Shopsmith Forums

I'm scratching my head over this...

If I take (for example) a 3 foot piece of 2x4 and make multiple passes over the jointer in the same orientation and direction, with each pass, the 2x4 becomes more and more tapered with the leading end narrower (thinner) than the trailing end. I am trying to be very careful to keep appropriate pressure on the infeed/outfeed table as I make the pass but I can't seem to change what is happening. Do I just need (a lot) more practice or is there some sort of adjustment needed on the jointer?

I had, have, the same issues. I think it is technique for me, and have spent some time practicing with a lot of old pine boards. I have not corrected all of it, but I'm better. I find that once I get the surface a bit out of whack, it is just about impossible for me to fix without going at it from the opposite direction. It is easy to put a bit of excess pressure on the in-feed side for me as I start. I had to work on the alignment a bit as well, but it was me, not the jionter.

Are the infeed and outfeed tables 'co-planer?

Take a known straight edge and after setting the tables to the same height, check that the straight edge touches the tables all the way from end to end.

'Proper pressure'. Downward pressure gradually shifts from the infeed side to the outfeed side as the pass is made.

Have you checked the blade height to outfeed table. When the workpiece just reaches the outfeed table. it should not have to climb onto the outfeed table nor clear it(minimum clearance).

Did you start with S4S lumber -- all 4 faces jointed and parallel?

If not,there may not be anything wrong with your jointer or your technique. A jointer has no ability to keep the edge/face being jointed parallel to the edge/face opposite it. It take off whatever high spots it needs to take off to make the edge/face flat and this will change the plane of the edge/face being jointed and almost certainly put it out of parallel in relation to the opposing edge/face.

If you are edge jointing, joint an edge. Put that jointed edge against a rip fence and rip to width (leave a little extra to allow for sanding if you don't have the capability to get a glue edge rip). If you are face jointing, joint one face and then take it to the planer and put the jointed face down and plane. Those are the only ways to get opposing edges or faces truly parallel to a surface you have jointed.

Now, theoretically, if you started with accurately milled S4S lumber and used perfect technique on a perfectly set up machine, then and only then would you not get taper. But why would you use a jointer on S4S lumber to begin with?

For more on why jointers cut tapers see http://www.newwoodworker.com/jntrtaprs.html and the accompanying video http://www.youtube.com/watch?v=5af_yZQHo8k

Just reread your post. You started with a 2x4. I assure you it wasn't S4S and things were at best roughly parallel to begin with. Your Jointer is doing exactly what it is supposed to do.

It is sometime hard to tell what is happening when you are seeing the results of working on jointing a board but a good first step is to make sure your jointer is setup properly.

I don't have the shopsmith jointer but in our home shop when I was but a lad had a look alike with the fix out feed table. When I looked for a jointer I looked for an out feed table that was adjustable. Why? Because at the time that was one of the hard parts of adjusting the jointer, getting the out feed table and the blades aligned just right.

If the table is too high you simply run into the out feed table and you know something is wrong. But if are just a smidgen off you can get past it, leading to issues. The opposite of this is to have the out feed table to low in relation to the blades, and this is the one that use to get me. The cutting edge needs to be at its apex or highest point and be level with the out feed table. Don't get this right and you can expect less then perfect results.

I have no idea what method you use for doing this setting. I have a gauge that I use that holds the blades in position with magnets and I can do a fine adjustment via a threaded knob. In the old days I did what we called a "tick" test, you hold a square on the out feed table then turned the cutter head backwards and listen for a slight "tic" sound from each of the blades at each end. Lots of ways to do this and the method is not as important as the result.

As was already mentioned you also need to know if the out feed table continues to be flat to its far end. I have read about shopsmith machines with this problem but I don't recall the solutions.

As far as other hints, use the safety pads that came with your shopsmith safety kit. Keep in mind wood may have a concave or convex edge that can and will determine how you joint that piece. Take a look at your PTWFE or the online version for more details.

Ed

I have checked that the infeed and outfeed tables are co-planer by clamping a wide straightedge to the outfeed table and confirming that there is a consistent gap on the infeed table. I adjust the knives using a dial indicator and then confirm using the metal ruler method outlined in the jointer users manual.

I fully understand that the jointer will not make opposing edges parallel, I just don't get why the board becomes more tapered with each pass. This implies that the jointer is cutting less and less as the board moves across the knives which, for me, implies either a setup problem or a user problem. I guess the third possibility is that this is a normal outcome.

I was hoping for some cut-and-dried answer like,

1) If the board is tapering on the leading edge do/check the following: ...
2) If the board is tapering on the trailing edge do/check the following: ...

Thanks to all for the help.

mountainbreeze wrote:I have checked that the infeed and outfeed tables are co-planer by clamping a wide straightedge to the outfeed table and confirming that there is a consistent gap on the infeed table. I adjust the knives using a dial indicator and then confirm using the metal ruler method outlined in the jointer users manual.

I fully understand that the jointer will not make opposing edges parallel, I just don't get why the board becomes more tapered with each pass. This implies that the jointer is cutting less and less as the board moves across the knives which, for me, implies either a setup problem or a user problem. I guess the third possibility is that this is a normal outcome.

I was hoping for some cut-and-dried answer like,

1) If the board is tapering on the leading edge do/check the following: ...
2) If the board is tapering on the trailing edge do/check the following: ...

Thanks to all for the help.

Exactly what procedure are you following? Are you repeatedly jointing the same edge/face in the same direction only? Or are you jointing two or more edges/faces? If you are jointing two or more surfaces are they adjacent or opposite?

I'm not really doing anything specific. I noticed this phenomenon when I was jointing one edge to be square with its adjacent surface. It took me 4 or 5 passes to get it square and when I was done, I noticed that the board, which had (nearly) parallel edges when I started, was tapered by a noticeable amount. So, to confirm what I thought I experienced, I took a scrap piece of 2x4 and made 15 or 20 passes cutting something less than 1/16" on each pass. What I found was that with each pass, the 2x4 became more and more tapered with more being cut from the leading edge than was cut from the trailing edge. Give it a try and let me know your results.

How about another way of looking at it..... There's a way to deliberately create taper on the jointer. Maybe you can compare/contrast with this method and its results:
http://woodworkingjointer.com/page17.htm

You might be having the same phenomenon, or the opposite sense of taper. Anyway, these are some useful geometry references to keep in mind.

Incidentally, I keep my jointer at very shallow depths, well less than 1/16". Oh yeah, my last job I was at about 0.010" depth-of-cut -- via my handplanes rather than the jointer .

mountainbreeze wrote:I'm scratching my head over this...

If I take (for example) a 3 foot piece of 2x4 and make multiple passes over the jointer in the same orientation and direction, with each pass, the 2x4 becomes more and more tapered with the leading end narrower (thinner) than the trailing end. I am trying to be very careful to keep appropriate pressure on the infeed/outfeed table as I make the pass but I can't seem to change what is happening. Do I just need (a lot) more practice or is there some sort of adjustment needed on the jointer?

Once you are sure your jointer is properly aligned including the tables, fence and cutter blades, there is a "push / pull technique many have found helpful.

When planing an edge start the board against the fence and infeed table. Push the board across the infeed table until it passes the cutter by about 6". At this point it is necessary to shift your weight and with your left hand begin to pull the board the rest of the way across the cutter. There is no need to use downward hand pressure to keep the board on the tables. The proper function of your hands is to push, then pull, while all the time holding the board against the fence.