Jointers and Geometry

[Christopher Reyes]

Hey Everyone!

New guy with a geometry/technique question.

I've been plugging away at making my first workbench, and I have had some growing pains learning how to mill lumber properly. The legs of the bench are 3" wide by 3" thick, I have been able to face joint one of the legs perfectly flat, but instead of moving on to the planer to plane the opposing face I just face jointed the adjacent edge of the bench leg, and did that all around until it was the size I needed (I don't know why but it didn't seem appropriate to put a piece that is only 3" wide through the planer, not to mention I was already at my jointer, so why not). All throughout the process of milling down that leg I kept checking the angles between the faces to make sure they were staying in square, and it seemed to me that they were, however when I went to check the thickness of the board at the other end it was at least an 1/8'th of an inch narrower.

So the question is a two parter:

1. Is it appropriate to use a jointer in lieu of a planer for all four sides? Or am I better just being happy that one side is jointed flat and then plane the opposing face?

2. Is it possible for all sides of a piece of stock to be 90 degrees to each other, and yet have two faces that are not coplanar? It seemed puzzling to me that I was measuring square all the way around, and yet the other end of the stock was a littler fatter. Was I just being sloppy with my square?

Thanks.

~Chris

[Van Huskey]

1. No
2. Yes, look a a leg that tapers on all 4 sides. which is similar to what you were getting close to making.

[keith micinski]

A jointer makes faces flat you can still be square and not coplanar. Your tools are working properly you are just trying to use them for the wrong thing. Flatten and square two perpendicular sides with your jointer then rip the piece to width with your table saw then plane your board to final thickness with your planer assuring a coplanar face on all 4 sides. There are some steps missed in there for allowing for drying and wood movement but that's the cliff notes version of how dimension lumber.

[Zach Callum]

2. Have you checked your square for squareness? I would start there.

[Van Huskey]

2. Have you checked your square for squareness? I would start there.

Why would that be an issue? The adjacent sides should 90* coming from the jointer, the opposite sides are not coplaner which is what you would expect trying to do it all on a jointer. What I would expect from his procedure is all sides being 90* to the adjacent side but if the opposite sides were complaner it would be a fluke.

[Alan Schaffter]

I suspect your jointer fence is not perpendicular to the tables. It is close enough for adjacent faces to appear at 90 degrees to each other, but when you work your way around the leg jointing each face the tiny error will be cumulative after the last pass. You are essentially doing the same thing as the "five cut test" which is one way to see if your miter gauge is square to the blade.

[Van Huskey]

Am I missing something? IF his adjacent faces are at 90* there is nothing wrong with the fence. As I understand it he has a taper in the leg, in this case unwanted. This could be a result of infeed/outfeed table coplaner issues given the number of passes he is making I could see a 1/8" difference. But even with a perfect jointer setup unless the opposite faces were coplaner to begin with he will have a taper. My guess it is a little of both, even if the jointer is close enough for normal work the multiple passes are adding up. Bottom line use a planer like one normally would and there will not be an issue, this is just asking a jointer to do something it can not do.

[Sam Murdoch]

Am I missing something? IF his adjacent faces are at 90* there is nothing wrong with the fence. As I understand it he has a taper in the leg, in this case unwanted. This could be a result of infeed/outfeed table coplaner issues given the number of passes he is making I could see a 1/8" difference. But even with a perfect jointer setup unless the opposite faces were coplaner to begin with he will have a taper. My guess it is a little of both, even if the jointer is close enough for normal work the multiple passes are adding up. Bottom line use a planer like one normally would and there will not be an issue, this is just asking a jointer to do something it can not do.

And so it is written and so it is... Nicely said Van.

[Rick Fisher]

When you try that, you can usually measure the difference in thickness from one end to the other..

[michael veach]

Yup. sounds like the out feed is not in perfect alignment. If the out feed is a few mils above the head, you will make a nice taper.

