Jointer Problem: Results in boards concave up along their lengths

[Brett Bobo]

To make a long story short, what started out as a knife change on my G0490 yesterday resulted in a reset of the infeed and outfeed tables to be coplanar as well. I've had this jointer for five years now and I initially setup the tables to be coplanar but some minor adjustments were required yesterday. Not a very exciting afternoon as I spent about five hours total to get back up and running.

I started milling up some rough sawn material that was in bad shape to begin with, i.e. twisted and bowed, so I first thought that the odd results were from the material. Out of curiosity, I switched to some fairly flat and straight rough sawn poplar about 5' in length and the results were the same. The problem is that the boards are concave up along their lengths, meaning the boards are thicker at the mid-span than at the ends so it rocks on the midpoint. After several passes, it's very visible sighting down the face of each board that a hump exists at the middle. I've run hundreds of board feet through this jointer so I'm very aware of stock orientation, consistent pressure across the length of the board on the outfeed side, etc. so I'm puzzled as to the problem.

I did speak with Grizzly's customer service but their only suggestion was about consistent pressure so no new revelations there.

What's causing this?

Thanks in advance!

[David Kumm]

That actually sounds like convex and usually means one or both table ends are pointing up slightly rather than parallel. Dave

[Mel Fulks]

Not understanding .If they are concave ,don't see how they could be rocking. Are you talking about facing or jointing edges?

[Brett Bobo]

Dave,
I was afraid this would require yet another several hours of adjustment to the infeed and outfeed tables and then probably resetting the knives too. Is there a more accurate way to verifying coplanar tables aside from a straight edge? Obviously, any error will be magnified with longer stock but I thought I had it dead on.

Mel,
I'm referring to face jointing and by concave up, I mean the concavity of the board faces the ceiling. Also, the ends of each board are thinner than at the midpoint.

Is there a good alternative at either HD or Lowe's for a straight edge, e.g. 80/20 aluminum angle, etc.?

[Lee Schierer]

Most 4' levels are pretty straight and stiff enough not to sag over their length due to their own weight.

[David Kumm]

I've found that aluminum levels are pretty good. I put mine against an 8' Pinske edge and now never use the Pinske. 80/20 isn't as straight. Dave

[Mel Fulks]

It's possible out feed table is just too low . I would not redo what you have already spent time to fix, without knowing for sure what is wrong . I have never owned a machinists level,but I think I would trust one more than something like a substitute straight edge. Accurate straight edges can be made in home shop,but a very time consuming process.

[Brett Bobo]

So much for a happy new year as the frustration continues and I'm not sure now what's heads versus tails. I ended up resetting everything again and the results are no better than my first attempt. I figured a picture is worth a thousand words so I snapped a few to hopefully key in on the problem or problems. Now, I'm thinking part of the problem may still be in the setup and part of it with the knives. The reason I now think the knives may be part of the issue is based on picture 231 and the face that the board rocks side to side slightly on the face, not just along the length.

I ended up marking the entire length of a scrap board to check the knives. In picture 231, the full width of the face of the board is cut up until about halfway, then you can see that only half is cut for the last two or so feet.

Picture 247 is an exaggerated version of what I was trying to convey originally. You can see that at the mid point of the board, it touches the surface; however, the ends in each direction get increasingly thinner towards the ends.

The other photos are trying to show the coplanar tables before making the adjustment for the cut on the infeed side. There are some shadow lines from the level, which are deceiving, that make it appear like there are gaps along the the length of the level.

Man, this is frustrating and I'm not sure what to do next. The installed knives may not be sharpened perfectly square across the ~8" length but it's ever so slight, if I had to get picky. What do you think is the problem with these symptoms? Any other ideas to correct these problems?

Thanks again,
Brett

[Rick Lizek]

A concave surface curves inward. It’s easy to remember because a concave indentation in a wall makes a cave. A convex surface curves outward. Like many pairs of antonyms that are relatively rare and similar in sound, these two adjectives (http://grammarist.com/grammar/adjectives/) are easy to confuse.

