Tool Height Gage, Okie Style
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  1. #1
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    Tool Height Gage, Okie Style



    Generally, it seems pretty good just to face the stock to set tool height. No nub, and you're centered.

    But, what with getting into more ground tooling, that changes geometry when it's resharpened………….needed sumpin' else.

    Cheapo mini dial indicator mag base.

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Size:  228.6 KB Grind a point on an old bit, and swap it out with the little arm thingy that comes with the base. Set it to the lathe center, and ya gots your own fancy height gage.

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    More accurate than facing to find center, and a lot quicker...…….

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    I knew that one day, I'd find a use for that stupid little mag base

  2. #2
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    ct.
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    Re: Tool Height Gage, Okie Style

    Ever use the “six inch scale method” of lathe
    tool height adjustment ?
    The 6” scale (machinist’s rule) is held vertically
    with the thin edge of the rule against the side of
    the workpiece. The cutting tool is brought in until
    the rule is ( lightly)pinched between the cutting
    tool and the piece. If the cutting tool is adjusted
    to the correct height, the rule will remain vertical.
    A slight difference in height will cause the rule to
    be noticeably angled. Works well when regrinding
    a HSS tool in the middle of a turning operation.

  3. #3
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    Re: Tool Height Gage, Okie Style

    Quote Originally Posted by jpump5 View Post
    Ever use the “six inch scale method” of lathe
    tool height adjustment ?
    The 6” scale (machinist’s rule) is held vertically
    with the thin edge of the rule against the side of
    the workpiece. The cutting tool is brought in until
    the rule is ( lightly)pinched between the cutting
    tool and the piece. If the cutting tool is adjusted
    to the correct height, the rule will remain vertical.
    A slight difference in height will cause the rule to
    be noticeably angled. Works well when regrinding
    a HSS tool in the middle of a turning operation.

    Yes I did, but not with a tool bit...…..tried it on the tailstock to check alignment MY FAVORITE 6" RULER NOW HAS TWO PERFECT POINTY DENTS Look like mega craters on the Lunar landscape I love that little ruler...……..I mean I LOVE IT. Took the better part of the afternoon to get over it I'm thinking therapy might be in order

    What worries me, is that years from now...…..maybe sitting with the family at K'kins Mom's house at Thanksgiving...……..there might be a flasback.

    I can see it all in my mind's eye.

    Them running out of the house.

    S.W.A.T. showing up.

    Me coming outta the house with a turkey drumstick in my hand.

    And getting shot multiple times.

    "He refused to put the weapon down"

    So...…..I made a height gage

  4. #4
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    Feb 2012
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    Re: Tool Height Gage, Okie Style

    I use old credit cards/gift cards instead of the rule method. Works the same. California style. The old cards are good for clean up oily chips, shims and they are easy to cut with scissors to make a T slot chip chaser tool. Btw, shouldn't the cutting tool be slightly below center for best cut?

  5. #5
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    Re: Tool Height Gage, Okie Style

    Firstly...…….I'm thinking anything below center (centre for y'all Way North of the border) would probably change the rake. Not the ground rake on the tool, but how it interacts with the cylinder. Instead of a shearing action, the rake angle would be effectively decreased, with more of a bulldozing action. On a less robust machine, this would contribute to chatter I think (and have actually experienced it)

    Then there's diameter...…….

    Assuming your cross slide is measuring forward progress in micrometer increments...….it's doing so in a straight line. To get an actual .001 reduction in part diameter, it has to measure thru the center of the part, directly to the center of the axis in a straight line relative to the axis.

    I'm thinking that if you're below the center line, the cross slide will show .001 in movement (obviously), but the actual travel from the OD of the part will be different in terms of how much you're taking off the part. You're coming into the metal at an angle. With the tool below the centerline, even though you touched off, zeroed, then proceeded...…...I believe the actual distance into the part will be different than what shows on the micrometer dial. I think the same would apply if the tool were above the centerline.

