On my Bridgeport clone, if I put the speed selector in neutral, I can turn
the spindle with one finger and either make it turn one or more revolutions,
or turn just the slightest amount. I don't have a 100hp CNC mill yet but
I'll figure something out when I get one (well into the future).
This makes several assumptions (you know what an assumption is). It assumes
the spindle locks. Most don't. It assumes the sides of the table are
accessible. Not often the case. It assumes that the edges of the table are
square and flat. Maybe, maybe not. There are finer details that I could go
into but I won't in the interest of keeping this short.
The mill doesn't have to have a built in spindle lock. You just need some
way to keep the spindle from turning as you tighten. You can clamp it
yourself with a clamp or magnet.
You don't have to use the sides of the table. You can use the side of a
T-slot. The indicator stem doesn't have to parallel with the table because
you aren't taking an absolute measurement.
Again, I will explain a few of the problems. I will leave out the more
subtle ones for brevity. Assuming that you can get to the T slots, you now
angle your indicators to be able to reach them. By angling them, you have
reduced the sensitivity giving you the impression, in use, of being closer
to "dialed in" than you actually are. You then say to rig something up to
clamp your spindle, increasing complexity (and time to execute) of the
operation. Now, here you are with your 3 indicators (though, I can't see the
point of the middle one unless it is for impression value) mounted on a 6
inch bar (to cover the distance of a 6 inch machine vise) with a spindle
mount in the middle of the bar. You are going to hold this with one hand,
adjust it for zero and hold it from rotation within .0038 degrees while you
tighten it. Okay, lets assume that you do it the easy way. Clamp it in the
spindle, bring the indicators into contact with the T slots (you did
previously verify the accuracy of the T slots, didn't you?) and adjust the
dials for zero. Now, you lower the table or raise the spindle while
retracting the indicator spindles to keep them from snapping to the extremes
of their travel. BTW, how many hands do you have? You now bring the vise
under the spindle and bring the indicators into contact with the vise jaws.
After all this, you can now proceed to align your vise. You did verify that
the vise jaw didn't have a bump or dip in it, didn't you? How did you check?
How did you check the T slot? Can you guarantee that nothing moved in this
whole process? How can you verify that? There seems to be a lot of blind
faith going on here.
I was starting to type out why I needed the middle indicator, but I couldn't
think of anything. I'm not sure why I initially said three. Two is enough
for what I'm proposing.
I concede that either the T slot or the side/edge of the table needs to be
straight and parallel to the direction of travel for this to work.
Otherwise it won't.
On my mill, I estimate that the indicators would need to be tilted 2 degrees
to access the T slot. Would a factor of cosine(2) or 0.99939 really reduce
the sensitivity of the indicator?
I don't see why more than two hands would be required. Mount vise on table.
Mount gauge in collet/holder/chuck. Raise knee, lower spindle, move X and
Y. Up to this point, you would have to do all of this regardless of whether
you are using one indicator, or more than one. When doing this, stop when
the indicators touch the T slot or edge of table near the vise. Square the
gauge by turning spindle with one finger (see other post). No need to dial
for zero. Both gauges just need to read the same. Clamp the spindle.
Raise the spindle slightly, and move the X axis slightly so that the
indicators touch the vise jaw. Now adjust the vise so that both indicators
read the same (they don't have to read zero).
You wouldn't move the vise so that the indicator points fall into (for
example), the vise jaw mounting holes. If the vise jaw isn't straight,
you'll have problems regardless of how many indicators you're using.
So, prior to setup, you calibrate the surface you are going to use for
calibration. Are you going to use another one of your rigs that needs to be
calibrated before you calibrate the calibration surface?
More like 30 degrees in a 5/8 T slot. In addition to the measurement error
that would be introduced, you now have put the indicator bearings in a bind,
further reducing sensitivity.
You are going to rotate that spindle .0001 or so and then expect that it
will maintain position while you clamp it... Right.
So, now you are just going to go on blind faith that the vise jaws are true.
The time to find this out is before you scrap a part. With your rig, you'd
never know. This is kind of like measuring the height of a wall with a 6
inch scale or, something many here will really relate to, using 4 different
tape measures on the same job. It might work but chances are it won't and
you can't be certain until you have produced scrap.
You would need to check the T slot or table edge/side one time, not every
time. You can also check the vise one time. On my mill, 2 degrees is
enough to access the T slot. I'm not trying to access the very bottom of
2 degrees isn't even enough to clear the indicator spindle, let alone the
body or the mounting lug. You'll be closer to 30 degrees by time you clear
everything. So, you're saying that you are going to have a calibrated
gagging surface on each machine. You are also going to have a dedicated
setting fixture for each machine. Obviously, you are going to have to have
calibration fixtures to calibrate those calibration surfaces and, as you
seem to believe the dual indicator set up is the way to go, you are going to
need a calibration device to calibrate the calibration device that you are
going to use to calibrate your calibration surfaces. Of course, there is no
telling if the original calibration device is correct. Might be close enough
in home shop where you can be reasonably sure of everything that goes on
and the accuracy requirements of the work are not that close but in a
commercial shop, forget it. To get back to your original thought. Why would
a commercial shop sell you an alignment device that is inherently less
accurate, by design, than the one they used when making the device? Ever
heard the old saying "anything that can go wrong, will"? Only make things as
complicated as they need to be to get the job done. Eliminate variables as
much as possible.
