spinning cones

[Tim Toberer]

It took quite a bit of trial and error, but I am spinning acceptable cones. I had no luck spinning the traditional way, spinning over a form. I found a few videos of people spinning this way, into a form. It is pretty simple once you get setup right. The forms are made of birch scraps I had from a butcher block counter. Maple would be better. The aluminum must be near pure aluminum and annealed. About .012 thick for biscuit and tricones. I think spider cones are thicker maybe .020 or so, not sure. Spider cones are cheap and available. Probably won't mess with that. I use an oil wax mix for lubrication, with maple forming tools. I try to use even pressure and speed. Not too fast on the rpms maybe about 500 to 700.

[Chris Clem]

I like it. Always seemed like a relativly simple job to turn cones and experiment with different designs. I have an old 1930s Atlas/Sears lathe that I want to restore, I just don't have all that much use for it. But I could mount it an old stereo console l have in the shop, just the right height and shape to do the job.

It's a bit of messy job restoring machines but I have done it before, and a wood lathe is not all that complicated.

[Tim Toberer]

Always seemed like a relativly simple job to turn cones and experiment with different designs.

I would say deceptively simple. You need the right aluminum, and it needs to be dead soft. If you run it too fast the aluminum work hardens. Internal spinning is way easier. I spent a couple weeks trying classic metal spinning and it is dangerous and frustrating. The trick is getting an even thickness

[Erv Niehaus]

How many of these cones do you plan on making?

[Tim Toberer]

How many of these cones do you plan on making?

As with most of the things I do, there is no plan. I just make it up as I go along. I suppose I will make as many as I need. Right now I need 3, but I will make some more to see if they sound different. The great thing is, now I know I can make them if I need them.

[Erv Niehaus]

Maybe you should go in the business.

[Max Lee]

Very cool, Tim. Thanks for sharing your experiments and lessons learned!

Something about having a spinning razors edge moving at 150fpm has scared me off of attempting something similar but I like your method of securing the free edge!

I wonder if a degree of work hardening in the formed reso cone might be desirable from a rigidity or tonal standpoint? Or, conversely, if a post-spinning annealing step could improve the acoustic properties.

In the same vein, I know brass drum cymbals are often hammered after forming which appreciably affects the natural resonant overtones. Not sure if the hammering introduces more work hardening, a surface shot peening effect, or more snake oil

[David Ball]

I started spinning cones back in the 80's. I found certain brands of aluminum flashing that worked quite well. I spun mine on a male form--wish I had tried your approach! But it worked well for me. I used a rounded wooden dowel as a spinning tool with a lot of vaseline on it as a lubricant to try to keep the work hardening to a minimum. I think a certain amount of work hardening was good, but if it got to be too much, it behaved like non annealed metal and tended to get ripply. And yes, those sharp edges spinning on the lathe would be scary if not for leather gloves!

Later on, I vacuum formed plastic cones, much like a lot of speakers use. They were mellower than the aluminum but were still very strong and sounded good. Plus, I could do them in cool colors! (I used plastic plates for my material. Vacuumed in the spiral ridges too). I had a Mattel "Vac U Form" toy as a kid, and sort of mimicked that using my shop vac as a vacuum source.

Dave

[Tim Toberer]

Maybe you should go in the business.

I realized a while ago that the second my hobbies become a job, they are no longer as enjoyable. My goal is to have something at the end I would like to play and at some point someone else might also. I will say the markup on these cones is pretty insane considering the price of the material is pennies and they take about 10 minutes to make.

I started spinning cones back in the 80's. I found certain brands of aluminum flashing that worked quite well. I spun mine on a male form--wish I had tried your approach! But it worked well for me. I used a rounded wooden dowel as a spinning tool with a lot of vaseline on it as a lubricant to try to keep the work hardening to a minimum. I think a certain amount of work hardening was good, but if it got to be too much, it behaved like non annealed metal and tended to get ripply. And yes, those sharp edges spinning on the lathe would be scary if not for leather gloves!

Later on, I vacuum formed plastic cones, much like a lot of speakers use. They were mellower than the aluminum but were still very strong and sounded good. Plus, I could do them in cool colors! (I used plastic plates for my material. Vacuumed in the spiral ridges too). I had a Mattel "Vac U Form" toy as a kid, and sort of mimicked that using my shop vac as a vacuum source.

Very cool ideas there David! I have been looking into low tech vac forming for guitar building.

I have been going back over the cone to kind of even it out and harden the materiel. I agree that a level of work hardening is good. The trick is to get the cone formed before it needs to be annealed again. As long as you have the right aluminum this doesn't seem to be much of a problem.

[David Ball]

Agreed. If you've got the right aluminum, it works out well as long as it doesn't harden to the point where it needs to be re-annealed.

I'll try to find some pics of my vacuum formed plastic cones. I had a frame for those--I'd put a plastic plate in the frame and put it in the oven. When the plate drooped and then tightened back up, it was ready. Then I'd put it on the vacuum form. Worked great. And as I said earlier, the tone wasn't the really brilliant tone you get from an aluminum cone, but for ukes like I was making back then, the extra mellowness of the plastic cone was just the ticket.

Dave