Page 1 of 4 1234 LastLast
Results 1 to 15 of 53

Thread: Miter slots NOT parallel - problem?

  1. #1

    Question Miter slots NOT parallel - problem?

    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
    Attached Images Attached Images
    Last edited by Chris Padilla; 03-17-2009 at 11:10 AM.

  2. #2
    Join Date
    Jun 2007
    Location
    Wichita, Kansas
    Posts
    1,795
    Quote Originally Posted by Kevin Downs View Post
    ...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.
    Tom Veatch
    Wichita, KS
    USA

  3. #3
    Join Date
    Jan 2007
    Location
    central PA
    Posts
    1,774
    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?

  4. #4
    Join Date
    Jan 2009
    Location
    Mosby's Confederacy
    Posts
    657
    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.

  5. #5
    Join Date
    Feb 2008
    Location
    Topeka, Kansas
    Posts
    311
    Quote Originally Posted by Rick Moyer View Post
    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

  6. #6

    Wink

    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 µm (0.002” to 0.004”) and Asians around 120 µm (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 !
    Last edited by Brian Frances; 03-17-2009 at 8:52 AM.

  7. #7
    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.

  8. #8
    Quote Originally Posted by Rick Moyer View Post
    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

  9. #9
    Join Date
    Aug 2007
    Location
    east coast of florida
    Posts
    1,482
    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.

  10. #10
    Quote Originally Posted by Brian Frances View Post
    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 µm (0.002” to 0.004”) and Asians around 120 µm (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 !
    Well, when you put it that way I feel a little foolish . 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!

  11. #11
    Join Date
    Jan 2006
    Location
    Chicagoland
    Posts
    2,800
    ...now I'll have to go measure my slots this weekend.

    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

  12. #12
    Join Date
    Feb 2004
    Location
    S.E. Tennessee ... just a bit North of Chattanooga
    Posts
    1,018
    Quote Originally Posted by Phil Thien View Post

    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.


    <<<__ Bøb __>>>

  13. #13
    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

  14. #14
    Join Date
    Mar 2006
    Location
    SoCal
    Posts
    22,492
    Blog Entries
    1
    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 ;-)
    "A hen is only an egg's way of making another egg".


    – Samuel Butler

  15. #15
    Join Date
    Feb 2009
    Location
    Cedar Park, TX - Boulder Creek, CA
    Posts
    832
    "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.

Tags for this Thread

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •