thickness planer question

[Scott Jungdahl]

What is an acceptable difference in the thickness of 2 boards sent through planer one after other.
Will I notice a difference of say .007" at glue up"

[Mark e Kessler]

How wide is your planer, how wide are the pieces, and are you running the pieces in the the same spot on the last pass? What machine? 7thou sounds a bit much, i think mine is maybe 1thou over 16 “ but would have to check to be sure

[Scott Jungdahl]

Actually the boards were not run through in a batch. I couldn't do that because by time I cleaned up saw marks the opening didn't have enough height to send other boards so I used a digital gauge to get them very close. I'm asking because I can batch them through once more if the planer can do better.
Yes, I know I could have avoided this by batching all passes from beginning. Live n learn
So the question, what is considered normal tolerance between two boards past through one - two.

[Mel Fulks]

I’ve used a lot of planers. They just do not usually make boards all exactly the same thickness. The traditional one piece knives are usually
not exactly straight even when brand new, and if you send knives out to be sharpened they usually have a little curve because the
sharpening grinder tracks have some wear. And some boards will be a little softer and compress some while getting their “flat top”.

[Bill Dufour]

Identical boards done on two different days will vary in moisture content. So even if planed to exactly the same thickness on the day they were planed the moisture content will equalize and one will get thinner or thicker then the other.
I have heard 1/1000 of an inch off at a joint in a plane surface is seen by the eye.
Bill D.

[Edward Weber]

What is an acceptable difference in the thickness of 2 boards sent through planer one after other.
Will I notice a difference of say .007" at glue up"


Woodworking rule #1 wood moves.
Personally a difference of 7 thousandths is dead even when talking about wood. .oo7" is about half as thick as a sheet of paper. You can literally breathe on a piece of wood and have it move that much.

[lowell holmes]

Why don't you run some tests and measure the results. See the results.

https://images.search.yahoo.com/search/images;_ylt=A0geKI6nZOhguUoA6rlXNyoA;_ylu=Y29sbwNi ZjEEcG9zAzEEdnRpZAMEc2VjA3BpdnM-?p=woodworking+calipers+home+depot&fr2=piv-web&type=E211US739G0&fr=mcafee

also,

https://search.yahoo.com/search?fr=mcafee&type=E211US739G0&p=jointer+push+block+plans

[Kyle Iwamoto]

Your second post contradicts the first. My opinion, if you have a pretty good planer, there should be virtually no difference between the 2 boards one after another. That said, all everyone else said holds true. If 1 board is drier than the other, in an hour they will be different thicknesses. If different species, they may be different in an hour.
If you run them through different settings, slim chance that they will be the same.

[Richard Coers]

Doesn't sound like a thickness planer question, sounds like an operator question. .007" is like 2 sheets of paper. Acceptability depends on the machines you have to make the panel flat after the glue. If you have a wide belt sander, it's perfectly acceptable. If it's figured hard maple and you have to make it flat by hand, it's going to take quite a while to fix!

[lowell holmes]

I agree with Kyle and Richard. If there is a difference, I suspect moisture content is the the reason.

[Mark Hennebury]

If you runt two boards through a thicknessplaner , one right after the other and they are 0.007" difference , then you have a problem with your thicknessplaner or your measuring.

[Mark Hennebury]

Absolute Nonsense!


Woodworking rule #1 wood moves.
Personally a difference of 7 thousandths is dead even when talking about wood. .oo7" is about half as thick as a sheet of paper. You can literally breathe on a piece of wood and have it move that much.

[Edward Weber]

Without being able to see or touch the wood in question, we're only guessing. I'm not sure what you think is nonsense but it's been my experience that wood moves, at times quite a lot.
I have no idea if the OP is experiencing snipe or inaccurate measurements, as you said.

[Phillip Mitchell]

What make/model is the planer and does it have traditional a straight knife cutterhead or some type of indexed cutterhead? Are you running the boards through in sequence without moving the bed height between each piece? Are you running them through in exactly the same spot on the bed? Ideally the planer should be in tune enough that there is minimal to no difference in thickness between one edge of the bed to the other, but this is a variable that comes up with the knives aren’t indexed and one could be hanging out a little more on one side of the cutterhead than it should be or the other knives.

There are several variables at play here that are more likely and significant than wood movement from humidity changes.

[Scott Jungdahl]

Thanks for a simple answer Mark. I will send them through in one batch.

[Edward Weber]

There are several variables at play here that are more likely and significant than wood movement from humidity changes.

I couldn't agree more.
My main point was that .007 is too minimal to be overly concerned about. I would have to have a bigger sampling than 2 boards. Also at .007, it could simply be a chip under the end of one of the boards. Not enough info to make an informed decision, guessing is pointless without feedback.

[Mark Hennebury]

"Wood moves" Yes it does, so does metal, yet they make high precision metal parts. so does the granite yet they make super high precision surface plates from granite.

The fact that something moves does not preclude it from making precision parts.

You can cut, dress and join wooden parts to high tolerances in the 0.001"- 0.002" range.


A joint that I did in 1990 (a lot tighter tolerance than 0.007")

460872

Thirty years later. Still just as tight as the day that it was made.

460873460874

Card cases that i made 30 years ago, also a lot tighter fit than 0.007"
0.001 - 0.002"makes a big difference to the fit of the lid on these, so you have to keep really tight tolerances. I am still using one today, and the lid still fits snug.

460875


Mitutoyo micrometer with a heat insulating cover.

460876


Without being able to see or touch the wood in question, we're only guessing. I'm not sure what you think is nonsense but it's been my experience that wood moves, at times quite a lot.
I have no idea if the OP is experiencing snipe or inaccurate measurements, as you said.

[Edward Weber]

I won't get drawn into an argument about wood movement, there are too many variables that come into play.

[andy bessette]

...if you have a pretty good planer, there should be virtually no difference between the 2 boards one after another...

This.

Anyway, such minor differences as 0.007" between board thicknesses is likely less than the misalignment to be expected at the glue joint.

[Thomas Fugate]

I typical piece of paper is 4 mil (.004)... so 7 would be noticeable, but I expect you would hand plane or sand the joint flat after glue up anyway?

[Scott Jungdahl]

Glue up then drum sander