Metal Spinning on a Metal Lathe

I was curious if anyone spins or has spun copper sheet on a metal lathe? I'm looking to try spinning about 0.020" thick copper sheet into a candlestick cup/husk that would be shaped something similar to the top portion of this one...



Thanks!

in2oblivion said:

I was curious if anyone spins or has spun copper sheet on a metal lathe? I'm looking to try spinning about 0.020" thick copper sheet into a candlestick cup/husk that would be shaped something similar to the top portion of this one...

Thanks!

Click to expand...

I'm trying to set up to do some simple spinning on my metal lathe. Haven't done it yet, but working on it. I closely watched the video from Penn State Industries (Metal Spinning at Penn State Industries) to see what I needed in the way of tools etc, and am now making those tools.

The bottom part would be relatively easy because of the gentle curves. The top will be difficult for a beginner because it's deep and narrow. Copper work hardens quickly, so you will need to anneal often.

How fast will your lathe go? The only spinning I have done was years ago and it seems to me that it was running about 3500 RPM

Thanks sbmathias for the video link. I had watched others on YouTube, but not that one. They make it look easy or no big deal, but I haven't gotten it figured out yet.

I also appreciate the feedback from elfrench and moonlight machine. I've tried a few things initially and will share them below.

My initial setup was with a wooden mandrel, but after finding it difficult to secure the copper sheet like shown in many videos due to it slipping, I made an aluminum mandrel and put a threaded hole in the center to aid in securing the sheet to it so it didn't slip while spinning. I know spinning doesn't require a hole, but in my case, the cup holders I want to make require a hole, so I just used it to my advantage. The first 2 pics show the aluminum mandrel. During these attempts I used the 2nd highest speed on my lathe - whatever that equals since many videos or online info talked about using high speeds.

The next 3 pics show attempts #4, 5 & 6, which are the first ones to use the aluminum mandrel. It's a little hard to see, but in all cases the center sheared away due to the high friction forces I experienced while spinning. I know the videos showed nice tooling, but I initially tried an old wooden broom handle since I was concerned that any metal tools would leave marks on the copper. Basically as I moved away from center, the torque got too high and caused the shearing. Like elfrench mentioned, I figured some work hardening was also occurring so during attempt #6, I positioned a propane torch on the lathe so the copper was heated continually while spinning. It didn't seem to make much difference.

I'm going to continue this message in the next message since it will only let me upload 5 pics totaling 3 MB and I got 3 more for the last part...

continued from previous message...

I figured I needed better tooling so I quickly fashioned the rubber roller tool as seen in the 1st pic. It's basically an old rollerblade wheel w/ bearings that I put on a piece of metal bar. The last 2 pics show the result of using that tool. I basically had to stop when the metal crinkled, but I did not get any shearing and the copper was more closely formed to the mandrel at the very bottom. I haven't tried it again, but for my next attempt I want to use the smaller size copper disc. I may also try different lathe speeds. Any other thoughts are appreciated. Thanks again!

OK, here are a few samples of work similar to what you are trying. Your project is a very easy and quick spin. I need to see your lathe setup, drag tool being used, type of lube, and rpm being used before I can offer help. Your spinning chuck is fine.
Jim

I have been enjoying this video (and part 2) showing spinning silver, including annealing.

Silver_Spinner_Part1.wmv www.taliesinpewter.co.uk - YouTube

Silver_Spinner_Part2.wmv www.taliesinpewter.co.uk - YouTube

Copper work hardens quickly. Heat it red and plunge it in water.

moonlight machine said:

Copper work hardens quickly. Heat it red and plunge it in water.

Click to expand...

No need to dip in water unless you are in a hurry. It is the heat that anneals copper not the quench.

Rob

It is not necessary to quench the hot copper to soften it. There is a very good reason to quench though. When the copper is heated to a dull red then allowed to air cool, the copper surface becomes covered with a black oxide. If this oxide is not removed, it will be spun into the metal and become impossible to remove. Quenching the hot copper in water causes much of this oxide to immediately flake off. As one who does hundreds of copper spinnings per quarter, I quench my copper in a diluted acid solution. After a minute or so in the solution, the copper is not only soft but clean again and ready to be spun. Many spinnings require more than one annealing. Quenching speeds the work along and allows for a quality product.

Now for the task at hand ... the candle cup can be spun with no annealing required. It is more a matter of technique than metal hardness. Poor technique over works the metal and causes early work hardening.
Jim

" but I initially tried an old wooden broom handle since I was concerned that any metal tools would leave marks on the copper. Basically as I moved away from center, the torque got too high and caused the shearing."

I would try making a steel tool with a point on the end such that you can get it into the 'nose' end of your form easily. Start spinning at the nose end and try to get the copper pressed down as tight to the form as fast as possible, that way you have more area grabbing the copper and the end won't shear off. The waviness you are getting can be controlled with the use of a backing stick. If you get a good tack between the cooper and form I don't think you'll need to anneal as you'll be able to form this pretty quickly. Are you using any lube?