The correct term is Convex in relation to your problem. You do not reference from the ceiling in this case. Seeing as the jointer was fine for 5 years until you changed the knives your problem is simple. Your outfeed table is a few thousandths too high. This will cause the problem you are having. You cannot check coplanar without a feeler gauge along with a straight edge. Since everything was fine until you changed the knives your tables are coplanar. If you drop the outfeed table down too far you will get snipe at the end of the board. Drop the outfeed table down a few thousandths will correct the problem. Too far down will cause the board to stop against the outfeed table. A jointer is very simple and at the same time very complex in the understanding of it's set up.

I have been adjusting machines for 30 years in commercial shops so I know what I am talking about!

[ken masoumi]

I think this youtube video might help,just be patient and watch the whole thing:

http://www.youtube.com/watch?v=fvbfdzkPPSg (http://www.youtube.com/watch?v=fvbfdzkPPSg)

[Brett Robson]

If you're a member of FWW's online content, this video shows some tips for jointer adjustment and addresses your issue.

http://www.finewoodworking.com/how-to/video/adjusting-a-jointer.aspx

If you're not able to view it, the summary is your outfeed table is likely slightly too low.

[Mel Fulks]

If the knives are not perfectly straight, have a nick, or not parallel with tables,that would cause trouble even if everything else was perfect. So you do have to be picky. A small nick means that the out feed table is now "too high"......even though it has not moved. On table heights ,2 thousandths is a lot. If you were in an old movie ,your best friend would hit you in
the jaw and you would say "thanks,I needed that" . Putting in more time without a good straightedge and perfect knives installed perfectly is not going to help...unless you are doing this on someone else's time. I would rest and regroup. You might want to look up making a straight edge

[Patrick McCarthy]

Drop the outfeed table down a few thousandths will correct the problem. Too far down will cause the board to stop against the outfeed table. ??????

Rick, i am confused by this statement. It seems that for the board to stop against it, the outfeed table would have to be too high, not too low. I have very little experience, so i am just trying to understand, not trying to criticize. Patrick

['Jacques Malan']

Our lazy way to set up the outfeed table without straightedges and gauges.

Take two pieces of wood the same length, and plane them both, keeping consistent pressure. Hold the jointed edges together against the light, adjust until no gaps can be seen.

It is a fiddly little job sometimes, and if you can feel or see the table moving it is too much.

What I often do to demonstrate the difference between too high and too low is to deliberately move the outfeed table way out and show the effect each setting have.

Personally I like to start of with the outfeed table too low and move it upwards against gravity until the snipe is gone.

[Shiraz Balolia]

http://www.grizzly.com/videos/

Take a look at the video titled "How to align the tables on an 8" Par. type Jointer".

You can then re-set your knives after that if the problem still persists.

[Mel Fulks]

Jacques,I agree that is the best method to adjust out feed table height.But in this case the tables have been adjusted ffor parallel ,and still might not be parallel .

[ian maybury]

My sympathies Brett! Per my recent posts it can all get a bit frustrating and mind boggling. Especially (as in my case too) after years of running a machine that just happened to be OK as delivered - that only ever needed the knife heights set.

There's a lot to be said for stepping back to let the head clear a bit. One issue (you can run into the same one when adjusting motorcycle suspension :) ) is that unless you are an experienced machine guy and very clear on what adjustment does what (and more to the point what it can and can not compensate for) it's easy to get lost as a result of making very small adjustments so that the change isn't evident in the performance of the machine. Sometimes it's worth taking a fairly large step to find out...

As the guys have said the good news is probably that since your machine was working acceptably well before adjustment it's likely to only be either table coplanarity or knife height that is the problem - and it sounds like since you adjusted the tables that that may have been the issue.

I'm still flattening tables on mine and have to put the theory to the final test, but i've concluded that even very minor dips and rises in the tables can especially if in the wrong place require the them to be set slightly out of apparent coplanarity to compensate - so that the actual parts of the surfaces on both tables that the wood rides over are flat/coplanar relative to each other. i.e. coplanarity checked over the full length and width of the tables with a long straight edge and feeler gauges can be misleading if the edge not resting on/passing over exactly the right part of the tables - at least not unless the tables are pretty much absolutely (within a thou or two) flat all over. Likewise if its not perfectly straight.

Which (in support of the 'who needs to measure to a few thou tendency) tends to suggest that once coplanarity is set in the ball park using a straight edge and the knife heights are about right that it's maybe best to 'dial in' the cut by raising or lowering the outer end of the infeed table (prob best leave the outfeed alone, as this avoids messing with its relationship with the knives/knife height) to get it cutting straight or slightly concave as you require. If by then it looks like the tables are drooping or its about to take flight then maybe look for causes.

