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Jointer jack screws don't....

forestgirl's picture

....do jack, so to speak.  This one blade (out of 3) is taking forever to set.  The jack screws work fine to raise the blade, but don't do anything when I'm trying to lower it "a smidge."  I don't understand exactly how they work and am not sure what to do to make them work better.  This jointer is relatively new, so I don't think there's anything worn.  Can you give some guidance?  Thanks!

forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-) 

forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-) 

JohnWW's picture

(post #124569, reply #1 of 9)

Forestgirl,


On most machines, the screws just bear against the back edge of the blade.  If you back off the screw, in an attempt to lower the blade, it won't pull the blade down because the screw isn't attached to the blade, a gap will just open up between the top of the jack screw and the back edge of the blade, unless the blade is so loose in the slot that gravity keeps it against the screw. 


Normally a blade isn't that loose when adjusting the blade height with jack screws, because you should set the gib screws to create a bit of friction on the blade to keep the blade stable in the slot, which means the blade won't drop back down if you back off the jack screws.


The way to use jack screws is to start with the blade too low and then gradually raise both screws more or less equally until the blade is at the height you want.  If you overshoot, and the blade is too high, back off the jack screws slightly and tap down the blade with a block of wood to reset the blade against the head of the jack screw, and then start again to raise the blade to the height you need.


After trying numerous ways of setting blades on a jointer, I came to the conclusion that using either purchased or shop made magnetic jigs is the easiest way to accurately and efficiently get the job done, but setting blades can be done with jack screws and some method of measuring the blade height.  The problem is usually that the height measuring process is fussy or inaccurate.


Hope this helps, feel free to ask any follow up questions if you are still having problems.


John


 

John White Shop Manager for FWW Magazine, 1998 to 2007

forestgirl's picture

(post #124569, reply #2 of 9)

Thanks, John, your reply confirmed what I was suspecting re: the way the jackscrews work.  It was just one blade that was being a royal PITA.  I probably didn't clean everything well enough (yes, I read your book!).  Haste makes waste.


I was trying the glass-and-magnet approach, which worked well for the other two blades.  Part of it is getting used to just how much the blade moves (up) when I turn the jackscrew.  Doesn't take much!  However, mission accomlished, and the piece of wood I face-jointed last night looked eversomuch better.


I'm going to send the old set out for sharpening -- I don't think they have a true straight edge on them -- they appear to be a bit higher on the ends.  Someday I'll get that Veritas honing guide for jointer knives and spiff them up myself.


thanks again.


forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-) 

forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-) 

JohnWW's picture

(post #124569, reply #3 of 9)

Forestgirl,


If you are using a magnetic jig like the one in my book, you shouldn't have to use the jack screws.  They should be removed in fact just to keep them from getting in the way.


I will have to go back and read some of the postings about using a plate of glass and magnets, but I thought they worked the same way, the magnets are supposed to hold the blades in place, and level with the outfeed table while the gib screws are being tightened, so again there would be no need to use the jack screws.


John

John White Shop Manager for FWW Magazine, 1998 to 2007

forestgirl's picture

(post #124569, reply #4 of 9)

Welllll, you're right about all that, but here's what happened.  I installed my third knife, and went to the part of lowering the outfeed table so that it was a tiny smidge below the knives (what is it? .002 or something like that).  That's when I discovered the Problem Knife wasn't where I thought it was.  So, I was re-installing it by using the plate glass and then raising it the .002. 


The method I want to use when I get good at this is (a) magnet aid to get all the knives level with the outfeed table and then (b) lower the table and use the hardwood-block-creep test to get the knives just above the table.  The jointer is working fine now, by luck somewhat.  I couldn't remember how far the block was supposed to creep, so I chose 1/16". 


forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-) 

forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-) 

JohnWW's picture

(post #124569, reply #5 of 9)

Forestgirl,


Perhaps I'm not following how you are doing your knife setting, but it doesn't sound right to me. 


On a jointer, the reference surface for setting the blades is the surface of the outfeed table.  The position of the outfeed table is set once, and locked in position, at the beginning of the job, and it isn't moved until all three blades have been changed out.  After the blades have been changed, the height of the outfeed table can often be fine tuned to get a perfectly straight cut, but that is a separate topic.


The proper height of the outfeed table for installing and setting the knives should be specified in the owner's manual.  It is a small dimension, like .020", that the table is set at higher than the cylindrical surface of the cutter head. 


It is easy to set the proper table height, just roll the head so that a round surface of the head, midway between two knife slots, is facing upward.  Now place a short straightedge on the outfeed table, extending it over the cutter head, and then measure the gap between the head and the straightedge with a feeler gauge. 


If the gap is off, always start with too small a gap and raise the table to the proper position, this eliminates free play that could allow the setting to slip if you started with a wide gap and lowered the table to the proper height.


Forget using the creep test to fine tune the outfeed table setting after you install the knives, this is alternative, and inferior, method for setting blade height, it is not used for setting the outfeed table height after new knives are installed. 


To fine tune the outfeed table height after installing a new set of knives, lower the outfeed table height a bit and then joint the edges of a pair of flat, straight grained boards, that are 2 to 3 feet long.  Because the table is set low, you will find that the boards aren't straight when the newly jointed edges are placed together and that there is probably a bit of sniping on the trailing edge of each board. 


Now start gradually raising the outfeed table, a bit at a time, until the two boards when tested come together in a gap free joint.  The whole process should only take two or three minutes if you have crank handles for raising the outfeed table height.  


If you have lever handles it is much harder to make this adjustment properly, or to set the table height for blade installation.  This is the main argument against buying a machine with levers on the outfeed table, they are worse than useless when you are trying to move the table just a few thousandths of an inch. 


Again, always raise the table to its final setting to prevent free play in the mechanism from allowing the setting to slip during use.  Hope this is clear and helpful.


John  

John White Shop Manager for FWW Magazine, 1998 to 2007

forestgirl's picture

(post #124569, reply #6 of 9)

Hi, John, just wanted to say thanks!  My jointer is working great now, and I've passed your tip along to someone at regular Knots.

forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-) 

forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-) 

JohnWW's picture

(post #124569, reply #7 of 9)

Glad I could help.


John

John White Shop Manager for FWW Magazine, 1998 to 2007

ndirish1's picture

jack screws/springs (post #124569, reply #8 of 9)

Where can i buy the springs for my grizzly 6" jointer.  Sent the blade out to get sharpened and ended up losing the springs and knife gibs.  Grizzly had the gibs but no springs.

leminhtien's picture

Download over 16,000 (post #124569, reply #9 of 9)

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