Spinning Metal - Part 2! - GODOX Strobe Reflector Build 

I love watching people upload their failures. Not because you learn more by owning up to your failures, just because it makes me feel better about myself.

Hey TOT, at my machine shop we do a lot of metal spinning, normally we work with aluminium, stainless steel and mild steel, but all this material when we order it we have to order it in a special order because it most be a in your case aluminium for spinning. But talking about the technical stuffs. For start before giving the final shape, you have to do a kind of bending like 10° for the side of the tailstock, and after that with a big round bearing you start spinning the material with some hand soap, but we start from the center to the top but this step ia just to stretch the metal for the final shaping you most do it with a egg shape bearing for that and more soap ( in titanium we use to wet a little bit the soap. Be careful with the force you apply in the material, because in some thin material it can broke from the center ( ah, and by the way, normally we have a spring load tailstock), that because as you start shaping the sheet the forces that you apply make the sheet go finer and finer, normally at our machine shop here at Portugal in aluminium sheet of 2mm after getting the final shape it gets 1.6/1.7mm. That why we order special material because aluminium sheets for metal shaping use to have 2.15mm instead of 2... because of the compression... Hope to be helpful.

My Father (who's now nearly 90) has talked about "the old guys" that used to do metal spinning where he worked for his whole working life, he said they all used to just stop working whenever anyone else walked into their room and if you ever asked them anything there wasn't a chance they'd let on any details. Over his working life he probably learnt pretty much every metalworking skill there is but he still calls spinning a black art.

Sometimes the path less traveled is overgrown for a reason but we can't deny it's appeal.

I struggle with just buying bowls myself. really the most efficient way is to just place the blank near a coconut tree wait for a falling nut to perfectly shape the bowl. WAY easier than all this lathe stuff!

First off I (clearly) am not an expert on metalworking. However as Physicist I've a few thoughts. Currently its looking like you work the middle exclusively before eventually getting to the outer edges. The commercial machines I've seen work along the entire length. The latter makes a lot more sense to me - by working the middle you are reducing the radius. Thus you have an outer edge holding itself at a large radius, an inner edge at a smaller radius, and so the outer edge (with less strength) wants to reduce its radius and the easiest way is either the crinkling you've seen before or the buckling you're seeing there. Two ideas speak to me as a physicist, though I'm certainly not sure if either is practical. First would be to try to work the outer edges early and to work your way along the entire form rather than just the part you're focusing on. A lot of commercial methods use multiple steps with multiple die to slowly work down to the form. The other, possibly unlikely method, would be using a hard die and using some real force to squeeze the work. That way the diameter at each point is the same but the larger surface area is made up by thinner metal. Either way good luck, no matter what happens this is pretty interesting. As an aside, why not use the bearing to form the shape properly then do a final pass with the blunt stick? You get both benefits there. The problem so far is the blunt stick is imparting too much force dragging the work back which the bearing doesn't, and as the only part keeping it spinning is that little circle you've got a problem, especially as you move further out and impart more force to it (force times radius). If you reduce the force, a lubricant like the wax you used, or you found a way to spread the rotational force, say coat the die in rubber, or you reduced the force on the ring, say loosen it a bit and accept it might slip, you might be able to just use the stick. I don't know a practical answer but I can comfortably explain what's happening. It would at least work as-is for smaller radii work which is comforting. Also its certainly not parabolic, it looks more elliptical. However if you're looking for more dispersion on the light you won't want parabolic anyway. You could scratch up the surface for more dispersion, though it looks like Ikea did that for you. The dimples in the real one have the same effect. The only problem with elliptical shapes is there are two focal points, the light from one will concentrate at the second and so you may get a differing effect with different distances. Still I'm assuming you're not at the focal point anyway so hopefully its just going to be a generally diffuse effect. You're of course going to lose a lot more light with your bowl flash, but I doubt that really matters and I'd imagine it works well enough. Another ghetto soft box for indoor use would just be holding up a white sheet between the flash and subject, light hits the sheet and diffuses and you can use just about any flash for it. Or aim it at a white wall, though you're pretty stuck with creative choices there but its useful to eat ramen noodles by phonelight at least.

