Setting jointer blades

[kenneth kayser]

I have a Powermatic 6", long bed jointer. I can easily get the blades adjusted until I tighten them. Tightening invariable moves the knife. I can tighten as slowly and evenly as I want, but the knives always move. The only way I can get them even is to run a diamond sharpener over them. (Powermatic recommends this.) Does anyone know a way to get the knives adjusted without grinding?

[David Kumm]

Make sure the gibs are snug against the knives when you make the final adjustment. The knives should raise up a consistent amount. Mine raise .001 to .002. Yours may be different due to the knife angle and grind but they should all move about the same so adjust shy by that amount. I try to get within .002. Any closer is great but doesn't change my life. I use oneway dial indicators although I haved replaced the dial with a Starrett because it is less jumpy. The key is keep the gibs putting pressure on the knife as you adjust. Dave

[Myk Rian]

Make sure everything is spankin clean.

[Stephen Cherry]

First, watch this video a few times.

http://video.google.com/videoplay?docid=2983839096587014177

I use a wixey digital height gauge and set the knives at .000 or -.001. To do this I snug them a little high, then beat them down with a wodden mallet. Once you do this a few times, you will wonder what all the talk is about, it really is that easy. It's a one beer job. (with the jointer unplugged, of course, with the jointer plugged in, you will need tequila)

[John Nesmith]

I've tried a variety of methods, but have settled on this one:

http://www.finewoodworking.com/ToolGuide/ToolGuideArticle.aspx?id=5294

It's by far the easiest of all I have tried.

[kenneth kayser]

I watched both of those. The one with magnets did not address movement when tightening. The other one was less than impressive. It seemed that he was just going back and forth: tap too hard and you are too low. Getting one nut just right moved the blade under another nut. My jointer has allen bolts under the blade. The blade cannot go lower than a bolt position. But it can, and does go up. the amount of movement is different from blade to blade and across the width of a blade. Maybe next time I will try putting PSA abrasive on the cutter head side of a blade.

[Stephen Cherry]

The other one was less than impressive. It seemed that he was just going back and forth: tap too hard and you are too low. Getting one nut just right moved the blade under another nut. My jointer has allen bolts under the blade. The blade cannot go lower than a bolt position. But it can, and does go up. the amount of movement is different from blade to blade and across the width of a blade. Maybe next time I will try putting PSA abrasive on the cutter head side of a blade.

That's about how it works. I can do it on my griz 12 inch jointer in less than 30 minutes, and if I try, probably less than 15. And the knives do move around a little as they are tightened.

There really are no tricks other than what is in the video, and the willingness to try it a few times without becoming frustrated. Maybe a Byrd head?

[Paul McGaha]

I've had good luck using a jointer pal knife setting jig.

Too easy really.

PHM

[Chris Parks]

Machine the end of the bolts that contact the blades and make sure they are perfectly flat.

[John Nesmith]

I watched both of those. The one with magnets did not address movement when tightening.

Hasn't been a problem for me. The jig is held down firmly to the table, so it would be nearly impossible for the knife to raise up while tightening. I suppose it could lower while tightening, but it would have to free itself from the magnet, which would create an audible click when it broke free. I've never experienced that.

[Paul McGaha]

On my jointer, A Powermatic PJ-882, When they are not tightened the knives are held up a little by a spring.

I try to tighten the knives evenly and kind of gently, they cant go up because the jointer pal has them, they cant go down because the spring pushes them up.

Maybe I'm just lucky as my jointer is just kind of easy in regard to knive changes.

PHM

[Chris Parks]

The blade moves because the bolt end that contacts the blade is poorly machined. Have a look and see if it is perfectly flat, generally they are not and everything else is a band aid to overcome the issue. It should be a two piece assembly so the contact face does not revolve with the bolt but that is a big ask from manufacturers trying to keep the price down.

[kenneth kayser]

I do have a method of measuring top dead center (TDC) accurately. Lay a good straightedge, edge down on the outfeed table. Now, rotate the blade under the straightedge. If the blade is too low, nothing happens. If it is too high, it will lift the straightedge and drag it toward the infeed table. You can put an indicator on the top of the blade (over the knife) to measure the lift. However, after a few measurements, you will know how much drag equals how much lift. On my jointer 0.001 lift equals 1/16th drag; 0.002 equals 1/8th inch drag, etc.

After I put new blades in last time, it trimmed them with a diamond board per mfgrs. instructions. They came out perfectly at 0.002 high; so 0.002 high must be correct for my machine.

