Parallogram 8″ powermatic jointer adjustment
I need advice please. I bought a new Powermatic jointer and after a few months it began jointing a bit off. I figured the metal had relaxed a bit so I realigned it as best as I could. Every adjustment guide I’ve found on the net only describes older, gib models and straight knives, which is no help to me. Now, after all adjustments, I get a slight concave edge. If I put two freshly jointed boards together I can just slip a playing card between them. This is about .005 concave on each piece. My friends tell me I’m being silly and that’s more than close enough for wood. I’m reading articles here that say otherwise. I’ve also done alot of checking and everything seems in order with my straight edges and dial indicators except for one thing that intrigues me. If I take a good straight piece of wood and run it partially over the cutters at the far side of the table it comes out perfectly even with the outfeed table. When I do the same at the near side it is also perfectly even. If I place the piece from the far side across the near side I now have a space between that far cut and the near outfeed if you can picture this. Any help would be greatly appreciated. Dave
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Dave,
Your jointer is producing a nice sprung joint. .005" sounds reasonable, but it really doesn't mean anything without knowing how long your boards are.
I understand the first two examples of your piece going over the cutters and coming out perfectly even with the outfeed table, but your last example where it comes form the far side across the near side has got me lost.
Often, a concave edge is the result of the outfeed table being too low. I would first try to raise the outfeed table and see if it goes away.
To further diagnose your problem, start by checking to see if your tables are coplanar. Set your straight edge on the outfeed table and measure the gap between the overhanging straight edge and the infeed table (it may help to raise the infeed table quite close to the straight edge so feeler gauges alone can measure the gap). Check the gap at about 2" and 12" from where the infeed table ends (the end towards the cutterhead), along each edge of the table. If all your measurements are the same, they your tables are coplanar. If not, you need to do some adjustments. My Delta DJ20 has four eccentric bushings per table that fine-adjust the height for each corner. I had to call Delta to figure this out, as it was not outlined in the manual that came with it. Delta e-mailed me the instructions and I performed the adjustment.
First that was using 2 boards that were 50" long and they were about .005 in the center.
I can see how my example could be confusing. First, move the fence to allow the widest cut. Slide a piece of wood about 1" by 2" by 2' long over the knives on edge and make a 1" cut on the end of the piece. This shows to be perfectly even with the top of the outfeed table. Now, turn off the jointer, slide the piece you just cut the 1" cut on away from the fence towards you and watch how it contacts the outfeed across the 8" travel. Mine ramps upward and climbs so as when I'm at the closest point to the near side of the table I'm off the table.
If I do everything in reverse starting at the closest point then sliding towards the fence my first cut is perfectly even with the outfeed then lifts the piece off the infeed because the 1" is now touching the outfeed table. The infeed appears to be perfectly parallel to the outfeed and the knives are as close as I can get to even with the outfeed. It's very difficult to check because of so many cutters instead of one straight knife. It's confusing.
I understand now. Over 50", .005" isn't bad at all. But of course, you can get rid of the gap altogether. When aligning the tables to the cutterhead, I would reference off of the cylindrical body of the cutterhead rather than the cutters.
I've got a 12" Grizzly
I’ve got a 12” Grizzly parallelogram jointer and I have spent an embarrassing amount of time getting the setup right. With this jointer, the adjusters are not directly below the table corners. As a result, any change in one adjuster affects all 4 corners of the table to some degree. In addition, tightening the lock screws on the adjusters can throw off the adjustment. The trick is determining where the errors are, figuring out which adjuster or adjusters to use to correct the error, making the changes, tighten the lock screws and repeat the process a few hundred times until you get it right. The following guidelines may help.
1) Make sure each table is aligned properly with the cutter head.
2) Make sure the tables are aligned with each other.
3) Align the blades to the outfeed table and set the outfeed table height.
To align a table with the cutter head, rotate the cutter head so the blades are out of the way. I don't have a spiral cutter head and don't know if this can be done with one. Lay a straight edge at the far side of the table, the near side of the table and both diagonals so the straight edge extends over the middle of the cutter head. Starting with one of those positions, adjust the table height so that the straight edge just touches the cutter head. I have found that by sliding the straight edge right and left, I can feel if it hits the cutter head, indicating I need to raise the table. I also try rocking the straight edge on the edge of the table, if it can rock down; I need to lower the table. Once the table is right with the straight edge in one position, check the other three positions. Use the adjusters to make any corrections and repeat the process until everything is right.
To align the tables with each other, place a straight edge so that it spans across both tables and doesn’t touch the cutter head. You need to do this in the front, back and diagonals. Adjust the table heights so they are equal. If you can rock the straight edge, you have a crown, if there is a gap at the table edges then you have sag. Another way to test for sag is to place the straight edge on one table and slide it toward the other table; adjusting the table height so the straight edge just clears the edge of the other table. Then place the straight edge on the other table and slide it toward the first. If it bumps into the edge of the first table, you have sag. You need to adjust one or both tables to correct the error. Since the tables should be aligned with the cutter head at this point, you should make the adjustments using a pair of adjusters per table; either the two closest to the cutter head or the two farthest from the cutter head. You want to make equal adjustments with each so you keep the alignment with the cutter head. This is easier said than done and you will need to double check you haven’t thrown off the alignment of the table with the cutter head. Repeat the process until you get things right.
I hope this is understandable. Even if you understand it, you will probably find it to be a maddening process. I started with two test boards about 18” long. With the jointed edges placed together, I could see a sliver of light in the middle which would be double the error. Now the boards fit together with no light and no pivoting in the middle. I sure hope it stays that way.
Thank you so much. I know exactly what you mean because I've done those exact same things a few hundred myself. They make it sound easier to adjust because of the 4 point adjustments but that just isn't true. Then I read where someone turns 1 screw a half turn on his and it has worked perfectly for 30 years. I'll crank up the heater in my workshop and see if I can determine where the problem is. I'll surely appreciate and other ideas from people who have done this before. There is just so little documentation on these jointers.
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