I'm convinced that TOT, AvE, and Chef John are all the same guy just using different voices.

Im far from any expert on this subject, Ive done a month of metal spinning at my shop, but I can see a couple common mistakes. 1. Hemis have a habit of going tight then loose against the tool as you progress further. That being said, the absolute worse thing when it comes to spinning is pushing against a part of the sheet that is already on the tooling (Mandrel). What you should really do is hit it with a stick, if you feel like touching spinning parts feel it while you tap. That'll give you an audible (and physical depending on comfort, you dont really need to touch it but it helps) indication of how it's resting. The back up you see, the sorta lumpy bits by the spindle, is caused most commonly because you are pushing against a part of the piece that is restrained by both sides. When the piece is floating, the metal will flow a lot more freely. Thus you as you move along you should aim to have the metal in contact with the tooling in your back and to have air against the tooling in the front OR air in the front and air in the back. We do all sorts of weird spinning shit at my shop but thats the typical ideology. 2. The rippling is caused due to not fully teasing her along. For a hemi I would do a swoop. You want to sorta aim at making a lip. This reinforces the sheet and allows it to flow without rippling. Come in soft, push hard, push out, pull in towards you nice and soft away from the tooling. It's sorta the same motion as when you finger bang a chick. As you go along and more of the sheet is in contact with the tooling it doesnt really ripple as much and so then you would flatten the lip. You may also start well far ahead, maybe in the middle or last quarter, and take a light pass to reinforce the edge via a lip of the material before you even start to get the beginning flush. 3. You are taking too many very light passes. You want to get in there with as few passes as possible. As you take a pass on a hemi like this with aluminum often you will feel the tooling as you take the pass. The more passes you take, the more damage and nastyness on the inside and outside. When you get a good feel, the shit flows like liquid metal. As well, if you take too many passes it will thin you metal out more. Some cases you want to thin the metal for a certain spec, or maybe you're putting a light radii for reinforcement or other reasons. The fuckers in the back at my shop that do hand spinning are stocky mother fuckers, albeit short, and they were taught by a 6'4 250-300lb man who scares the piss outta me and Im a welder. 4. Handspinning lathes and turning lathes are sorta the same. Idfk enough about them, but it's mainly a modification of the toolrest to turn a turner to a spinner. That being said you get a very nice feel with "scissors". They're like the roller you have, but the roller pivots on a hockey stick (not actually a hockey stick, looks like one and make of metal) and the hockey stick pivots on the tool rest. That way you can easily change angles, you pull in with both arms and the roller moves forward, you can do all sorts of weird shit. That being said, METAL SPINNING MAKES NO FUCKING SENSE. It's like welding, you just gotta do. I did pretty good, I only did it during some down time, but it helps to have people who been doin it 15 years to show ya a couple things

At the last place I worked (making whisky stills) we had to convert a (much larger) normal lathe into a metal spinning lathe, to make some fancy Greek amphora looking bits to go between the pot and the neck of some stills. It worked after MANY trials and tribulations, and probably in excess of $1500 of copper wasted in R&D, along with a few thousand bucks worth of time, both in building all the tools to convert the lathe, and trying to figure out what the heck we needed to do - incidentally, the tooling we made had a much tighter arc on the turny-bearingy-thingy that contacts the work. Maybe a 25mm-ish, but oblong, arc. Dunno if that made it better or worse than yours with a larger radius though (getting back to the 'dunno what the heck we were doing' thing). We kept breaking off the centre of the copper also, ended up welding an extra turned disc of 3mm copper onto the middle, that helped it hold. Also worked out we needed to set up the oxy torch breathing fire on the lathe, to keep the part annealed the whole time. All in all, would have been soooo much easier if we could have just bought those parts. We ended up with MANY lampshades, which I think my bosses wife turned into bird baths.

LOL. I've made flash diffusers out of bowls from Ikea in the past, but mine look like terrible middle school science experiments compared to what TOT comes up with. Well done!

