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Kevin Downs
03-17-2009, 3:15 AM
I just purchased a Grizzly G1023SLWX - it's about two weeks old. After setup I did some checking and noticed that when I set the miter at 90 to the blade in the left slot and move it to the right slot it's no longer 90 to the blade and needs a little tweaking. This made me think that the slots weren't parallel to each other.

The left slot is perfect to the blade with a reading of 0.000. The right slot is almost perfect to the blade with a reading of +0.001. Run out check - good enough for me.

But my problem (?) is that the miter slots aren't parallel to each other. I've done two different readings. The first (two pictures below) came out to -0.0075 and the second (done just now to check) came out at -0.0055 (no picture). These two were from the left slot to the right slot. I did a reverse - right to left and it came out to -0.0095 the worst reading (see second set of pictures).

This tells me that when I stand at the front of the table saw the two miter slots spread away from each other going from front to back.

After adjusting the fence to -0.002 (no picture) from the left miter slot I checked it’s parallel to the right slot and it came out to +0.007 (picture below) the first time and +0.005 (no picture) the second time.

This leads me to the simple question: is this something I should call Grizzly about?

I understand the each slot is just fine to the blade. But, my issue is that I'd like to build a sled using runner guides in both slots. This will bind my sled as I push it through. Right?

Thanks for your help and thoughts!

Kevin

Tom Veatch
03-17-2009, 3:41 AM
...This leads me to the simple question: is this something I should call Grizzly about?

I understand the each slot is just fine to the blade. But, my issue is that I'd like to build a sled using runner guides in both slots. This will bind my sled as I push it through. Right?...

Might have a problem, might not. Best way to find out is make a quick and dirty dummy sled - just a couple of runners with a solid connection between the two that simulates the bed of your proposed sled. Run it through the slots. If it doesn't bind, no problem. If it does bind, and if whatever it takes to make it stop binding is unacceptable to you, then it's time to talk to Grizzly.

Rick Moyer
03-17-2009, 8:03 AM
I didn't closely read your post, but it would be impossible for both slots to be parallel to the blade and NOT parallel to each other, wouldn't it?

Jeff Willard
03-17-2009, 8:49 AM
I have always been told that the miter slots on a table saw will not be perfectly parallel. On my old Contractors saw, I just took it for granted that they were not, and limited my use to one slot. Slapped a sled on there-no problems. I just recently had need to use the other slot on my 66, dropped the miter gauge in the slot, threw a square up against the blade-spot on. If I broke out the dial indicator, I'm sure I could measure a discrepancy, but at 95 ten thousandths of an inch, I don't think it should cause you any major problems.

Mike Gager
03-17-2009, 9:33 AM
I didn't closely read your post, but it would be impossible for both slots to be parallel to the blade and NOT parallel to each other, wouldn't it?

+1

my thoughts exactly

Brian Frances
03-17-2009, 9:50 AM
Generally, the diameter of human hair ranges from 17 to 181 micrometers or 0.0007” to 0.007 “ according to most sources that I’ve found. It varies slightly with ethnicity, where Europeans generally have 57-90 m (0.002” to 0.004”) and Asians around 120 m (0.005”). I would tend to think that a tolerance in a range of 0.006” to 0.0095 “ you should be okay -within a hair http://www.sawmillcreek.org/images/icons/icon12.gif!

Phil Thien
03-17-2009, 9:55 AM
From what I can tell by your pics, your measurements may be skewed.

That is because you have your indicator angled down, and the jig is riding on the surface of the table.

So, if the table isn't perfectly flat, it will lift the indicator slightly. And because the indicator is angled, it will amplify the uneven table in the reading.

I'd suggest getting some gauge blocks and retesting with your indicator tip parallel to the table's surface.

Kevin Downs
03-17-2009, 9:59 AM
I didn't closely read your post, but it would be impossible for both slots to be parallel to the blade and NOT parallel to each other, wouldn't it?

I thought this as well, but the right slot to blade did come out at +0.001. Now that isn't much and I'm totally fine with that. But that measurement is for only (about) 10" of travel. The measurement for the miter slots was done using the TOTAL length of the slots - about 21" of travel.

