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Thread: Jet JJP-12 table adjustment procedure

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  1. #1
    Join Date
    Apr 2009
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    Connecticut
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    Jet JJP-12 table adjustment procedure

    A while ago I said I was investigating a good procedure for doing this, but life got in the way (twin girls came, business, etc....). I just put my shop back in order and decided to tackle it. I don't really post here anymore, but I did promise to post back with what I came up with, and I'm a man of my word, so here goes.

    - throw out the manual...it's worthless
    - If you're going to do it my way, you will NEED a dial indicator and a long straight edge. The alignment will only be as good as your straight edge.
    - I'm going to assume that you have some working knowledge of how to use an indicator and a straight edge.

    Obviously, unplug it before you start.

    First remove the fence, the entire blade guard (two screws on the left bolt it to the outfeed table) and the piece of sheet metal attaching the tables to each other (4 bolts hold this on). You will have to remove the knobs for the table height adjustment too to get the sheet metal off. All this will give you free access to most of the adjustments and will decouple the tables from each other. CAREFUL...with the tables decoupled and no handle, there are lots of pinch points and the outfeed side will no longer lock in the up position. You've been warned.

    Now lift the outfeed side, loosen the 3 bolts on the rear table mount and unscrew the 4 hex set screws until the mount is sitting right on the base. That completely removed that stupid mount from the adjustment procedure. It's not necessary and it's just one more variable to confuse things. On mine, that still leaves plenty of adjustment for the table height to get it flush with the knives. When that's done, torque down the bolts for good, snug up the set screws so they don't rattle, and forget about it forever. You'll never need to touch those again.

    Bring the outfeed back down but don't lock it. Take your indicator and indicate off the HEAD, not the knives. Forget about the knives. Go right off the head. Pick one of the front adjustment screws and adjust it until the table is level with the head. It doesn't have to be FLUSH with the head (and probably can't be). Just level, i.e. you can drag the indicator across the head and the reading doesn't move. Now here comes the "hard" part, though it's easy when you understand the problem. When you go to lock down that adjustment screw, there is play in the threads. It's a really poor design. The locking screw should be on the BACK of the mount, not on top. When you lock down that locking screw, it pulls the bolt UP, knocking off your adjustment. With the indicator still on the head, you will have to use two wrenches and play with them as you snug it down in order to not throw off your adjustment. It's easy, but you need to understand what's going on.

    When that's done, you have one more bolt left. Get that adjusted so it's just barely making contact with the table (keep an eye on the indicator) but don't lock it down just yet. Lightly lock down the table. If you need to adjust the locking post, you'll see that by removing that front sheet metal cover you now have free access to the locking post, and there's even a convenient slot in the top of the post for a screwdriver. Adjust this so it locks nicely, but keep an eye on that indicator.

    Your goal with this last adjustment bolt is to make it so that the reading doesn't move when you lock it down. I can usually get it better than .001", which is pretty good. You'll soon get it figured out, but if you have no experience doing precision machine setup it will take you a few minutes to get your brain and hands wired together so that they're in sync with what the indicator is doing. When it's close, you might find it easier to lock the table and make the final adjustment locked. Anyhow, when you're done you should be able to set the table on the adjustment bolts, lock it down, and the reading won't change.

    So now the outfeed is level with the head, and with any luck you'll never have to touch it again. On to act two....
    Last edited by John Coloccia; 04-25-2016 at 1:44 PM.

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