Making a SELF-CENTERING Boring Bar for GHz Radomes
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- เผยแพร่เมื่อ 17 มิ.ย. 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?
Undoubtedly! This comment wins the internet today.
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.
I often have to turn 2mm and 3mm diameter tuning pips. They are a nightmare. I even tried freezing the material and using freezer spray to see if I could get it below the glass transition point for long enough. On the second part, the cut went really well, but I'm certain that if I could find 2mm or 3mm wall tube at least 42 mm diameter that I'd use that and make a mount that clamps it inside and out. Still, it was a load of fun, I'm making five more of those parts, then Never Again! Fibreglass with a good RF resin , plus a foam fill is the way to go next time, and I'll machine the slot array from aluminium and anodize it.
This really makes me wonder how radio transparent Delrin is? It machines easily in comparison, but I don't know what it's dielectric properties are.
@@UD503J see my other comment!
That's a lot of effort to avoid doing the right thing and buying a bigger lathe 😂
I feel seen!
"... please click the like button so TH-cam 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!
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?!?!
You are lost, that's the End Times approaching. Bring on the Singularity,
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 have got all of that PTFE Angel Hair now though, that must be expensive to buy, given the price of that plumbing tape.
Wow that PTFE tube must have cost a fortune!
Two metres was about £80 delivered I think. I can make five radomes from that, so the unit cost is quite reasonable. I can rattle them off quite quickly now of course!
@@MachiningandMicrowaves Thats no where near as bad as I thought, we obviously pay through the nose in New Zealand
I do not know why I like machining videos so much.
I have never machined anything, but I do love making Rc toys.
they are from kits Thow.
I love watching them too. No idea why, they just scratch an itch somehow
Love these videos, they're informative and funny ay. 👌👏
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.
Fantastic price!
I would've liked to have seen a threaded insert 'spinback' boring bar exiting a mounted draw bar.
Beautiful tooling, but lots of expensive chips (ribbons).
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.
I wasn't sure how it would perform so I went a bit over the top. Seems fine, and you're right, I could have got away with less.
7:30 nice continuous chip there...
stringy.... I was standing a few paces back and guiding that chip into the waste bin. It wasn't as spectacular as the flying HDPE ribbons I often produce though. They fly without the need for manual guidance.
That is impressive :)
For a bodge job, it's kinda averagely not terrible I guess?
@@MachiningandMicrowaves It works at the end of the day!
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.
And otherwise, nicely done!
I have trust issues I guess! These are really nice split-point high-cobalt HSS and they're beautifully ground. I get them from Drill Service of Hawley. Why I think that using a cheap centre drill makes any sense at all is hard to say. I'm going to hide the centre drills and use them for drilling centres. Thanks for the reality check, sometimes I just do things from habit!
That reamer at 16:52 looked pretty wonky, but I know nothing
The flutes and shank are well aligned, but the reduced shaft is definitely off to one side. Doesn't matter of course, it's the shank to flute alignment that's critical, although for larger reamers I use a fancy reamer holder than can float laterally
@@MachiningandMicrowaves thanks for clarifying that, the actual cutting bits do look nice and straight
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.
Oooh, those long pointy knitting sticks could do you a mischief. Macrame might be less risky
@@MachiningandMicrowaves Good point 😁
@@mackdog3270 Heh heh!
I would've thought that you'd make a line boring tool, that would've worked as well and you could've flipped it end for end with a round cutting bit.
I couldn't work out how to grip the OD of the tube without making a long vee bed or something to support it, but I could have used the plug approach with line boring as well. I need a longer lathe!
@@MachiningandMicrowaves Most lathe owners 'need' a bigger lathe.
@@Andrew_Fernie Universal truth indeed
Nothing to worry about. Your secret is safe with me :)
And yes, I undersand "hobby" and "having fun in the wotkshop".
Heh heh, I am SO happy that I don't have to earn a living from my terrible machining, Michel. That would spoil the fun completely!
I’ve seen various people mention these “bright boy sticks” for debuting, but can’t find a source for them. Are they actually different from regular Cratex rubberised abrasives, do you have any suppliers? I’ve used Garryflex as well but like you say it’s a bit crumbly!
My original Brightboy polishers were parallelogram shaped abrasives that were designed for cleaning the tracks on model railways. They just happen to be the precise texture and hardness that's perfect for polishing threads in brass and stainless and Tellurium copper. Garryflex is too crumbly and the Cratex bullets I have are rather too hard. I see them occasionally on ebay in the US, but the carriage makes it impossible. I've bought every one that's appeared on UK ebay, but that's only three in the last eight years!