I'm going to do the test sled as Tom Veatch suggests and see if it binds. I'll report back after my test.

Question to John W. Nixon of Eagle Lake Woodworking (creator of the super sled that I'm looking to build) or anyone what has a double runner table saw sled: are your miter slots parallel?

Thanks to all who replied!

Kevin

keith ouellette
03-17-2009, 10:05 AM
I would check the blade run out again. As stated above the blade can not run out by .001 compared to one slot and be perfect to the other while the two slots run out by .007.

If you are getting a reading that is different by .002 each time you are doing the measurement then the problem is (probably) that you are not doing everything the same each time.

You have to push the miter bar against the slot the same each time and make sure the horizontal pressure isn't tilting the dial indicator even the slightest bit.

These are very fine measurements and have to be taken carefully.

I myself would worry about being off by .007 after seeing what a difference correcting a .003 run out made in my cuts. They don't sound the same or look the same.

make all your measurements again and again. They should come out the same each time you do them.

Kevin Downs
03-17-2009, 10:08 AM
Generally, the diameter of human hair ranges from 17 to 181 micrometers or 0.0007 to 0.007 according to most sources that Ive found. It varies slightly with ethnicity, where Europeans generally have 57-90 m (0.002 to 0.004) and Asians around 120 m (0.005). I would tend to think that a tolerance in a range of 0.006 to 0.0095 you should be okay -within a hair http://www.sawmillcreek.org/images/icons/icon12.gif!

Well, when you put it that way I feel a little foolish :o. That .0095 just looks SOOOOOO large! I used a dollar bill (okay, it was a $20 - a dollar wasn't good enough for my Griz!) when I did the fence test and that accounted for .003 - so .0095 is like $60 of un-parallel-ism! :eek:

Mike Goetzke
03-17-2009, 10:18 AM
...now I'll have to go measure my slots this weekend:D.

I would use your gauge and measure both slots relative to the face of your rip fence. Maybe write down the readings every couple of inches.

Everybody uses their saws differently. I usually use the left slot for my miter gauge and would expect to need to re-set it if I went to the right. I only use both slots at the same time for my miter sled - don't know it 0.007" off front to rear would hurt.


Mike

Bob Wingard
03-17-2009, 11:35 AM
So, if the table isn't perfectly flat, it will lift the indicator slightly.

And because the indicator is angled, it will amplify the uneven table in the reading.




C'mon .. we're talking about a thou. or so .. how much can it possibly affect the reading ??

The angled plunger will actually make the indicator read a lesser number .. not greater. The shortest distance between 2 points is still a straight line, and the best resolution for a dial indicator is a path along that line.


<<<__ Bb __>>>

James White
03-17-2009, 12:53 PM
The way you are measuring is not reliable. The point of the indicator will pick up every nook and cranny. You need to put a bar like your miter gauge or something similar to that in the slot. This will negate the minor variances in the slot being measured. This is probably why your blade measures parallel but not the slot to slot measurement. You need to simulate the way the slot will actually be used. In my opinion your miter gauge would be best. Put a dot on the side of the gauge were the tip of the indicator will register and be sure to put the point of the gauge in the same spot when measuring.

James

glenn bradley
03-17-2009, 12:54 PM
I would measure to something riding in the miter slot (with a snug fit) as opposed to the edge of the slot itself. Miter slots are not given a mirror finish. I would worry about the behavior of a miter bar riding in the slot as opposed to a small spot on the miter slot wall which is of minimal impact in actual use. You may see measurements that make you feel better when checked in this manner.

P.s. Miter slots should definitely be parallel. Accepting that they "just aren't" as a matter of course is kind of silly to me ;-)

Wes Grass
03-17-2009, 2:53 PM
"are your miter slots parallel?"

Miter slots? What are miter slots? ;-)

Wes
Felder KF-700

P.S. It's possible the blade measures out of parallel .001 while the slots are .007, as the blade is much shorter than the table. And while the math may not work out, it's possible the slots aren't straight to begin with. Might have a slight curve to them. As mentioned, table may not be flat, etc.

