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Jointer Tune-up
http://mowrystrings.luthiersforum.com/forum/viewtopic.php?f=10102&t=14387		 Page 1 of 1
Author:  Kent Chasson [ Mon Nov 05, 2007 3:49 pm ]
Post subject: 

I'm a little embarrassed not to have figured this out sooner but I don't think I'm alone on this.  Maybe it will save someone else some time too.


In many years of woodworking, I don't think I've ever put knives on a jointer where the cutterhead was perfectly parallel to the outfeed table.   So like most folks, I've just always adjusted the blades referencing the outfeed table (as opposed to the cutterhead).  This works but takes a lot of time to get them true.  The knife setting jig that comes with the jointer (photo) works much quicker and is very accurate but only works if the cutterhead is parallel to the table.

 

I finally got tired of it and got out the jointer manual (8" Jet), searched the internet and only came up with what I assumed all along....you can shim the table ways (a giant pain) or regrind the table (cost prohibitive).

 

Well, there's a much easier way.

 

After looking at how the cutterhead goes in I realized I could shim up one end of it.  (photo)  One end was about .009" lower than the other.  So the .009" blade on my feeler gauge got sacrificed to the cause but it was a small price to pay.  Within a few minutes, the head was perfectly parallel and I can now use the original knife setting gauge.  It takes 5 minutes to install blades and they are true end to end to within .0005".

 

And it looks like this type of shim would work on many brands of jointer, not just Jet.

 

Now someone please tell me that this simple solution never occurred to them either!

 


 
Author:  Steve Walden [ Mon Nov 05, 2007 4:14 pm ]
Post subject: 
Kent - great idea but for a few details.  As a former maintenance engineer, oh oh here he goes again... It looks like you have shimmed the outboard bearing support with a small shim.  The cast iron base used to hold the bearing tightly and now it may be able to move fore and aft slightly which may cause chattering.  Also the bearing outer race may be deformed by the clamp holding it in place.  These fits are designed for full contact the complete circumference of the bearing.  You may be better off by lapping the other side the 0.009" down and using several shimms on the top of the bearing to take up the now fingernail/new moon shape.  Put your 0.009 at the top and a pair of 0.004s at the 45 deg spot on either side of the bering.  If I had a drawing program I would show you.  There are other ways to do this but I am fatigued right now... And the wife says come to bed!  So gooodnight!
Author:  Kent Chasson [ Mon Nov 05, 2007 5:29 pm ]
Post subject: 

Thanks Steve.  You can't see it but the shim does go pretty much all the way around the mating surfaces and there is good contact all the way, except where the hold down bolt comes through at the very bottom.


By the way, the black ring that is visible is not the bearing but the bearing housing so the bearing is still fully enclosed within it and the race shouldn't be deformed in any way.  I guess a possible issue is that the housings may not be in perfect alignment (if they were to begin with) and that could put some torque on the bearings.  But don't most bearings have a fair amount of built-in play in that axis?  .009" over about 9" seems pretty minimal.


Sleep well.  I'm off too.....
Author:  Shawn [ Tue Nov 06, 2007 1:13 am ]
Post subject: 

I may be missing something but why are you focusing on shimming the cutterhead instead of shimming the ways for the outfeed table.  If you have any instability in the way that the bearing block seats for the cutterhead, it would be really dangerous.


It is is to shim one of the ways of the outfeed table.  See in your second picture the slanted path of the outfeed table.  If either side (front towards you or rear away from you) is lower it is very easy to shim that way and bring it back to parallel with the cutterhead.  In 99.999 percent of the time this is the preferred way to true your outfeed table.  I would never mess with the bearing blocks or the cutterhead unless they were drastically out of alignment.  Once the outfeed table is shimmed it will stay that way forever so it is not worth messing around with anything else.


 
Author:  Kent Chasson [ Tue Nov 06, 2007 3:33 am ]
Post subject: 

FWIW, I agree with Steve that a small shim with poor support for the bearing shell could possibly generate some cutterhead vibration.


As I said in my second post, it is not a small shim with poor support. It is a stainless shim with even support on all mating surfaces.  If anything, there is less room for play/vibration than before as it wraps around the sides of a simi-circle.


And, as I said, I've set jointer knives off the outfeed table for more than 20 years and it's a pain no matter how you do it.  Takes me at least 30 minutes, usually more, and I've never gotten them to within .0005" which I did in 5 minutes this way.


I may be missing something but why are you focusing on shimming the cutterhead instead of shimming the ways for the outfeed table.  If you have any instability in the way that the bearing block seats for the cutterhead, it would be really dangerous.


Again, as I said in the first post, shimming the ways is a pain. First, the ways are at a 45 degree angle to the table so shimming requires some trial an error.  Second, the lift you get from the shims is somewhat dependent on the tightness of the gibs.  More trial and error.  Also, you are shimming a surface that moves and rubs as opposed to one that is stationary.  Also, it would require much longer shim stock to shim the entire way.


So shimming the cutter turned a minimum 4 hour job (plus a trip to the hardware store) into a 5 minute job.


And, one more time, it is very well seated and very secure.  I realize the danger of a loose cutterhead and see no reason why this would cause such a thing.


The setting jig you show is great for a planer...


Just like the jointer, it only works well if the cutterhead is parallel to the table.
Author:  Steve Walden [ Tue Nov 06, 2007 9:15 am ]
Post subject: 
Kent - I see what you mean now and I agree that it should be OK.  As long as the entire circumference of the bearing housing is clamped with no large gaps between shims you will be fine.  Just be very careful not to distort the bearing housing.  I would imagine that this bearing has minimal clearance or a "pre-load" which will eliminate clearances.  The bearing clearances will close up with heat.  Does the bearing have a method to lubricate like a grease fitting or oil port?  Just curious as to the level of preventative maintenance the manufacturer designed in.  What lubrication does it use? Light oil such as the old sewing machine oil or something more viscous like motor oil? Or it could be grease with a zerk fitting. 
Author:  Kent Chasson [ Tue Nov 06, 2007 12:42 pm ]
Post subject: 

Steve, thanks for the feedback. The bearings are sealed, no maintenance.  I imagine they are the "pre-load" kind like the ones in my 50 year old Unisaw.  I just had to replace the arbor in that as the threads were worn after 50 years of blade changes.  I put in new bearings since I had the thing apart but the old ones still had no detectable play.  Amazing because that saw has seen some serious use just in the 20 years I've had it.  What a great machine!


Todd, certainly jointers work just fine if the blades are parallel to the table but not the cutterhead.  And it's a good thing since most of them are like that!  It was just a matter of making blade changes easier.  Now I can remove the blades, sharpen them on my Makita water stone rig, and have them back in and perfectly adjusted in about an hour.  That makes me happy and I thought the idea might appeal to some other folks.
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