internal 6 start, 30mm dia, 111mm pitch thread
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    Default internal 6 start, 30mm dia, 111mm pitch thread

    Got a part only 58mm long but has an internal 6 start 30mm dia 111mm pitch thread. Does anyone know a manufacturer who deals with these kind of monstrosities?

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    111 pitch thread? Could we see a picture of the thread I’m just curious?

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    Quote Originally Posted by Ianagos View Post
    111 pitch thread? Could we see a picture of the thread I’m just curious?
    ugly-thread.jpg

    The thread profile is essentially a 8mm slot with straight walls extruded and rotated.

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    Ok that’s sort of what I imagine other than the straight walls. It looks like you could grind up a tool with the profile and proper relief then orient it to you are essentially broaching in the lathe. Take many .001” passes and should be ok. If you are interested in a quote let me know I cannot guarantee anything but I can run a test part for you.

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    111 lead, so "pitch" is 18.5

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    Quote Originally Posted by johnoder View Post
    111 lead, so "pitch" is 18.5
    John, if I'm interpreting this correctly then this is basically a twisted spline, with a full revolution of one spline "thread" being completed in 111mm.

    OP, correct me if I misunderstand. And ditto if I'm not getting what John's described.

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    Quote Originally Posted by Milland View Post
    John, if I'm interpreting this correctly then this is basically a twisted spline, with a full revolution of one spline "thread" being completed in 111mm.

    OP, correct me if I misunderstand. And ditto if I'm not getting what John's described.
    You are correct. I should have said lead instead of pitch. The distance of one revolution is 111mm

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    Quote Originally Posted by reidhardy View Post
    You are correct. I should have said lead instead of pitch. The distance of one revolution is 111mm
    Sounds good. Is this a one-shot, or a run of parts? If one shot, either try the home-made single tooth broach, or if there's money available, you could find someone with a helix-capable sinker EDM, and after prepping a blank with the circular features needed, sink the spline into it.

    The electrode could be a simple as a short slug of graphite projecting from an arbor, or as complicated as the full helix form.

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    Depending on minor dia, (and pitch diameter) helix angle will be LESS than the roughly 40 degrees that 30mm dia. would result in - and this is off horizontal, not vertical (as related to lathe spindle axis) One begins to appreciate the extraordinary front clearance angle required on any lathe type cutting tool

    30 (or whatever the pitch dia. turns out to be) times "pi" divided by 111 = tan of angle

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    A lot of clearance would be required for sure. Really the only other way I could figure to do this would be on an edm.

    If this is in anything hard to machine the single point broaching probably is not the best option but if it’s in a decent to machine material I think it would be possible. Key word there is I think.

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    I made a few very similar to this on the lathe (cnc). It wasn't that difficult, worst part was measuring and hoping to get all six threads the same depth. Lucky it was aluminum and only a few parts. Used an old-fashioned boring bar with the broached square for the tool and a hss tool ground by hand.

    Lucky I had a bottom end of 50 rpm on the spindle, and the z was moving right along like a rocket sled, roughed all six starts then came back and did each one at the same depth all the way around once, twice, three times, until the male part fit. Second one was easier because I now had an idea of the full depth.

    Took maybe a day ... fun but not real profitable.

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    Quote Originally Posted by Milland View Post
    Sounds good. Is this a one-shot, or a run of parts? If one shot, either try the home-made single tooth broach, or if there's money available, you could find someone with a helix-capable sinker EDM, and after prepping a blank with the circular features needed, sink the spline into it.

    The electrode could be a simple as a short slug of graphite projecting from an arbor, or as complicated as the full helix form.
    Customer is looking for 250

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    Well, you could have a broach company make a "for real" broach for that, but I hate to think of the cost. You'd also want a special seat for the part with a good (shielded) thrust bearing on it to allow the part to spin freely while the broach passes through.

    If you can fake it with a tool in the lathe you do the other features with that sounds like the best bet...

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    no affiliation or experience with these, I remembered an old video where some Russian made a tool like this, chain driven, but it was probably for a larger diameter work piece, he used it to mill straight internal splines on a manual lathe, so I started searching and found these:

    Live Lathe Tools | Sizes & Dimensions | How to Order | Eltool

    and they even have a video:

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    Quote Originally Posted by jz79 View Post
    no affiliation or experience with these, I remembered an old video where some Russian made a tool like this, chain driven, but it was probably for a larger diameter work piece, he used it to mill straight internal splines on a manual lathe, so I started searching and found these:

    Live Lathe Tools | Sizes & Dimensions | How to Order | Eltool

    and they even have a video:
    I was thinking of something like that but I didn’t think it existed. With one of those and a short endmill the part could probably be made pretty easily.

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    Quote Originally Posted by Milland View Post
    Well, you could have a broach company make a "for real" broach for that, but I hate to think of the cost. You'd also want a special seat for the part with a good (shielded) thrust bearing on it to allow the part to spin freely while the broach passes through.
    They make helical broaches. The part stays still, they twist the broach itself as it pulls through. There's a helical guide for the broach. You better have a lot of money.

    I was thinking it could maybe be done in a Fellows shaper, but not sure. Depends on a lot of things, but also needs a guide and a helical cutter. $$$$

    There must be a way to make half-nuts that is not so expensive ? You know those linear guides that reel winders and so on use ? Because of the helix angle, even thread milling would probably not work ?

    If you can fake it with a tool in the lathe you do the other features with that sounds like the best bet...
    Five or ten I'd say yeah, big bubbles no troubles but I'd not be happy looking at 250. Not enough to go for bigtime tooling but too many to do it the cheap way.

    Those internal right-angle milling heads don't work for shit. Been there, tried that.

    Maybe a giant tap ?

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    Quote Originally Posted by EmanuelGoldstein View Post
    Maybe a giant tap ?
    You'd be around the cost of the broach, wouldn't you? I bet tap companies would turn pale, shut their doors, and place the "gone fishing" signs in their windows if you showed up with a print and RFQ...

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    Quote Originally Posted by Milland View Post
    You'd be around the cost of the broach, wouldn't you? I bet tap companies would turn pale, shut their doors, and place the "gone fishing" signs in their windows if you showed up with a print and RFQ...
    I could probably get one made here for 1/5 the cost of the US. Ja, it wouldn't last thirty years but it would do the job.

    Sometimes Harbor Freight is good enough, ya know ?

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    Looks like something that could be done with a rifling cutter type setup

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    What material, could they be cast?


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