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Thread: deep hole drilling in Acetal
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30th Nov 2019, 09:45 PM #16
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
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30th Nov 2019, 10:57 PM #17
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.
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1st Dec 2019, 11:00 AM #18Most Valued Member
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1st Jan 2020, 08:44 PM #19Novice
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