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How can I morph a nearly 1/4 " aluminum disk into a cone? Answered

Attached is a crude Paint drawing of what I am after (the cone doesn't have to have  that much of a "throat" on it, I just need it to be slightly funnel shaped.

I need to do this without "firing up" or heating the metal, and hopefully without marring the surface very much.

Any ideas? 



Get a pointy metal thing:                                                                                   ^
and metal cylinder that has a slightly less than diameter of your disc:    | |
get a vice:                                                                                                            =

put it in this order:                       ----------
                                                         |        |
                                                           /  \

And squeeze it.
I hope that made sense. Now bask in the glory of my terrible ASCII depictions. I'm sorry for any confusion / hurting of eyes.

  No, no problem with the depiction, it is clear enough.

I was thinking about this....and I have a vise, but I am wondering if it will apply enough equilateral  pressure in a equally perpendicular way, even with the "cone form" being used.   I had the perfect "form" for this too,  about 3 years ago, but can't get them anymore. I guess I will have to try, IF I can find something suitable again.

It's still cool where you are, right? Gallium in a mold. Use that.

Or Bismuth. Alot of the suitable alloys such as "field's alloy" or "Wood's alloy" is quite hard to acquire.

It is cool in temperature, but the rain is helping the snow melt more quickly then expected. Being in the low to mid 40's F, it isn't exactly COLD though :-) 

What am I to do with the "Gallium in a mold"?    I do want to use the original HD platter.

I was thinking of you using it as a sort of press / mould / thing.

Thanks for the best answer!

THis is typically done on a lathe using a wooden "paddle" to work the metal down against a wooden form that is the shape you want to end up with.  Most of the pieces I've seen are made out of aluminum.  I don't know how easy or hard it would be to spin other metals.

Here's a detail on how to do it.

And here's a sample of some shapes that can be made.

Yeah, because I am without many power tools, including a lathe or access to one, I will have to find another way, although this looks like the BEST way to actually do it if I could.

It IS aluminum, thankfully....I will make that part of the description so as not to have further confusion on it.

find a brass bushing the right shape of the impression put a bolt through it use a socket wrench as a receiver 1/4" bolt grade 8 snaps at about 50 foot/pounds of Torque 3/8" maybe 100 . or big C-clamp and a ball bearing same socket wrench receiver ? I use that to press out u-joints on trucks.also need to lube the die, electrical wire lube works ok http://www.jhlarson.com/ind_tables/lube/lube_table.htm , or beeswax

Thank you. I will have to see what I can muster up :-)


8 years ago

If the disc is half an inch thick, you'll need a few dozen tons of pressure to get that shape.

If it's half an inch across and relatively thin, you could "machine" a die out of hardwood and use a bench vice as a press.

My apologies,  typo,  it is about 1/4' thick....corrected above

Ah, at 1/4" thick, without wanting to mar the surface too much, your best choice is a big, heavy press.  You could use a lathe and draw it out, but that would indeed mar the surface.  You'd have to polish it afterward.

I suggest calling some small machine shops in your area to find out if they can do it.  I doubt this is something you can do at home, without the right equipment.

polishing is not an option, as the "shiney surface" is no more then a few micrometers thick.

Yeah, I was thinking a press, and wondered where I would find one to "use" in my area.....I hate paying any steep fees just for a simple project.

That would imply that there is a different material plating the aluminum - is that true?

Yes,  HD platters, old ones, are what I am dealing with here.

Ah, well why didn't you say so!  OK, so you want to force a hard drive platter into a cone or funnel shape.

A press is the only way to do it, and that will depend on what alloy the aluminum is.  There's a chance it will be too brittle to force it into any shape.

Do you have any other platters that you don't mind sacrificing?  What happens if you jam one in a vice and try to bend a radius into it?

This is an old moster 10 meg  (I am being fecisiuos here)  HD, so it has 3 or 4.  I would like to get at least two to work though.

I AM thinking about putting a triangular slot into one side (middle to edge) and forcing the edges together to make my "slight" cone shape....I am not sure yet.

...if its half an inch thick, you'd just turn it in a lathe.


My apologies,  typo,  it is about 1/4' thick....corrected above

If the dimple isn't VERY deep, go to your nearest sheet metal fab shop and ask for some of the punch outs from their flypress - a manual fly-press die has a locating tit which is engaged in a centre punch mark on your job, but which then gets pushed out in the waste into JUST the shape you want.

If you have the brass already, they may be quite happy to dunk a few holes in your sheet.

If you want a deeper cone, epoxy a few washers in the centre of the intended disk, punch it, boil the brass in water, and the epoxied bits should fall out.

The aluminum disc is a tiny bit bigger then a CD, and polished on both sides, thus my desire not to mar it.

Nothing will not mar the surface...I think you'll have to re-polish what ever. Spinning is the obvious method - a wood working lathe is a good way to do it, but it takes a heck of a lever arm to do it. Anneal the aluminium first.

polishing is not an option, as the "shiney surface" is no more then a few micrometers thick.

You're stuffed then, it will not be possible to form that without marring the surface.

Why can't you re-polish the metal ? We do it all the time at work.


Any "polishing" will take off the "almost perfectly mirror-like" coating on the platter itself.  I would only be able to obtain a polished aluminum surface then, once that is removed.  

The platter is made of aluminium, it can be repolished. There ain't no way you can avoid marking it.

I can polish it about about as easily as I can "form it" at home.  Sadly I may have to hack out a wide slot and try to get the edges to meet again....to form the cone. It need not be bent very far.

Marring one side won't be a problem, as long as I can keep the "inside" mostly free of defects.

You could use a shaped charge, but you'd better have a few to practice on since you'll probably ruin/loose a few before getting it right.

charge, as in explosives?  Hmmmm, I think I will look into using a torsion/tension bar/pulley/come-along system or something first :-)  but thanks for the suggestion

At ~half an inch, you'll need some force, a press would be the sort of thing. Otherwise whacking it with a big hammer I suppose.
Could you drive a car over it?


My apologies,  typo,  it is about 1/4' thick....corrected above