1. #1
    Wal's Avatar
    Lives in Stockport, United Kingdom. Last Activity: 14 Hours Ago Has been a member for 6-7 years. Has a total post count of 382. Received thanks 41 times, giving thanks to others 15 times.
    Back in my day, if you didn't pay attention they'd give you a clout 'round the ear, nowadays, it would seem, they give you a fidget spinner.

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    A good friend of mine asked if I'd make her seven year old son a custom fidget spinner - in fairness, he's a top little fella and very bright, so a total pleasure to make him something he's gonna (hopefully) enjoy.

    Didn't have the first clue about these things, but after a bit of searching (both the internet and my offcuts bin) I decided on a lightweight 7075 body, CZ121 brass weights and a miniscule R188 stainless/ceramic hybrid bearing. I kept the design deliberately simple, as my main priorities here were about focusing on decent interference fits for the weights and the bearing and having the thing actually function! - I may re-visit this project at a later date and try a more 'interesting' shape, but for now I'm okay with the (elegant?) simplicity.

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    Here's a vid of the 7075 body being machined:



    ..and a couple of pics of the results:

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    Then it was the brass - I used a hole-saw to cut out some blanks from a piece of 1/4" scrap - then machined 'em to size - well, 0.025mm undersize with a couple of spring passes.

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    Once that was done, I made a little press out of some oak:

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    Here it is in action:



    Then it was a case of jigging that lot up and engraving the lad's initial (G) onto the brass, along with a bit of a ball-nose chamfer. Don't have any video of that, but here are the results, fresh from the kitchen sink:

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    The last bit (and probably the trickiest) was to make the caps. Here's a vid of the round-over being machined to give a bit of clearance on the underside followed by a clip of the ball-nose cutting the circular contours.



    The female cap needed tapping which meant grinding a flat nose onto one of my M4 taps to give me the extra 'reach' I needed.

    The male cap had an extra layer of complexity insofar as it needed to be thread-milled (I don't have a lathe, but really want to get my hands on something small for jobs like this) - the M4 die barely starts cutting by the time it hits the underside of the cap, so no use in this situation. You can find a reasonably detailed write up on how I went about this over on my blog. Here's a vid of the operation:



    The design relies on a couple of little 'shelves' that clamp the inner race of the bearing. Then there's a bit of clearance within the interior of the rest of the cap - the inner race is a bit baggy by design, so you don't want the outer race that partially protrudes from the body fouling the caps.

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    Once these were polished I pressed in the bearing with no issues - and fitted the caps. The finished article:

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    ...and with a wooden carry case:

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    And who could resist revving it up with the air line..? Not me:



    That's only at 2 Bar... <Opens it to 8, thinks carefully, then closes it again..>

    Wal.
    Last edited by Wal; 09-05-2018 at 05:15 PM.

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