck than I have had!

From contributor L:
I can only assume that this jointer has only an infeed adjustable table and not an adjustable outfeed table. This means that you need to adjust the knives very accurately. You also need to account for the initial wear that will occur in the first few boards you push through it. This is when the ultra sharpness goes away from the freshly sharpened knives and it just becomes very sharp. So you need to take your freshly sharpened knives and set them slightly above the level of the outfeed table. Maybe .001", maybe .0005".

When you feed the board through the jointer, start with the pressure on the infeed table. As you pass over the knives and onto the outfeed table, keep the pressure there so the board will let the jointer straighten it out. I always lay the convex side down on the tables so that the board doesn't rise on the curve as it hits the leading edge of the infeed table. If this doesn't work, you need to look at the alignment of the tables in respect to each other. When they are set at zero (equal heights) they need to be on the same plane. Take your most accurate straight edge and lay it across the two tables making sure the knives don't interfere. Take a feeler gauge and see if you have any gaps; if you find that you have gaps, turn your straight edge over and try again. If the gaps are in the same area, then your table alignment is out (and your straight edge is really straight). If the gaps show up at the opposite end of the straightedge, then it is not straight enough to use for this test - you will need to find another. If you find your tables out of alignment, then you need to adjust them by turning the gibbs. These are eccentric pivot points that will move the table alignment up or down. They are very interactive with each other, so turning one forces you to adjust the others to compensate. You can really screw things up if you do a bad job, so mark the starting points before you begin so you can return them to home if things get bad.

From contributor B:

I'll start with what probably is *not* your problem, but should be mentioned anyway. If the infeed and outfeed tables are not in parallel planes, then you will never get the machine adjusted. That is, if there is a twist in one table or the other, then you cannot make both tables parallel to the knife edges. This is a major issue and if it is the case, then the machine should be returned.

Now, to the items that are most likely the real cause of your problem. First, you say you understand the concept of the infeed and outfeed tables. However, do you really understand that the outfeed table relationship to the knives is the key to the entire operation? The outfeed table needs to be dead nuts even with the knives when they are at top dead center. If your outfeed table is not adjustable height-wise, you will have an extremely hard time accomplishing this.

As the wood passes over the knives, it needs to be immediately supported by a table at the exact same height as the knives. If the outfeed table is higher then the knives, the board will be lifted higher than the knives as more and more board rides onto the outfeed side.

If the outfeed table is lower than the knives, then the further the board travels onto the outfeed table, the more the knives will cut into the wood. Just picture the outfeed table at an extreme misalignment of 1/4" below the knives and you should be able to see the wood is tilting downward toward the outfeed table. Try and picture these issues in the extreme, but the reality is that even .01 inches is more than enough to make the jointer not cut true.

To make sure the outfeed table is even with the top of the knives, just take a short straight piece of wood and place it on the outfeed table. Then slide this piece of wood backward until it extends over the cutter head. Rotate the head by hand and each knife should just kiss the bottom of the piece of wood. Do the test at either end of the cutter head and in the center. If a knife lifts the piece of wood as it goes by, then that knife is too high. Note: be sure to unplug the machine first.

Once the knives are parallel and even with the outfeed table, your troubles should be over... That is, as long as the two tables are in parallel planes as mentioned above. All the infeed table does is determine how much wood will be cut off with each pass... nothing more other than supporting your board.

Also, as contributor L said, you must place all pressure on the infeed table only until you have enough wood on the outfeed table to support the board. As soon as you have adequate material for solid hand placement, you have to transfer your hand pressure to the outfeed table. Remember, that is the table that is straight and even with the top of the knives, so you want to make sure the jointed surface stays in solid contact with its surface. Once the front end of the board is on the outfeed table, the infeed table is completely out of the equation for anything other than minor support of the weight of the board. You could actually lower the infeed table 1" so that it is completely clear of the bottom of the board at this point (not necessarily a good idea... this is just for explanation purposes). So long as you keep pressure on the outfeed table end of the board, you will joint the bottom straight as it is pulled over the knives.

The last key item is bow direction of the board... again, as mentioned by contributor L. Picture an extreme situation with a 2" bow in a 6' board. If the board is jointed bow down (upside down rocking chair rocker) then when you start it through the jointer, the trailing end will be hanging below the infeed edge of the infeed table. As you push the board forward, it will be constantly rising as the trailing end is pushed up by the infeed edge. You can't joint a board that is rising as it is going through the knives... It just keeps getting pushed higher off the knives and outfeed table. That is why you joint boards bow up (rocking chair rocker up as mounted on a chair).