The downside of this approach is that the machine may joint differently depending on where across the width of the table the work is placed - an issue perhaps masked by the fact that many jointer tables are very narrow and hence not much out of flat across the width of the tables. (potentially a much bigger deal on a 12in or 16in machine though)

Knife height (once all three knives are set the same and parallel to the edge of the outfeed table by your favourite method) as the guys say seems fairly straightforward. Start with the outfeed table a bit high and the work will drag on it - you feel the resistance, and it increases any tendency to cut convex. (which could be masked/reversed/exacerbated by the effects of table coplanarity) Gradually lower the outfeed table (maybe 0.001in or less at a time) and the resistance fades and the cut straightens out a bit. Keep on lowering the outfeed table/raising the knives and eventually it will start to produce obvious snipe at the trailing end of the piece as it drops on to the knife just after it clears the indeed table - depending on the table situation it may by this stage be by now starting to cut a little concave as well.

Trials so far seem to suggest that knife height doesn't make all that much difference to the straightness of cut however. If the knives are high relative to the outfeed table there probably is the potential to cut an apparently (but not truly) concave edge if weight is transferred to tip the work off resting on the infeed and on to the outfeed table at about half distance - but at the expense of the need for sensitivity as to how the work is handled to get consistent results, and getting snipe at the trailing end.

My tendency is to suspect (despite the tendency of machine makers to suggest otherwise by listing very wide flatness tolerances for tables, and to describe apparently straightforward adjustment procedures) that in practice there's only a very very narrow range of knife heights over the outfeed that work well, and that after that it's about practical flatness/actual coplanarity of the tables...

ian

[Mel Fulks]

Ian,I was with you until close to the end where 'knife height doesn't make all that much difference to the straightness of
the cut'. That is the only routine adjustment, excluding depth of cut by infeed adjustment, and it's the main cause of climbing ,snipe ,and unwanted concave or convex surfaces. An understanding of that adj and how nicks and slight dulling to the knives affect it is primary. I can't reconcile your rejection of that with your determination and credible knowledge on scraping the tables.

[ian maybury]

That's OK Mel, you did well to even read that far ;) It's a great help to be able to double check stuff with others. I'm as you know just finding my way on this. Could be that I've been too cautious on my knife height adjustments, or that i'm missing something. I seemed to get instant responses to small changes in table coplanarity, while on the knife height snipe seemed to be setting in before there was much change in the cut...

ian

[Mel Fulks]

I read them all several times, keep us posted ! Don't recall reading what type and length straightedge you are using...

[Brett Bobo]

Thanks Ian, your sympathies are much appreciated!

So, I'm about twelve hours in now and still don't have acceptable results. I feel as though twelve hours is a very generous amount of time considering the setup time indicates one hour in the manual and video. I think as woodworkers we all have a sharp eye to detail and precision and I'm an engineer by day so point being is that I feel that I should be getting very accurate results.

The problem is that I don't know what to do next. Just to reiterate, I've reset both the infeed and outfeed tables twice now, along with the knives each time. I've watched the videos and I find myself saying "yep, did that" over and over. Insanity is starting to set in and I don't know if trying again for a third time is a losing battle. The factory settings are long gone so what should I do?

I don't have a high quality straight edge so I could start there. Any recommendations? I noticed Lee Valley has a reasonable anodized aluminum for about half the prices of the steel edge.

I'll also check on the knives and maybe another sharpening service. I do take my knives and blades to a local supplier and sharpening service where the pros go so I do have confidence in them. Any recommendations on a magnetic knife setup jig? That should help minimize any additional error, even if it's .001". Maybe as an excuse, I looked at the Byrd replacement head and didn't realize the sale was though 12/31 so that's probably out.

It's too bad none of you are close because an experienced second set of eyes sure would help.

Thanks and keep the ideas coming.

[Mel Fulks]

I googled making a straight edge ,the one useing three pcs to verify looks good.

[Ken Fitzgerald]

Brett,

I have a G0490X. I felt I needed a straight edge to check it's set up. I bought this one from Grizzly http://www.grizzly.com/products/36-Bevel-Edge-Straight-Edges-with-Scale/T21580 . The first straight edge showed up and it had one end that the last 3" weren't withing the 0.001" guaranteed specification. I called Grizzly...no problem....we'll ship another right out and keep the first one.