[keith micinski]

I am going to have to agree with Van here and say I don't see why everyone is telling him there is an equipment issue. There is nothing wrong with his equipment, if you use a jointer to make two opposite side coplanar and it actually works its a fluke. There is nothing wrong with his square or his jointer set up. His process is wrong not his tools.

[Alan Schaffter]

Am I missing something? IF his adjacent faces are at 90* there is nothing wrong with the fence. As I understand it he has a taper in the leg, in this case unwanted. This could be a result of infeed/outfeed table coplaner issues given the number of passes he is making I could see a 1/8" difference. But even with a perfect jointer setup unless the opposite faces were coplaner to begin with he will have a taper. My guess it is a little of both, even if the jointer is close enough for normal work the multiple passes are adding up. Bottom line use a planer like one normally would and there will not be an issue, this is just asking a jointer to do something it can not do.

Opposing faces of a leg will NEVER be coplanar. They can be intersecting or parallel but never coplanar. To be coplanar they must be in the same plane. Based on his description, he may have more than one issue, but if he fed the board in the same direction on each pass and ended up with unwanted taper then either the board started that way or he has a problem with his jointer's outfeed table not being set to TDC of the cutters. This is a tough one to diagnose without seeing it first hand, but that is the best guess. He should have used a planer or tablesaw to mill or rip leg to the proper thickness and width.

I would be surprised also if the corners of his legs were truly 90 deg.

[Van Huskey]

Opposing faces of a leg will NEVER be coplanar. They can be intersecting or parallel but never coplanar. To be coplanar they must be in the same plane. Based on his description, he may have more than one issue, but if he fed the board in the same direction on each pass and ended up with unwanted taper then either the board started that way or he has a problem with his jointer's outfeed table not being set to TDC of the cutters. This is a tough one to diagnose without seeing it first hand, but that is the best guess. He should have used a planer or tablesaw to mill or rip leg to the proper thickness and width.

I would be surprised also if the corners of his legs were truly 90 deg.

You are correct I used the incorrect term, everywhere I said coplaner it should have been parrallel. Other than that your new post agrees with most everything I said initially, either it started out tapered and/or the jointer was inducing taper. Since a jointer would have to be "perfect" not to cause taper my point was even a planer close enough to perfect to not cause issues with normal operations all the extra trips would compound the errors until they were and issue, as you note if the direction of travel were always the same.

I would be surprised if the corners of his legs weren't acceptably close to 90* since there are few things on earth that are truly 90* and there are probably more things in the world that are perfectly 90* by accident then on purpose. Bottom line why would you have any reason to think based on what he said that they weren't ~90* within reason? Out of all the things that could be causing his issue a fence slightly out isn't one of them.

[Rick Fisher]

My Jointer is set up 99.9% right and I still get a tiny amount of taper when face jointing .. its just life.. The planer fixes it in the first pass. Always figured it was just the way it was..

[keith micinski]

You can't cut parallel with a jointer no matter how it is setup. This was answered in the first reply. I am baffled at the confusion in this post.

[Alan Schaffter]

Bottom line why would you have any reason to think based on what he said that they weren't ~90* within reason? Out of all the things that could be causing his issue a fence slightly out isn't one of them.

Based on his technique decision and what he says in his post- "my first workbench", "growing pains learning how to mill lumber properly," "it seemed to me that they were (square)", all lead me to believe that over the short span of 3" it was reasonable to suspect his legs weren't precisely square. If he used Norm's technique- jointed one face then used the fence to square the second face, and did that for the subsequent faces, a fence error would continue to grow each time he rotated the leg. It wouldn't cause the taper but would result in the faces becoming more and more out of parallel as he rotated and jointed. We don't know how many times he rotated it but he says he "did that all around until it was the size I needed." Again, without being there and lacking more specifics, it is hard to tell what caused his problems.

[Phil Thien]

You can't cut parallel with a jointer no matter how it is setup. This was answered in the first reply. I am baffled at the confusion in this post.

+10.

You can't do what the OP is trying to do. Jointers do not generate parallel surfaces. Only flat surfaces.

If jointers were cable of providing flat, parallel surfaces, we wouldn't all have planers.

