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.