Now to the movement problem. I don't think it is possible to maintain the bolt heads parallel to the knife. However, I think I will try smoothing the bolt heads and rounding them just a bit. Then, I will apply some anti-seizing compound to reduce friction. If that does not work, I will try removing some bolt head material in the area of the bolt head which is turning "up" when tight. This will force the bolt to move the blade down. The blade cannot move down because there are adjustable bolts on the bottom of the blade. Relying on anything to keep the blades from rising will not work well because the cutter head will simply rotate off center a bit. Also note that TDC for the blade is not equal to TDC for the cutter head because the blade slot does not go through the center of rotation. As the blade goes in and out of the slot, TDC for the blade edge moves.

[Tom Esh]

Been there. I got the best results by experimenting with the bolt tightening sequence on each gib. Tighten the ones that cause the least movement first.

[Myk Rian]

Kenneth has good points.
I use a ruler on edge to adjust mine, setting for 1/8" drag.
Jointing the blades after installation will guarantee they are all set the same.

I have a slightly different situation on my newest jointer. An 8" late 1930s JD Wallace. The head has what they called "skewed knives". They are set in the head at an angle, like an early helical head.
They require jointing after installation, because the ends of the knives are .002" higher in the arc than the centers.

[george wilson]

I'll bet that if you can machine the heads of the gib screws into a very slightly cone shape,so that only the apex of the cone touches the cutterhead,the creeping when tightening will cease. When the points on those gib screws contact the cutterhead,they will make a single point contact,and will make a little dent there,and will stay in it.

The cone shape I am referring to is very,very low,just enough that the centers of the gib screw heads touch the cutter head. I am aware,of course,that the hexagonal portion of the gib screws,for example,on old model Delta 8" jointers,are already narrow,and you don't want to waste any more of this hex surface than you have to. If the Wallace has wide enough hex areas on its gib screws,it would be very beneficial to do this to avoid the gib screws sliding due to the tapered knife placement. I don't know if the Wallace has room enough on its hexes to do this.Plus,you can't buy new screws for it. I could make them out of drill rod and harden them if necessary.

[Myk Rian]

The Wallace uses circular wedges to tighten the gibs. A 3/8x24tpi Allen bolt holds them in. Allen set screws set the knife height. All these screws are available at ACO, etc.

[Ken Harris]

Ken
I feel your pain,I spent several frustrating days trying to set my knives on a delta.I finally gave up and purchased a Byrd head and have not looked back.

[Will Blick]

Different jointers, different screw fastner types for tightening, represent different problems setting knives, many posts above express some of the problems. Making sure your contact points are flat or symmetrical in some manner can often solve the problem as George and others mention. I used the magnetic straight edge jigs as well, and while it helps, it does not always solve the problem, as the jig can lift off the table a few thou before you notice it... or the other end can drop.... the magnetic force is not as powerful as the mechanical force of tightening the fasteners. My only additional contribution is..... slowly sneaking up on full tighten state to prevent any major jumps....very time consuming making 1/16th turns on each bolt.

Like Ken, I gave up on straight knives... I am picky about jointer knife settings...if one knife is high by just a few thou, it will get most of the action and will dull very quickly.... I would spend hours getting them set accurately, then would fear removing them for sharpening... i used the honing sharpening jigs as much as possible to keep an edge on the blades while still set in the machine....but there is limits to how long you can get away with this technique. I then tried the auto-set systems, still had problems for numerous reasons. It can be a frustrating task indeed, much depends on how picky you are about the final product...

The reason I went with a helical cutter head was.... once the heads cutting length is planar with the out-feed table, you NEVER have to deal with this issue again! Now in my case, installation on my Grizz Extreme 12" was no easy task, took 2 guys about 4 hrs to set the massive 65 lb head w/bearings into place...lots of testing and shimming to get cutters planar with out-feed table. I am lucky though, as my jointer has perfectly coplanar tables, so the cutter height was the only variable to perfectly jointed wood. Now that the helical head is set "near perfect", to change blades, twist cutters 90 deg. and its done. Sure, it still takes 20 minutes, but its rare you need to turn the carbide cutters. I found my out-feed table needs to be about .003" lower than the blade height for a clean cut...which also takes some time to tweak to the ideal height. The point is, once it's right, you NEVER have to adjust the out-feed table height and cutter height EVER again. Quite a treat.... oh, did I mention the 75% noise reduction, not a single bit of tear-out yet, less fine dust in the air?

Granted, if you want perfectly smooth wood out of the jointer, my straight blades (when set perfectly and SHARP) did a slightly better job on woods that would not tear out..... but the difference = one swipe with 220 grit paper and its a level playing field... I much prefer that over messing with straight knives. Not suggesting this is for everyone as it's quite costly, but when purchasing a new machine, it pays to consider the cutter type as they "can" be challenging to install helicals after-the-fact. Some jointers are designed with little consideration for a head change-out. Sorry if I drifted off topic....

[Kevin Presutti]

And a doctor!