Vibroplex bob weight thread?

Discussion in 'Straight Keys - CW Enthusiasts' started by G0ILN, Jun 11, 2019.

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  1. G0ILN

    G0ILN Ham Member QRZ Page


    I have made 22gram bob weight for my Vibroplex 1947 bug key but am not sure of the screw size.
    Can someone help me please.
    Many thanks.
    P.s. sorry if this is the wrong forum but it seemed the most appropriate!
  2. KE6EE

    KE6EE Ham Member QRZ Page

    It's a U.S. #8 machine screw. Nominal diameter 0.16 in. Measured diameter on my Vibroplex 1940s Original
    mode 0.157 in. 32 threads per inch.

    If sizes you have to use are metric, the size is up to you.
    K5VZD likes this.
  3. G0ILN

    G0ILN Ham Member QRZ Page

    Thanks for the reply. I can't find a #8 tap in UK so I will have to order it from China. Hi.
    Postage from the US is a lot higher than China!
    Thanks again,
  4. WR2E

    WR2E Ham Member QRZ Page

    I take it you don't care to re-tap the hole, or drill a new one and tap for metric?
  5. KE6EE

    KE6EE Ham Member QRZ Page

    Any tap you are likely to buy here in the U.S. will be made in China. I'm confident that will have such things
    as taps available from their U.K. warehouses which may shorten the delivery time. On the other hand I've ordered
    all sorts of small parts directly from Chinese suppliers and the delivery is less than two weeks.

    On the third hand, why bother to maintain the same screw size? If you use a similar size metric tap (and set screw)
    your bug will work just as well!
  6. G0ILN

    G0ILN Ham Member QRZ Page

    Thanks for the replies.Why I wanted too keep the original screw was to make the new weight look authentic ( Ish!) with the original screw that has it's rope knurling and chrome plated . The comments that I have received made a lot of sense .
    So I will make a 4mm knurled screw and it will look obviously after market! Problem solved.
    Thanks again and I appreciate the interest.
  7. N2EY

    N2EY Premium Subscriber QRZ Page

    Bob weight?
  8. KE6EE

    KE6EE Ham Member QRZ Page

    And Bob's your uncle.
    K8AI, KA2CZU and N2EY like this.
  9. G0ILN

    G0ILN Ham Member QRZ Page

    A " Bob" weight is the weight on a pendulum. There are several references on the internet to Bob weight.
    So there we are, Robert's you fathers brother. ;0)
    K8AI and WR2E like this.
  10. WB5YUZ

    WB5YUZ Ham Member QRZ Page

    Perhaps you have previous experience with Chinese tools, or perhaps rules in the EU (which are still effect) provide some kind of control over the quality of imported tools.

    If neither of the above is true, though, do not order the cheapest Chinese tap you can find. This will be a one-use tool, and probably not a very good one.

    From my own experience with Chinese tools, I would not own a Chinese tap/die. There's just no way to tell what the quality of the tool is until you try to use it. But the odds are, even it is a relatively expensive one, it will be not quite the right size, and will also dull very quickly.

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