The indicators are hanging below the spindle. At 90 degrees it is already
clear of the spindle. At 88 degrees, it is clear of the spindle and can
touch the top of the T slot. No dedicated setting fixture or calibrated
gauging surface required. Just check (once) if the the T slot or surface
table if flat and parallel to the axis of travel.
I just had another idea. If using an end mill holder, forget the spindle
lock, using the neutral lever, and turning the spindle by handle. Leave the
spindle in gear so that the weight of the gears, belts and motor keeps it in
place. Mount the gauge but leave the setscrew loose. When the gauge is
square, tighten the setscrew.
So, this is where this discussion got off to!
I read through all the messages. Al, I have to say, you could benefit
from a lot more knowledge and experience. I applaud your ingenuity
and desire to invent new ways of doing things. But, if you're honest,
you'll have to admit that all of this is just conjecture. You really
haven't done any of this. How do I know this? Because your method
seems to evolve as objections are raised. You're talking to people
who have been doing it for a long time. It's not a matter of being
closed-minded to new ideas. It's a matter of knowing without a shread
of doubt that the multi-indicator idea is chock full of pitfalls.
And, you are stepping into most of these pitfalls without even knowing
The single indicator method is very elegant, functional, efficient,
and most of all RELIABLY ACCURATE. I can't turn or clamp a spindle by
hand, any spindle on any machine, to 0.0001". But, I can very quickly
use a 0.0001"/div test indicator to align a vise in less time than it
takes for you to get your rig installed. I don't have to trust that
the table slots are aligned to the table motion. Honestly, I don't
even care! And, your rig would be useless on any machine where they
weren't (which is all the machines I've ever used!). Yes, they are
usually close, but not good enough to beat the single indicator
Read, learn, practice, and understand how and why things are done. If
you don't, then your ideas won't benefit from the thousands upon
thousands of minds which have already pondered these things and
evaluated the alternatives. Without this benefit, you are likely to
stumble into all kinds of embarrassing pitfalls.
WRT the topic of the other thread:
"The sine angle caused by misalignment with a flat contact is a much
more serious cause for error than the cosine error" "Fundamentals of
Dimensional Metrology" Second Edition (c) 1989 Delmar Publishers Inc.
The example given shows how a one degree tilt on your indicator can
cause more than 0.002" error in reading. That's with just one
indicator. You've proposed using two. The error multiplies! While
you're busy trying to align your indicators with less than one degree
of tilt, I've already aligned the knives on the jointer using just one
indicator and a round stylus point.
Read, learn, practice, understand, and then innovate. Your ideas will
gain much more respect and your life will be a lot easier.
Perhaps you should elaborate even more about your ideas! I'm thinking
that you should try them and then make an honest report back to the
group on how they worked. Maybe after you have actually tried these
things they won't seem like such great ideas.
I guess you got my dander up because you specifically mention my
product (TS-Aligner Jr.) and how much it could be "improved" with this
idea of yours (multiple indicators). I think that it's enough of a
lesson if you are forced to try your own idea and report the results
back to the group - honestly. Then maybe you might think twice about
trying to fool members of this group into thinking you know anything
about machinery alignment or Metrology.
In your two posts, all I see is a personal attack. Fair enough because I
insulted your product. However I don't see anything that says why the
jointer and table saw gauge that I described won't work.
I fully intend to build them and will report back on how they turned out.
Right after I install the DRO on my planer. Unfortunately it will be a few
I'll build the jointer gauge pretty much as I described. But I'll be
building a few different table saw gauges. One will be as I described. In
addition, I want some way to get the two indicators to touch the fixed
washer on the arbor, so that I can remove the blade and not worry about it
being warped. I'm still thinking about how to do that.
OK, I guess you are asking me to help you get started thinking about
the problems with your ideas. I don't mind doing this, as you've
pretty much admitted in the request that you haven't tried your ideas
(or even given much thought to their feasibility).
Whenever you have one measurement device on one fixture you have a
stable reference. All subsequent measurements using this same exact
setup will be relative to this same exact reference. All the
individual variables which make up that reference will be included
identically in every measurement so that their relative effect from
measurement to measurement is completely nullified. If you introduce
a second measurement device and attempt to make the same measurements
in a repeatable manner then you create a second reference. All of the
variables making up both references become significant. Each variable
must be addressed individually and it's contribution to the results
quantified and/or eliminated. If this is not done, then you will
never know if the readings accurately represent the objects being
measured or the effects of these uncontrolled variables.