This has nothing to do with the fence or technique in using the jointer. Some crucial steps are being missed. It was stated above, but again, the process is:

1. Get the face of the board flat, on the jointer.
2. With that face against the fence of the jointer, get one edge flat and 90-degrees to the face.
3. Use the table saw to get the 2nd edge flat, and parallel, to the first edge (the one you jointed).
4. Use the planer to get the 2nd face flat, and parallel, to the first face (the one you jointed).

[glenn bradley]

+10.

You can't do what the OP is trying to do. Jointers do not generate parallel surfaces. Only flat surfaces.

I agree a higher level of caution is called for in these responses. Discussion is good. Arguing reality is not quite so valuable. I hope Christopher is able to glean the simple fact that has been stated here previously; jointers make surfaces flat, planers make the opposite surface parallel to the already jointed surface.

Despite this fact, folks try to convince themselves (and worse, convince others) that they can reliably thickness material on a jointer or can reliably flatten a board with a planer. Opinions are opinions but, let's be considerate of newcomers and be careful to observe the line that divides generally correct information from the "I had a friend who had a cousin who once thicknessed a board on a jointer and it worked great" sort of stuff.

P.s. A jointer will also make a perpendicular edge 90* to the already flat face being used as a reference surface against the fence. Neither of these things take the place of a planer or a tablesaw :). A hammer is a hammer and not everything else is a chisel :D

[Eric DeSilva]

I'm with Van on this one. Let me try this way. Imagine you have a 4' long piece of wood that starts 6"x4" on one end and tapers to 6"x2" on the other end. It should be quite clear that such a piece can be constructed such that each 6" wide face is 90* to the tapered face (the face that is 4' long, 4" on one end and 2" on the other). The *only* edge that is not 90* is the long face/end intersection (i.e., the 6"x4" side against the 6" wide side, or the 6"x2" against the 6" wide side). But the non-90* angle will never be between the bed of the jointer and the fence--the only way that would happen is if you were "jointing" the end grain. Now run the 6" wide faces of the wood through the jointer. Since the faces are flat, you will continue to shave them down evenly. Even with a perfect fence and perfect registration, if you keep going, you will end up with a piece that is 6x3 on one end and 6x1 on the other. The jointer, even with a perfect bed and perfect fence and perfect technique will never render the two 6" wide faces parallel.

[Alan Schaffter]

+10.

You can't do what the OP is trying to do. Jointers do not generate parallel surfaces. Only flat surfaces.

If jointers were capable of providing flat, parallel surfaces, we wouldn't all have planers.

This has nothing to do with the fence or technique in using the jointer. Some crucial steps are being missed. It was stated above, but again, the process is:

1. Get the face of the board flat, on the jointer.
2. With that face against the fence of the jointer, get one edge flat and 90-degrees to the face.
3. Use the table saw to get the 2nd edge flat, and parallel, to the first edge (the one you jointed).
4. Use the planer to get the 2nd face flat, and parallel, to the first face (the one you jointed).

You are right OP can't guarantee his result. He might be lucky if he starts with a board that is square and his jointer is adjusted perfectly, but it will be a miracle if he is able to keep the corners square at 90 degr., square dimensionally, and with no taper.

A properly adjusted jointer and fence "can be used" to square the stock like Norm does, but I don't do it that way, especially since the fence detents are unreliable and with what appears to be widespread reports of fence twist.

I may have gotten lost between your edges and faces, but it seems your step #2 follows Norm's technique and success is based on the jointer fence being 90 degr. to the table. If it is not then adjacent faces will not be at a right angles. The same goes if your tablesaw blade is not at 90 degr. I used "face" to describe all sides of a square leg.

Depending on the order of jointer and tablesaw cuts you may end up with a very nice looking parallelogram shaped leg when viewed from the end! The fence on my DJ-20 does not always go back to 90 after being set to a bevel, so I rely on the tablesaw for 90 degr. cuts. Trust me, I've been there, done that.