The 2nd one was dead on.

I prefer steel over aluminum because aluminum is softer and more prone to "dinging". As sure as the sun rises in the east, if I bought an aluminum one, I would damage it accidentally. It only takes one moments slight carelessness to make a ding.

Did you watch the video to which Shiraz linked? Have you checked your jointer using the methods shown in that video?

[ian maybury]

I have a 24in Woodpecker's guaranteed straight edge Mel - but because it's too short to use to check coplanarity have been using a good quality extruded box section aluminium level a bit longer than the two tables to check that. It too seems to check out as being straight.

Pardon my coming in again on the main topic Brett/guys, it's to head off (hopefully) any risk of my having caused confusion. I should just say that despite my comment to Mel about not finding that knife height adjustments changed the cut on my machine so much as dropping the end of a table (which latter shouldn't be a required normal running adjustment) that of course the knife heights are a key factor and still need to be set right.

It's definitely necessary as the guys are saying to check them before anything else if they have been sharpened and re-fitted - but the heights not subsequently checked against the out feed table and each other.

+1 with Ken and Mr. Grizzly on working through the set up in the Grizzly video too. Since the tables have been disturbed they need checking for coplanarity. Since the machine was previously working well then table flatness should as before NOT be a factor. i.e. set the tables coplanar and get the knife heights 'right' and it should joint straight.

One standard way to check knife height is the 'carry forward' test recently discussed and also described in my own ???? jointer set up thread - but be careful of the knives and make sure the power is off before rotating the cutter by hand.

As a starting point they should probably be set to generate around 2 - 3mm of carry forward to within way under 1mm variation (in carry forward) across the width of each knife and from knife to knife at every point checked - which means checking at say the middle and at both ends of each knife and adjusting it's height where needed until the carry forward is within this range. Depending on the blade holder and adjustment method (machines with built in height adjustment in the knife holders may not need anything) you may need something like a magnetic knife holder to hold them in place when doing up the locking screws.

If its still not cutting quite right then some fine tuning of the knife height may be required as has been described earlier in the thread...

ian

[Brett Bobo]

Ken,
Yes, I did watch the video that Shiraz shared and as mentioned before, I found myself mentally checking off the boxes of doing all of the steps they went through. Of course, I followed the detailed instructions in the manual as well and in the order suggested--outfeed, infeed, and knives.

The eccentric bushings are not easily turned as indicated in the video using a punch even after removing and loosening both sets of set screws. I tried a punch initially (as recommended in the instructions too) and found that I was damaging the two grooves on the eccentric bushing with each blow. So, I switched to a wrench but with such a large mouth opening required for the wrench, some spots are very difficult to maneuver the wrench. The instructions did also mention a mechanics wrench (can't recall exactly) but similar to a wrench used on an angle grinder to lock and unlock the blade.

I did look at that particular straight edge so are you happy with it now? I read a few reviews on other sites that weren't favorable so I wasn't sure of the quality, especially to risk it as my go-to precision straight edge. Also, I wasn't sure if the accuracy of 0.001" was over the entire 36" or over 12" as some are specified, resulting in 0.003" tolerance over 36". How did you measure the inaccuracy in the last 3"--feeler gauge?

[Ken Fitzgerald]

Brett,
I am happy with the replacement straightedge today. The first one I got did have the last 3" that didn't meet the 0.001" specification. I placed it on a machine surface and it was obvious the last 3" weren't touching..I could see light...I used feeler gauges to measure the error.....carefully marked on the surface.....swapped it end-for-end....180º putting it back within the marks and the error followed the same end. When I got the replacement, I checked the original against the replacement and it showed the same thing....one end of the original straightedge.....3" on one end wasn't straight. Would I buy it again? Yes...it's a good value for the price.

I would recommend rechecking everything using a straightedge......don't check them off mentally...take time check them as shown in the Grizzly video....don't make any adjustments initially....... This isn't rocket science....the jointer is one of the simplest stationary power tools in our shop but ...it requires that very tight tolerances be maintained between 4 surfaces. Three of these surfaces must be parallel....the 2 beds and the cutterhead....

Good luck!