Is there a reason why you needed a precision machined teflon tube, instead of protecting the antenna with $9 of PVC pipe and endcap from the hardware store?
PVC is a very poor dielectric at microwave frequencies, so it would absorb some of the signal, also it crumbles after a few years exposed to UV light from the sun. Polyethylene pipe is a better RF performer, but it's not brilliant long term with UV and weather. This installation needs to last 25 years or so with minimal maintenance
... is this the mechanical equivalent of taking hours to make a script to automate a task that would have taken max 1 hour manually ?
Pretty much, although the job was urgent and I couldn't find a supplier who could get stock to me in the UK at anything close to a reasonable price. I'm sure there are much better solutions, but I'd had a bottle of Porter from an excellent local brewery, and I thought "why not?". Turns out there are good reasons why not, but I did it anyway.
@@MachiningandMicrowaves But that's where the fun is.
There is something so thereputic about watching this stuff!
Heh heh, wait for the next one in this series, I had to get the rotary table and boring head out. In other news, I'm talking to the CNC vendor next week about getting an order placed so I can do compound curves and arbitrary surface profiles.
What do the different colored bands on taps mean?
Yellow is for general use and low strength steels, red's for fancy alloy steels; blue is for stainless steels and some exotics (I think), white is for cast iron, sometimes black is for aluminium, and there are a few other colours depending on the manufacturer. I always check the manufacturer's data sheets and label any that are really weird. In general at the speeds I'm tapping, yellow and blue work on most materials
I wonder if one could make a kind of air bearing in the part tbat rides the inside of the original tube thickness...this might make it useable in some other materials, also....and...if you had an "end cap" that fir inside the new diameter, and could slide on the length of the tool's main bar, it would keep that thin tubing from wandering after itps cut to size?
I'm making a vacuum chuck which has a rotary union to pull air through the headstock, so I could probably use that in reverse, but it would need a wild amount of pressure and flow rate unless I could fit some sort of piston-ring seal perhaps!
On the second tube I made, I tried to use a disc to keep the end of the tube from wandering and it sort of worked, I can see that a tapered or stepped plug would work, I'll try that on the third one!
Now if you added a tapped hole to the front of your boring head (or several), you could have replacable discs on the front as pilots for different starting diameters. Nice job though.
That would have saved me from the problem I caused by changing the stickout! Excellent thought
@@MachiningandMicrowaves I'm surprised that your highly intelligent computerised sidekick did not point it out in disapproving or exasperated tones...
@@occasionalmachinist AIMEE is equipped with the latest beta version of 20-20 hindsight. I'll raise a bug report to the vendor
i wonder, if you had a through hole and it was fed pressurised air from the back, and some nozzles...could it self center in the cut?
Depends on how big the gab between the tool and the wall of the part is
Air bearings need very tight clearances and the tube is juts an extrusion, so the tolerances are all over the place, but as the diameter increases, that just might work, as the walls would tend to form a perfect circle under pressure
@@MachiningandMicrowaves probably works better in a enclosed macine using hig pressure coolant
But when you have access to that we woud probably not have this problem in the first place
I think you forgot to put a link in the description for that lovely brown gunk
Aaargh! Yes I forgot a load of things in the description as well as messing up the compression and limiting of the machine shop audio
Only available from Amazon UK I think, link is now in the description
Silly question, but does regular 50mm solvent weld waste pipe have sufficiently inferior properties that you couldn't use it? Seems like a very expensive plastic sleeve! Also I think there's some audio issues in the first machining section?
aaargh, I thought I'd triple-checked all of the audio segments dammit. I'll have a listen and mute it if it's annoying. Polyethylene pipe is fairly good, but I don't know how well it lasts in sunlight if it isn't full of carbon black (bad). PVC is terrible stuff and falls to bits after a decade or less.
Oh dear, I see what's happened, the audio track for that bit is on the wrong audio track and that track has compression and limiting applied, but then the overall gain is dropped after processing. Shouldn't be, but it was to stop the generated noises from being overpowering. I just need to listen through the entire thing every time I make a minor change, but life is way too short!
Aren't those spiral taper taps just the Shizz!
For curiosity, why not PVC or ABS pipe? Do those conduct at all?
