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  1. #16
    Join Date
    Jan 2004
    Location
    Mackay North Qld
    Posts
    6,446

    Default

    Here is a link I found helpful.

    http://www.dotmar.com.au/images/mach...structions.pdf

    I read elswhere, (and now can't find where that was) that the max temp was 125 Celcius and beyond that shrinks inwards.

    I found that the drilled 8mm hole shrinks to grab the 8mm range rod shafts, despite use of coolant. Mind you, I knew not about "pecking" at this stage.

    I hope it helps.

    Grahame

  2. #17
    Join Date
    Sep 2012
    Location
    York, North Yorkshire UK
    Posts
    6,438

    Default

    Hi Guys,

    At the time I was drilling long holes in PTFE (Teflon rod) It being a very soft and flexible material that came in long 10 foot lengths, it was very difficult to maintain a straight precise diameter hole. I also had the problem that the outside diameter had to be controlled to within a few thou over the 8" inch length.

    I solved both problems by turning the whole ten foot lengths of Teflon rod down to the correct diameter, I forget now what that diameter was, but the rod came in to me at 1/2" diameter. Then cutting the 8" inch lengths on a chop saw.

    When it came to drilling the bore, the Teflon rod after turning to size was pressed into the heated pre-machined aluminium housing and placed into cold water. This caused the alloy to shrink and grip the Teflon rod. It couldn't move when that was done. You cannot use adhesives with Teflon, it doesn't stick to it. The aluminium housing was then spun in the lathe for drilling. I could easily maintain a straight hole within a thou or two.

    Afterwards a turned brass rod was pressed into the bore after being threaded at both ends, then assembly took place.

    I made a couple of hundred of these items. However all the jigs and tools were passed on to the company contracting me to do this work, so I'm sorry there are no pictures that I can show !
    Best Regards:
    Baron J.

  3. #18
    Join Date
    Oct 2010
    Location
    melbourne, laverton
    Posts
    1,910

    Default nice

    Quote Originally Posted by BaronJ View Post
    Hi Guys,

    At the time I was drilling long holes in PTFE (Teflon rod) It being a very soft and flexible material that came in long 10 foot lengths, it was very difficult to maintain a straight precise diameter hole. I also had the problem that the outside diameter had to be controlled to within a few thou over the 8" inch length.

    I solved both problems by turning the whole ten foot lengths of Teflon rod down to the correct diameter, I forget now what that diameter was, but the rod came in to me at 1/2" diameter. Then cutting the 8" inch lengths on a chop saw.

    When it came to drilling the bore, the Teflon rod after turning to size was pressed into the heated pre-machined aluminium housing and placed into cold water. This caused the alloy to shrink and grip the Teflon rod. It couldn't move when that was done. You cannot use adhesives with Teflon, it doesn't stick to it. The aluminium housing was then spun in the lathe for drilling. I could easily maintain a straight hole within a thou or two.

    Afterwards a turned brass rod was pressed into the bore after being threaded at both ends, then assembly took place.

    I made a couple of hundred of these items. However all the jigs and tools were passed on to the company contracting me to do this work, so I'm sorry there are no pictures that I can show !
    that was a good idea baron. Well done

  4. #19
    Join Date
    Nov 2019
    Location
    NE Victoria
    Age
    75
    Posts
    14

    Default deep hole drilling

    Quote Originally Posted by mechdraw View Post
    I'm turning between centres at the moment, but it means I have to use larger diam material, just extra waste.
    I purchased a new, extra long series. "split point" drill bit, slowed the lathe down further and increase the peck rate, drilled a near perfectly straight hole 265mm long.
    Thanks to all for advice, it makes you think differently.

    Regards

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