[Dustin Brown]

Just out of curiosity, how are the knives set in relation to the outfeed table? Sorry if I missed it already listed in the thread. I had this same problem when my outfeed table was too high. It wasn't high enough to stop a board on the outfeed table though. I adjusted the outfeed so that rotating the knives would move the straight edge forward by 1/8". That did the trick.

One thing that may be worth mentioning, before doing this I also experienced a fair amount of resistance when pushing a wider board through. After the adjustment, boards go through pretty easily. Mine is the G0490X by the way.

[Brett Bobo]

Dustin,
The knives are set following that same approach of just "kissing" the bottom of the straight edge as the cutterhead is rotated around. I probably spent a hour alone each time trying to dial in the knife heights to be sure that was correct as well. I've noticed that when tightening the gib bolts, the knives can shift slightly so there's some trial and error to set them correctly. I do still have a concern that the knives may not be perfectly square across the 8" length as previously mentioned. This becomes obvious when the knives don't touch the straight edge exactly the same way, e.g. moving 1/8" forward, at all positions along the length of the knives. Granted, this is being very picky and shouldn't yield the results I'm getting but it is something.

Since you're in Houston, I take all of my blades and knives to Circle Saw and have had good success with them in the past. In fact, they use a 24" planer knife that they've machine sharpened as their straight edge to setup their equipment so I do feel confident that my 8" knives should be straight.

I'll take another stab at it and probably post some more photos in the next couple of days on my progress.

[ian maybury]

Hi Brett. Sounds like you set the knife heights, but just be aware (as you may already know) that a thou or two in height relative to the out feed table can make quite a difference. The guys have seen it more clearly than I have, but it sounds like it can affect the curvature/straightness of the cut quite bit too.....

ian

[Mel Fulks]

On planers and jointers I spray oil on the gibs, cutter head,and knives .Adjust gib screws to where knife easily moves.Hold knife with magnets ,tighten .Knife does not move when being tightened . Exact procedure varies with each machine but
favorite system on jointers are the old ones with knife index wheels and my homemade magnet gauge.

[Brett Bobo]

Ian,
Good point and well taken. I shouldn't minimize the setup of the knives and given that I've spent a majority of time on the outfeed and infeed tables, I'll probably revisit the knife heights first before making any other adjustments.

Mel,
Do you mind sharing your magnetic setup jig, maybe a photo of it too? I've looked at the Oneway multi-gauge, jointer pal, etc. but I figured there has to be an inexpensive method that is just as effective. I have some rare earth magnets that are begging to be used.

[Mel Fulks]

Don't know how to do photos.But this is simple. A 16 inch jointer knife cut into 2 pcs.Its 5/32 thick and about 7/8 wide.
Each has 3 rare earth magnets glued on with epoxy. A 1/2 mag is on one end and a 3/4 on the other end.Another 1/2inch
mag is 5/8 inch from the 3/4 inch mag. I make a wood jig to immobilize cutter head .Consists of a block clamped to jointer
and a adjacent pc which is slid into the end of head and clamped to the other pc. Gauges stick to out feed table held by
the 2 small magnets,the 3/4 mags hold up the knives. I cover the 3/4 mags with elec tape. I pry the gauges off with a ppc of plastic. Works much like magna set,but I like to immobilize the head

[jim gossage]

I believe you are wasting your time until you get a true straight edge. The lee valley is excellent, mine was within 0.001 over 48".

[Brett Bobo]

Jim,
No doubt, I agree with you as I've ordered the Veritas 36" steel straight edge so it's on it's way. The 36" was the longest steel straight edge they offer now so did you purchase the 50" anodized aluminum?

Mel,
Thanks for sharing. Considering that we're talking in thousandths of an inch here, should there be a concern about the possible inconsistency in the thickness of the epoxy when gluing the magnets? I'm just thinking in terms of too much epoxy on one, not enough on another, uneven pressure, etc. Shouldn't bar magnets do the trick?

[ian maybury]

Pardon my coming in Mel. It might make sense Brett to eyeball some stuff on the web regarding the design of commercial versions of those units, and how they are used - there's various versions about.

Chances are the epoxy film will be OK provided the bearing surface underneath is flat and at the correct level, and provided the magnets are clamped firmly enough to ensure that the magnet actually bottoms on the bearing surface. i.e. don't let the thickness of the adhesive film to determine the height. It could be worth measuring the magnets to ensure they are all of the same thickness too if the design you adopt relies on this to set the height of the active face of the magnet.

