Sine Bar Go/NoGo
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    Default Sine Bar Go/NoGo

    I was posed a question by a student today and after some discussion with our math coordinator, I wasn't sure we came to a good answer, so I thought I would pose it here: Can you set up a sine bar go and no go gauge blocks? Is there a valid check that can be done with an indicator to test if that part is within tolerance? If an angle is off of nominal and blocks are set on nominal, there would be movement in the indicator. Would this limit you to checking movement over a set distance?

    Thanks for your thoughts!

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    Usually, you set a sine bar to the angle and the error is to your setup or the ability on your machine.
    JoBlocks are near exact, and if you don't have joBlocks then you grind your own gauge block to a micrometer reading often within .0002 or so.

    .0002 or less over the length of a sine bar, and often less over the length of the part is very close.

    Considering the part tolerance and then calculating the high and low JoBlock stack is possible and might be a good classroom learning task..but in the shop a waste of time IMHO>.








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    That's kind of where we landed, if it's not on nominal, our simple solution with our resources is to check it on an optical comparator. Outside of that, I can't think of a good and reliable reason for go and no go set ups on a sine bar.

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    Handy for setups is a set of angle parallels including a 1,2,3,4.5* along with the 5, 10, 15, and such.

    Students might make them. A surface grinder parting wheel can cut then from perhaps 1/4" flat stock. yes, with teaching students to not cut into the grinder's chuck. breaking off the part t about .030 left is one Ok way. down feeding on the grind-side is another safety method with a parting wheel.

    Students should learn how to check a part to a few tenths of squareness.

    Turn a screw thread..perhaps design a new screw thread a 1/2"-10 would be good.

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    Could you elaborate on the last two pieces for me (checking squareness and screw threads)?

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    Quote Originally Posted by JPedersen017 View Post
    That's kind of where we landed, if it's not on nominal, our simple solution with our resources is to check it on an optical comparator. Outside of that, I can't think of a good and reliable reason for go and no go set ups on a sine bar.
    I'm confused.
    Angle has a tolerance. Sine bar can be set up on these numbers just as easily as nominal.
    If you had two bars one could be set for high and another for low.
    Part has to be uphill on one and downhill on the other.
    I thought this common practice for limits.
    Bob

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    QI:Could you elaborate on the last two pieces for me (checking squareness and screw threads)?

    Checking a part for it being square can be done with a surface gauge and an indicator. Even a homemade surface gauge. You bump rub aa a known square something like a 123 block and set zero, and then rub check the part in question to see it also zero checks or it checks off that zero../

    or you make two part-sides parallel, top and bottom sides perhaps with a skim on the surface grinder...then with bottom side on your surface plate you indicator rub with your surface plate and set indicator to zero... then you flip the part so the top side is on your surface plate and rub check that same side, to find the error of squareness.

    Every tool maker student should know how to check the squareness of a part.

    Likely you can find a YouTube on this.

    Screw threads ..Every tool maker want to be should understand threads so well that he/she can engineer a thread that is not on any chart..first you divide one inch by the pitch 1 divided by 10 for the 1/2"-10 thread. 60 degrees has 3 equal sides so the student knows that at a 30* infeed a 100% thread will have that figure on a 30* infeed....and minus the flat is the infeed for a 75* thread..then add the clearance for the fit of a male and female...so design all the stats for an invented thread.

    Yes, the same applies to a metric thread , it just in MMs

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    Taking a small part like a tool bit to the comparator to check angle is Ok but a larger part perhaps on the mill can't be easily taken off, checked and then placed back on the mill with not taking a chance to set it a little off-angle. A height gauge, even a homemade one can strike a sine bar set to angle and set on that part as it is fixtured on the mill. Or an indicator can be mounted on the mill head and strike a sine bar set to angle and set on that part.

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    I understand that angles have tolerances like anything else. So, within a certain range a part would be acceptable and outside it's rejected. What seems a little goofy to my is the gauge block alternative stacks representing those limits. Going back to shop procedures, if I were checking the angle of one surface of a part, I'd make up the gauge block set, adjust the sine bar or sine table. place the part in question on the sine bar and use an indicator to see if the reference surface shows zero deviation compared to the surface plate.

    So a go/no-go could translate into an "out of parallel to the surface plate". For any length of traverse with the indicator, you can calculate what the limits are. So the sine bar is set to the nominal angle, the max indicator reading is calculated, and then after zeroing the indicator you just traverse the part surface. The angle out of limits is then just an indicator reading greater than plus or minus X.

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    Yes, this technique is used for in-process gauging of tapered bolts used in aerospace applications. There, the taper rates are limited to a few fixed ratios, so, instead of using a sine bar and gauge blocks in a production situation, there is just a hardened steel support block ground with the correct slope. The bolt is laid on the tapered block so that the top line of the bolt is nominally horizontal and the top line is probed with a DTI to see if it actually is horizontal. There is also a stop on the block to set the axial position of the bolt relative to the underside of the bolt head. This lets the operator gauge the diameter once the DTI is zeroed using a master tapered bolt or pin.

    Quote Originally Posted by michiganbuck View Post
    Usually, you set a sine bar to the angle and the error is to your setup or the ability on your machine.
    JoBlocks are near exact, and if you don't have joBlocks then you grind your own gauge block to a micrometer reading often within .0002 or so.

    .0002 or less over the length of a sine bar, and often less over the length of the part is very close.

    Considering the part tolerance and then calculating the high and low JoBlock stack is possible and might be a good classroom learning task..but in the shop a waste of time IMHO>.








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