Both are absolutely terrible dielectrics at microwave frequencies. Choices are HDPE, UHMWPE, PU, Cross-linked polystyrene and a very small number of others in solid plastic, or alumina (!) or sapphire (!!!) or a very thin GRP material, but it has to withstand repeated temperature cycling, strong wind, hail, rain, freezing fog/icing and permanent UV irradiation from the sun. Thin polyester GRP with a PU foam fill is probably the best compromise
@@MachiningandMicrowaves Thank you, Neil. I have a non-trivial quantity of ~50mm diameter acetal round bar I acquired after a foot/meter conversion error favoured me; if you're interested in a piece I'll gladly mail you one.
Shoulda just returned it. Too much time and effort!
Im editing my post because, on the other hand, its great content!
I would have had to pay return carriage, and I thought it would be an amusing challenge. Now I have four more orders for similar radomes, so the tool is paying back some of the effort. Once this tube is used up, It might get adapted for something else, but sets of 100 mm x 16 diameter rods that screw together are bounds to be useful for SOMETHING...
@MachiningandMicrowaves That's terrific. When I think about is, it's not the easy, simple and convenient solutions that enrich our work and lives, it's the challenge of the tricky and inventive workarounds that brings satisfaction and a sense of having solved a problem. Apparently, it is on TH-cam as it is in life.
Your ingenuity and cleverness is always worth watching.
Spanner....wrench.... when i was taking a training session in München, many years gone by, one instructor could not be talked out of telling us to use a "12 mm key" for taking a nut off of something, because, sure enough, a spanner is a wrench is a "key" in German...
All i read was: Making a self sealing stem bolt......
More Boring that that, sorry
Spotting drill? plug tap? Now you're just showing off.
I have to walk AT LEAST six paces to open the drawer where the spotting drills live. Well, maybe five. And I have to open the drawer and the carefully-labelled containers they live in. Might get oil on the labels. That would never do. I have some lovely carbide spotters, 6 mm and 3 mm. Total joy to use, but instead I picked up the cheap HSS centre drill that lives on top of the tailstock. I need to have a word with myself.
Well as long as this doesn't devolve into a lean manufacturing rabbit hole I think you'll be fine.
@@Leadvest Zero danger of THAT
I mentioned it as a reply to another comment, but does anyone know the dielectric properties of delrin? It machines quite easily in comparison.
White pure POM usually has a tan-delta at 10 GHz of less than 0.01, sometimes as good as 0.006 at room temperature. Compare that with PTFE at about 0.0004 or cross-linked polystyrene at 0.00045 or HDPE and polypropylene at 0.0001. It's a little better than ABS, much better than PVC and a little worse than PMMA or polyamide. So about 15 times more loss than PTFE/Rexolite and 50 times more than HDPE. Rexolite machines really well and is rigid. For thin sections, lossy materials like Kapton are fine because their mechanical characteristics allow very thin films to be used, but for several wavelengths thickness, the losses in Delrin or Nylon or ABS are a problem. When you are chasing the last 0.1 dB or performance, you need high performance materials, but if you have a transmit-only system with excess transmit power available, you could use Delrin for lensing, although not the carbon-filled version. Also I'm not sure how long it lasts in UV light or if it absorbs water like Nylon does. Water is very lossy even in small percentages
So much tapping, so little chip clearing!
Neil are we supposed to not have noticed the fact that you did the work to use the MT3 in your tailstock, and then the video shows you clearly using a collet chuck in the tailstock to hold it? :)
I only used the MT3 for the last section as with the collet it's much easier to tighten the sections by rotating them in the collet. The last section is a bit of a nightmare to tighten up!
I saw nothing at all....
Me neither!
Man orders wrong stuff and then spends 40 hours machining bits and pieces to turn the wrong stuff into a wobbly version of the right stuff, but gets away with it because he left 40mm of the original thickness at the bottom almost as an after thought and therefore calls it bespoke.... Superb!
Question - You used a lot more cutting lubricant in this video than I have seen previously. Is that due to the hardness of the steel you used?
That 40mm of thick wall makes for a very solid fit into the mounting collar. It could have been planned! So far it seems to be working as I've been able to receive the 10 GHz beacon signal from 342 km away every day since it was installed. I tend to avoid using lots of lube when I'm filming, mainly to give a clearer view of the cutting process but also I don't have to run the noisy smoke extraction fan or worry about getting oil and water on the camera and lenses. I use lube a lot more off camera, either from a sprayer, pressure mister, coolant pump or brush. Some carbide tips are designed to run dry, sometimes I use an air blast from a Noga Cool Mini to help clear chips away so I don't end up recutting them, but that's mainly on the mill. Short answer is "it depends...". I use coolant with Titanium so it doesn't catch fire
@@MachiningandMicrowaves that's excellent. Are you receiving via a dish and sat. LNB?