And the angled indicator *will* read more than the actual runout in this case. So if it was 'straight' when he measured the blade, and angled in the slot that will make up some of the difference. Not a lot though. At 30, you should subtract about .001 from a .007 reading.

I have to admit, I never built a sled for a conventional saw. So I have no direct experience whether using 1 or 2 runners makes any difference. My gut feeling (based on years of mechanical design and precision machining) is it doesn't, in terms of angular alignment, torsional rigidity, whatever you want to call it. The 2nd rail isn't in the right place to improve things, it just increases the chances of racking and binding. Making a single rail a really good fit, with plenty of engagement, is the best it's going to get.

Chip Lindley
03-17-2009, 4:23 PM
It is understood that both miter slots are milled in a CI tabletop at the same time on the same machine! Thus by all reason, slots will be parallel! I will qualify that statement by adding: *If the table has not otherwise distorted, or the milling operation was flawed!*

Another issue to consider: Look into your miter slots closely and you will see some very coarse mill marks. Your indicator point could be *in* or *out* of these rough spots. File the sides of your slots ever-so-slightly with a flat bastard file! Same amount of strokes on each side! See if your measurements do not improve!

In the event both slots will not accept absolutely parallel bars (such as sled runners) the right runner can be made narrower, drilled, and those spring-loaded buttons inserted to the right, to take up the inconsistency. Lots of ways to *skin the cat*!

Kevin Downs
03-17-2009, 5:35 PM
Wow! So many thoughts. Using some of the suggestions above I went about retesting my measurement. I ended up using an Incra Miter Slider (what I may use for the sled) and locked it down in the slot.

Then I used a different tip on the A-Line-It indicator (great tool) to remove some more 'varables' and guess what!?

-.0015

That's .0005 different than the saw blade measurement. Check out the pics.

Now to prove that there isn't any issue with using double runners I'm going to build a temp sled and run it through! I'll post the results.

Thanks to everyone for ALL the ideas/thoughts. I'm going to go out on a limb and say that having a supper accurate gauge made me think the worst.

Now that I think about it I don't remember seeing David Marks using a digital indicator. And Charles Ingalls didn't have a supper flat, super accurate table saw - and he built a house!

I guess I can live with .0015. :D

Kevin

Tom Veatch
03-17-2009, 7:02 PM
... I'm going to go out on a limb and say that having a supper accurate gauge made me think the worst...

Sometimes having too much information is as bad as not having enough. At least it can certainly be unnecessarily unsettling.:D

If your miter slots are parallel within .0015 TIR, I'd hazard a guess that's about as close to perfect as you can expect from a mass-produced consumer product.

Bob Wingard
03-17-2009, 7:18 PM
"are your miter slots parallel?"And the angled indicator *will* read more than the actual runout in this case. So if it was 'straight' when he measured the blade, and angled in the slot that will make up some of the difference. Not a lot though. At 30, you should subtract about .001 from a .007 reading.




NO .. NO .. NO !!

The angled indicator will read LESS than the actual amount.

Look at it this way .. using your method, if the indicator reads more than the actual amount at, say 30 deg .. it will read even more at 45 deg .. more still at 60 deg .. even more at 90deg !!!!

At 90 deg. if you put pressure on the stylus, you will destroy it.

Now, my way .. at 0 deg = accurate & actual .. 30 deg. .. less resolution and less accurate .. all the way up to 90 deg .. zero accuracy, 'cause you're pushing sideways on the stem, which won't move the needle at all.

Now, does that make sense ??


<<<__ Bb __>>>

keith ouellette
03-17-2009, 8:15 PM
Sometimes having too much information is as bad as not having enough. At least it can certainly be unnecessarily unsettling.:D



Man, You said it there.

Kevin Downs
03-17-2009, 8:41 PM
Now, does that make sense ??


Almost totally! Please add pictures as I am only 99.999999 sure I understand. ;)

Wes Grass
03-17-2009, 8:54 PM
Nope, doesn't make sense at all.

