Making a SELF-CENTERING Boring Bar for GHz Radomes
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- Опубликовано: 17 июн 2023
- I made this custom boring bar tool with a hand-ground Cobalt HSS cutter to thin out part of the inside bore of an expensive PTFE tube for an urgent RF-transparent 10 GHz Microwave Antenna Radome machining job. I bought the wrong size tube, the wall thickness was way too large. Can I recover my financial loss and still deliver the project on time?
The radome was far too long to line-bore on my Colchester 1800 lathe. The walls needed to be thinned over part of the length to reduce RF interaction with the 10 GHz microwave waveguide slot array antenna inside the radome. PTFE is about as rigid as Jello, so it was amusingly challenging, and I nearly messed it up completely.
Lots of machining action on the Bridgeport mill and Colchester lathe.
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Wouldn't it have been easier to set up your own hydrocarbon polymers lab and make a fresh batch of Teflon?
That's a lot of effort to avoid doing the right thing and buying a bigger lathe 😂
Teflon is an interesting material. The properties, in specific areas, are so incredibly beautiful that we think it must be like any other plastic otherwise and be easily machinable. The problem is that there's no such thing as a free lunch. As far as a material, it squishes, flows, compresses, and moves out of the way of any cutting tool, and otherwise should be assumed to be warm taffy. It's simply the worst material to work with, as far as I'm concerned. You're not the first person to make similar assumption, so don't feel bad. Being wiser now, if I absolutely had no choice but to have to do what you did with what you did, I would reinforce the outside tube with a reasonably snug metal sleeve to make it move a lot less. That won't solve all the problems, but you don't have a rod of taffy anymore. The cutting tool must be very sharp and take off a chip thin enough to prevent the tool from pulling the work up into the tool. Mind the rake angle . The sharpness minimizes the amount of material compressing under and relieving itself behind the cutting edge but will take a dive into the work if too aggressive. Keep your tolerances sloppy and you won't be disappointed.
"... please click the like button so RUclips will impose this on other unsuspecting souls." I don't think I've clicked like so fast before; I absolutely love the way you phrased that!
Machining teflon accurately is certainly a challenge. As you said buying a tube with the correct wall thickness makes it easy. Really appreciate all the steps and tools you used and your approach. You do need a steady rest! I don't know if you know this but Amy has her own channel and looks forward to getting material for it at your expense. Cheers!
Seems like a lot of time and money spent to transform an expensive piece of material into a less expensive piece of material 😉 .... Nonetheless, a great custom deep boring solution, thanks for sharing how you worked out some challenges.
I've just had a rare go on my lathe... and i noticed something rather disturbing... all the swarf from the drilling operation leaped out of hole with a "weeeee" and my cutting oil now makes a squelching noise when I apply it.... WHAT HAVE YOU DONE TO MY MIND?!?!
I do not know why I like machining videos so much.
Wow that PTFE tube must have cost a fortune!
I thought of you when I saw a 8" x 3ft log of PTFE at the local industrial surplus store. They wanted several hundred dollars for it, but I'm sure that was a good price.
Love these videos, they're informative and funny ay. 👌👏
I would have thought the generous chamfer would have been enough clearance for the base of the spiggot without having to drill some extra relief.
Time saver - Stub (Screw Machine) Drills were created to eliminate spot drilling holes when drilling thousands of holes with those incredible machines. Nobody wants to hear it, but it is in most every tool supply catalog stating that as their purpose.
I would've liked to have seen a threaded insert 'spinback' boring bar exiting a mounted draw bar.
7:30
Beautiful tooling, but lots of expensive chips (ribbons).
That is impressive :)
LoL I'll take your sort of mistakes any day. Mistakes in my shop generally come with a moderate risk of dismemberment, puncture, burns (either friction or thermal), laceration, and or contusion. That's not to mention the variety of emotional injuries caused by general inattention. I think I should take up knitting, for my health.
Nothing to worry about. Your secret is safe with me :)
... is this the mechanical equivalent of taking hours to make a script to automate a task that would have taken max 1 hour manually ?