That sounds right to me - the starting point is a coplanar bandsaw.
I haven't argued for anything else. Screwing around with a wildly
ooc bandsaw is a good way to waste a lot of time.
Splitting hairs isn't going to solve anyone's problems. If making it
coplanar requires a gazzillion dollar widget and several days to get
it perfect, there's a perfectly reasonable expectation that folks
will balk. However, using a straightedge and aligning it accordingly
is a reasonable attempt at making it coplanar. If you're still
out by 1/8" or more, then you probably shouldn't be using a bandsaw.
You aren't by any chance the fellow that goes by George
Preddy in the digital photo NG are you? He is a Foveon
fanatic who's posted OVER 3,500 posts on the merits of that
sensor over Bayer sensors which are used in Canons, et al.
This coplanar thing is gonna become your legacy.
Go have a beer and relax, Michael...
Michael Daly wrote:
cf: "plagues of egypt".
cf: "children of israel".
cf: "kant tried to determine a rational basis for the inclusion of
irrational beings into the polis - he was unsuccessful". (op cit ref
JOlP, v. 4, Letter 12.3).
cf: "turds float".
Thomas J. Watson-Cabinetmaker (ret)
Real Email is: tjwatson1ATcomcastDOTnet
Mike, as a digital professional (I R 1), sometimes it's it easy to forget
the leave the discrete world or 1's and 0's and return to the real (in the
mathematical sense) world. There is no such thing in the real world as
straight, flat, perpendicular, flat or coplaner. If you think it is, then
you need a better measuring tool. Even light bends.
Common usage of "straight" really means "straight enough" or "relatively
straight". The same thing goes for "coplanar".
I would submit that in the context of woodworking, "similar" at least as
often as not *does* mean "same".
As a "software engineer", I am invoking the right bestowed upon me by my
employer and the State (University) of New York, to split that baby right
down to the follicle :-)
Here's why I think the coplaner thing doesn't matter if the misallignment is
not too large:
Your ascii art suggests that the wheel (tire more specifically) is a
cylinder. It's not. Properly formed tires have a crown. If the wheels are
parallel but in different planes, the blade will ride in on one tire and out
on the other (slightly). The inner surface of the band will still be tangent
to the curve of the crown. Therefore there is no "twisting" of the blade. It
is, however, running at a *very* slight angle to the table.
The crown of the tire not only allows tracking but mitigates any modest
(Jeffrey Thunder) wrote:
I know that and addressed it in another post. However, I keep asking -
What is "modest"? It's one thing to keep saying x amount of misalignment
is ok, but no one wants to make a statement on what x is! If you phrase
it like some do - "coplanar is nonsense" that's clearly wrong! However,
making it perfect is not possible.
Edwin suggests that if it tracks, then the misalignment is not significant.
On one level, I can accept that, but it still doesn't address whether
you can make it track but still be stressing the blade more than necessary.
Personally, I think you should make it as coplanar as possible - as I said,
that's not hard to do.
I'll go out on a limb and say 1/4". I think it is reasonable to assume that
any new saw ought to be manufactured to within that tolerance... even
"chiawanise junk". On older saws, I would suspect abuse.
No. i would not go quite that far. I would say that it's worth checking. If
it's so far out that seriously effects tracking on new tires with a proper
crown, I would call it a "defect" not and "adjustment".
Let me say this alittle differently: The blade is not twisting, It is riding
normally, but in a *slightly* different axis. No twist = no additional
I agree, It certainley can't hurt. I have a new bandsaw. I forgot to check
it while the table was off, and chose not to bother once I found that
everything tracked well. Maybe I'm just lucky. BTW it was ade in Taiwan.
Why? Based on what?*
I don't see why they can't make a bandsaw that's better than that even
if assembled by demented monkeys. Even in the days before assembly
lines and standardized parts they could make things better than that!
Unisaw claims his is out of alignment and _doesn't_ run on a different axis.
Two different stories. Which one is correct?
Put two wheels out of alignment by 5 inches and try to get them to run a blade
without twisting. Now tell me how you know that, oh... 2" will ride flat without
twisting. How about 0.5"? You're making an assumption based on thinking that
the tires will magically account for any out-of-plane error. I agree that they
_can_ correct for some degree of misalignment, but I don't know how much and I'm
not going to guess. I do know that the crown on the tires on my BS are large
radius and I doubt it can handle a big misalignment without twisting.
I'm still waiting for the "myth of the coplanar" crowd to come up with some
facts instead of opinions. We already know they're misquoting and misinterpreting
Duginske. They still can't come up with anything to quantify their claims.
* My BS came out of the factory with around 1/4" error and did track. Didn't cut
well, but it did track. YMMV
For starters, I do not own a band saw and I do not recall ever using one. There have
been times when I wished I had one, but got along somehow without buying one.
In reading this thread from the beginning, It has occurred to me that it might be
possible to put one or more washers on one side or the other of one of the wheels -
say the top wheel if it is not driven. Could the remedy of the out of coplanar
situation be as simple as that?
Yes, shimming with washers is the common way to go. [Dave: your
average 5/8" hardware store variety work fine on Deltas and clones.]
My first measurement, which was a 3/8" out-of-alignment wheel (and
which measurement turned out to be wrong), made it impractical to fix
with shims since the bearing shaft on the upper wheel has only so much
room before you run out of thread for the nut.
In addition, I didn't like the idea of a half-ass workaround to fix
alignment that was that far off; if I could get the thing aligned at
the frame level that would be better, and since I was putting on a
riser block anyway why not try to fix it then.
I have, owing mostly to this thread, realized that may be more
difficult than I had imagined, but I had the good fortune of realizing
that my alignment was not out 3/8", but only 1/8", so shimming is not
so onerous, if necessary at all.
1. Assume your upper wheel is alligned plumb.
2. There should be enough extra space on a tire for the blade to shift at
3. draw a line tangent to the crown of the blade at a position 1/8" off
center. This will "point" more than 1/4" out of the axis of the wheel. This
is the "fudge factor" of non-planer acceptability
You are reinforcing my point that out of coplaner by more than the "fudge
factor" is a major DEFECT, not a setup issue withing the normal parameters
I will not speak for unisaw.
That is what any reasonable person would call a defect. My assertion was
that a perperly manufactured saw could handle a "modest" (which I have
defined) non-coplaner situation
No magic. The geometry of crowned tires as explained above.
It is a function of the radius of the crown. Granted, tough to compute
accurately, because it should be done as a function of the crown under
tension (rubber sightly compressed), but I think eye-balling it is good
enough to show that it works.
With axels 48" apart, 1 degree equals just inder an inch of fudge factor.
e.g. tan(a)= fudge/angle
Later I will take some accurate measurements of the crown and comute the
actual angular change associated with the proposed 1/8th inch shift.
Why? I can't help but think you're making this up as you go along.
Defect or not, it still comes into play. If someone has a defective BS,
the advice they get on the wreck is not "get the manufacturer to replace
your BS", it's "Don't worry, coplanar isn't an issue."
You're not following. At what point does the crown cease to correct the
Ahh, you do know conceptually.
By eye, I can barely detect any compression on my tires. The radius seems
large and even a small error in assumptions will have a large effect on
the result. We're not talking about large angles here - eyeballing it won't
Can anyone realistically eyeball less than one degree? I know that most
folks can't judge angles worth a damn.
But it still relies on your 1/8 assumption. A good start if you can justify
that. Better than anyone else has done so far.
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