To put it another way, it might seem rather inconvenient to use one
measurement device and one fixture to do multiple measurements, but it
is an effortless method which guarantees that each measurement is done
with an identical setup. No external variables will influence the
results. If two measurements come out differently, it's because the
objects being measured are different. If two measurements come out
the same, it's because the two objects being measured are identical.
For example, in your jointer knife alignment idea, a rather elaborate
calibration procedure would be necessary to ensure that the two dial
indicators were providing the same readings for any given measurement.
Just because they read the same for one measurement pair (say, the
top of the outfeed table) doesn't mean that they actually provide the
same measurements. What if one indicator isn't tilted at the exact
same angle as the other? What if one side of the fixture flexes more
than another? What if the measurement force of one indicator is more
than the other? What if the two stylus points are slightly different
sizes or shapes?
Yes, it is possible to create a fixture, choose indicators, and
account for all the possible variables which can significantly alter
the results so that two identical measurements can be performed at the
same time using two indicators. But why would you ever want to go to
all this trouble when you could just use one indicator on one fixture
to make two measurements?
Also, I just can't imagine trying to manage two indicator styli on a
knife edge at the same time. You may decide that it's good enough to
just worry about one at a time but then where's the advantage of
having two indicators?
All of the above applies to your tablesaw alignment example too. In
addition, you have assumed that blade warp is always bi-lateral and
symmetrical. Sorry, that's a bad assumption. It's also not valid to
assume that the arbor and flange (what you call the "fixed washer on
the arbor") have no runout. You can obtain different readings on your
two dial indicators and not be able to discern if they are due to
misalignment, runout, warp, or one of the variables mentioned above.
If you obtain identical readings on your two dial indicators, there is
no assurance that proper alignment has been obtained. This is truely
a case in which no amount of "factory calibration" will help. It's a
setup which voilates all the applicable Metrological rules.
An alignment tool must be able to perform it's task without being
adversely affected by these uncontrolled variables. Making two
measurements with a single indicator setup using a fixed reference
(the dot on the blade) is completely immune to all of the variables
mentioned. When the two readings are the same then the saw is
definitely aligned beyond any reasonable doubt.
This is just the tip of the iceberg. These are just conceptual level
reasons why your idea is impractical. There are lots of other things
to consider which you'll discover when you attempt to build your
prototypes. I would be more than happy to discuss these things and
I'm sure that there are others in the group who would be interested in
reading along. But, we must agree not to name specific products and
identify them as "inferior" when we really don't understand the the
most basic principles of the topic at hand. Agreed?
Regarding the jointer gauge, what I plan to do is get an angle plate of the
right size, drill and tap two holes on the sides and then mount two
indicators. Both indicators first touch the outfeed table. The dials get
zeroed. Then the gauge is moved forward to touch the knife edge. Because
the goal is to get the dials to read zero again (ie. I'm not measuring a
linear distance. Cosine of the angle multiplied by zero.), I don't see any
effect if either indicator were slightly tilted (even thought it will be
very easy to be sure they are not). The angle plate is identical on both
sides so one side wouldn't flex more than the other. The spring tension on
the indicators may not be the same, but won't have enough force to either
lift the angle plate, or lower the knife. The stylus points won't matter
because the part of the point that initially touched the outfeed table, will
be touching the edge of the knife. However, I may use disk-shaped points to
make it easier to put the point on the knife.
The table saw gauge is more complicated. I am assuming that a warped blade
is cupped such that you can turn it so that the curve is in the vertical
direction. I'm not sure how to describe this in words. Imagine looking at
the blade from the side and seeing something shaped like a left bracket ( .
If the warpage is more like a ripple than a cup, then what I am proposing
won't work. I'll have to measure a few of my blades and see just what they
The only reason I mentioned your product by name was that everyone knows
what I'm talking about when they hear it. If there was a popular brand of
jointer gauge like the one I was talking about (Oneway and Powermatic make
one--I've seen several more), I would have used that name. In retrospect,
it was a bad idea.
This is an interesting discussion with good points on both sides.
However, I would like to interrupt this presentation for a moment to
continue this thread started with the $16 digital caliper. This is an
unbelievable price since I paid $50 for a dial caliper from Mitutoyo
(sp?) in 1976 and thought it was a good deal.
I bought 2 of these calipers. One went on my drum sander to measure
its height and one I am going to use for its intended use. If I did
not already have a digital readout I bought for over $100 for my
planer, I would have CERTAINLY used one on it. Since the mechanical
scale on my Delta planer is nearly unusable, I would think that every
owner of one should buy one of these calipers for use on their planer.
By the way, I would recommend clamping the caliper arms somehow to the
planer. They are hardened and will ruin drill bits if you try to
drill through them for attachment. I was able to drill the holes, but
I ruined a couple of bits doing it.
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