Oh man. Clickspring, AvE, Abom and TOT on the same day. Life is good.

Back when I used a press camera I had a monster portable flash with a lead acid battery. I really liked the results from the bare bulb when used in an enclosed room, natural shadows and sharp definition, like north window light. Try it, you may throw your reflectors away. I've watched spinners churning out air diffusers. They made it look easy. Tempering may be the key. Great video.

I work for a firm with two cnc spinning lathes (and a herd of sacrificial goats). The things are massive with a hydraulic power pack the size of ToT's time machine. I tried my hand on one lathe once , it seemed completely uncontrollable and likely to kill .Spinners are not human! The lathes do not use g code : the experienced spinner makes the part, controlling the machine with a knob and a joystick - they move the hydraulic rams that hold the forming roller in a manner that makes no sense at all to a humble turner like me. The lathe records the motion and repeats on command

o man, this video........... The first 1 minute 35 seconds. Brilliant. Just pure perfection.

Not being a perfect parabolic mirror is not too much of a worry. The lamp is not a perfect point source anyway. Not even close to it. And if using a diffuser a parabolic mirror is not any better than a half-spheric. Just make sure any light heading away from the diffuser is reflected back onto it, disregarding the direction of the photons when they hit it. So now that you have a buck, find a hammer and make the failed attempts fit the buck. You can even use the wooden tit as a hammerform and not just a buck. And i have now given you so many thumbs up that i have only 2 thumbs left of the 10 i started out with.

I should preface this comment by saying, I know nothing about real metal working or machining, but I am a theatrical carpenter. Take that to mean what you will. Regarding the center of your blanks breaking out while spinning; it looks like as you work outwards on the blanks they haven't conformed to the buck tightly enough and the blank bends at the interface of the buck and clamping face. As you know, aluminum fatigues quickly, and I believe this is what is happening at this point. Perhaps if the edges of your clamping piece were a more gradual taper, or if it was a softer material (rubber?) it would better distribute the forces and delay metal fatigue. Similarly, if you were able to consistently pull the aluminum away from this junction it may remove the side-loading of the blank that causes the fatigue in the first place. I realize this is probably a moot point as you've finished your piece, but I also suspect you're as annoyed by unmet challenges as I am.

I hate to tell you this, but your 99.9% aluminium bar isn't "uncut" - I can see the saw marks on the end. :-D

Me and my son have been watching your work when I put him to bed. I really appreciate your sharing your knowledge with us Tony. God bless.

Err............... have you tried annealing the aluminium? At school, 55 years ago, I did some metal spinning, using aluminium. We rubbed it with a bar of soap then heated it with a gas torch until the soap turned black. It spun like putty.

5:38 I laughed so hard at this xD Your editing is above and beyond, I am blown away by what you do on this channel time and time again ^^

At least you can make cymbals. That's not nothing.

Tony I'm in a precision machining class at tech right now and lemme tell you that we have every new hass machine in the books. You ignited the passion in my soul. I hope that ignition doesn't come close to our titanium cus then we have a problem

This saturday evening has just improved dramatically!

My mind was blown when you sliced the aluminum bar in half, string, fire, water... I'll never be the same !

Hmmmmmmmmm..... No. I will never ever spin sheet metal on the lathe! But I will send few bucks to You, cover the hospital bills :)

Tony, you need a holder on the opposite side... (a roller bearing holding the opposite side (180 degrees form the tool holder across the work)firmly in on the wooden mold...) As you force the tool on the material, it buldges back hence the reverse bend! Can be seen at 5:26

My dad used to work at the bronze plant over at Hobarton. He could spin 20 pairs of baby shoes in a day. He made school shoes for my sister too, but he could only make two pairs of those a day. The stiletto heels slowed him down quite a bit. He always said that bronze shoe-making was in the wrists. That advice never helped me one bit.

Unbelievable. Every video is entertaining no matter how simple the item may be. Although, simple, that doesn't imply easy to make. Great work around in the end, and the welding was pretty amazing in my book.