  6. #6
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    Re: Tool Height Gage, Okie Style

    South Bend has a book How to run a lathe. They say for ordinary straight turning, the cutting edge of bit should be 5* above center line or 3/64 " per inch in diameter. I said below center earlier and below makes more sense imo but it may have to do with direction the lathe is turning, I don't know. They do say for threading, boring, tapering and "tenacious materials" such as brass and copper, then, the cutter should be exactly on center.

    As for error in cross slide travel: the cross slide travel is parrelel to the ways, I see no reason for error in measurement but good observation sammm.

  7. #7
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    Re: Tool Height Gage, Okie Style

    “The rule is lightly pinched between the cutting tool and the piece “.
    I’ve done this with my beloved Starrett rule many times with no
    physical scarring to the rule or emotional trauma to me.
    Miller a/c-d/c Thunderbolt XL
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  8. #8
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    Re: Tool Height Gage, Okie Style

    I refer to that as excellent work.

  9. #9
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    Re: Tool Height Gage, Okie Style

    Quote Originally Posted by Insaneride View Post
    South Bend has a book How to run a lathe. They say for ordinary straight turning, the cutting edge of bit should be 5* above center line or 3/64 " per inch in diameter. I said below center earlier and below makes more sense imo but it may have to do with direction the lathe is turning, I don't know. They do say for threading, boring, tapering and "tenacious materials" such as brass and copper, then, the cutter should be exactly on center.

    As for error in cross slide travel: the cross slide travel is parrelel to the ways, I see no reason for error in measurement but good observation sammm.
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    There would clearly be an error in determining the actual diameter removed from the piece. You can see that the tool, below/above the centerline will take less material off per .001 of cross slide travel. It's the same as when a tool isn't centered, and leaves the little tit on the face of the stock. Granted, it's a small error, but in a numerical control machine, it's huge.

    I too wonder at the info from South Bend. Hell...…...for a 2" diameter piece, that's almost .010 above the centerline. The bit would be skating off the side of the piece. Might be that because the South Bend was such a light machine, no rigidity, the recommendation took tool flex into consideration. Once it took a bite of the apple, it got deflected downwards, dunno.

  10. #10
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    Re: Tool Height Gage, Okie Style

    I'm finding the same reference to tool height in my material.

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    I'm gonna throw my eggs in the Tool Deflection basket. That's gotta be the reason they were recommending the extra height. "Downward spring" Is specifically mentioned in my materal.

    I know there's "push off" when turning without a tailstock. You can see the deflection that was there when you do your spring cut. That second pass will take off a considerable amount of material relatively.
    Last edited by farmersammm; 06-25-2019 at 11:48 PM.

  11. #11
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    Re: Tool Height Gage, Okie Style

    sammm, they say 5* (five degrees) or 3/64" per one inch diameter. That comes out to 5*22'12" or 5.37*. I also found a South Bend crib sheet that shows setup different than the book.

    As for error in travel; if the cross slide travels perpendicular to the work then I see no reason for error but we can debate that another time. If you feed with compound post set at 29.5 degrees or feed at an angle then you get an error.
    Attached Images Attached Images   

  12. #12
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    Re: Tool Height Gage, Okie Style

    I think generations of well meaning idiots, like us, have been laboring over a mis-print/bad info, simply because some tech writer didn't have his act together.

    Even my initial math was fuzzy 3/64=.047 (I was thinking .004)

    CAN YOU IMAGINE BRINGING A CUTTER INTO THE WORK .047/INCH OF WORK DIAMETER ABOVE THE CENTERLINE

    Moron writer,, or moron editor (shrug)

    THE D.O.D EVEN PICKED UP ON IT

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    Page 7-29 of said document

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    AT LEAST SOMEONE OVER AT THE PENTAGON HAD THE SENSE TO CLAIM THAT THIS RECOMMENDED HEIGHT IS FOR ROUGH CUTS/TOOLS. AT LEAST, IN THE SAME PARAGRAPH THE FOLKS OVER THERE RECOMMEND CENTERLINE FOR FINISHING TOOLS/CUTS DUE TO LESS TORQUE

  13. #13
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    Re: Tool Height Gage, Okie Style

    It MIGHT make a difference, back when this was written about 80yrs ago, that they were dealing with an Armstrong cutter holder with a huge built in positive toolholding rake. Indeed, a rocker style holder is also capable of changing rake angle, but nobody in his right mind would bring the cutting edge of the bit into the work at .047 above centerline on a 1" diameter piece of stock.

