Machining Metal Membrane Strainers for a Secret Project

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i need to stretch some metallic membranes  almost to the point where they rupture   they're for a special project i can't talk about  yet but i am able to share how i made the membrane   stretching fixture be careful with that foil  it's only 10 micrometers thick that's four tenths   for any imperialists in the room the tensile  strength is only about 200 megapascals dagnabit   muskie, foiled again i've lost count is that the  seventh or eighth time you've messed it up so far   as AIMEE said the foil is a copper alloy and  it's about half the thickness of household   aluminium baking foil i need to stretch it  beyond the elastic limit so work hardens and   becomes extremely flat it has to be stretched  radially rather than linearly so i designed a   fixture to clamp the foil over a void and then  force a radiused polished stainless steel piston   against the foil to stretch it in all directions  at once first steps making the piston for a piece   of 316 stainless bar i don't know how well it'll  machine and i'm trying a new yg1 insert from   cutwel that's designed specifically for good  performance on stainless i didn't take a deep   enough cut off the face so i'll try some  more optimistic cuts to see how it behaves it's not dumping much heat into  the workpiece although the chips   aren't coloring up like carbon and  alloy steel does i can see there's   a bit of tool deflection those spirals in  the machined surface are a dead giveaway taking four millimeters off the diameter  it's two millimeters depth of cut   seems to break good chips as long as i keep the  feed rate high i'm not over impressed with the   finish though it's definitely nothing  like the finish i can get on 4140 and   tool steel using a similar depth of cut and chip  load useful data for a future application anyway oh nice chips right now i'll face off using a polished insert  intended for aluminium as i know they'll give   a very good finish with light cuts in stainless  i need to hog out a pocket into the face of the   bar so i'll drill it with some cobalt split point  drills to six millimeters then 12 millimeters and   then move to a 16 millimeter two flute end mill  and finally a four flute 20 mm roofing end mill as expected that's a  reasonably good surface finish that's a nifty sheepskin taper  wiper available from all good stores i'm using the big jacobs ball  bearing chuck on an mt3 taper now this next step is going to alarm some folks   but it's a safety measure because  i'm going to be doing something   sketchy next disclaimer time do not copy  what i'm doing here as it is all ill-advised i do love this comedy size center  drill it must be half an inch diameter yes i know i shouldn't be using it in a  drill chuck but this material isn't grabby   and i've got one foot on the emergency  brake the tail stock doesn't have a draw   bar so even if it was in a collet chuck it  could still grab the chuck out the mt3 taper well that was surprising that four flute high   speed steel rooughing end mill cut the  stainless very cleanly with no chatter   unlike that coated two-flute job  which screamed like a banshee doesn't this little 12 millimeter boring bar  came from Arceurotrade it was very   low cost perhaps 15 pounds it's using a ccmt060204   insert which is the usual polished and  uncoated carbide for aluminium that i like now for a trick i learned from my dad when  he had a scrap end mill or radius toll with   one or more broken teeth he'd bring  them home to use on his little lathe   this is an almost new four millimeter radius  cutter it should do very well as a form tool   to make the smooth radius on the edge of  the piston so the foil can flow over it i'm moving the tool radially and  axially so that i don't get any chatter   if you just try going straight in the cutting area  so large that thing yells like a yelling thing i'm being extremely careful about not allowing the  scotchbrite to get into a position where it could   wrap around the work piece or catch on the lathe  polishing fine details like this is potentially   very dangerous indeed i use small pieces of  abrasive tiny bits of aluminum paper or small   blocks of brightboy or cratex and i  stay highly aware of what's going on   that's shorthand for if anyone feels the  need to yell at me in capitals about how   i've definitely lose body parts from doing  this please don't bother trolls gonna troll off camera i reposition the tool to round  over the top and inside edges and then give it   another polish finishing with some extremely fine  diamond paste in fact i think it's safe to say   i think that'll do the piston needs an m6 threaded  hole through the axis i'm going straight in with   a five millimeter cobalt split point stub  drill from drill service as i've got plenty   of tolerance for concentricity those drills  self-center really well my dad used to hand   grind split points that were a work of art he was  a tool and cutter grinder after all sadly it was a   learned skill and not a genetic trait so i haven't  inherited that ability whatever mr lamarck says   fair to say you're almost as bad at grinding  split points as you are at tig welding that lovely ear wax on the tap  is ct-90. it's an unattractive   shade of brown but sticks like a  thing that doesn't come unstuck   it also makes taps glide through even  quite horrible material marvelous and that's my lovely starrett 93b tap  wrench it's an absolute joy to use   if i remember i'll put a link in the description  the taps are spiral flute m6x1 it might be a Volkel the length of the piston isn't a critical  dimension so i'm aligning the right edge of   this 1.5 millimeter mgmn parting  tool with the top of the curve   then taking an extra half millimeter  that i'll machine to size later so far so good i'm quite liking this  316. it's got a reputation for being a  