Man after long, long day it is truly a treat to find a new TOT video to accompany me and me beer before I fall asleep drooling on the couch. Love your stuff, always lifts my spirits and makes me chuckle.

There's no shame in repurposing something. That's called being resourceful. Being able to think outside the box is a trait that many don't have anymore. It's kind of like common sense. Which is becoming so rare, that it should now be called uncommon sense. Thanks for another great TOT video!

Jeeze, a new TOT video, a new clickspring video, how am I supposed to get anything done today?

'Hide our shame?' if my shame looked like that I'd be proud of my shame. I think there's a German word for that...

How come my garage doesn't play music for me when I'm working?

Hey love the video! I believe what is happening is the disc starts wobbling as it is worked around the form causing the aluminum to work harden and fracture around the center. I used to use an old wood lathe to spin mettle and I would use a Oak bar in my left hand behind the mettle while using the forming bar in my right hand to get a consistent turn. VERY DANGEROUS! But works well. I learned from a Audells sheet mettle book from the 1950s if you look online you can probably pick up a copy. Happy Mettle Shaping! Cheers!

Like the cake, the black bar is a lie. Became a Patreon but was unable to see behind it. Will still keep up the Patreon support ;-)

You, sir, are the Bruce Brown of metal working: "On Any Tuesday: Chips Akimbo!"... Always enjoy your stuff. Thank you.

I have never let not knowing stop me either. Recovering physically from it though...

I believe professional metal spinners dip their spoon in a lubricant. The one I saw looked like the consistency of motor oil. And I also believe they often use heat from a torch on their work. Also, great videos, Tony. You are awesome.

I've got the same monolight, it's a beast...could we get a TOT photo channel as well? As a matter of principle I don't watch photography videos anymore, but i'd watch yours!! 🍻

Tony,Buy some of the specialty sheet metal spinners grease.Sometimes orange in color.Thickly coat the whole disc with that.Use your roller tool (although the round nose tool would probably be better since you are not a cnc machine) and put only a little pressure going back and forth across the work from center edge to edge at a moderate speed heating the work from friction without yet trying to form the metal.The heating of the work makes it much more malleable to form under pressure and the grease keeps you from burning or scaring the surface of the work so there is a lot less post finishing work..After a few passes to heat the work,then with greater pressure and one or two every even and continuous swinging motions (depending on the complexity of the shape of your mold master) go from center to outer edge with the forming tool pressing hard to form the work against the mold master.Don't press too hard as you may pierce the work.Proper sheet metal spinning tools are much longer than standard wood lathe tools because of the increased leverage needed for this work.They are usually used with a multi position tall pin style sheet metal spinning tool post/rest set close enough to the work to allow the edge of the tool to swing the full span across the work face in one pass without adjusting the tool post/rest for more travel.But set up to have a big leverage advantage.There may still be a slightly ragged edge on the outer diameter of the work that a metal spinning cut-off tool can trim off.Or your metal lathe tools can do it.The safety guide hole in the center of the metal is unnecessary if you screw your tail-stock in tight enough.There are a couple of great websites that sell excellent sheet metal spinning tools,lathes, pre-cut sheet metal discs of the correct alloys and spinning courses on DVD if you look.But really what do I know?This is all just something I read off a bathroom wall in high school.Good luck.By the way can I get a patreon account so you can pay Me?

🎉😊 what a way to start Sunday.... ToT , Clickspring , AvE , Hudrolic press and Xynudu 👍 edit.. 2 min later add Codys lab and finally Alec Steleh has finished that bloody sword 😂

Have you tried annealing it? I'm not sure how often aluminium needs to be, but silver and copper will need annealing between each round of raising. A bowl like that will require at least 10 rounds of hand raising.

i am a simple man, i see a TOT video, i watch.

Tony, when you press on one side of the disc, it bends that side down, and the other side up. If the bottom of the bowl stays in place, you are basically just bending it back and forth until it fails. I bet you could get this to work if you could apply pressure symmetrically.

