Thread major/minor for apparent M16L-11tpi thread?
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  1. #1
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    Default Thread major/minor for apparent M16L-11tpi thread?

    Hi all, a previous thread was closed, hopefully this will be more the the admin's liking.

    Previous thread here: Frustrating nut!

    The consensus was that my pedestal grinder from Portugal (in the 70's, when they were still using some inch stuff) might be threaded M16 but 11tpi. I'm as sure as I can be that it's 11tpi and not 2.0mm - the 11tpi thread gage definitely fits better.

    The major is 0.6299" (16mm). I just used 11tpi thread measuring wires to get a thread diameter of 0.5703". I'm not very experience with non standard threads.

    What will my ID of the nut be (external thread minor dia plus tolerance?) How much will I eventually feed a 29.5 degree compound once I touch off of that bored ID to cut the thread?

    Thanks a lot, a weird thread like this is new territory for me, but I'd like to get my grinder fixed.

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    Perhaps the safest way to deal with this is make a test thread on a short shaft that matches your grinder thread on OD and measured pitch diameter. Then use this shaft for fitting the nuts you'll machine. You can make the nuts a little loose to ensure they'll work, a super-close fit to the grinder spindle isn't needed here.

    After you've made the test thread, lay it into the grinder thread to ensure the longer section of 11tpi still matches.

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    There's a rule of thumb for determining "tap drill diameter" -- which I'm pretty sure is what you're asking about -- for both the Unified (aka ISO Inch) and ISO Metric threadforms: tap drill diameter = Major Diameter minus Pitch. Using that rule of thumb, your tap drill diameter would be calculated as 16 millimeter minus 1/11 inch.

    1/11 inch is very nearly 2.3 millimeters, making your tap drill diameter very near 13.7 millimeter.

    As for the required infeed of the toolbit . . . it can theoretically be calculated, but it's dependent on the actual diameter of the yet-to-be-threaded hole, the infeed angle, and the length of the flat at the tip of the toolbit. It's a calculation I hesitate to make, and have found it's far more direct to simply make a short counterbore a proverbial hair over the Major Diameter at the mouth of the hole to be threaded. Color the counterbore surface with a permanent ink marker that contrasts with the metal color, use a toolbit with a proper-length flat at its tip, and stop cutting once the tip of the toolbit grazes the color.

    John

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    I could be wrong but Im willing to bet its a 5/8-11 thread.

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    U been trying to figure this out for 2 years?

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    Quote Originally Posted by kevin66 View Post
    I could be wrong but Im willing to bet its a 5/8-11 thread.
    That would be wonderfully easy, but the Dewalt grinder sitting right next to it uses 5/8-11 nuts (one left and one right), and it won't thread. Half a revolution, but once yet get past the chamfer, it won't go any further.

    The RH threaded nut for this Siemens grinder in question, the nut that I do have, will thread onto the 5/8-11 thread of the Dewalt spindle, but the reverse is not true - which makes sense given that this spindle measures over the OD it should for a 5/8-11 thread.

    Wish it were that easy! If I, for some reason, had an M16L-11tpi tap, I'm pretty sure I could run it through a normal 5/8-11 nut and I'd be off to the races. Don't seem to have that tap sitting in my toolbox though!

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    Quote Originally Posted by StinkyDan View Post
    U been trying to figure this out for 2 years?
    Living in West Africa for a decade has taught me the value of refocusing on something you *can* push forward when you hit an unsolvable dead end.

    It's also greatly heightened my tolerance for working with half-broken equipment, unfortunately.

    The other side of the grinder works fine, and I have five pedestal grinder spindles in my shop. To be honest, I don't really need the 6th, I just don't like it having beaten me!

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    Even a true 16mm male thread probably shouldn't be a full .6299" OD, as any bit of contamination or denting in handling can make the nut want to seize on. Does the male thread appear to have a sharp crest? It might just have a burr raised that could be filed off. I'd probably just file the damn thing down to .624" OD anyways, to avoid having to have a 'special nut' for one damn machine.

    Edit: scratch that, I checked the PD you gave, it does appear to be a bastard metric.

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    i have seen rod start out .625 diameter and get bigger cause the dull thread die pushed the metal around a bit and made it bigger diameter like .630 dia.
    .
    dont matter its still a 5/8-11 thread cant get nut on, run a file on it while turning or use a hand thread die. only take maybe 10 seconds either way

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    Triangular file, thread chasing file or threading die...
    Make it fit a 5/8-11 one way or another.


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