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Thread: Large jointer planer combo tables not flat, looking for suggestions

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  1. #1

    Large jointer planer combo tables not flat, looking for suggestions

    So far the company I purchase the jp combo off of has been extremely accommodating and for that reason I care not to mention their name. I purchased the tool about a year ago and quickly brought to their attention that the tables where not flat. With a little effort on my part within a couple of days they agreed to send me a new machine and promised to thoroughly check it before it arrived at my shop. Now I have two machines that I find far from acceptable when it comes to the tables being flat never mind coplanarity table to table or table to cutter head. Please see my attached picture and confirm or dismiss my concerns. Are there any techniques that I can use while jointing to produce a high quality product with in of these machines? I expect to be able to straighten/flatten a 10' board within a 32nd. Is all hope loss?
    Attached Images Attached Images

  2. #2
    How many thousandths of an inch are they away from being flat? (I can't see the picture, sorry)

    My 16"x47" jointer beds have around 0.002-0.003" dip in the middle going left to right. However, with them dialed in, I can get a perfect seam (under 0.001", infact I can't even measure it with my machinist feeler gauges) across 6' boards. Haven't really jointed anything longer in a while. Now, if they go out of alignment by just a few thousandths of an inch, or if the outfeed drops a thousandth or two below where it needs to be, I'll get a gap in those same 6' boards of maybe 1/64".

    As long the beds are within tolerance of most manufacturers (I think most are 0.010") you should be able to get a good seam, but it's VERY MUCH in how well you set everything up, as far as alignment. And don't neglect the importance of having an outfeed table perfectly parallel with the knives. Your beds can be set to NASA-level precision as far as coplanarity, but if the outfeed isn't perfect with the cutterhead, you'll never get a good seam. Vice-versa too. That's all from my experience at least.

  3. #3
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    Josh I have no idea where to even start trying to help . I think if you want help from anyone who knows anything about your machine you will first have to identify it. Do I understand you correctly that you now have two of the same machine and neither of them is acceptable to you ? There must be some measure of adjustability in the tables of these machines,but there is no way for any advice to help you if you can not tell us what the machine even is. Good luck.

  4. #4
    Stop measuring and cut some wood. I've never set up or checked any machine beyond what a couple of levels and a and a machinist square can do. Too much time on these forums will have you trying to split an atom.

  5. #5
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    A few things, first, what are you taking measurements with? Is this a certified straight edge? Next, and maybe more important, but what are the manufacturer's specs? This came up somewhat recently in the FOG with a guy who just received a new AD941. He was pretty miffed at spending $10K+ and the machine being out .002" over 16". I think Felder's spec was about that, which isnt 'perfect', but still pretty precise when it comes to woodworking. Next, what are the dimensions of the tables? In your one diagram, i see .003" over the length of the table, which i assume means it has a .003" dip or hump across the length. If your tables are 48" long, then that is really not bad at all. I think my starrett straight edges are only guaranteed at .001" per 12". Anyway, post your method for measuring the bed errors, size of the beds, and maybe look up the manufacturer;s spec.

  6. #6
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    My suggestion is to return both machines.
    Start a quest for a use jointer. Buy a 36 inch groz straight edge to take with you so you can inspect the tables before you buy it.
    Even if it takes a year or more looking at a half dozen machines.
    Heres what the groz straight edge I have.
    Good Luck
    Attached Images Attached Images
    Aj

  7. #7
    Quote Originally Posted by Andrew Hughes View Post
    My suggestion is to return both machines.
    Start a quest for a use jointer. Buy a 36 inch groz straight edge to take with you so you can inspect the tables before you buy it.
    Even if it takes a year or more looking at a half dozen machines.
    Heres what the groz straight edge I have.
    Good Luck
    Time is our most precious resource.

  8. #8
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    Quote Originally Posted by johnny means View Post
    Stop measuring and cut some wood. I've never set up or checked any machine beyond what a couple of levels and a and a machinist square can do. Too much time on these forums will have you trying to split an atom.
    Like this. Properly set up machines make joinery easier & better ... to a point. Where is the point of diminishing returns? What's the question.

  9. #9
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    I wonder how flat they would stay even if they were re-machined.

  10. #10
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    Quote Originally Posted by Tom M King View Post
    I wonder how flat they would stay even if they were re-machined.
    +1

    I also wonder how much the measurements/shapes of the castings continuously change due to temperature changes in the shop, Δt values and differential thermal expansion within the castings.


    With all the talk you hear around here of feeler gages, mils, tenths, interferometers and Planck lengths, it's a wonder any wood ever gets cut.


    Just sayin'.

  11. #11
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    Quote Originally Posted by Jacob Reverb View Post
    +1

    I also wonder how much the measurements/shapes of the castings continuously change due to temperature changes in the shop, Δt values and differential thermal expansion within the castings.


    With all the talk you hear around here of feeler gages, mils, tenths, interferometers and Planck lengths, it's a wonder any wood ever gets cut.


    Just sayin'.
    Unless it's a complete disaster of a casting then change in temperature is not going to affect the flatness so much. Yes, if you're scraping in a machine table, then you'll want the temperature consistent. But in a realistic use scenario a bit of temperature change isn't going to be so drastic an effect that one should not consider flattening a table considerably out of flat.

    No need to make the great into the enemy of the good. A .001" change in flatness over the course of temperature change isn't the reason why you stick with a .010" out of flat table.

    I like to consider the fact that having a machine which provides repeatable results is a time saver in my shop. Putting the effort in to ensure that it is accurate is relatively painless by comparison to fighting joinery/glue ups.
    Bumbling forward into the unknown.

  12. #12
    I introduce enough human error all by myself. I always try to reduce error coming from my machines, whenever possible. I always think about the 5-cut method as an example of how a tiny error can result in a huge error in the end. I can't predict what the castings will do over time, but I can look for the best starting point as possible.

  13. #13
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    I guess I never broke out the feeler gages with my jointer. I put a Starrett 24" combo square blade onto the tables of my PM jointer before accepting delivery and unloading it off the lift gate, set it up, tried it – it worked – and called it good. Let's not try to make this into a false dichotomy between those who hate accuracy/measurement/minimizing error and those who don't. Everybody settles. The question is merely, where?

    If a 10-mil belly in the middle of a 4' outfeed table is unacceptable, then jointing with nothing more than a Stanley #7 must introduce astronomical errors by comparison. Yet somehow, it works – and has for centuries. If a tool does what I want it to do, that's good enough for me. Life's too short. YMMV.

    Good luck with whatever you decide to do, Josh.
    Last edited by Jacob Reverb; 01-23-2020 at 11:43 AM.

  14. #14
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    In a time period where one can purchase a granite plate 18x24 flat to three one hundredths of a thousandth for a couple hundred dollars, I can’t see where a precision ground table can’t be made near perfectly flat. The difference is that one set of customers will definitely reject poor quality results and in the other case the customer most likely will simply let it slide.

    The point at which to settle, in my opinion, is the point at which the level of surface flatness or similar metric no longer has a meaningful influence on the work. That number is closer to .001” than .010” in my experience.
    Last edited by Brian Holcombe; 01-23-2020 at 12:54 PM.
    Bumbling forward into the unknown.

  15. #15
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    .010 dip on either end isn't a deal breaker. A hump is worse and either across the width near the head on the outfeed is really bad. Given that the tables are relatively small, the standard should be better but we should also ask what that standard is before buying. Knowing the possible error at least allows for an email history of expectations between buyer and seller. I rejected a 20" , 8' Porter with recently ground tables that were .008 off. I figured if newly surfaced tables weren't flat, it was better to avoid. Seller actually agreed. Dave

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