Jointer Bed Tolerance ?

[Alan Greene]

I have been having a tough time getting my jointer knives set. I have used several different methods and techniques "you" have suggested and been unsuccessful. I purchased my 8" Jointer about 7 months ago. It is my first real jointer and I have been learning as I go. I have found my problem, I believe, with the aid of a neighbor who is a machinist.

When I originally checked my jointer out feed table for flatness the fence was on so I did not get a really good measurement across the table evidently. I have also had trouble with flattening boards(tapers). When changing the knives (blades nicked) I could not get consistent measurements on the knives. I found that I have a cup in the out feed table, across the width, that starts 6 inches from the knives. When holding my Veritas straight edge across the table it rocks. When the straight edge is held against the table on the fence side I can get a .005 feeler gauge under the straight edge on the other side. I know this is unacceptable (at least to me) because it makes it impossible to get a good setting on the knives.

I am talking to the company who sold this to me and they are going to get back to me with some ideas. But they are initially saying that this is within their tolerances, the average error being .0025 and their allowance being .004. I am purposely not mentioning any names here because although I am questioning the tolerance amount, my conversation with the company this morning was helpful, productive and they were extremely professional and they gave me some things to try to see if it would help.

So after a verrrrry long ramble, what do you think about this tolerance being OK?:confused:

[Michael Schwartz]

.005 is quite a bit, enough to feel a difference with your fingers between two objects.

[Rick Lizek]

That shouldn't be a problem. .005" on a small jointer should be fine. I remember on my 16" Oliver .010" was their tolerance and from my days of servicing machines for a dealer .005" sounds about right for a Delta 8" jointer.

I set a lot of knives and prefer to use an indicator with a 1/2" flat tip. An example is here... http://www.sawmillcreek.org/showthread.php?t=61334
A block of wood, $15 indicator from www.wttool.com (http://www.wttool.com) and flat tip will take care of any knife setting problems you may have.

As I understand the cup...it starts 6" from the knife edge of the outfeed table. So you have 6" inches of flat table from the edge of the table to the cup. I don't see how that would be a problem using a straight edge to set the knives. If using a 12" straight edge there should be enough support so the cup shouldn't be a factor.
As for edge jointing, I can't see how a cup should make much difference unless I'm not understanding the exact nature of the cup. ----------------____----- How long is the cup? Woodworking machines don't have the tolerances of metal working machines.
Is the cup the length of the bed? Then there could be an issue. I don't really understand how much cup there is I guess.

[Paul Canaris]

Rick, do you mean .005" or .0005" as the earlier post you referenced indicates.

[Rick Lizek]

.005". It's woodworking. The earlier post referenced .0005" as to what I can set a knife at. Tolerances of tables in woodworking varies with each tool. For instance PM allows .015" for flatness of the table top on their # 66 saw.

[Alan Greene]

To clarify, the cup, _ _ ---_ _, across the out feed table, is worst right at the beginning of the out feed table and continues for 6 inches towards the end of the out feed table. the rest of the out feed table is fine. The problem occurs when I use either my TS-Aligner Jr or the block of wood with the indicator. Because the small error is right in the middle and is where the alignment equipment sits it seems to be causing a problem getting the knives set right. I would not worry so much about the numbers, but, when I joint a six inch board and put a straight edge on it I can see that it is not flat.

maybe I am worrying to much about this.

[Rick Lizek]

If it's in their tolerance, it would be up to them as to whether they will fix it or give you a new machine. There is no reason you can't measure from the infeed table. I assume you can adjust the outfeed table up and down. Often one can just set the knives to a similar height and adjust the snipe factor with the outfeed table by dropping it down until you have snipe then raising it slowly until the snipe disappears. I understand your concern over the issue but from your descriptuion it doesn't sound as bad to me as it does to you. I've had plenty of older machines with similar issues and showed folks how to make it go. If it's really bad I've had tables ground. My 16" Oliver had a .015" dip in the middle of a 48" long outfeed table. I had it ground to within .008". (Oliver considered .010" their tolerance). It worked fine after the grinding with .008" tolerance.