The goal is to ensure the opposing faces are parallel AND adjacent faces are at right angles. To avoid relying on my jointer fence and be sure I have a square (or rectangular) leg, that also does not taper I:

(faces numbered sequentially around the leg)

1. Joint face #1
2. Joint adjacent face #2 just to make it flat (the jointer fence doesn't need to be perfect)
3. Rip face #4 with face #2 against the fence and face #1 on the table (blade MUST be 90 degr.) clean up saw marks on jointer if you want.
(Now I know faces #1 and #4 are perpendicular. If I could trust my jointer fence I could eliminate step 3.)
4. Plane faces #2 and #3 until leg is desired size. (faces #1 and #4 are the references faces)

The result is a leg whose cross-section is square (or rectangular) and whose faces are parallel so there is no taper.

If I have a square leg whose dimensions exceed the capacity of my TS blade, then I spend a little extra time setting the jointer fence.

[Phil Thien]

If I have a square leg whose dimensions exceed the capacity of my TS blade, then I spend a little extra time setting the jointer fence.

Do you adjust your jointer fence away from 90 that often?

I know some must. That is why they have those knobs on them. Me, I never did.

[doug faist]

I just found this thread and admit that I am confused by the confusion. This is NOT an equipment problem, it's a procedure problem. To get parallel sides just with a jointer would be a huge stroke of luck.

Jointer: flat and square
Planer: parallel

Doug

[Rick Fisher]

I have not changed my jointer from 90 degrees in a long time .. Its probably 89.8 degrees or similar.. dunno.. The only time its not square enough is for glue up's .. I flip face in, face out .. works fine..

[Will Blick]

Doug, jeeez, I agree with you....how can such a simple question go this far off track?

Bottom line:

Jointer references one surface, it can therefore make the ONE referenced surface flat. Nothing more...

Planar references one surface and cuts the opposing surface, assuring FLAT and parallel cut surface.
(to be clear, assuming reference surface was FLAT)


Done...

[Alan Schaffter]

Do you adjust your jointer fence away from 90 that often?

I know some must. That is why they have those knobs on them. Me, I never did.

Just often enough that when combined with its slight twist, I don't trust it. For edge glue-ups I flip the faces like Rick does.

[Alan Schaffter]

I just found this thread and admit that I am confused by the confusion. This is NOT an equipment problem, it's a procedure problem. To get parallel sides just with a jointer would be a huge stroke of luck.

Jointer: flat and square
Planer: parallel

Doug

I disagree, in that what was presented by OP could be caused by a whole host of problems. For sure it is most definitely a procedure problem that could have been solved by just flattening one face on the jointer then using the tablesaw and planer to finish up the other three faces, but without knowing specifics you can't say there is nothing else going on! Not even discussed yet is what happens if the jointer beds are not parallel across their width with the blades. If everything else is set properly, it will joint straight along its length, but will make an angled cut if one face is registered to the fence, just like if the jointer fence or tablesaw blade aren't at 90.

[keith micinski]

I disagree, in that what was presented by OP could be caused by a whole host of problems. For sure it is most definitely a procedure problem that could have been solved by just flattening one face on the jointer then using the tablesaw and planer to finish up the other three faces, but without knowing specifics you can't say there is nothing else going on! Not even discussed yet is what happens if the jointer beds are not parallel across their width with the blades. If everything else is set properly, it will joint straight along its length, but will make an angled cut if one face is registered to the fence, just like if the jointer fence or tablesaw blade aren't at 90.



You forgot to mention what if his jointer was struck by a meteorite while jointing as a possible problem. You couldn't be more wrong about his problems. Even if his jointer is setup perfectly if he continues with the wrong procedures for milling up wood he will end with the same exact results. Nothing else needed to be discussed or brought up until the procedural flaw was addressed. Then you can start to address any other issues that my be present.

[Zach Callum]

I may have mis-read the original post. I thought at first that he meant one face of the leg was measuring wider than the rest, this would make a trapezoid, and his square must be off. Now I see that he meant one end of the leg was fatter... Its still a good idea to check the squareness of your square from time to time.

