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Single pointing 0-80 internal thread

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  • MattiJ
    replied
    Originally posted by PStechPaul View Post
    The SFM is just a guideline for optimal productivity and tool life, especially for HSS. You can turn the spindle by hand if you wish. This may not apply to carbide, however, and high surface speed may result in a better finish.
    Carbide is not any different, works also at sloow speed. There is actually a mid-speed range that often sucks and going either way improves your results.

    I used carbide tooling to turn the 0.014mm or 5 "tenths" shaft shown in the microscope thread.
    Even at 4000rpm that works out to roughly zero SFM

    I'm affraid I'm not able to match up OP's internal thread.. even if I have the 127TPI screw already done:
    https://bbs.homeshopmachinist.net/fo...threads-127tpi

    Leave a comment:


  • PStechPaul
    replied
    The SFM is just a guideline for optimal productivity and tool life, especially for HSS. You can turn the spindle by hand if you wish. This may not apply to carbide, however, and high surface speed may result in a better finish.

    Leave a comment:


  • Bented
    replied
    How fast did you turn it? The major diameter of a number screw is .013 X # + .060 (I have no idea why I remember this)
    At a reasonable 30 sfm for HSS the spindle speed is 1900 rpm's at .060" diameter.

    Leave a comment:


  • Rich Carlstedt
    replied
    Atlas / (Craftsman) went from Bronze Bearing Head-stocks to Timken Bearing head-stocks and the Head-stock became a square casting (More Modern ) at that time .
    Also changed the spindle thread (larger to 1" ? ) as I recall
    Rich

    Leave a comment:


  • mattthemuppet
    replied
    Originally posted by 90LX_Notch View Post

    Matt- The lathe is a 618 Square head. They changed over to this style in the early 1970's.

    -Bob
    ah, gotcha, thought a few things looked different

    Leave a comment:


  • PStechPaul
    replied
    That may be an urban legend. My father told me that the Russians (USSR) sent a tiny screw to Switzerland, expecting them to be awestruck. It was sent back to them with no comment. Ivan replied, "What did you think about that?". The Swiss replied, "Look at it closely". They had bored a hole through it (and possibly tapped it as well). This was in the late 50s or 60s, IIRC.

    These are variations on similar exchanges, going back even to 300 BC, according to Snopes.

    Leave a comment:


  • bborr01
    replied
    Regarding small stuff, I remember a story that my dad told probably back in the 60's. He worked in a department of GM that made diesel injector spray tips and the holes were drilled by hand with sensitive drill presses. I think the holes were a little bit under .010". They sent a drill bit to Japan for a trade show and it came back with a hole through it.

    Later they started to burn the holes with a piece of wire on special built edm's. I worked in that department for a while and the holes were usually burned in with .004" wire.

    Leave a comment:


  • 90LX_Notch
    replied
    Thank you for the compliments.

    Doozer- I guess we are just wired differently.

    Matt- The lathe is a 618 Square head. They changed over to this style in the early 1970's.

    Bob-
    I actually considered running the lathe in reverse with the tool mounted upside down. I would have had to rewire the motor to do it. I just didn't feel like going to that extent for this. I "tuned" the lathe years ago and took all the slop out. This included the half nuts and the lead screw bearings. I also combined the best parts from three 618s to build this one.

    I used an indicator to to disengage the half nuts. At 80 threads per inch the carriage is not flying along. I could pretty much hit zero on the indicator, a few times I missed by .005. This was fine because I had a .020 safety margin. I just used the same number on the threading dial to engage the half nuts.

    -Bob

    Leave a comment:


  • Paul Alciatore
    replied
    When I saw the title I was all set to advise you to use a tap. 0-80? I have the tap and have tapped 0-80 holes. But single pointing it? I would have sworn it was all but impossible. Just making that tool is a real challenge. But you DID IT!

    I am impressed.

    Nothing is impossible if you set your mind to it. We all need to remember this. Thank you for showing it anew.

    PS: My wife and family would also be totally clueless.
    Last edited by Paul Alciatore; 02-24-2020, 04:35 PM.

    Leave a comment:


  • PS4steam
    replied
    Bob

    Now that is really a challenge and skill building exercise.

    The smallest internal I have done is 2 - 112 TPI for a mixer needle. Another modeler suggested at that size to make your tool upside down and take the cut off the back side(that way you are still going CCW if you have threaded spindle) and so you can see it (ha ha) still needed a magnifier but at least I did not have to twist my neck all around. Or use a left hand tool and run the lathe in reverse, either way a little better view.

    I am curious how you kept all the play out of everything ie lead screw, and half nut. Did you do anything specific? For example not disengaging the half nut just running under power backwards, not cutting the thread under power but turning the spindle by hand?

    Again fantastic challenge.

    Bob

    Leave a comment:


  • mattthemuppet
    replied
    I was trying to place the lathe and you said it was an Atlas 618 (woot!), but it has a sealed cartridge spindle bearing - how did that come about? Any details?

    Leave a comment:


  • nickel-city-fab
    replied
    Originally posted by old mart View Post
    The lathe I use only goes to 76tpi so I'll give it a miss, also, the finest laydown inserts I have are 0.5mm, a little coarse.
    Ja, I was going to say.... I don't think I have enough magnification to grind a suitable tool!

    Leave a comment:


  • mattthemuppet
    replied
    Originally posted by Doozer View Post
    I applaud your deed.
    I really do.
    But personally, my time is worth more
    than farting around with something like this.
    Maybe if you are waiting for a part that is holding up a production line or something,
    but other than that, nice to keep in practice I guess.

    -D
    but I'm sure that you didn't get to the level you operate by doing the same thing over and over, right? Skills come from challenges and mistakes, which usually come from doing something you don't know how to do A life without intellectual challenges is my idea of hell.

    Leave a comment:


  • old mart
    replied
    The lathe I use only goes to 76tpi so I'll give it a miss, also, the finest laydown inserts I have are 0.5mm, a little coarse.

    Leave a comment:


  • Doozer
    replied
    I applaud your deed.
    I really do.
    But personally, my time is worth more
    than farting around with something like this.
    Maybe if you are waiting for a part that is holding up a production line or something,
    but other than that, nice to keep in practice I guess.

    -D

    Leave a comment:

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