HELP! Jointer has started to taper boards

[forrestb]

I am jointing Qtrsawn hard maple for some drawers. My first 5 boards (16 inches long) jointed flat in around 2 passes at 1/32 cut.

On the 6th board it required more passes until it was obvious that the leading edge was being tapered. The 6th board was adjacent to the 5th board from a longer piece but it was the end piece.

Since this has never happened before, I assumed it was tapered to begin with since it was an end piece so I tried a longer piece, 34 inches, and after 2 passes it had tapered 1/16 inch at the end first through the jointer. I had measured the thickness before the jointing and it was spot on the same end to end.

It acts like my infeed table has drooped away from the cutter, but I would like to find out if anyone else has noticed this and found the cause - before I start looking in the wrong area.

Thanks

Forrest

edit: I did raise the table to the zero mark and using a trusted straightedge there was no tilt of either table - flat one end to the other. So it must be technique? I have been jointing for years (boards, not bars ) and have not changed my technique. Especially on the shorter boards my push pads covered the whole thing. 5 went perfect, then 2 started bad using the same technique?

edit2: I ran the infeed down and measured the offset from the cutter edge to the trailing edge.

Leading.jpg (293.42 KiB) Viewed 4023 times

Trailing.jpg (281.08 KiB) Viewed 4023 times

I can see no more than 1/128 taper - but that could easily be measurement error. The level at those 2 points is 1 0/128 inch.

[rjent]

I am jointing Qtrsawn hard maple for some drawers. My first 5 boards (16 inches long) jointed flat in around 2 passes at 1/32 cut.

On the 6th board it required more passes until it was obvious that the leading edge was being tapered. The 6th board was adjacent to the 5th board from a longer piece but it was the end piece.

Since this has never happened before, I assumed it was tapered to begin with since it was an end piece so I tried a longer piece, 34 inches, and after 2 passes it had tapered 1/16 inch at the end first through the jointer. I had measured the thickness before the jointing and it was spot on the same end to end.

It acts like my infeed table has drooped away from the cutter, but I would like to find out if anyone else has noticed this and found the cause - before I start looking in the wrong area.

Thanks

Forrest

edit: I did raise the table to the zero mark and using a trusted straightedge there was no tilt of either table - flat one end to the other. So it must be technique? I have been jointing for years (boards, not bars ) and have not changed my technique. Especially on the shorter boards my push pads covered the whole thing. 5 went perfect, then 2 started bad using the same technique?

Can you run it through a planer, and then try again to see if it is still tapering?

Just a thought from a newbie ....

[Gene Howe]

Not sure that 1/128 would cause that much of a taper. Maybe, just not sure.
To minimize any effects of the difference and/or technique though, flip the board end for end and joint the opposite side, as well.

[JPG]

"Push pads covered the entire length."

Question is, where was pressure applied and when.

As you start the pressure must be on the infeed table.

Once sufficient length is on the outfeed table, the pressure is all there.

There should be NO rocking as the pressure is shifter from infeed to outfeed.

The infeed table is the reference surface initially, but the outfeed table becomes the reference later.

Now have you determined the cutter blades are coincident with the plane of the outfeed table at their apex?

[algale]

Ok, this subject has come up at least two times before.

There's nothing wrong with your jointer or your technique.

I've said it before and I will say it again (and I know some others will disagree ): if the edge you are jointing isn't straight and flat to begin with, the jointer has to cut more of the board in some places than in others and this reduces the apparent height of the board in those places and thus causes a taper. The taper may not be very obvious or even noticeable on shorter boards or where the edge doesn't have a bad defect.

Here's someone else who agrees with me. http://www.newwoodworker.com/jntrtaprs.html

[jsburger]

"Push pads covered the entire length."

Question is, where was pressure applied and when.

As you start the pressure must be on the infeed table.

Once sufficient length is on the outfeed table, the pressure is all there.

There should be NO rocking as the pressure is shifter from infeed to outfeed.

