Jet JJP 12HH issue
#11
I had a Jet authorized tech install a helical head in my machine a few weeks ago.  I having an issue that has me scratching my head.  
Confused . While in jointing mode, either face or edge, the machine only takes off material on the front half or maybe a bit more of the workpiece.  The end result is a "banana boat" edge which means if you lay it on edge on a table, it will rock.  My local Woodcraft instructor said it was a technique issue where I was pushing down to hard at the beginning of the cut and the end and thus causing the issue.  i didn't think I was doing that but was willing to see if that was the problem.  It's not.  I ran some test boards through on edge and kept the pressure light and extremely even. It was very evident that something must be out of whack.  Any ideas?  I'm thinking about having that tech back out to see if everything is within spec on the tables.
Howard
The Dallas woodworker

"I didn't attend the funeral but I did send a letter approving of it"
Mark Twain
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#12
(10-12-2019, 05:36 PM)howardh Wrote: I had a Jet authorized tech install a helical head in my machine a few weeks ago.  I having an issue that has me scratching my head.  
Confused . While in jointing mode, either face or edge, the machine only takes off material on the front half or maybe a bit more of the workpiece.  The end result is a "banana boat" edge which means if you lay it on edge on a table, it will rock.  My local Woodcraft instructor said it was a technique issue where I was pushing down to hard at the beginning of the cut and the end and thus causing the issue.  i didn't think I was doing that but was willing to see if that was the problem.  It's not.  I ran some test boards through on edge and kept the pressure light and extremely even. It was very evident that something must be out of whack.  Any ideas?  I'm thinking about having that tech back out to see if everything is within spec on the tables.

Your outfeed table is too high, lower it.
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#13
Could be technique... downward pressure should be applied to material on the outfeed side ASAP, otherwise you will have issues.

Could be mechanical... outfeed table needs to be adjusted so it is even/level with the new cutterhead blades.
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#14
(10-12-2019, 07:24 PM)Lumber Yard® Wrote: That's what I have been doing.  Light pressure on the outfeed side.  Really weird.


Could be technique... downward pressure should be applied to material on the outfeed side ASAP, otherwise you will have issues.

Could be mechanical... outfeed table needs to be adjusted so it is even/level with the new cutterhead blades.
Howard
The Dallas woodworker

"I didn't attend the funeral but I did send a letter approving of it"
Mark Twain
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#15
If you didn’t have this problem before the helical head was installed, them I’d suspect (as already mentioned) that the outfeed table needs adjustment. I can’t imagine that you would need to adjust your technique now if the machine was otherwise setup properly. 

Not related to your immediate concern, but did the Jet technician also change the planer mode feed rate? The factory feed rate on the helical head version is 12 fpm while the straight knife version is 20 fpm. The JJP 12HH is underpowered with the 3 hp Jet motor and 20 fpm feed rate. I converted mine to a Byrd head several years ago and I bought the parts from Jet to also change that to 12 fpm, and I’m glad I did.
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#16
(10-12-2019, 05:36 PM)howardh Wrote: I had a Jet authorized tech install a helical head in my machine a few weeks ago.  I having an issue that has me scratching my head.  
Confused . While in jointing mode, either face or edge, the machine only takes off material on the front half or maybe a bit more of the workpiece.  The end result is a "banana boat" edge which means if you lay it on edge on a table, it will rock.  My local Woodcraft instructor said it was a technique issue where I was pushing down to hard at the beginning of the cut and the end and thus causing the issue.  i didn't think I was doing that but was willing to see if that was the problem.  It's not.  I ran some test boards through on edge and kept the pressure light and extremely even. It was very evident that something must be out of whack.  Any ideas?  I'm thinking about having that tech back out to see if everything is within spec on the tables.

Start by bringing the infield table even with the outfeed. Check with a straight edge across both tables to see if they are aligned. No light under the straight edge , then lower the infeed table and take a cut. The cut should be even now. I doubt your technique is at fault. More of a co-planar issue.
mike
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#17
(10-13-2019, 04:29 AM)Greg Jones Wrote: If you didn’t have this problem before the helical head was installed, them I’d suspect (as already mentioned) that the outfeed table needs adjustment. I can’t imagine that you would need to adjust your technique now if the machine was otherwise setup properly. 

Not related to your immediate concern, but did the Jet technician also change the planer mode feed rate? The factory feed rate on the helical head version is 12 fpm while the straight knife version is 20 fpm. The JJP 12HH is underpowered with the 3 hp Jet motor and 20 fpm feed rate. I converted mine to a Byrd head several years ago and I bought the parts from Jet to also change that to 12 fpm, and I’m glad I did.

What parts were needed to change the feed speed? How big a PITA? It seems like a lot of the planer power feed mechanism is pretty difficult to access.
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#18
If you look at a recent manual, it identifies which parts are specific to which model. Order the parts that are specific to the helical model. Pretty much everything is a pulley or gear swap, with a different belt. It’s straight forward, and the parts were surprisingly inexpensive. The only downside when I did the conversion was that there was a 3-4 week wait for a couple of the parts.
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#19
I have the same machine, and have a similar issue in the past, usually, the outfeed table is too high.     Here is one video that shows the adjustment on a straight knife jointer, though it is the same for the Jet.  https://www.youtube.com/watch?v=PNOt1SvjoLs  .  It helps to have some straight stock to get the set up right.  Lay it flat on the one of the tables, or the fence, to be sure.  One test, that they don't show on the video, is to mark the bottom trailing edge with chalk or a pencil, then place the straight stock so that most of it is on the outfeed, and only an 1 inch or so is over the infeed, then turn on the machine and push it the rest of the way.  If all the pencil mark is taken away, the outfeed table is too low.   It usually takes me some fiddling,  too high, then too low, to get it right.
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#20
(10-13-2019, 07:20 PM)barryvabeach Wrote: I have the same machine, and have a similar issue in the past, usually, the outfeed table is too high.     Here is one video that shows the adjustment on a straight knife jointer, though it is the same for the Jet.  https://www.youtube.com/watch?v=PNOt1SvjoLs  .  It helps to have some straight stock to get the set up right.  Lay it flat on the one of the tables, or the fence, to be sure.  One test, that they don't show on the video, is to mark the bottom trailing edge with chalk or a pencil, then place the straight stock so that most of it is on the outfeed, and only an 1 inch or so is over the infeed, then turn on the machine and push it the rest of the way.  If all the pencil mark is taken away, the outfeed table is too low.   It usually takes me some fiddling,  too high, then too low, to get it right.

Problem solved.  Seems the HH is ever so slightly smaller in diameter than the one that came on the unit.  The outfeed table was slightly too high. Once adjusted, it cuts evenly all the way down.
Howard
The Dallas woodworker

"I didn't attend the funeral but I did send a letter approving of it"
Mark Twain
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