Jointer Problem: Convex Joint

pjallen · Post by **pjallen** » Mon Jan 25, 2010 6:30 pm

Hi all,

Over the holidays I bought a used Shopsmith Jointer (505681-B). The blades are razor sharp after my Tormek finished with them (ouch! that jig was expensive!). I carefully set the blades and I followed the instructions in the manual to make sure everything is square. And now when I joint a board I get a nice flat silky smooth joint with no sniping.

But!, there is always a but, when I joint 2 boards (30 inches long/short) to be glued together they both have a very gentle convex joint which leaves ~0.5-1mm gap at the end. For the first few boards I took a cabinet scraper and cleaned up the joints enough so they could be glued.

So what am I doing wrong?
I am putting pressure on the out-feed table.
The out-feed & in-feed tables appear co-planer. Based upon my Groz 40" metal ruler the in-feed side "might" be ever so slightly low but definitely not high.

Any suggestions? I admit this is my first jointer.

thanks,
Phillip Allen

mbcabinetmaker · Post by **mbcabinetmaker** » Mon Jan 25, 2010 8:59 pm

Phillip

It sound to me like the knives are set just a bit low. Have you waxed the bed and fence on the jointer? Does the wood have a good glide feel going through the machine or does it feel like you are having to push to hard? I find that the knives work better a couple of thousands above the outfeed table but never low.

charlese · Post by **charlese** » Mon Jan 25, 2010 10:22 pm

Agree with Mark!

reible · Post by **reible** » Mon Jan 25, 2010 10:45 pm

Hi,

I concur with the advice given.

You can check it out with a steel rule on the out feed table, disconnect the jointer from the power source and spin the jointer head backwards and listen for a tick as the blade passes the ruler.... no tick blades to low.

Ed

JPG · Post by **JPG** » Mon Jan 25, 2010 10:57 pm

And are you maintaining contact with the outfeed table towards the end of the 'pass'? The pressure must be concentrated on the infeed table at the beginning of the 'pass', evenly through the middle of the 'pass' and concentrated on the outfeed table toward the end of the pass. If the workpiece is not held securely on the outfeed table, it will tend to 'drop' towards the end of the 'pass' making the end skewed.

heathicus · Post by **heathicus** » Mon Jan 25, 2010 11:19 pm

JPG40504 wrote:And are you maintaining contact with the outfeed table towards the end of the 'pass'? The pressure must be concentrated on the infeed table at the beginning of the 'pass', evenly through the middle of the 'pass' and concentrated on the outfeed table toward the end of the pass. If the workpiece is not held securely on the outfeed table, it will tend to 'drop' towards the end of the 'pass' making the end skewed.

I've always heard to shift the pressure to the outfeed table as soon as possible and keep it there through the whole pass...

JPG · Post by **JPG** » Tue Jan 26, 2010 12:14 am

heathicus wrote:I've always heard to shift the pressure to the outfeed table as soon as possible and keep it there through the whole pass...

Yes, but if on both midway, you are putting pressure on the outfeed table. There must be enough surface of the workpiece on the outfeed table to provide the required 'reference'.

The infeed table provides the 'reference' at the beginning of the pass and the outfeed provides the 'reference' at the end. Mid way through the cut is when proper alignment of the two tables(and the blades) becomes relevant. If they are not 'coplaner' they each provide conflicting 'references' causing some shift of the cutting plane on the workpiece at some point through the 'pass'. This produces an edge with two(or more) non-coplaner surfaces. If the workpiece is not held against the table(s) an additional source of non-coplaner surface is created. The blades must be in line with the outfeed table surface at their 'apex' position).

Therefore, hold it tight to the infeed table at the start and shift the emphasis to the outfeed table when adequate workpiece edge area is obtained.

Equally important but not mentioned is holding the workpiece tightly against the fence(if used/relevant)!

dusty · Post by **dusty** » Tue Jan 26, 2010 7:03 am

These discussions are so very true and accurate even with the apparent differences in technique. This task is very difficult (as are many) to adequately put in words. To become expert at this, it is necessary to turn a few board feet of lumber into tiny curls that lay on the floor beneath the jointer. Once you have done that, you will be as expert as any of us in using this equipment. Only with that experience will you repeatedly "get it right".

tdubnik · Post by **tdubnik** » Tue Jan 26, 2010 7:43 am

I believe that the jointer is one of the most important tools to get tuned right as it is the foundation for subsequent cuts. If your board doesn't come out straight and flat it could easily lead to problems with later steps.

The first thing I would do is lay a known straight edge on the outfeed table overhanging the infeed table. Adjust the infeed table up or down so that it is level with the outfeed table. Using feeler gauges between the stright edge and the infeed table measure for any gaps or "out of plane" conditions. If you find any they need to be corrected to get a true cut.

On my Shopsmith jointer the tables are co-planer but my fence has a .005 twist in it. I discovered this because I couldn't get my boards to have an invisible joint. I used an engineers square to set the infeed side of the fence square to the infeed table. When I move the square to the outfeed table, I could stick a .005 feeler gauge between the square and the top of the fence. As I jointed my boards starting with pressure on the infeed side and transferring to the outfeed side I was actually jointing a twist into the edge of the board. I fixed this by attaching a sub-fence to the jointer fence and shimming the outfeed side to get it square.

My twisted joints are now history.

dusty · Post by **dusty** » Tue Jan 26, 2010 9:11 am

tdubnik wrote:I believe that the jointer is one of the most important tools to get tuned right as it is the foundation for subsequent cuts. If your board doesn't come out straight and flat it could easily lead to problems with later steps.

The first thing I would do is lay a known straight edge on the outfeed table overhanging the infeed table. Adjust the infeed table up or down so that it is level with the outfeed table. Using feeler gauges between the stright edge and the infeed table measure for any gaps or "out of plane" conditions. If you find any they need to be corrected to get a true cut.

On my Shopsmith jointer the tables are co-planer but my fence has a .005 twist in it. I discovered this because I couldn't get my boards to have an invisible joint. I used an engineers square to set the infeed side of the fence square to the infeed table. When I move the square to the outfeed table, I could stick a .005 feeler gauge between the square and the top of the fence. As I jointed my boards starting with pressure on the infeed side and transferring to the outfeed side I was actually jointing a twist into the edge of the board. I fixed this by attaching a sub-fence to the jointer fence and shimming the outfeed side to get it square.

My twisted joints are now history.

Thank you for this insight. I had never checked my jointer fence in this manner. A simple check to square it with the infeed table seemed adequate.

I just checked mine and I find that I can get a .003" feeler between the square and the face of the fence (on the outfeed side) when on the infeed side I can not.

I believe that this is "close enough". For my work, "nearly invisible" glue lines are good enough.

I have read criticism about the 4" jointer but I am very pleased with the performance of mine. Yes, there are limitations. But this is a 4" jointer and I believe that is adequate for my work. I do not recall having ever needed to joint a board that could not be done here.

It would be interesting to have a round table discussion with those who feel they "need" a jointer larger than that. Just what do they joint?