If the knives on your jointer are sprung so they rise when the locking screws are released a sheet of float glass is pretty effective to set them too. If there are jacking screws in addition to those locking the blades in place that allow the knives to be eased up or down then you may not even need the magnets or the glass - go straight to the carry forward test or use a dial gauge.

Either way the carry forward test or a dial gauge will pretty quickly pick up any variation in knife height above the out feed table...

ian

[Mel Fulks]

Brett, I did check the thickness when I made them .Cant remember what glue I used first ,but I remember it threw every
thing off. Started over with the epoxy and micd them and they were fine. Bar mags might be as good or even better .
I just found freezing the head a big step toward accuracy. But I don't mind adjusting table heights,in fact,on the old jointer that had the knife index feature I would routinely drop out feed before I started putting in the knives.That allowed me to hold the knives in a vertical posistion. And obviously up is the direction to want to go to adjust,I do that by jointing and
checking two pcs together.Tastum Soupo! Please look up the info on making a straight edge. The one you are buying would be a great help in making a longer one.

[jim gossage]

Yes, my bad, its the 50" aluminum

[Bill Space]

Brett,

Just to give you a little encouragement...

After replying to your other thread about the tool for turning the bushing, and reading this thread, I got worried about my own setup, on the G0490X that I just received and set up this week. I had to set both tables slightly. I followed the instructions in the manual and video. Then after reading this thread I got worried that I did not check the test board that I face joined to flatness. It looked good BUT I did not check it with a straight edge...it was red oak, 40" by 6".

This morning I did check it and was dead flat against my 48" Starrett straight edge. Whew! Relief!

My experience reflects what has been said by others above: A good straight edge is necessary. This is the first jointer I have set up it went smoothly, probably only because I have a good straight edge.

The spiral cutter head in the G4090X removes the variable of knife position that you have. My longer straight edge probably benefited me in the set up(don't want to ignore the luck aspect). I did not use feeler gauges, rather, I used a bright flashlight behind the straight edge and visually adjusted things until no light passed between the edge of the straight end and table surface.

I wish I would have took a better look upwards from under the jointer before putting it on the stand, as I don't really understand the mechanical working in there. Maybe I can figure out exactly how the thing is put together from looking in the parts diagram. I did come to the conclusion that there is some interaction between the four adjustment points of each table. I mean, the table is not going to change shape, so if you get out of whack, you can end up with three of the support points being tight against the table, and the fourth not touching. So rocking may be possible.

I will bet once you get the good straight edge you will be able to set the tables right and then address the knife issue if it still seems to be an issue.

Your sequence seems to have been: No problem; Change knifes/problem; Adjust the tables/second problem?;

In my mind, logic dictates that your initial problem is related to the knife change, and a second problem was introduced by making table adjustments. The resolution will be restoring the tables to their correct relative positions and then addressing knife-related issues if problems still exist.

Bottom line is that when you get the new straight edge you will be better positioned to what you need to. I am sure you can.

Keep us posted!

[Brett Bobo]

Thanks Bill, I appreciate it. Given that I've had the jointer for about five years, I'm certain now that I didn't do enough an initial setup to ensure coplanarity since I didn't have an adequate straight edge. Of course, I've made knife changes throughout the years so even though it wasn't using a spitfire method with a dial indicator, jointer pal, etc., I haven't had any issues with larger scale furniture projects, including a bed. Therefore, I would have expected any issues in the setup or knives to be magnified and be noticeable.

Also, my sequence was as you mentioned. I think what compounded the problem is that I needed a knife change at the same time I was trying to mill up some very warped material, which added one more variable into the mix. Despite using much better material as a test of the setup, I still got odd results, which lead to starting over from scratch.

The good news is that my straight edge and feeler gauges arrived yesterday, I purchased the Oneway multi gauge here locally, and I went ahead and got my second set of knives resharpened. So, I plan to start again from scratch, even replacing the knives. While I don't expect it to be an easy task, I'm confident that any error will be legitimate, instead of guessing which variable it could be--the tool, me, setup equipment, etc. I'll tackle it tomorrow, snap some photos, and may even shoot some video but I'll re-post the outcome, which is hopefully success...