@@theradiorover I have an EME waveguide LNA, then waveguide relay, then a Kuhne transverter that I built from a kit. I made a Pickett-Potter feedhorn for the dish to get the best sidelobe performance. Dish is 95cm steel perforated offset parabola. For portable I have a folding 18 inch steel dish that's sturdy and won't bend when I bash it.
You know you can always go on the game, and/or sign up to OnlyFans, should you find your financial reserves dwindling... 🤣🤣🤣
Excellent work as always Neil, great to see you wielding the tools in the workshop.
Question, and I apologise if this is an idiotic one, but why not just take the excess wall thickness from the outside of the tube?
Right, I should have explained that. The issue is that putting a curved dielectric surface close to a waveguide slot array acts as a focussing lens and also detunes the slots a little, so thinning it from the outside when it's designed to run in free space end up affecting the horizontal directivity and return loss. Thinning it from the inside leaves a larger radius curve that's 4 mm further away from the antenna face. There is still a detuning effect, but it's not significant, and a small adjustment of the matching screws fixed that. Full details of that on my OF page.
The antenna system and mounts are now installed down in Somerset and when I checked this morning, I was hearing a strong signal from the propagation test beacon over a 342 km path from here almost at sea level in the Vale of York. Beacon runs 1 watt to a slot array, I was using a 95 cm offset dish at about 5 metres up on my pneumatic mast, with a Pickett-Potter waveguide feedhorn, flexiguide and waveguide relay into a waveguide LNA designed for moonbounce. It's great to have that beacon back to be able to check for troposcatter, ducting, aircraft scatter and rainscatter on 10 GHz
@@MachiningandMicrowaves Ah, that innie vs outie material removal makes perfect sense now.
"When I made my mistakes" goes the opening line of this video, and when one watches it with CC on, then... Oh yes, I'd certainly agree, Sir. ALL the subtitles shown in the first second of it, and then... nothing - nothing whatsoever for the whole entirety of it. How fitting, indeed...
Working fine for me in Chrome on Windows 11 and my iPhone. Timings are correct in the CC configuration too. I think TH-cam had some glitches a few weeks ago where this happened, but nobody else has mentioned it for this video. I wonder if they are doing engineering changes? Which browser and OS were you using? If you restart it, does the fault recur?
@@MachiningandMicrowaves Thanks for your response and explanation. Well, I'm kinda an old-timer, y'see - Mac, OS X 10.9.5, Firefox 78.15 (can't get any higher on this machine and OS - and frankly, I don't... well y'know, don''t ya? ;-)
So yes, it might be some glitch with either YT, my browser, or it's just time to die for myself, but then again this doesn't happen "normally".
Sometimes videos starts with CC on, by default, sometimes I switch then on cuz my hearing is just as good as my rusty-trusty 15-yrs old PowerMac, but I hardly ever see such "all in one go" CC issue.
But hey, don't pay too much attention to my complain, I'm just an old farty knocker. Cheers ;-)
@@MrKotBonifacy My Macbook died so I can't check, but I'll ask around to see if anyone else is getting that glitch again.
@@MachiningandMicrowaves Actually, "fuhget it". I just saw your reply, decided to make a screenshot and sent it to your email address (one provided in "About" section), and... fork.
The video opened with German auto-translated CC (another recent YT glitch - it turns on auto-translation based on "recently watched" videos, I guess - which could be English, German or Russian ones), but those German CC were displayed properly. I switched it back to English, and those English CC were also displayed correctly now.
I just thought it might also have something to do with me "overloading" my browser - as of know there are 54 windows open, with anything between 5 to 15 tabs in each of them, and Firefox isn't the greatest browser when it comes to resource managing to put it mildly. (And to put it less mildly it's a CPU hog, and it seems like the ad blocker is trying to fight ads in all those "undisplayed" windows and tabs all the time, which forces me to force quit some of those every now and then.)