I see no reason you can't get it to work. I'm fussier than anyone as I set up machines for other folks so my standards are very high. I have a 4' and 6' Starret straight edge and indicators to measure pretty close tolerances.

I think woodworkers are better off with an import indicator gauge and a few simple bases instead of the expensive Master gauges.

[Pete Bradley]

I have been having a tough time getting my jointer knives set...

I have also had trouble with flattening boards(tapers)....

So after a verrrrry long ramble, what do you think about this tolerance being OK?:confused:

My recommendation is to get some more experience and feel for your machine and not worry about it. Yours is a common question on the internet since Veritas came out with those straightedges. Fine Woodworking also did the community a disservice when they published some very misleading jointer "precision" measurements in a review a year or so ago.

Since you asked, there's nothing in the measurements that you post that suggests a significant problem with the jointer. .005 across an 8" table is acceptable, and yours is better than that since your measurement method will accentuate the difference (the straightedge is on an uphill, you're measuring the space on the downhill side).

Taper can be minimized with practice, but there's nothing in a jointer that prevents taper and it doesn't indicate anything wrong. A jointer is intended to make one side flat. If you take a bunch of passes, it's a virtual guarantee that you'll get a tapered board. If you want two parallel sides, you then have to put the flattened board through a planer.

Knife setting is fiddly and as with any precision machine, there's no such thing as absolute zero. I use the simple "just tick the ruler" method. If you work the trig, you can confirm mathematically that it's remarkably precise. The fiddly part is that tightening the knives may cause them to rise off the jackscrews. I use a block of hardwood to hold the knife down, but it's still fiddly.

Enjoy your machine!

Pete

[Basil Rathbone]

That's a great answer Peter.

I thought it was either my 6" Beaver Jointer not being set up right or just me. I guess if one pass is .001 out, then 10 passes will be .010 then it will be noticeable.

I have also read that if there is a nick in the blade, that leaves a little ridge which then affects the base on the second pass and may make the .001 on the first pass a .003. This is apparently a magnifying affect.

If I have anything wrong here, please let us all know so any misinformation can be nipped in the bud.

Basil

[Doug Mason]

I too had an outfeed table slightly out-of-flat on my MM jointer/planer combo--which I have had now for two years. When I first got it, I drove myself crazy trying to align everything w/the straight edges/dial calipers/etc. So I discarded w/the tools and tried the Tage Fried method (per his book)--which was to use squared scrap to set the outfeed table to the blade, and then a combination square to set the infeed to the outfeed table. Then some test cuts/adjustments. And it worked--no fancy equipment or hours of frustration.

I was quick to critize the machine--when in fact a large part of the problem was me (technique and "reading" the board)! As for my out-of flat outfeed table--I have forgotten about it for now.

[Alan Greene]

I used Rick's suggestion about using the infeed table this afternoon and was able to get some consistent readings that let me level the knife. Three more to go. I believe my problem was that with that cup I was trying to force the knife into a cup to match the bed and that was giving me an uneven surface on the board. I have been very happy with my jointer. My learning curve is still very steep. Thank you for all your help. Now its just the fiddling.

[Wilbur Pan]

ISo I discarded w/the tools and tried the Tage Fried method (per his book)--which was to use squared scrap to set the outfeed table to the blade, and then a combination square to set the infeed to the outfeed table.
Doug,

Would you mind giving some more details about how you did this? It sounds similar to how I aligned my jointer bed, but I'm curious as to exactly what you did.

Thanks!

[Alan Greene]

I used the advice that you all gave me and got the knives set this morning. It took about 3 hours and after finishing I ran a piece of cherry that came out flat and and will need little sanding. Again thanks for the help and patience with "another" jointer question.