[John Coloccia]

Yeah, but what if the fence isn't 90 to the table? I wouldn't just assume that the machine is properly set-up, and the square is accurate, which is what you are doing.

Well, he measured 4 sides of a polygon and says that they all measured 90 degrees. I'm pretty sure the only way that can happen is if all 4 sides and the square are accurate 90 degree angles, since the sum of angles of any quadrilateral is 360 degrees.

So now we know his fence and square are accurate, and we can concentrate on why using the machinery in this way can give a taper despite proper machine setup and proper technique.

[keith micinski]

I can't believe more people keep responding that it still might be a machine setup issue. I keep thinking that it is April Fools day every time I open up this thread and the joke is going to be on me.

[Dave Zellers]

At this point, Chris is probably wondering why he asked. :)

[Alan Schaffter]

Looks like Asa was on target.

[Christopher Reyes]

Last night I was sitting at the dinner table trying to explain to my wife that I had caused a stirring debate about geometry and woodworking tools...she was not impressed. lol

Anyway, I just wanted to thank everyone for their input, it is clear to me that I was expecting too much out of my jointer and was using it for something it was not intended. I think I am a victim of dumb luck, in my first project I had managed to mill the lumber in the same fashion with no apparent taper... I know better now.

This forum has been a great find, I hope to learn more from ya'lls experience in the future.

~Chris.

[Andrew Hughes]

I know the look my wife gives me when i try to talk about woodworking particulars.Kinda glazed.I dont know if anyone mentioned that a jointer is like a upside down japanese hand plane.One could flaten one side then scribe a line around using the flat side as a guide then remove the wood up to the scribe line.But the stock would have to be turned around back and forth causing tear out and missing finger tips.Its not easy to create a hollow in the middle of a board sometimes you will get a piece shaped like a football.But its kinda dangerous. That why i have two planers.small one for small parts big one for long boards.

[John Hemenway]

Interesting thread. I'm surprised how many don't seem to get it.

This is my thought process. Think about what a tool uses for a reference.

A jointer (or hand plane) references off the table. It makes wood flat with reference to the table. It 'knows' nothing about the opposite face of the board.

A thickness planer references off the opposite face and makes the face being cut the same distance from that face. If the reference face is flat, the board will come out flat.

Did that clear it up or muddy the waters? :)

[Alan Schaffter]

The problem arises when you combine bad technique with improperly adjusted equipment. The proper technique is to joint then thickness plane, but when you are dealing with four surfaces like on a leg, a whole bunch of other issues can occur if your equipment is not set up properly.

"Theoretically speaking" if you start with a square or rectangular leg whose faces are square to the adjacent face and parallel to the opposing face in cross section and along their length, AND your jointer is set precisely, you "should" be able to size the leg with a jointer only, without any adverse effects. However that is taking a BIG chance!!!

If the jointer outfeed table is not set to TDC you may be jointing a wedge- taking more off the leading or trailing end of the board. It may not even be flat. If it is flat you should follow up with a planer which will mill the opposing face parallel. A similar result can happen when you feed a thin, warped board into the jointer and press down on it and so the arch is flattened slightly. You may eventually be able to get it flat but you stand to lose an unacceptable amount of stock- see the drawing:

http://www.ncwoodworker.net/pp/data/500/medium/Jointing_Problem-1.jpg

The second issue is created if the fence on your jointer is not vertical (90 degr.) to the bed and you use it to make the second face perpendicular to the first (before planing the other two faces). Even if the board started out having a square cross-section (like the drawing below), you will end up with a leg that has a trapezoidal cross-section. No amount of planing will fix that, and if you make a lot of jointing passes, rotating the board after each pass, before planing it, you will have a really skewed trapezoid!!! Unless the stock is too thick, it may be easier and preferable to establish the first set of square faces (square corner) on a tablesaw.

http://www.ncwoodworker.net/pp/data/500/medium/Jointing_Problem-2.jpg

Bottom line- you need to use correct technique AND ensure your machinery is set up properly.