Anyway, the issue seems to be gone (for now?), so no need to bother. Thanks for your attention to it anyway. (Also, I'm leaning toward considering the possibility of getting a somewhat newer Mac, but this eventual decision needs to go through the proper evaluation process, so don't hold your breath ;-)
Actually, saying "M8 x 1.25 mm" or "M6 x 1 mm" is a rather redundant pleonasm ;-) It's like saying, say, "A4 page/ sheet of paper 297 x 210 mm" since "A4" (or A5, A1 or any other "A") already defines the size - ditto for metric threads.
Standard M6, M8, M10 (and all other "Ms") have their pitch specified, or fixed (in this case 1, 1.25 and 1.5 mm respectively), and adding the pitch size after the "main diameter" - be it M8, M12 or M36 - is done only for fine(r) threads - like, say, "M10 x 1" (a standard thread in lighting fixtures; note the dropped "mm" - as specifying the unit is also unnecessary, since the "M" at the beginning already says "metric thread" - thus all sizes are in mm).
It's a nitpicking of sort, agree - still, it sounds kinda funny for "metric" ears. But hey, it won't harm nobody ;-)
A significant proportion of my audience use imperial units natively, and a lot of the threads I use are non-standard fine pitch like M12 x 0.5 or M8 x 0.5 or M12 x 1 or M22 x 1. To be a bit more inclusive for folks that aren't machinists and engineers or native metric users, I tend to over-describe my threads deliberately. I suspect a fair proportion of UK viewers older than me, and a pretty large fraction of casual viewers in the UK or US wouldn't be familiar with the standard pitch of an ISO M8 thread. Of course, I suppose I could instead quote M8 as 0.315 inch x 20.32 tpi, but there lies madness.
@@MachiningandMicrowaves
_"A significant proportion of my audience use imperial units natively"_ ...
_"To be a bit more inclusive for folks that aren't machinists and engineers or native metric users, I tend to over-describe my threads deliberately."_ - well, that makes sense. I guess being a "metric native" makes me tad biased, or blind/ ignorant of "imperial lot" viewpoint...
But yes, "nothing too strong ever broke" and over-describing won't hurt nobody either - but then I guess for them "true imperialists" that "0.315 inch x 20.32 tpi" oddball number would still make more intuitive sense than M8 x 1.25 mm... probably.
Maybe you could just put a hard-embedded "fully imperial" conversion (like the one above) while saying "M8" only in the narrative? Whad'ya think, good idea, eh? ;-)
Never mind, it's Sunday evening and I guess I just have too much free time at my disposal right now. Do as you please and see fit. Cheers!
@@MrKotBonifacy Yep, I have to be at the Day Job in 10 hours time, working as a wage slave so I can feed my machine tool purchasing habit, and I've just discovered that the small dovetail cutter I was going to use to make a critical feature of the next project is a 45 degree cut, not 60 degrees. The carbide-tipper dovetail cutter I have is too wide, so I'm tool-shopping as I can't take the workpiece out of the mill vice to do anything else.
I am pretty much unit-agnostic, I was taught in Imperial, Avoirdupois, Troy, CGS, MKS and SI, plus Angstroms. I think natively in barleycorns, acre-feet and parsecs. Nice human-centric units.
@@MachiningandMicrowaves Not sure you could call the parsec a human-centered unit, but maybe it's just me. Happy shopping anyway! ;-)
@@MrKotBonifacy I can measure the angle to a star at two times 6 months apart and see how what angle it moves by relative to background galaxies and know directly how many parsecs that star is away. Yeah, maybe not as intuitive as thinking of my garden with 30cm of water in it, or the UK/US size of my shoe in barleycorns (offset by different amounts per country of course).
Not having to mention "male grooming products"
Why,
Which male grooming products could he mean? 😆
I'm with you there
It's not just the intimate Lawn Mower, they also do nose hair trimmers like the Weed Whacker and lotions and unguents like Crop Reviver. Splendid and highly products I'm sure, but not quite core to my chosen subject niche, if you catch my drift. More suitable for Brandon Herrera to promote. Now THAT would be a sponsored video I'd watch. I'm still on my summer break, working hard on a load of new video projects and sponsor deals and doing a complete rebuild of my working spaces, I expect to be back in production next week
@@MachiningandMicrowaves I'm just in awe of your channel.
All the stuff that was impossible for me back in the day, seeing it happen.
I thought I was pretty sly when I cobbled together isolated polarity antenna mounts on the bumpers of my old beater cars and trucks.
Sometimes I think you take the long way to get attention from Amy...