Help Please: Jointing problem

[Ruhi Arslan]

Sorry for the strange typos in advance; I'm using a two inchscreen to post this.
I started work on the top of the bench I'm building. I have 8/4 hard maple that I'm going to prepare to make a two layers laminate top. Boards are 5-8" wide. I've gone over my jjp12, checking the blades, coplanar allignment and fence. Boards are relatively nice and straight. When I started to join one face which is 5" wide and about 70" long I've noticed that it wasn't cutting any on the trailing end of the board. Continued hoping that it will flatten it. Ended up a tapered board with trail end is not even touched. I have rollers on both feed and outfeed ends to support the piece well leveled. I ally pressure on the infeed side till I have enough on the outfeed and shift pressure to outfeed maintaining full contact with the table. I think my technique is correct. I tried with a three feet parallel edge board. 10 passes created 1/8 taper. Cutterheads are as level as humanely possible. It's paininthe rear to adjust them on the jjp12 by the way. When thigtening they move. Both tables have less than 0.002" depression in the center parts of them. I have less than 0.001" error on coplanar allingmentvusing a steel straight edge and machinist feelers.
Please spare me from desperation as I'm loosing my fate on all my abilities. I canno figure out what's wrong.

[Stephen Cherry]

Of course it could be many things, first I would ditch the rollers. It only adds another thing to mess up. I struggled with my jointer until I got a wixey digital height gauge. The outfeed table needs to be .000 to the maximum height of the blade. This adjustment is critical, and hard to sense any other way.

[David Thompson 27577]

I agree with Stephen -- roller guides are not your friend when jointing. If their height is off by a few thousandths (quite likely), then you're hosed. And you'd get exactly the result that you describe.

[Ruhi Arslan]

I was not connected at home for some time so I couldn't check it earlier.
I am not quite sure if the rollers have anything to do with it. They do NOT touch the wood while joining. They are only to hold it before and after. During jointing, wood only touches the infeed table first and as it moves over the cutters, I shift the pressure onto the outfeed side, keeping it fully in contact across the table. I check the jointed edge with a six foot straight edge. First 2/3 is "flat and then there is a visible kink like bend.

[Kent A Bathurst]

Check to see that the jointer's infeed and outfeed tables [and cutterhead] are aligned correctly. Raise the infeed to same height as outfeed, and use your straightedge. Check straight down the tables in multiple spots, and also angle the straightedge as much as possible.

[Ruhi Arslan]

Coplanar within 0.001" error, checked with Woodpeckers 3' steel straight edge. I've spent hours to make it "perfect" as much as I can do...

[Victor Robinson]

What is the status of the board when you position the start of the kink over the cutterhead? Where is it in relation to the rollers and tables?

[Darius Ferlas]

I had similar issues a while ago until I figured out what was and what wasn't working for me. This happened to me when I tried to flatten bowed boards that leaned towards the U shape. It turned out that I needed to either turn the board for it to be rather planed as an inverted U. But if the board was too long and the touch points (i.e. the ends of the board) were not at least almost fully on the infeed then I reverted back to the bow facing downwards. In this case I would not cause the wood touch the blade until somewhere close to about 1/4 to 1/3 from the bottom of the bow.

[glenn bradley]

If your tables are co-planer as described then I sense a support issue. You say the rollers are not involved when the cutter head is in contact with the material so that leaves the material itself. With the jointer unplugged, place your board on the infeed table and slide it forward till it touches the cutter head. Check the other end of the board. I assume it is off the end of the infeed(?). I also assume the "bottom" edge is not co-planer with the table(?) Please let me know what you find. Is the end away from the cutter head hanging below the table or is it above that plane?

[Brett Bobo]

Ruhi,
Darius beat me to it but I think it may be related to the orientation of the stock through the jointer. Before taking the stock to the jointer, in this case you're jointing the face grain, sight down both faces of the boards to determine the orientation of the bow or warpage. The board should be placed down on the infeed table as an inverted u-shape, i.e. concave down, so only the ends of the board are cut by the jointer initially. Depending on the bow of the boards and the setting on your jointer for stock removal, e.g. 1/16" removal, you'll be required to take at least several passes before the middle portions of the boards are jointed. To me, listening, along with feel, is the key to getting even stock removal on the entire length of a board. Just to double check your progress, review your cuts on the ends of the board after each pass to be sure that the stock is continually being removed until the entire board is jointed flat. Hope that helps.