From contributor H:
After reading the post, I conclude that it is the driver and not the car. You were successful 3 times out of 5 or six. The machine does not change itself between attempts. But we as humans do. I say it will take practice on your part to know how much pressure to place on the stock and where. As you stated, it was your first jointer, so logic would lend itself to the fact you need to adjust just as you would adjust to anything new. And how much of a taper are we talking about here? Four hours of dialing the knives in? Are your expectations a bit high? It's called "woodworking" for a reason. One of the reasons is that it takes time. Use the machine more and you will think about it less and it will all work out. It does not require decades, but it does require some time.

From the original questioner:
Thanks for all the input. I've been doing more searching on this topic and even though I've been successful a few times with the planer, I believe I may have a problem with the tables not being parallel as some have mentioned. I called Jet after I put the thing together because I noticed that the outfeed table seems to tilt downward in relation to the infeed table, maybe 1/32 or 1/64 or something. They told me that should not be the case and would not affect the performance of the machine - it was just me and that the joiner is one of the hardest machines to use and adjust. It sounds like this does affect the machine. If I think about it, when I rotate pressure from the infeed to the outfeed, the back (tail end) of the board will be slightly lifting off the table as the board starts the slope downward on the outfeed table. Can I be thinking correctly? This would give me one heck of a taper, which I seem to be really good at making. Once again I am going to start checking and rechecking the tables and the adjustments. My manual talks about gib screws and how to adjust them, but they don't mention what they are for and what they adjust. Sounds like this could be where I start? Maybe also placement of metal shims/feeler gauges under the outfeed table. The outfeed table is adjustable, but once it's set I have no need to adjust it... hopefully for a while. Can I be making sense of this or am I still in the dark?

Contributor B, you mentioned if the tables are out of whack, return the machine. It sounds like the tables are adjustable so I can fix the problem. Has anybody noticed that the tables need adjustments right away in order to get them parallel? I can see adjusting the knives but I would think the table would usually come dead flat from the factory.

From contributor B:
I'm not sure if there is an adjustment for downward lean on the outfeed or infeed tables. A good jointer will have tables that ride up and down on dovetail ways. You can tighten the ways but I don't know that you can lean the tables up or down with them. I also don't know that you can twist out of the tables this way.

What you want to do is take a dead straight metal straight edge and lock it down on the outfeed table (get the knives out of the way). Have it extend over the infeed table and measure the distance between the straight edge and the table, both close to the knives and at the infeed edge of the table. This measurement should be same at both locations.

Another thing you can try is to joint a 6' to 8' long board halfway. Turn off the jointer and press down on the lead end. If the outfeed table is drooping, the back end of the board should rise and fall as you press the lead edge down hard to the table. This would be a bad thing! I suppose theoretically you could still joint straight if an outfeed table were drooping, but it sure would make the process more difficult.

Bottom line is that as you joint a board, it should be solidly down on the full length of the outfeed table all the time. If you cannot accomplish that, then the machine is quite possibly out of whack. I say "possibly" instead of "definitely" only due to operator inexperience.

From the original questioner:
I was messing around today and even though I set my knives to the height of the outfeed table with a dial indicator, I lowered my outfeed table just a hair, something like a CH or smaller, and voila! I kicked out three flat, square, and true posts from a piece of (about 3x7) in about 20 minutes - no problems at all. If that was the only problem with my jointer, I am happy. I just wish my jointer could talk to me and tell me what it needed to operate properly. I'm keeping my fingers crossed.

From contributor F:
I had similar learning curves, but the one thing no one has mentioned is: Take a long straight edge (preferably a metal flat bar but very accurate, i.e. gauge plate) and bring both tables up to above the blades or turn the blades so they are out of the way and you do not damage them. Place the straight edge across both tables and use a set of feeler gauges to align the pair of them straight and flat.

If you get this right you can then adjust your outfeed table as mentioned by contributor B. In other words, place a flat piece of timber on the outfeed table just over the blades and rotate to blade set and the piece of wood should be touched and move every time a blade contacts it (but only just touch - not engage).

That sets up your outfeed. Now all you should have to do is set the cutting depth of the infeed, say 0.5mm per pass. Start small; do not try to take off more than 1mm whilst you are learning. If none of this works, sue the supplier or get them to set it for you. From my experience with JET machines, the machine will be fantastically well made and fully adjustable.

From contributor B:
Just curious... How many others call these machines "joiners" instead of "jointers"? I see this on a regular basis and wonder about the derivation of the name. I know they straighten boards for "joining" together, but I see it more as creating a straight "joint".

