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  1. #1
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    Default Steering shaft worm thread

    How to make it and what to make it from ?

    **edit* If done in one piece most of the shaft is fairly straight forward machining. The variable pitch thread is a problem for my YouTube machinist education. **

    The pictured (borrowed) steering shaft is from a 1950's vehicle. The worm section of the shaft files harder then HRC65 whilst the main shaft files metal with a HRC40. Sections joined by some form of press welding. Looking at the pictures the tool marks of the milling of the worm thread is easy to see.

    I've done the usual Google and had a ganda at PM with no luck apart from how-to variable thread CNC programming.

    I don't have CNC so thoughts anyone?
    Attached Images Attached Images

  2. #2
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    Where I worked once, we made irrigation equipment that had a screw thread that was done on a milling machine. It was similar to what you're looking for.
    Would it be possible to screw cut it on a lathe, then get it hardened?
    Kryn
    To grow old is mandatory, growing up is optional.

  3. #3
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    Default

    I fergot to add the variable pitch reference to the title.

    First post edited.

  4. #4
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    Quote Originally Posted by KBs PensNmore View Post
    Where I worked once, we made irrigation equipment that had a screw thread that was done on a milling machine. It was similar to what you're looking for.
    Would it be possible to screw cut it on a lathe, then get it hardened?
    Kryn
    If I carn't do the thread on my mill then may have to look at getting it done at a machine shop on a CNC. Though I'll be looking harder at swap meets before then.

  5. #5
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    If I had to I think I'd cut it as a helix on the mill (vertical head but driving the dividing head from the table), first cutting one side of the groove and then resetting back to the same starting point and cutting the other side of the groove with a slightly different lead so the worm changed.
    What does the driven part look like though? It's not just wear?
    Without the universal dividing head it may be you have to step the profile out (that is, rotate x degrees, advance longitudinally y mm). After that, clean up with a file.

    Michael
    Last edited by Michael G; 7th Feb 2017 at 05:12 PM. Reason: fixed mistake

  6. #6
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    Quote Originally Posted by Michael G View Post
    What does the driven part look like though? It's not just wear?
    Michael
    I'd second this question. My head hurts even attempting to think of what a variable pitch worm wheel (segment) might look like...... let alone how to cut one.

    PDW

  7. #7
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    Default

    I am no expert in this, although I have had steering worms rebuilt on non replaceable items, the company I used built up the worn surface and then reground on a grinder that was equipped with a pattern follower

  8. #8
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    Quote Originally Posted by Michael G View Post
    ...What does the driven part look like though? It's not just wear?
    Without the universal dividing head.....
    It looks to me like the hard facing has fractured off the worm which then flogged out the "driven part". I've acquired a few similar steering boxs which all have the same problem.

    Looks like I need some new attachments for me mill.

  9. #9
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    Quote Originally Posted by China View Post
    I am no expert in this, although I have had steering worms rebuilt on non replaceable items, the company I used built up the worn surface and then reground on a grinder that was equipped with a pattern follower
    I've just done a google for that company though no luck. All I get is parts replacers instead of parts repairers. Do you have a link for them?

  10. #10
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    Possiblymade on some special machine with non circular gears.
    Gold, the colour of choice for the discerning person.

  11. #11
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    What is the part from, besides a steering box, someone may know where to find a good one? To look at getting it repaired, look up hard chroming, they can build up all sorts of worn shafts and gears.
    Kryn
    To grow old is mandatory, growing up is optional.

  12. #12
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    Quote Originally Posted by KBs PensNmore View Post
    What is the part from, besides a steering box, someone may know where to find a good one? To look at getting it repaired, look up hard chroming, they can build up all sorts of worn shafts and gears.
    Kryn
    I source vehicles and components from all around Oz so a useable shaft will come up eventually. Though, I keep looking at the shaft and thinking how hard can it be to make me own.

    Getting some good hits with the "hard chrome plating" search. Even a video of a machine shop in Brisbane - https://m.youtube.com/channel/UCsVIiQtVgyH8rnSrX_Ja9-g

  13. #13
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    Quote Originally Posted by .RC. View Post
    Possiblymade on some special machine with non circular gears.
    Pre-dates CNC so there must be a 'relativly' simple way to do the variable thread. My youtube education is found lacking.

    Surely there is some-one around here who knows how to do it ?

  14. #14
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    If the pitch was uniform it would be easy to do as a spiral milling job, and I think the tool marks in the bottom of the grooves support that idea. First photo is post one suggests it is a uniform pitch worm, but the last pitch is worn.

    Michael

  15. #15
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    In a modern shop, servo controlled lead screw with feedback to the spindle, yeah I know that's pretty much NC.

    Old school, rack and pinion driven lead screw controlled by a cam driven from spindle? Complex to set up and not easy to change but I'm thinking this was produced on a dedicated machine.

    I'm trying to work out the benefit of the variable pitch unless the steering is lock to lock in one revolution.
    Is this from a racing box of some sort?
    Cheers,
    Greg.

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