The production value of these videos is over the top. thanks for doing them. JUST because of you, I am considering making a patreon account :-)

That ring sound when you did the flash transition resonated with my tinnitus

That was weird, I was watching AvE, and then my This Old Tony senses when off and I cheched your channel for a new video, and sure enough new video, fuch yeah

The thing is, this is another super-duper and informative video. Tell your son from me that he did a great job.

Great stuff as always! I don’t know what the OD of the “bowl” is but would it be possible to use a closing strap (for lack of a better term) from a metal bucket to hold the diffuser on?

I have a pair of AD200s and LOVE them. I've been toying around with the idea of making custom reflectors and this video has inspired me. Thanks!

Ah This old Tony, always with the black. PAMPH! MY EYES!

Tony, I’m not sure if you will read this or not. It occurred to me that you’re working the large diameters of the bowl at the same RPM as the center. You wouldn’t do that with a turning tool. Calculate some surface speeds and adjust. When I turn parts over 20” I don’t mess with RPMs above 40 or 50. Slow it down out there towards the edge!

Most saladbowles are pressed, not turned ; ) Don't feel bad... ALSO YESSSS finally love to be a patreon!!

A couple of casual observations (Note: I have not done/tried any spinning myself, but I do have an understanding of physics and experience of metalworking); Try using two tools on opposite sides of the workpiece. --That way you'll balance the working forces and not put any torque on the spindle. (which is whats breaking the middle out) Try warming up the workpiece --a bit of heat will make the metal softer and easier to work; less stress on the workpiece/spindle.

Hold all calls to Victoria's Secret, because the "spun metal brassiere" thing doesn't look like it's going to work out.

Hey ToT, I work a lot of aluminum sheet metal every day, perhaps I can lend a couple suggestions? I can say that setting up a heat gun to keep constant 180 deg Fahrenheit on the area you’re working, it will let the aluminum sheet metal relax. One other thing that could help is a way to apply pressure 180 degrees out, so it’s not wobbling on the live center hub and work hardening the center. It could be just enough to allow you to finish out the edge without work hardening the center or the outside edge. Even though you made the bowl work, I’m still interested in seeing you succeed with this! This may not be the answer, but who knows? Sheet metal has interesting characteristics, especially aluminum!

I know that my smiles are usually expected in the morning but there still OK in the afternoon and late evening too so thanks again for the smiles. ( Your OK Tony ) :o)

I don't know anything about anything, but for the reverse bend you mention @4:50 I'm pretty sure we can see how it happens @5:25. When you apply pressure the blank bends up (away from the form) on the back side of the lathe. I think that's also making it wiggle back and forth on every revolution, right on the edge of the holding tool which is why it just fatigues and breaks there.

Patre..? SELLOUT!

4:56 Reverse bend is happening because when you're pushing against the metal on one side, it is curling up on the backside 180 degrees from where you're pushing. Evidence 5:53 Could you have made a concaved wood bowl to press the metal disc against the wood buck into a bowl shape? And then instead of welding the nozzle fitting, could tig brazing have worked? It might've prevented the weld-thru (whatever it's called when you burn through it.) In any event, great video yet again!

Tone. Really crankin’ Out the videos lately baud. Glad you got so much more success :):). The wife and I appreciate the videos.

I'm super stoked you did this. I tried doing something similar a few years back with some Bowens and Paul Buffs. I've said it before and I'll say it again, I'm glad you're a fellow Nikon shooter.

My Patreon is pretty crowded already, but there's always room for good ole ToT. Pledged :)

one other thing, use aluminum to make your molds as the finish of the mold is what will reflect in the final product, better you make it, better the outcome. Anything harder than soft woods will work but depends on the material you are wanting to spin.

Paused video, set up patreon, resumed video.