[Ruhi Arslan]

... Is the end away from the cutter head hanging below the table or is it above that plane?
I've placed a six foot long straight edge (aluminum level - a good quality one) on the infeed table all the way to the cutter head and ensured that it will span across the table hanging out freely. Material is next to it and fully in contact with the infeed table. It hangs lower and lower below the level as it gets further away from the edge of the table. When I started the material was 9/4 thick roughly (5" wide). I ended up taking about half an inch from front but without touching the rear 1/3. Where it is joined it is "straight". I am applying all the pressure I can exert on the material on the outfeed side once there is enough to hold by two hands. What puzzles me the most is that when I experimented with a 3' long 3/4" piece, the leading edge tapered but jointed edge stayed straight.

[Don Jarvie]

To ensure the jointer is set up correctly take a shorter board, maybe 3ft, that you ran thought the table saw so you know the slides are square. Run that piece through the jointer and check to see if the piece remains square.

If that is fine, then your technique with the longer boards is the issue. Try to work with some scrap, say a few 2x4 that have some twists and see if you can work it out.

[bob hertle]

Ruhi,

Got an indicator? If so, start by lowering your outfeed table a known amount. I would suggest .002" to start with. YOur goal is to have the plane of the outfeed table aligned with the knives at the top of the cutting arc, or very slightly below. If you get snipe at the end of the board, you've gone too far. Using a shorter board to troubleshoot was a good suggestion, but forget the 2 by material unless it's been in the shop for at least a year, and it's very straight grained. It makes no sense to adjust a jointer while chasing internal stresses and differential moisture content in construction lumber.

Regards
Bob

[Matt Kestenbaum]

Sure sounds like something isn't set to be co-planer. Are you using feeler gauges with the steel straight edge (I am assuming that's how you measured the gap)? Do you have a knife setting jig to ensure the knives are all uniformly seated in the cutterhead?

SInce I did not see anyone mention specific order of operations for making a jointers tables co-planer...hear goes:

1) Find top dead center for the cutter head.
2) Assuming the knifes have been set and secured uniformly...
3) Make the out-feed table co-planer with cutter head (only the cutter-head at this point!) with the knife rotated to top dead center. With the straight edge on the out-feed table and over lapping the knife at TDC, check with feeler gauges and make small adjustments as needed. Be sure to check with straight edge straight along the fence edge, then the front edge, down the middle and then diagonal each way.
4) When the out-feed table and the cutter head are coplaner, lock the table.
5) Rotate the cutter head manually to check that each blade is at the same height as the first. If you rotate slowly each knife should just barely pull the straight edge 1/16".
6) Now check to see that the in-feed table is co-planer with the out-feed -- rotate the cutter-head so no blade is at TDC and lay the straight edge so that it contacts the out-feed table for a few inches and extend over the cutter head onto the infeed table. Use the straight edge in the all the various positions making small changes as you go.

[greg a bender]

Ruhi,

I know you are an experienced WW. So I will dispense with the useless and ask the basic. Is this a new JJP-12? If so, was it ever correct? If it was correct, what changed? If not new, what changed?
I am asking because I just unpacked my new JJP-12 and took a couple of test cuts and it seems fine, but have not done any real work with it yet.
I'm interested to hear what the outcome is.
I also plan to so some serious checking / working this weekend (supposed to be above freezing this weekend in NJ!).

Greg A.

[Leo Graywacz]

Sounds like your outfeed table is a bit to high. Lower it until you get a bit of snipe on the trailing end of the board and then adjust it a bit up to get rid of the snipe. It should be as perfect as it is going to get at that point.

If you don't have an outfeed adjust....

well that would just suck.

[Ruhi Arslan]

Is this a new JJP-12? If so, was it ever correct? If it was correct, what changed? If not new, what changed?