Set it 10 from vertical, and the tip an 1/8" past the slot. How far will you have to pull the indicator stem up so the tip will drop into the slot?

Answer: ~.72"

Phil Thien
03-17-2009, 11:23 PM
C'mon .. we're talking about a thou. or so .. how much can it possibly affect the reading ??

Maybe your table saw is flat to within a thousandth, most aren't. The specs from Rockwell and Grizzly call for tables to be flat to within .01" (one-hundreth of an inch), IIRC. Many will be less. Some will be .0099 and will be within spec.


The angled plunger will actually make the indicator read a lesser number .. not greater. The shortest distance between 2 points is still a straight line, and the best resolution for a dial indicator is a path along that line.


No, sorry, that isn't correct.

When the plunger is angled, you are no longer measuring a straight line from one miter slot to another.

Here, let me give you a for instance. Assume a perfectly flat table saw. Measure the distance between slots at the front of the table using the setup as indicated in the photo (with angled plunger). Now move the gear to the rear of the saw, but add .005" of shim under the indicator to simulate a table that isn't flat. If you just solve for the triangle (figure a right triangle with side a of 1" and side b of maybe 2 or 2.5") you can see that a table that is out of flat by .005" can cause an error on the indicator of as much as .002".

.002" is 1/4 to 1/2 of his error.

Bob Wingard
03-18-2009, 1:17 AM
If it makes you feel better, go on believing that ..

John Lucas
03-18-2009, 2:44 AM
A couple of simple statements: 1) when you make the sled, use only one runner...I would use the left miter because I am right handed and I generally work on the left side of the blade. With only one runner, it should track fine and no need for 2nd anyway. 2) don't measure; cut wood

Tom Veatch
03-18-2009, 4:56 AM
...Look at it this way .. using your method, if the indicator reads more than the actual amount at, say 30 deg .. it will read even more at 45 deg .. more still at 60 deg .. even more at 90deg !!!!...

And that is correct except for the singularity at 90 which involves a division by zero and is undefined.

The tip of the indicator moves along the hypotenuse of a right triangle while the carrier of the indicator moves along the base of that triangle. When the carrier moves a distance X along the base of the triangle, the indicator tip moves along the hypotenuse a distance X/cosA (or X*secA) where A is the included angle between the base and hypotenuse of the triangle. The larger the angle between 0 and 90, the smaller the cosine and the greater the multiplier effect.

Get a piece of paper and sketch out the geometry involved.

John Grossi
03-18-2009, 7:12 AM
Kevin, As I was reading your initial post, my first reaction was the way you were measuring the slots to the blade were the reason for those numbers. When I got my 1023 I set it up blade to the left slot, then blade to the fence. I was in such a hurry to see dust, I never checked the right slot. My first project was to make a sled, and I used 2 runners. It is not pretty but it works great. I use it every chance I can. John

John Keeton
03-18-2009, 7:55 AM
I have no idea how parallel the slots on my 1023 are - nor do I care. They are close enough for me to work safely - and that is the important part for me. Without a high tech instrument, I took a reasonably accurate measurement of the blade-to-left slot alignment. My double runner sled works fine - using some tips from other creekers. I don't get any burning on my cuts. No binding or hint of kickback. Using my crude methods of measurement (same ones they used 200 years ago) I get good cuts.

Well, here is the amazing thing! When I cut a bunch of wood, after it gets through moving and doing its thing, I get through planing and sanding, I'll be danged if it all doesn't go together just fine! But, I will admit, it may be off by .001 or more:(

You guys are all apparently machinists or engineers. I am just a lowly weekend woodworker. I agree with John Lucas - just cut wood. Odds are, if you don't have black saw marks on the wood, or hear funny noises or feel some odd forces on wood going thru the saw - everything will be OK.

Think of the wood you could have cut while worrying about this stuff. Lighten up and enjoy this hobby - unless your hobby is finite adjustments on your woodworking tools. If that is the case, have a good 'ol time. I'll be cuttin' wood:D

Kevin Downs
03-18-2009, 10:38 AM
I think I need to make my problem clear. I'm VERY happy with the left slot, the blade and the fence - heck the saw itself! My 'problem' was with the slots to each other and a double runner table saw sled. I wanted to know if having my slots spread away from each other (going front to back) would BIND the sled. This problem had nothing to do with cutting and everything to do with a double runner sled.