Tony,In one of my first engineering classes we got to turn a nice little dish similar but smaller than your reflector. The main tool was an old repurposed wooden base ball bat with a reshaped end. There were some smaller tools as well for rolling the bead on the lip. The buck was hard wood, clamped by another piece of wood with I think a rubber pad attached for friction. The blank was 4 ot 6" in dia dead soft Al with no center hole. I think it took a couple of pieces to get it to work. The trick was to go slow, use plenty of bees wax, trying to move the metal too fast was a disaster. Think the metal always needs to be stretched, don't think one can shrink the metal while spinning. Try starting with a smaller diameter piece then draw the material to the outside edge to get to your final size -- This was decades ago so the memory is a little sketchy. The dish had a Greek looking spun base as well -- the bowl and base were epoxied together instead of TIG welding. Sat on my shelf with keys and pocket coins for years and never came apart

oh no, this bowl thing again, im gonna get mad at somebody today.

I did electrical wiring in a factory where they were spinning aluminum. They did it exactly as you have done it, but they used a wooden rather than a a metal bearing on the aluminum.

Get yer TOT wok lids now!

Tony you need to push the material not only upward but also downward. It keeps the material a little thicker at the bottom. Also, when you get the material resting near the center first, you won't stress the Aluminium and it will not rip off

Melt down the ruined ones and cast them back into some rough stock

As a commercial photographer I can say thank god you pulled that attachment out. We were gonna have to have a serious talk about recessed flash tubes and geometry

@10:00 - "I always wanted a larger one", that's what she said!

I have to say I never cease to be impressed by just how funny your videos are.

Careful of the 10:00 minute mark, you're gonna be mind wiped.

I think applying pressure with two bearings 180° apart would help, and stop the torsion causing metal fatigue near the centre, also perhaps rotating them with a degree or two of tracking would apply a slight outward shear force to keep the material taut.

6:20 This makes my blood boil LOL 😂

tony! your patreon is skyrocketing! +43.000% in three days! your going to be a rich man! please bless us with even more videos, jokes, and msd editing skills!

11:04 I died.

This is great. I have the same lights and really wanted a larger Mola style beauty dish for my Godox. This gives me ideas...

I'm disappointed... Perfect chance for some Men In Black neuralizer references or jokes that you missed.

Nice tony! What about cutting some clear (rubberized?) tubing the circumference of the diffuser. The right diameter of tubing to slice it centered the entire length so you could slip it over both lips- the diffuser and the reflector lip. Might work nicely for a removable quick clamp. Love your videos man!

Did you just patreon on me? How dare you support yourself, sir!? I will be unwatching every ToT ever. Can u make a video showing how to play RU-vid videos in reverse? Then - then I will unwatch!

To prevent the cracking you have to form the part enough to get the buck to carry the shape. Quickly getting the center of the part against the buck will allow the additional shaping without constantly flexing your part. It's that constant flexing that causes those cracks. You can also try some annealing, but honestly I would master the concept of getting the metal to fit the center of the buck first. I learned this the hard way (probably why I remember it so well). Word of caution - I am an amateur - if a PRO contradicts what I said you may want to ignore everything I wrote! :-)

Can I get a heart please?

I appreciate the fine details, like the bottom of the disc blank still being wet after the hammer blow.

Try breaking the edge first. Starting at the center of the blank just creates excess "bad way" curvature that only gets worse until you finally try to roll it over at the end, yielding the lampshade effect. Try rolling over the outside edge a little first, then go back to the center and move out from there like you have been doing. You should get much better results with the outside edge already started.

just as a matter of interest - have you thought of trying the less than perfect but looks quite passable reflector you almost made? Uness you need a perfectly focussed beam you might be surprised what you get back. You might be shocked speechless - but just possibly the grunge o'scope might do good. I've used various amounts of vaseline on a uv filter for soft focus and different nylon undergarments and scarves draped over lights as diffusers with mixed results and degrees of flammability - but some were better than anything you could buy. I once did a job at a works that spun copper hot water tanks ... They used two bars the first had a hole at one end slotted over a pivot on the lathe. about 6" back was a peg that the second bar slotted onto. That bar had a curved arm that the bullet ends screwed on to. The two pivots were like a pantograph so the bullet end could cover a disk about 4' dia. while still maintaining firm enough force. They said the "trick" was to set the disk tight round the boss in two passes, then to use use single centre to edge passes to even out the thickness and produce a perfik' dome. I did "have a go" and I still wake in the middle of the night sweating over the results.