bit tough but actually it's machining beautifully right then it's fixture time i'm making a  mandrel from brass facing it then fitting   an m6 thread for the piston to screw  onto so that i can machine the back flat that's an m5 stub drill for the m6 thread i drilled and tapped the hole rather deeper than  strictly necessary of fitting a short grub screw   or set screw down the hole to act as a stop for  a longer grub screw i could have jammed a bolt   in and then sawed the end off and machined it to  length but the box of stainless grubs was nearby luckily concentricity is not important  because i'm only making the back flat   if i'd done this properly i would have single  pointed a thread on the end of the solid bar well i think that passes muster it'll get  a final polish before it's actually used   but i think that's nearly good enough i'd be  really grateful if you could click the like button   it makes the youtube algorithm ever so happy and  then it'll show this video to loads more people this is my splendid chuck stop from edge  technology link's in the description the   parallels are able to move a little to  ensure they're flush with the chuck face   i like it because it's quick to deploy  and doesn't need any changes to the chuck this part is going to be the clamping  ring that holds the foil membrane down we start by facing it off for no historical  or cultural reason at all is that better it's time for a huge apology for the next 39  seconds of blurry video my inability to operate   a camera is legendary the focus was probably  fine for anything buried 30 feet below the floor i can't reshoot the footage but if i  miss it out there's a gap in the story anyway that's the body and  clamp ring surfaced and faced next step's to clean the faces with acetone and  use little high viscosity ca glue or super glue if   you prefer to fix the clamp ring to the body so i  can machine them and ensure they remain concentric what are the chances neil's thumb will be glued  to the work piece where are your nitrile gloves well the cap is a bit wobbly but there's  more than enough material needs removing the seam's almost invisible i like the way the  glue doesn't run and drip like some ca glue does   i've lost count of the number of  pairs of jeans that i've ruined that's a decent finish as well  now i need to drill and bore   out the center of the body and  hope the cap stays glued in place   fingers crossed well actually not  makes it very hard to operate the lathe i'm taking easy steps up to 11.5 millimeter  drill and then i'll use a 12 millimeter   machine reamer to finish the rear bore. ominous  foreboding as quinn would intone at this point the front part of the body and the ring need  opening up to about 35 millimeters but although my   confidence in that glue line is rising i'm still  going in steps 17 milli first then 20 and then 25. that 25 millimeter drill does look  a bit brutal for that small part   and it's singing a bit too much for my liking but  it's sharp and it's removing 2.5 millimeters per   side without breaking the glue line also i've got  excellent 3m ear defenders hashtag not sponsored i'm not going to risk using my giant  drills i've already used up my entire   store of good luck with that 25 millimeter  so i'll remove the rest of the stock using   a boring bar with the same ccmt060204  insert that i used on the stainless piston the tolerance on this hole doesn't justify the use  of my spi 25 to 30 three point bore mic but i'm doing   some tests of tool deflection against feed rate  depth of cut and spindle speed in my never-ending   quest to hit the dimension of every part i  make smack in the middle of the tolerance range   so any excuse to gather a bit more data it also  means i can check the calibration of the ancient   1980s new all digital readout on my equally  ancient lathe the dro uses a lot of ttl chips   doesn't have a processor and it's very  analog it's still going strong after 40   years if you don't know what ttl is try  asking a techie who was born in the 50s the hole needs a proper chamfer  on it rather than just deburring   so that the piston will drop straight in this new wall uses original spherosyn scales  which are a marvel of old tech working rather like   a linear variable differential transformer but  using a stack of precisely machined ball bearings   measuring the phase difference between an incident  and an induced oscillation damn clever stuff i'm leaving the ring glued to the  body so i can drill the bolt circle   in one set up for the ten tapped  and clearance holes spoiler alert   close your eyes and count to five if  you don't want to see into the future you didn't really close your eyes  did you safe to open them now anyway this little part screws into the piston and  acts as a pusher and a rough alignment bearing   it needs an m6 thread on top  to fit into the piston thread   i'm not single pointing it as it's not a  high tolerance part the split dial do fine a quick check to make sure everything  fits and then we can part it off now it's time to put the dimple in the end of  the push rod and make all the other parts but   that'll be in part two which will be up  there quite soon oh i love cliffhangers

2022-06-03

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