Sounds like your outfeed table is a bit to high. Lower it until you get a bit of snipe on the trailing end of the board and then adjust it a bit up to get rid of the snipe. It should be as perfect as it is going to get at that point.
It is not new but didn't see much use. I did some long boards before about the same thickness. I had out-feed table stuck - the sticky protective oil - and I had to do some arm wrestling. I had it got loose but I discovered it after I had the problem and wanted to lower the out-feed table side to experiment.

I tried to check the "flatness" of the both tables with a straight edge and a feeler. When I place the straight edge (Woodpeckers Steel 3') on its spine across the back edge by the fence, in the middle and the front edge towards the cutter head but all within the table, I measure about 0.003-4" depression in the center on all three positions. It is the same on the in-feed side too.

I've re-checked the coplanar. It is as good as I can adjust I believe. I took the blades out, cleaned them and repositioned to match the out-feed table. I think I am as perfect as it can be in terms of height matching the out-feed table. When I do co-planar adjustment I use the 3' straight edge; placing it by the fence and front. I don't see the point of checking it in the middle because there is nothing I can do to adjust it anyway. If both outer edges are in the same plane, center must be too. Tables are straight back to front parallel to the blades and blades are parallel to the out-feed table edge. Straight edge mostly over the out-feed, resting on the table, I adjust the in-feed for both front and rear ends. Feeler has 0.002" so I raise the in-feed till I cannot get the 0.002" anymore along the two points nearest to the cutter head and furthest edge on the in-feed table side. I think I am doing it right. On the other hand, when I place the 6' level as straight edge, it rests on the outermost edges of the in-feed and out-feed tables. Around the cutter head, the gap is about 0.004". I cannot figure it out how does this happen unless my 6' is not straight.

When I joint, in between each passes, I mark the face with pencil to see how it is taking the material. It still takes from the front and leaves the trailing edge untouched. :confused:

[Jason Coen]

I feel your pain, Ruhi.

I'm trying, apparently in vain, to set up a JJP-12HH. When delivered, the infeed/outfeed tables were nowhere near co-planer. To make matters worse, the motor is overheating and causing the thermal overload switch to trip and shut the whole unit down after only 20-25 minutes of operation. I've spoken with WMH about the motor issue, and they couldn't have been more helpful in arranging the delivery of a new motor.

On to the table issues - I just spent another 3 hours (conservatively, I'm up to about 12 hours now) trying to get everything parallel. I might as well have been herding cats for the progress that was made. I'm having the opposite problem of Ruhi - everything I joint has a concavity of about .008 over 4' or so. I'm using a 38" straight edge and feeler gauges, and have been able to dial everything in down to .001 or better. Everything, that is, until I check the tables diagonally, and then I have a depression on either side of the cutter head of about .004. As Ruhi said, there's no way to adjust this out, so it's not even worth checking.

All that said, at this point I'm very, very disappointed with the JJP-12HH. I'm going to give it several more attempts this weekend, and if I can't cure things after this effort, I really have no idea where to go from here.

[John Pohja]

in my experience when the trailing edge is not touching and the board winds up tapered, the problem could be the dreaded too high outfeed table as already mentioned. good instructions were given on how to correct this. John

[Eiji Fuller]

Try this. If everything seems to be in alignment??? You cutters might be a bit dull and as you push the board acoss they take a little bit less off and push the board up slightly so when you get end of the cut it has tapered. You won't notice this as much on edge jointint because your taking off less material and downward pressure is easier to keep consistant.

[Jay Allen]

If the outfeed table is too high, the stock would hit it when it passed over the knives. This should be a very obvious problem.

[Sam Joyce]

Bob is correct on this one.

I had the same frustrating problem and checked everything before finally making the knives TDC ever so SLIGHTLY higher then the outfeed. This cleared the problem up immediately and Im now in jointing heaven. Hopefully you will be shortly.

[John Pohja]

If the outfeed table is too high, the stock would hit it when it passed over the knives. This should be a very obvious problem.

Not necessarily. At least not in my experience. There seems to be a "too high" level at which the stock does not hit the outfeed table yet the jointer is creating tapered boards; further lowering of the outfeed table is still needed in this case. Again, i know this through experience. IMHO the jointer is one of the tougher machines to setup. John