Help, can't use a jointer....

Could someone help me out with using a Jointer please. Mine skills are obviously lacking.
I have a PM model 50 6" and have been using it happily and without problem on shorter stock (<=3') for a while.
Here's my problem; Want to straight edge longer stock to take to the table saw and I can't get it right. The stock is cyprus I'm using for outdoor stuff and is ( thankfully ) flat, straight and parallel faced at 7/8ths thickness. The 7/8th edges are another story and are curved or cupped. On the longer stock (4-6') which is presently cupped or curved on the edge I cannot appear to get a straight edge what ever I do. I've checked the machine for table coplanar and it's ok so it's definitely my technique or lack of.
So how does one use this beast on longer stock? Going back to first principles; If the board is cupped do you put the board through with the cup /\ or \/ ? Or in the case of some I have /\/\/ ... Holding the board against the fence and starting a board you have to hold the board against the in table first. What do you do then? When do you move the 'pressure' to the out table? If you continue feeding and holding from the in table on a continously cupped board the back end will rise ( /\ ) or the front end will rise ( \/ ) ? so Does depth of cut affect the working? So far my best result is taking small cuts and doing multiple repeat passes until i get something straight enough but it's still 'rough carpentry' rather 'cabinet' straight. I can get a straighter edge with a circular saw and a straight edge which defeats the object of the machine somewhat. thanks
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Do you have a hand plane or band saw that you can knock the ends of the /\ cupped sides off? You can then get it perfect on the jointer.
Roller stands or auxiliary infeed tables can help, but require some futzing to get right.
You can also use a router, with a bearing guided bit running along the factory edge of a sheet of ply or MDF, to get things close enough to run across the jointer.
If all else fails, can your wood dealer give you a quick straight edge?
Barry
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well there's your problem right there. your jointer is for wood, not islands.

as an exercise, before you start jointing the wood, draw a line where you want to end up. make sure the line is straight (edge of plywood is straight enough) and check during/ after each cut to see what's going on.
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1. You could try to take out some of the cupping if the board is wide enough by layingon a wet lawn in the sun. Water swells on side and the heat drives moisture out of the other to reshape it. Keep an eye on it.
2. When reasonably (?) straight, run through a thickness planer, or thickness sander. If not, use it for smaller pieces and start again with a better piece.
3. Cut a straight piece from a 1/4" masonite or thin scrap, about 1 1/2' wide. Tack to the material [you will have a little waste!] and run through the table saw to get one straight edge. Run through a second time taking only a fine cut to avoid wavering.
4. Turn the board around and cut the second edge parallel to the first.
5. Now joint if you really need to.
Bill.

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wrote:

Then build whatever with it real fast before the moisture content equalizes and it warps again.
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I find it works best to put a cupped board this way /\. If it's /\/\, I dunno, I'd probably go by the one that seems to be dominant if there is one, otherwise toss a coin.

I transfer the pressure to the outfeed table as soon as there's enough board there to allow it. It's the outfeed table that's coplanar with the knives and that's what you want to hold the board flat against.

If the cup is over a long distance, what I might do is to first run one end of the board through (in the /\ position) for a couple of feet and then turn it around and run the other end through. But don't try to do the whole board at once. This way the ends of the board will be straight and pressing the straight section on the outfeed table will support the part of the joint that's being cut. With each pass the straightened section will get a little longer and eventually the board should get close enough that you can run the whole thing through at once. (I admit I haven't tried this, but it seems like it ought to work.)

Yes, that's what I would do.
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I try to cut my lumber into shorter pieces when ever I can and then run it thru with the crown up. Rule of thumb is the lumber shouldn't be more than 1-1/2 times the length of the jointer. Mike
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I didn't know that - why, so you don't make one long curve or something?
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Only if the entire board is in contact with the jointer bed the entire way, will you get the full accuracy of a jointer. As the board gets longer, the accuracy slowly degrades. That rule of thumb will leave you with a straight enough edge for a good glue joint. Nothing hard and fast here, and going twice the bed length will work if done well. That also depends on the thickness and width of the boards, IOW with 1x2s several times longer than the bed, the clamps will serve to pull them together without causing too much stress in the joint. Regarding the long curve, remember you're talking about thou's of an inch here (for a good glue joint). To end up with a noticable curve, you'd need a really long board. Back at the original post, IMO John's response is pretty good. Also make sure you don't use too much pressure and flex the board. For long boards, you also need to first figure how far out the whole board is. I once forgot this and happily flattened the face on a 6' board, only to then find out that one end was 3/4" and the other maybe 3/8. GerryG

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Well, no. It's got to make it flat off the end after cutting. As you mention, it doesn't need to touch everywhere on the infeed to make a flat or straight board.
Glad to see that someone else realizes that taking off the high spots selectively versus running the whole board without sighting is the proper approach. Strangely, it's advocates of hand planing, where this is normal procedure, who have the most difficulty comprehending.
I recommend a hand plane, a jack, if not a scrub and jack to knock off the high spots selectively where there are severe differences.

way,
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GerryG wrote:

I'm not sure that you said what you were trying to say here. Seems to me that if the entire board is in contact with the jointer bed the entire way, then you didn't need to joint it to begin with.
If you mean that in an ideal world the weight of the board would be supported by the jointer bed along its entire length during the final cut I'd certainly agree with that. But darned few of us have jointers with even 6-foot beds, so we have to make do with what we have.

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Okay, I think you said what I meant. But I also said the "optimum" is often more than you need, thereby we have the rule-of-thumb here, and I'm another have-to-make-do also. GerryG
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The tables may be coplanar, but it might be that the outfeed table's height is not adjusted correctly with respect to the height of the knives (or the opposite actually, but I'm too lazy to re-type it all). This would give you a cupped edge evry time. DAMHIKT :(
Just guessing.
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On Mon, 05 Jul 2004 18:45:36 +0000, Jeff wrote:

Blind leading the blind?
I will be buying my first ever jointer tomorrow. It sounds to me like you are saying that you have a plank whose faces are fine, but with a bow in the edges. IF you have or can make a long enough straight edge, lay it from end to end in the cup of the wood (the concave side) Measure from the straight edge to the deepest part of the concavity. Make up two blocks this size and glue them to the ends on the opposite side of the board (the convex side) from the cupping. This will give you 'legs' that you can plane off at the same time as you plane off the convexity.
Mathematically, this solves your problem although I'm totally clueless as to how you will attach those legs.
One additional thought: you could use a shorter straight edge to measure a shorter distance. Then make the legs and affix them opposite the end points of the straight edge. This would be especially appropriate if the board is much longer than your table.
Like I said; I get my first ever taste of a jointer tomorrow evening. Be governed accordingly.
Bill
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On Thu, 29 Jul 2004 21:42:04 -0400, Anonymous
......and in reply I say!:
remove ns from my header address to reply via email
You will at least then need infeed and outfeed long enough to support the legs right at the end of the board, right through the stroke.

How would that get rid of the bow if it's the full length of the board?
Not just nitpicking. I am interested, as you have tried to provide a solution. ***************************************************** It's not the milk and honey we hate. It's having it rammed down our throats.
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If it's really far out on a long board (longer than jointer table), it's just as easy to scribe a line and use a bandsaw or even a sabre saw to just get it close. I omitted a TS from above, assuming the other side has an opposite bow. I'd then use the jointer to just smooth those areas, going by eye, until you're pretty close to the line. The process is quick and easy. Finish using the jointer normally. GerryG
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