Turns out my measurements were off and due to the MANY GREAT posts in this thread I was able to remeasure and get a truer reading.

Duncan Horner
03-18-2009, 10:01 PM
C'mon .. we're talking about a thou. or so .. how much can it possibly affect the reading ??

The angled plunger will actually make the indicator read a lesser number .. not greater. The shortest distance between 2 points is still a straight line, and the best resolution for a dial indicator is a path along that line.


<<<__ Bb __>>>

That's the same mistake in reasoning you made in another thread on checking runouts Bob. It still doesn't work. Best resolution is not along the shortest distance, it's the opposite. Once again, draw it on paper.

keith ouellette
03-19-2009, 12:01 AM
Good work then.

Bob Wingard
03-19-2009, 1:35 AM
O.K. one last time, and I'm giving up .. ..

Those of you who have dial indicators and doubt my logic, try this.

Mount your indicator to a stud chucked up in a drill press, making sure the stem is as perpendicular as possible to the table ..

Set the quill to stop somewhere near mid-travel of the indicator stem ..

Lightly bring the quill down to the stop, and read the dial ..

Now, tilt the indicator such that the stem is at a 45 deg angle ..

Bring the quill to the stop, and read the dial ..



Test #1 .. the stem perpendicular to the surface will read a greater number .. and that is the way any machinest or tool & die maker will tell you how to setup an indicator.


<<<__ Bb __>>>

Kevin Downs
03-19-2009, 11:37 AM
I have to say that I'm now confused. Any chance you can snap some pictures to show/prove what you are saying? Please

Tom Veatch
03-19-2009, 4:49 PM
...Those of you who have dial indicators and doubt my logic, try this.


Challenge accepted:
Here are the pictures for the 90 case:

First piicture is the setup. Note the quill stops are set to limit the travel to about 0.10 inches. Second picture is the dial indicator with the quill at the upper stop and the scale zeroed. Note the small pointer is at the "5" mark. Third picture is with the quill at the lower stop. Note the small pointer is at the "6" mark. Total quill travel is about 0.10 inches. See the next post for the 45 case.

Tom Veatch
03-19-2009, 5:03 PM
Here are the pictures for the 45 case:

Quill stops have not been changed, dial indicator has been rotated so that the plunger is at an angle to the direction of quill travel. Angle was not measured, but is shown in the first picture.

The second picture is of poor quality, but I think you can make out the pointer positions. The quill is at the upper stop and the dial has been zeroed to the large pointer position. Note the small pointer is approximately on the "3".

The third picture is with the quill at the lower stop, a quill travel of 0.10 inches as measured in the prior 90 case. Note the readings. The small pointer is past the "4" and the large pointer is at approximate "44". A total plunger travel of approximately 0.144 inches.

These are exactly (within experimental error) the results predicted in my previous post, #26 in this thread.

Chip Lindley
03-19-2009, 5:09 PM
Bob, I assume you are speaking of *plunge-type* dial indicators most common to woodworking machine setup?? Any measurement taken with a plunge indicator NOT at a right angle to the work will give a skewed and proportional measurement instead of a *true* reading!

But what about Dial Test Indicators?? The indicator point can be affixed at many angles relative to the head! ....Ya know what? Never mind!

For our woodworking purposes, would you not agree, that as long as that same angle is *somewhat* maintained, *proportional* readings will still be sufficient to indicate any runout or out-of-parallel condition?

Woodworkers are not machinists. A fraction of a Thou makes little difference in our work!

george wilson
03-19-2009, 5:38 PM
Bob is correct.I am also a machinist. To prove,or understand what he is saying,draw a right angle triangle on a piece of paper,with the longest side parallel to the bottom of the sheet of paper. Make it aproximate a standard 30-60-90 degree drafting triangle. The exact angles aren't important,just approximate it. Next,some distance from the top corner of the triangle,draw a horizontal line across the vertical side,and extend it across the hypotenuse(sp?),or angled side.