I'm pretty sure the bending at the top and breaking isn't caused by pushed the metal up. It is caused by the force you are applying tilting the part and thus pushing the opposite side out. See if you can push down both sides at once.

In my metal spinning class we used a bar of soap as lube, also the tools we used were quite long. You put the handle under your arm and push with your body, your hands are just used to steer the tool.

I was legitimately impressed by the photonic impression that camera flash made. WOW. Just, WOW.

You might want to make sure the spindle bearings in your lathe are designed for that kind of axial load. Tapered roller bearings are. Very few ball bearings are and applying axial thrust to standard ball bearings quickly wears them and that wear instantly becomes radial clearance and "runout".

Hey Tony! Would just like to say that your shenanigans are contagious and have reignited my hobby! Being a CAE during the day I never get a chance to see how things are practically made and it's impossible to find "old timers" in my country and where I live that can show all those skills - and it might not be obvious. So just seeing someone talented making just about anything will teach so much more than you might think :-) And you are hilarious, entertaining and one hell of a storyteller/moviemaker! I am very thankful and happy to be a patreon! Greetings from Denmark! PS: You inspired me to build a CNC too. But sorry to say it: moving gantry for lyfe! :-))))

I understand the need to make it yourself. I wish I had your talent. Sometimes you're just remaking the wheel. The adapter is flat and fits in most bags. Once you're at a common mount the world is your oyster. I use mine so I can use the same modifiers on the go as I do in my home studio.

Jesus your videos have such charm. My heart, soul, and poor attention span sing when I found you yesterday.

beautiful bayonet mount, and the fitting came up a treat.

Don't give up on the spinning, it works fine on metal lathes. It's the tool that is holding you up. It's all about lowering the friction you create on the blank vs the friction that holds the center and spins the piece. The roller is the better tool. You should bevel round your roller much more, because the flatter it is the more friction it will cause(bad). Usually it's made from stainless and highly polished. again, to eliminate friction. Also, polish the form as much as you can (bondo or epoxy)and, try oil on the blank, if wax or paraffin are not doing it - the blank will take on all the imperfections of the form. I would use a bronze bushing instead of a roller bearing, to eliminate any possible give when pushing with the tool. A good shortcut is to buy a trailer hitch knob as they are usually the ideal size(2" dia or 1.5 depending on what you find). Throw it on the lathe with some soft jaws, create 2 parallel flats, and drill a slide fit for a 1/2" OD bronze bushing . It should be look kinda like a donut about 1- 1.25" thick,. The idea is to meet the blank with a single point of contact NOT a surface, so depending on how you make the yoke, you might need to enhance the roundness of the donuts. The holder/yoke is really a Y or a U shape, with the axle also polished as much as you can. You need to ensure that the roller can spin with little resistance and that the geometry is such that as you turn the tool it still contacts the blank on a rounded point without sticking. If your roller tool is well made, it will not create friction on the blank. Unexpected friction causes you to exceed the drag force on the outer rim of the piece, which heats the piece too much and messes up the finish, and most importantly it causes the shearing you saw at the center. You are doing it correctly, you are just using bad tooling. If you do try again and god forbid begin to like it, you might also want to create a few dished "holders" to increase the gripping surface. They will be necessary if you go much wider.

That is why #thisoldtony is one of the RU-vid OGs... Finally a Patreon campaign that doesn't feel patronizing....

do you think some of your problems might be related to the position of the tool? In a typical spinning setup, the tool rest is the pivot point on which the tools placed to spin the metal. The bearing might actually be limiting the ability to stretch the metal. Finally, periodically annealing the metal will be helpful, especially if you don't start with "0" aluminum blanks

Haven't tried it myself, but my first thought is you're thinking it'll deform like mild steel - aluminium is brittle as hell, so i would imagine to make it more malleable would take a blow torch and some soap or a heat stick marking so you could get it up to a couple hundred degrees. Trying to cold form it to that much of a shape would only work with a bump bend or an actual die and punch.