    I've seen the Chinese write better stuff than South Bend did

  14. #14
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    Re: Tool Height Gage, Okie Style

    Then, there's the fact that I "roll my own".

    If you look at this pic from another post...…………

    Name:  carbide sucks19.JPG
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Size:  198.5 KB You can see that raising the bit, with a standard textbook clearance angle, will change the geometry.

    BUT...……...I grind with a minimum clearance angle, in order to reinforce the cutting tip. I don't need to raise the cutter to increase the effective back rake. My huge back rake is ground into the cutter itself.

    So...…………………….it's something that has a ton of variables.

  15. #15
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    Re: Tool Height Gage, Okie Style

    And few people are still using the lantern style tool holders; most are using quick change style. Big geometry difference, as was mentioned previously.

  16. #16
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    Re: Tool Height Gage, Okie Style

    I checked the math too.

    5 degrees does come out like they said.

    I do tend to set a little high on my lantern post - with a south bend book grind.
    Likely may not be needed on modern tool holders.

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    Dave J.

    Beware of false knowledge; it is more dangerous than ignorance. ~George Bernard Shaw~

    Airco 300 - Syncro 350
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    Tried being normal once, didn't take....I think it was a Tuesday.

  17. #17
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    Re: Tool Height Gage, Okie Style

    I don't try to measure 3/64 or five degrees, just a slight offset. I've now learned why my quick change bit holders have an off angle.

    My math shows 3/64" divided by 0.5" equals 0.09375

    0.09375 inverse Tangent equals 5.36 degrees or 5 degrees 21 minutes 36 seconds.

    3/64" per inch of diameter is not exactly 5 degrees.

  18. #18
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    Re: Tool Height Gage, Okie Style

    Quote Originally Posted by Insaneride View Post
    I don't try to measure 3/64 or five degrees, just a slight offset. I've now learned why my quick change bit holders have an off angle.

    My math shows 3/64" divided by 0.5" equals 0.09375

    0.09375 inverse Tangent equals 5.36 degrees or 5 degrees 21 minutes 36 seconds.

    3/64" per inch of diameter is not exactly 5 degrees.
    That's correct, the decimal representation I showed above also shows they do not quite match. Just a fairly close approximation.

    But, 2.8/64 = 0.04375
    (0.5)(tan(5)) = 0.04374

    Although 2.8/64 would be harder to measure by hand than 3/64 (I would imagine).
    Dave J.

    Beware of false knowledge; it is more dangerous than ignorance. ~George Bernard Shaw~

    Airco 300 - Syncro 350
    Invertec v250-s
    Thermal Arc 161 and 300
    MM210
    Dialarc
    Tried being normal once, didn't take....I think it was a Tuesday.

  19. #19
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    Re: Tool Height Gage, Okie Style

    Haha, made me think 2.8/64. I get it, that's exactly 5*. Now I get why you showed two slightly different numbers. I got slightly different numbers using different calculators (Business calculator and scientific) . One showed 5.37 the other showed 5.6.

  20. #20
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    Re: Tool Height Gage, Okie Style

    Quote Originally Posted by Insaneride View Post
    Haha, made me think 2.8/64. I get it, that's exactly 5*. Now I get why you showed two slightly different numbers. I got slightly different numbers using different calculators (Business calculator and scientific) . One showed 5.37 the other showed 5.6.
    I like to use decimal numerators sometimes - they show a more accurate picture than just rounding off in some cases
    Dave J.

    Beware of false knowledge; it is more dangerous than ignorance. ~George Bernard Shaw~

    Airco 300 - Syncro 350
    Invertec v250-s
    Thermal Arc 161 and 300
    MM210
    Dialarc
    Tried being normal once, didn't take....I think it was a Tuesday.

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