Measure the length of the straight side from the top corner down to where you drew the horizontal line. then,measure the length of the slanted side from the top of the triangle down to where the horizontal line crosses it. You will easily see that the slanted length is longer than the vertical side's length. Apply that to what he has been trying to explain.

Tom Veatch
03-19-2009, 6:07 PM
...
Test #1 .. the stem perpendicular to the surface will read a greater number ...


...You will easily see that the slanted length is longer than the vertical side's length....

George, I fully agree with you. And that cannot be reconciled with the above quote. As you said, the slanted length is longer and an indicator stem lying along that hypotenuse will read that greater length as a greater deflection than one that is lying along the vertical side, perpendicular to the surface. My previous post showing the experimental results should conclusively prove that.

David Keller NC
03-19-2009, 6:22 PM
"My 'problem' was with the slots to each other and a double runner table saw sled. I wanted to know if having my slots spread away from each other (going front to back) would BIND the sled. This problem had nothing to do with cutting and everything to do with a double runner sled."

I think this will depend on the sled and how you make it (or how it's designed if you buy it). Generally speaking, you will not want to use a sled with wooden runners without at least 10-15 thousandths "slop", because humidity changes will likely lock it in place on the saw - you may need to use a hammer to remove it.

Similarly, I rather doubt you can make a sled with aluminum runners and place the screws so accurately that you can use aluminum extrusions that fit in the miter slot within a couple of thousandths. This, by the way, is something I learned the hard way, and had to take off significant portions of the side of the aluminum runners to get it to slide smoothly on the saw table.

Wade Lippman
03-19-2009, 7:41 PM
Drop Grizzly an email and tell them your slots are out of parallel by 0.001" and post their reply.

Phil Thien
03-19-2009, 11:14 PM
Bob is correct.I am also a machinist.

Boy, you guys almost convinced me.

But then I remembered that when I was 20 (almost 25 years ago) I was designing control systems for final dimensioning/polishing of control rods for nuclear reactors. So I can't be wrong, otherwise we'd all be dead. ;)

Duncan Horner
03-19-2009, 11:23 PM
You will easily see that the slanted length is longer than the vertical side's length. Apply that to what he has been trying to explain.

That's also precisely what I'm trying to explain.

The slanted line is longer, and this makes the measurement more sensitive to deviations. I'm not talking about absolute measurements, only that measuring at an angle will make any deviation more obvious, due to the greater travel of the gauge.

Duncan Horner
03-19-2009, 11:29 PM
From yesterday



The angled indicator will read LESS than the actual amount.




The angled plunger will actually make the indicator read a lesser number



From today.

At about 90 degrees.



Total quill travel is about 0.10 inches.



At about 45 degrees



A total plunger travel of approximately 0.144 inches


Didn't this experimental result posted by Tom (thanks for the correction Tom) directly contradict what you earlier said?

george wilson
03-19-2009, 11:30 PM
Usually the metal lathe's cross slide,which is graduated in thousanths, is used at its "straight in" angle of 90 degrees to the work,to reduce the diameter of work being turned. If you want to remove a very small amount,like .0001",ten times smaller than the .001" graduations,you set the swiveling compound ,which is on top of the carriage,to 8 degrees from the work,or nearly parallel to the work,8 degrees from being parallel. Then,when you move the dial on the compound .001",the cutter moves mostly sideways,only advancing .0001" into the work.

I'm not explaining this very well,sorry.

Duncan Horner
03-19-2009, 11:33 PM
I'm not explaining this very well,sorry.


You explained it perfectly, and I understand completely. Thank you.

Bob Wingard
03-20-2009, 12:29 AM
Usually the metal lathe's cross slide,which is graduated in thousanths, is used at its "straight in" angle of 90 degrees to the work,to reduce the diameter of work being turned. If you want to remove a very small amount,like .0001",ten times smaller than the .001" graduations,you set the swiveling compound ,which is on top of the carriage,to 8 degrees from the work,or nearly parallel to the work,8 degrees from being parallel. Then,when you move the dial on the compound .001",the cutter moves mostly sideways,only advancing .0001" into the work.