From contributor V:

Here's something that might interest jointer buffs (or a buzzer as we say in NZ). At the factory where I did my time, we glued all panels up with animal glue using just one sash cramp per joint cramped across the middle. That required a hollow joint to get the ends tight. This was achieved by slightly raising the outfeed table on out old Wadkin buzzer on the final cut. The board would keep rising above the outfeed table till halfway, then begin to drop back down. Pressure was kept at the middle point of the board, and voila - hollow joints of about a millimeter gap! Now to prevent the joint from springing with the one sash cramp on one side, we slightly tilted the fence forward a degree or two. When the cramp was tightened the boards all pushed towards the cramp! It all made for rapid cramping with the use of hot glue. Only one side, the 'face', was planed and this side went to the fence of course. We had another trick for rapid stacking to paste on the hot glue quickly both edges except the outer. The next day the glue was scraped off the great pile of joints and they all went through the thicknesser. Anyone else done this method?

From contributor J:
To the original questioner: From the sound of it you may be okay now. But let me say without any doubt that if Jet told you the tables cannot be out of alignment, or if they were it would not affect the cut, they lied on both accounts. If your outfeed table is off by more than a couple thousandths from dead flat and parallel to the infeed table, you are not getting an accurate cut.

The good news is it is a fairly easy fix. The bad news is it will probably take you a couple more hours of adjusting. I have the same jointer, new, and went through the same trial and error process.

As said before, you will need an accurate straightedge the full length of your jointer beds, (I use an 8' aluminum 1"x4" tube - inexpensive and accurate enough for this operation) and a set of feeler gauges. Your tables should not be out by more than a couple thousands of an inch. If they are, you will need to shim them into alignment. There are adjustments on the infeed table, but I never could get them to work right. With some patience and a couple shims, you can get it right on the money. I believe the instruction manual covers most of this method, if I remember correctly.

From contributor R:
You should also site the board before starting the cut. Machine the board so the ends of the board are touching the table; the crown should be up. Like the rockers of a chair, but upside down. If you have the middle of the board only touching the table, it will rock back and forth with your hand pressure changes and it will never straighten.

From contributor A:
I know this is a pain in the butt, but it might be worth paying a tool guy to come out and set up the tools right the first time. Last IWF I picked up the new parallelogram jointer from Powermatic. Right out of the box that thing was out of whack. I called my local Powermatic guy, paid him a few bucks, and he adjusted the machine. It worked great for a few months. About 6 months ago, the machine started to joint on a curve. Long boards started to "fall off" the cutter when the fence was all the way back. When the fence was pulled to the front of the machine, the jointer worked fine. Last time he was here he looked at the machine and told me the knives were wearing on the backside and just had not been used on the front side as much. New cutters would fix the problem. One thing I've learned over the years, these tools need regular maintenance or they just get out of whack. Find a good tool adjustment dude and make friends.

From contributor W:
Hope you got it figured out. Once you joint one face flat, the 90 degree side will be jointed by holding the first side against the fence. It must be square! The first pass of the second side is the only pass that you must be sure to have good sideways pressure to keep the new cut exactly 90 degrees to the first one.

From contributor O:
The questioner says: ''It gives me at least one flat side with no twist so that I can turn it around and send the other side through. Now I have two parallel sides."

It's not the machine. Even if it works dead-on accurate, it won't give you parallel sides. You need to flatten one side and take it through a planer. That will give you parallel sides.

From contributor T:
You took it out of context. If you re-read the questioner's post, you will see he is describing the use of his planer to generate two flat and parallel faces. Then trying to get a third flat face on the jointer. As he says, "this works," except for his inability to (consistently) generate that third face.

From contributor Y:
Contributor O, I think you have it right you're not going to joint four sides on a jointer and find it square unless you're lucky. Two sides and a planer or run it through a table saw.

From contributor O:
The 3rd and 4th sides will only become parallel with a planer or tablesaw. Since when does anyone run four sides through a jointer?

From contributor T:
The questioner says "...given up the joiner and have made a carriage jig that I put these rough post(s) into and send them through the planer this works! It gives me at least one flat side with no twist so that I can turn it around and send the other side through. Now I have two parallel sides and need to get my one square side on the joiner..." We all know this works - very old technique for boards wider than your jointer, like a 1"x12" board and having only a 6" jointer. As for the questioner's making it seem like he has been able to (sometimes) get a square 4-sided post on the jointer only, I'm as much in the dark as anyone.

From contributor O:
If the questioner can get one flat side on this jointer, his jointer is working just fine. The jointer's job is to do just that flatten one side!

From the original questioner:
Yes, I was talking about running my carriage jig through the planer and then flipping the board 180 to get two flat sides. How do I get a good flat 90 adjacent to my two flat sides? That was the problem I was having when I was having problems with the joiner. Well the joiner is now working great, and the problem has been solved. It really is an amazing machine when it's working properly... When it's not, that's another story and a headache all the same. My prayers go out to anyone learning to use a new joiner out of the box with no guidance, but stick with it - it's a great machine when it finally comes together.