Any sources for coarse 1/4" thread other than 1/4-20? - Page 3
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  1. #41
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    Find an old, preferably telephoto, 35mm camera lens and take it apart. The focusing thread will be a two, three, or four start.



    Quote Originally Posted by plastikdreams View Post
    I e never seen one in person, I'd love to get my hands on one just to check it out.

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  3. #42
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    A bit off topic, but I've just had to make some footrests for a 1960s Italian motorcycle which had a very coarse knurl on them of 4 mm pitch. Did a 12 start thread, 48mm lead at 4mm pitch, left and right hand which turned out well. Wouldn't have liked to make the nut that fits mind you!

  4. #43
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    Quote Originally Posted by EmanuelGoldstein View Post
    Unclear on the terminology then, normally "pitch" is determined by threads per inch,
    Un-quote
    NO! it's determined by the "crests per inch". A thread is determined by following one crest around the shaft.

    If we'd QUIT using the word "Thread" when talking about multi start ones. :-) and just use pitch and lead it would be less confusing. "Pitch" is the distance from one "Crest" to the next .
    ...lewie..

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    Quote Originally Posted by plastikdreams View Post
    I guess my biggest question is how to index the start...I would guess it has to do with the thread dial but it's just a really w a g lol
    I believe the lazy method is to index them off of the chuck jaws. Number your chuck jaws. A double start lead would need a four jaw (or two jaw, or six jaw) chuck though. Triple start would use a three jaw. Quad start would use a four jaw, etc.

    At least so I've heard. I'm not a multi start thread expert, but I am aware of them. Quite useful for getting very coarse pitches.

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    Quote Originally Posted by Lewie View Post
    NO! it's determined by the "crests per inch". A thread is determined by following one crest around the shaft.
    Sorry, not true. It can be any feature - crest, root, flank, whatever. They are all the same.

    Quote Originally Posted by CatMan View Post
    I believe the lazy method is to index them off of the chuck jaws.
    Easiest way is to do it in a thread mill and use the index plate

    But in a lathe, putting the compound parallel to the Z axis, coming in straight and using the compound to set the distance between starts is the easiest ?

  7. #46
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    Apparently, like McMC, Regal considers Ozzies enemy aliens. No joy with Limi's link.

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    Quote Originally Posted by swarfless View Post
    Apparently, like McMC, Regal considers Ozzies enemy aliens. No joy with Limi's link.
    Ask and ye shall receive (if I can figure out the embedding schtick)
    Attached Thumbnails Attached Thumbnails one.jpg   two.jpg  

  9. #48
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    Quote Originally Posted by EmanuelGoldstein View Post
    Unclear on the terminology then, normally "pitch" is determined by threads per inch ...

    Therefore, 16 pitch is 16 tpi, no matter how many starts ...
    Wait - I always thought pitch was the reciprocal of tpi, and vice-versa. Metric threads are measured in pitch (distance between threads), while imperial are measured in tpi ( = 1/pitch ).


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    Quote Originally Posted by awake View Post
    Wait - I always thought pitch was the reciprocal of tpi, and vice-versa. Metric threads are measured in pitch (distance between threads), while imperial are measured in tpi ( = 1/pitch ).
    "Is determined by", hippy Not "is the same as" ... Pitch = 1/tpi

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    Quote Originally Posted by EmanuelGoldstein View Post
    "Is determined by", hippy Not "is the same as" ... Pitch = 1/tpi
    Hmmm ... for a second I thought you had wiggled out of it, but as I thought further: When it comes to metric threads, I'm pretty sure no one "determines" the pitch on the basis of tpi. They determine the pitch on the basis of distance between the threads. To say it another way, in order to measure the pitch, you would count out, say, 10 threads and measure the distance, then divide by 10 - exactly the opposite of measuring a distance (10mm? 25.4mm??) and counting the number of threads in it. The latter would assume that you can expect a whole number of threads within a given distance, but with metric threads, that would not be guaranteed, not at all.

    Still

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    Quote Originally Posted by awake View Post
    Hmmm ... for a second I thought you had wiggled out of it, but as I thought further: When it comes to metric threads,
    Oh yeah, metric. That shit's upside-down and backwards, we don't go there


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