Reverse Countersink

Discussion in 'Maintenance Bay' started by weirdjim, Jul 11, 2018.

  1. weirdjim

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    I have to countersink an aluminum radio on the INside of the chassis. I can't get a regular countersink inside even with a shaft extender because of the angle and the internal construction of the chassis. I remember a long time ago a master machinist showed me a REVERSE countersink set he had for doing stuff inside where you couldn't get a regular tool. (Instead of PUSHING the countersink with the drill, you insert it from the inside and PULL on the drill to countersink.)

    I need a #4 and a #6 reverse countersink and I see where some manufacturers have them listed, but nowhere I can buy just one or two. Anybody (a) know exactly what these things are called and (b) where you can buy them in onesies and twosies?

    Thanks,

    Jim
     
  2. slacktide

    slacktide Line Up and Wait

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  3. Grum.Man

    Grum.Man Pattern Altitude

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  4. slacktide

    slacktide Line Up and Wait

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    eBay for one or two?

    Paul
     
  7. weirdjim

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    Youse guyzez are great. Never thought about using the drill bit as a shank. But I need a #4 as well as a #6 and don't see them. Yes, I would LIKE a 100° csk. but I'll use a 72° and be VERY careful.

    Thanks again.

    Jim
     
  8. slacktide

    slacktide Line Up and Wait

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  9. slacktide

    slacktide Line Up and Wait

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    Here you go. I cut off the parts I didn’t need, cross-drilled a new hole for the setscrew, and tapped it.
     

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  10. flyingbrit

    flyingbrit Pre-Flight

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  11. weirdjim

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    JEEZUZ ... 30 bucks a size is a little pricey. I think I'll see if I can get a hand sink in there and cut the shank down for a small dremel tool. HEY, now that's an idea I hadn't considered. There has to be a dremel tool somewhere that has a reverse cutting edge on it ... and miraculously enough the dremel shank is exactly the diameter of a clearance hole for a #4 screw. Bingo.
     
  12. weirdjim

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    That's not a bad way to do it either, but nobody in the "Home Depot" class has a #4. They all start at #6, which is doable for me, just not as neat. I wonder if some hobby store has smaller csk tools.
     
  13. DOC

    DOC Filing Flight Plan

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    Not many reverse countersinks are made outside 40, 1/8, 5/32, 3/16 and 1/4. Standard aircraft structural fastener sizes. A 3/16 might work if your carefull. Brown Aviation Tool sells them individually.
     
  14. steingar

    steingar Taxi to Parking

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    That’s actually a move in Origami
     
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