The infeed table is the reference surface initially, but the outfeed table becomes the reference later.

Now have you determined the cutter blades are coincident with the plane of the outfeed table at their apex?

That is a perfect explanation of jointer technique. The out feed table is always the reference once the cut is started and the pressure should be there.

However, the jointer does not and is not intended to make surfaces parallel. The purpose is to flatten one side of a board regardless of the other side of the board. Then you put the flat side of the board down on the planer and make the other side parallel (length and width) to the jointed side.

So, yes I don't think you should see any tapering unless it was there to begin with. It should not be a problem if you are jointing and planing the stock to obtain the correct thickness.

If your jointer is properly adjusted as you suggest then the only variable is technique.

[algale]

Folks, if jointers were capable of cutting the face/edge being cut parallel to the opposite face/edge, we wouldn't need thickness planers. Now ask yourself, if the jointer isn't making that fresh cut face/edge parallel to the opposite face/edge, what is the result? A taper.

[jsburger]

Ok, this subject has come up at least two times before.

There's nothing wrong with your jointer or your technique.

I've said it before and I will say it again (and I know some others will disagree ): if the edge you are jointing isn't straight and flat to begin with, the jointer has to cut more of the board in some places than in others and this reduces the apparent height of the board in those places and thus causes a taper. The taper may not be very obvious or even noticeable on shorter boards or where the edge doesn't have a bad defect.

Here's someone else who agrees with me. http://www.newwoodworker.com/jntrtaprs.html

If it is flat and smooth to begin with why would I want to joint it?

The jointer is designed to make a surface flat and smooth from a rough edge. Taper is not an issue since the jointer is not intended to make surfaces parallel. Having said that, there is a way to purposefully taper a piece of stock on the jointer. I do it all the time.

Here is how it is supposed to work. I certainly think most of you know this. First let me say I use rough sawn wood 99% of the time. However, the same principles apply to S4S from the big box stores.

I cut the stock to length plus an inch or so. I run the flat side over the jointer until all the saw marks are gone and it is flat. Then I put the flat jointed side of the stock against the jointer fence and joint one edge. Two sides square. Next I run it through the planer (flat side down on the table) to get it to the proper thickness plus a little bit to run it through the horizontal drum sander. Three sides square. The I cut to width on the table saw plus 1/64" or less. just enough to make a very light cut on that edge on the jointer to clean it up. Four sides square and NO TAPER.

Again, a jointer does not make surfaces parallel and is not meant to do that. That is the job of a planer.

Small/light cuts will improve your results. I don't ever take more than 1/32" cuts on my jointers and usually less. I can't imagine why you would want to make a deeper cut. I cut pieces to width on the table saw.

Sorry, algale I am not dumping on you just trying to explain what I know about jointers. They are not a finish machine.

[jsburger]

Folks, if jointers were capable of cutting the face/edge being cut parallel to the opposite face/edge, we wouldn't need thickness planers. Now ask yourself, if the jointer isn't making that fresh cut face/edge parallel to the opposite face/edge, what is the result? A taper.

Huhh???

Our posts crossed but now you are saying what I am prior to your previous post.

[algale]

Read my first post again, JSBurger. I think it is NORMAL for a jointer to cut a taper on any surface that needs jointing. The fact is that to try and prove a jointer doesn't cut a taper, most folks take a piece of relatively short lumber that is already S2S or S4S (so they have a consistent thickness) and run it through the jointer once or twice and take a very slight cut. Gee, no appreciable taper. (Run it through five or six times, however....). The reality is that when you need to use a jointer, it is because you've got a face or edge that isn't straight to begin with and that's when you get really obvious taper on one or two passes.

Folks, if jointers were capable of cutting the face/edge being cut parallel to the opposite face/edge, we wouldn't need thickness planers. Now ask yourself, if the jointer isn't making that fresh cut face/edge parallel to the opposite face/edge, what is the result? A taper.

Huhh???

Our posts crossed but now you are saying what I am prior to your previous post.