Shown here are the tools I would use. To lock the metal to the chuck I would most likely use the center point tool as I would utilize the larger diameter (3/4") of the shank to help with the spinning. Yes, I will use the side of a tool if appropriate to the spinning being done. Once the metal was locked on, I would switch to the combination tool. Both sides of the tool may be used as required. The flat side helps to maintain a good funnel shape and smooth over any spin lines. The combo tools shown are 5/8" in diameter.

The third picture illustrates the stages of spinning a special copper cup. Notice the funnel shape throughout the process.

The .020" copper used by the OP is thin. Therefore, virtually ALL movements with the tools are sweeping gently from the rim towards the center. This helps to prevent thinning and stretching the metal. The funnel shape and movement towards the center are critical for success here.

All of that being said, I could spin the whole thing with a dull point shaped broomstick handle.
Jim

P.S. This might be of interest to you:
https://www.dropbox.com/s/8qrh0tftxu4noc1/HeavyRiserStageAndStreetCups.pdf

Thanks all for the info and links. I'm getting closer, but I'm not there yet...

I'm using a 9" South Bend Model A lathe at the fastest speed with the small pulley on the 1725 rpm motor. I'm thinking that speed may not be fast enough and I may need to go to the other high-range pulley on the motor.

I'm using Varsol as the lubricant and a round-nose stainless steel tool I made.

The first pic shows how far I got this attempt. No annealing was done since magicmaker said it was not needed. The second pic shows the 5/16" diameter tool I'm using.

Not sure what to try next, but I first may just try again with the same setup, then I may also try using the higher speed range. Any other thoughts or suggestions? Thanks much!

You obviously stretched the metal. Move the spinning tool from rim towards the center. This actually moves metal to prevent thinning/stretching. I would spin this at around 1700 rpm. Speed of the lathe is not as critical as technique. Your tool will work. Again, technique is more important than the tool. I have well over 100 spinning tools and do at least 95% of my spinning with the same handful of tools. Technique is your problem.

Until your technique improves, you might try .032" thick copper. Before that try a smaller diameter circle to help get the feel for the job. Move your spinning tool only toward the center after locking on!!!!!
Jim

Thanks magicmaker for the tips & info. I did another attempt and got further, but like you said, I need to get my technique down. I also noticed what you said about going from the rim to the center. I have been mainly going the other way thinking I need to stretch the metal over the chuck, but I see that when you go from rim to center, you also move the metal. In the 1st pic, you can see the copper is more snug to the mandrel/chuck except at the very bottom where you said I would have some difficulty. In the 2nd pic there are 2 tears that can be seen at 3 & 9 o'clock positions.

Here I'm thinking that I needed to have more funnel shape for the rest of the copper disc like you said since it seems to shear where I have that small radius I created with the tooling and my poor technique. I'm also debating whether I'll need an annealing as a result of work hardening due to my technique. Any other suggestions? Thanks!

You are getting closer. By leaving the rim at right angle to the cup shape you force the metal to thin. Work on the funnel shape and bring it back to where you want the large flat rim AFTER neatly spinning the cup portion. If you do not do the funnel, there is nowhere to get the metal from to form the cup portion. You are getting there. I wish I was there to show you. You are soooo close. Think funnel.
Jim

I know I need to crawl before walking or running, but I'm wondering what changes or what else I'll need to worry about when I spin brass instead of copper, or even some other sheet material? I'm thinking the thicknesses will be similar, but will they be harder or more difficult to spin the same exact part. The customer was looking to have cups made in 3 materials of differing colors. Brass & copper are two, but what would be a good choice for the 'silver' color? Aluminum? Some steel? The items will have a clear coat finish over the metals. Also, what type/grade brass would you recommend?

I would also appreciate knowing what lubricants I would need for those choices. Thanks.

I have covered such things on my CD-ROM on metal spinning and have no time to repeat them. Here is a link to the info on the CD:
CD Preview

Jim

I am almost there and it seems now I just got to get better at technique since I'm still getting thinning & cracking in spots. This time I had difficulty getting the metal tightly locked against the chuck at the start and I think that's because I was worrying more about outside in and funneling than getting it locked-on first. The 3rd pic shows a metal burr/overlap on the copper cup at the bottom chamfer, which was a result of this type of action. I could have probably smoothed it out, but still it's the technique I need to work on. There were also cracks at the upper radius, but I think that's more a result of my 'oops' when I put the wrong end of the tool to the copper and basically started cutting metal instead of moving metal. I tried to work around it, but once it's gone, it's hard to replace.

All-in-all I'm pretty pleased with my progress and figure my technique will improve as I continue. The pics below are from attempt #13 and I think that's not too bad a learning curve considering I never spun metal before. I can also see the need for a few more tools, which I'll make.

I would like to thank all those who helped by providing links & additional info which was very insightful.