I'm not explaining this very well,sorry.

Thank you, George .. GREAT analogy .. I wish I had thought of that several posts back !!

I knew if these folks would just ask a Machinest or Tool Maker, they'd get an explanation that would satisfy them.

I knew I was correct, just couldn't explain it as simply as you just did.



<<<__ Bb __>>>

Duncan Horner
03-20-2009, 12:35 AM
Thank you, George .. GREAT analogy .. I wish I had thought of that several posts back !!

I knew if these folks would just ask a Machinest or Tool Maker, they'd get an explanation that would satisfy them.

I knew I was correct, just couldn't explain it as simply as you just did.



<<<__ Bb __>>>

So working at an angle makes the machining scale more sensitive, but makes the measurement of deviation less sensitive?

Your experiment showed my point. Measuring at the 45 made the same deviation show up as a larger number on the plunger. The absolute measurement isn't accurate, but it does allow you to see a smaller deviation. More angle = more (qualitative) sensitivity, less (quantitative) accuracy. When you're looking for relative differences, an amplified scale increases the visibility of such differences.

Bob Wingard
03-20-2009, 12:43 AM
measurement taken with a plunge indicator NOT at a right angle to the work will give a skewed and proportional measurement instead of a *true* reading!

For our woodworking purposes, would you not agree, that as long as that same angle is *somewhat* maintained, *proportional* readings will still be sufficient to indicate any runout or out-of-parallel condition?


I THINK this is what I started out saying .. .. for the purpose of comparing one end of a slot to another, in an attempt to align same, the actual number is meaningless .. you are trying to get both extremes to the same spot. All I started out saying was that in a skewed position, the "NUMBERS" are not true. I've used a screw in a piece of wood and a set of feeler gauges to determine alignment, and didn't care WHAT the number was .. only that it was the same at both ends !!


<<<__ Bb __>>>

Tom Veatch
03-20-2009, 12:50 AM
...Your experiment showed my point. Measuring at the 45 made the same deviation show up as a larger number on the plunger. The absolute measurement isn't accurate, but it does allow you to see a smaller deviation. More angle = more (qualitative) sensitivity, less (quantitative) accuracy. When you're looking for relative differences, an amplified scale increases the visibility of such differences.

You've got it, Duncan! (but, for the record, it was my experiment, made in response to Bob's challenge, that was posted.:))

Bob Wingard
03-20-2009, 12:51 AM
So working at an angle makes the machining scale more sensitive, but makes the measurement of deviation less sensitive?

Working the cross slide at an angle allows you to take very fine cuts because each 0.001" movement of the cross slide yields something less than 0.001" of travel. You can take extremely fine cuts, but the accuracy of the dial on the lathe is gone .. unless you are an experienced Machinest and you know what the travel indicated on the dial equates to in the advance of the bit. As I stated in the drill press challenge, it takes more travel at an angle to accomplish the same forward advancement of the tool.

That probably didn't help, but I'm running out of ways to get my point across .. .. maybe George can help again ??


<<<__ Bb__>>>

Duncan Horner
03-20-2009, 12:59 AM
You've got it, Duncan! (but, for the record, it was my experiment, made in response to Bob's challenge, that was posted.:))

I knew I'd mess up the quotes somewhere, and I did, sorry, and thank you :) I'll go fix 'em



You can take extremely fine cuts, but the accuracy of the dial on the lathe is gone

Exactly what I've been saying. I think we've come to an arrangement. I was never interested in the number of the measurement, although it can be calculated rather easily given the angle. I'm simply interested in using the angle the measurement is taken at being used to amplify the magnitude of the dial travel.

Phil Thien
03-20-2009, 10:36 AM
I knew I was correct, just couldn't explain it as simply as you just did.
<<<__ Bb __>>>

If it makes you feel better, go on believing that ..

Bob Wingard
03-20-2009, 10:56 AM
If it makes you feel better, go on believing that ..

It does .. .. I will .. ..

thank you .. ..



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