Jointer Question

[Mike McCann]

I have a ridgid jointer I bought off craigslist. I have run some test boads thru on edge and I am getting some scalloping. From what I understand one blade is too high. When looking at the manual it says to loosen the jack screw.

My question is what in the world does the jack screw do. I have loosened the blades and have taken them out to make sure no dust or such is under there. but when I loosen the jack screws they do not seem to do anything.

Please advise

thanks

[Lee Schierer]

As their name implies, the jack screw is under the blade and jacks it up. It also prevents the blade from being pushed into the blade holder by the act of cutting wood.

To determine which blade is high, disconnect the jointer from power. Place a straight piece of wood on the out feed table so it hangs over the cutting head, but doesn't quite reach the in feed table. By hand rotate the cutter head so the exposed cutters move toward the in feed table. If one of the cutters moves the piece of wood toward the in feed table that is the high blade. If they all move the piece of wood then your out feed table is set too low or all the cutters are set too high if your out feed is non-adjustable. If you find one high cutter you will want to loosen the jack screws so they will allow the blade to set lower in its holder.

You may need to repeat this test several times and repeat it at each end and center of each cutter. Ideally each cutter should just touch the wood, not enough to move it as you rotate the cutting head.

[Chip Lindley]

Good advice from Lee! It appears there is something lost in translation when Chinese folks write a jointer manual in English. Instead of "loosen" perhaps they should have used the word "adjust", which tells you to "loosen" OR "tighten" the jack screws to effectively raise or lower the knife in it's slot. When all knives are levelled to barely brush a block of wood held across them off the outfeed table, tighten the gib bolts. Then recheck their height again. All should grab the wood equally and drag it forward same amount.

Since you have taken out all knives to clean them, re-check the tightness of every gib bolt. You want equal torque on all. After installing knives, I go around the head 3 times to check tightness before turning on jointer or planer.

[Victor Robinson]

Now that you've removed the knives and cleaned them, you're going to have your first experience with resetting jointer knives. :) Grab some coffee and make sure you're relaxed - this is going to take some time.

As Lee and Chip pointed out, the knives need to be set at the EXACT height of the outfeed table at their highest point, which you'll notice is somewhere between the outfeed and infeed table. If they are higher or lower by even 0.002", you won't be able to joint flat surfaces.

The jack screws control the height of the knives by acting as a support under the knife. Once you put the knives back in their spot (don't tighten the bolts yet), turn a jack screw and watch the knife rise or fall. Get a feel for how much turning the jackscrew moves the knife - when you actually get down to doing this, you're going to be moving the jackscrews in small increments, say 1/8 of a turn or less.

There are many jigs and measuring tools available to help set jointer knives. The cheapest and first method requires a good straightedge. If it's metal, cover the straightedge part in packing tape (so it doesn't nick your knives). Place a knife in the cutterhead and barely tighten the bolts so that they don't move on their own. Place straightedge on the outfeed table and hang it over the cutterhead. Work on one side of the knife (e.g. fence-side). Adjust the jack screw so that as you rotate the cutterhead back and forth near the knife's high point, the knife barely touches the taped straightedge. You want to hear the sound of the knife scraping the packing tape but not gripping it and moving the straightedge. Adjust knife with jack screw until the knife barely grips the tape/straightedge and moves it around a quarter inch. NOTE: When you raise the knife too high, loosening the jack screw may not seem to lower it because it's held in place by the bolts. You might need to apply a bit of downward pressure on the blade to seat it back onto the jack screw (BE CAREFUL!). Once you are satisfied, move to the other end of the knife and repeat. You want to repeat the sound/distance your straightedge was moved exactly the same as the other end.

Once you have done that, tighten the bolts slowly. The final tightening may shift the blade up ever so slightly, throwing off your hard work. This is somewhat inevitable, so proceed slowly, tightening each bolt a little bit at a time. Check the knife again after tightening - hopefully your straightedge moves the same amount as before (somewhere in the neighborhood of 1/4"). If it's moving more than 1/4", you will need to loosen the knife and start over.

Repeat process on other two knives.

Above all, this is a tedious process and will take a few hours. Just be patient, and if you find yourself getting frustrated, come back to it later. Good luck!

[Russell Smallwood]

I would also add that scalloping (if my memory serves) can also be caused by an over-aggressive feed rate. It's not hard to move a board too fast over a 3/4hp jointer particularly when edge-jointing.

P.S. - I used the straight-edge method for a long time, but recently switched to using a magnetic jig. I find it much faster. Typically, the magnetic jigs are used with cutterheads that use springs instead of jackscrews, but I use it anyway. I just adjust the jackscrews up to the knife bottoms AFTER setting them with the jig.

Works pretty well, and takes about 1/4 of the time.

YMMV

[Mike Schuch]

If this is a used jointer and you are going through all this work to set the knives properly... I would install a fresh set of knives at the same time. No use going through all this work with dull knives!

[Harvey Pascoe]

I think some make this sound overly difficult - either that or they have a difficult machine. I got the same advice when I first tried this, but was pleasantly surprised to find it not nearly so difficult. I can set all three knives in my Delta in about a half hour. Granted, your first time will take longer. Use an aluminum straight edge if you have one, it won't nick the knife, and this will avoid messing with tape and you'll be able to see the knife kiss the edge ever so slightly.


I take exception to working one end first, mainly because when you lift/lower one end the other end reacts oppositely, try setting the center first, that way any additional movement will be lessened significantly.

The advice about not letting yourself get frustrated is good advice. Use a stool and take your time.

Also, check the lateral parallelism between the two tables by bringing both tables level and using the straight edge. Tables are likely to get out of kilter when being moved.