Turning metal on a wood lathe

I wrote this PFD document for a demo I did on turning metals, primarily aluminum and brass, on a wood lathe with woodturning tools. Relativity easy to do!

For an example I show how I make inserts for lathe tools. The one I show is fairly small but the method is the same for any size.

JKJ

 

[Michael Anderson]

This is great, thanks John. I’ve been thinking about a project that involves turning brads for a while.

 

[Tim Hunter]

…a task where pattern maker’s (wood) lathes shine.

An example:

Lathe-mounted sanding disc - Old Woodworking Machines

Tim

 

[John K Jordan]

I do use my metal turning lathe (and mill) where appropriate and especially when I need precision. (And if my little machine shop is insufficient I have friends with bigger machines - and CNC.)

The main point of the demo was turning some softer metals freehand might be useful on occasion, and quite practical on the wood lathe with woodturning tools. There was considerable interest at the woodturning club, many who wanted samples of the aluminum and brass to take home to play with.

 

[Bill Alston]

I do use my metal turning lathe (and mill) where appropriate and especially when I need precision. (And if my little machine shop is insufficient I have friends with bigger machines - and CNC.)

The main point of the demo was turning some softer metals freehand might be useful on occasion, and quite practical on the wood lathe with woodturning tools. There was considerable interest at the woodturning club, many who wanted samples of the aluminum and brass to take home to play with.

I too use a MW Lathe and Mill. Your PDF though is a valuable resource for those that only have a Wood Turning Lathe. Thanks for posting.

 

[Jim Grieco]

I wrote this PFD document for a demo I did on turning metals, primarily aluminum and brass, on a wood lathe with woodturning tools. Relativity easy to do!

For an example I show how I make inserts for lathe tools. The one I show is fairly small but the method is the same for any size.

JKJ

Great info - thanks!

I stink at getting a good polish/finish on acrylic. Tried using cast acrylic to make object cells for my kaleidoscopes but never could get rid of the cloudiness! All types of dry sanding, wet sanding and different polishes gave me the same results. Obviously a user error somewhere lol

 

[John K Jordan]

I stink at getting a good polish/finish on acrylic. Tried using cast acrylic to make object cells for my kaleidoscopes but never could get rid of the cloudiness! All types of dry sanding, wet sanding and different polishes gave me the same results.

Just curious, where did you get your clear cast acrylic? What I have is quite clear and polishes nicely.
I understand extruded acrylic is harder to polish to an optical clarity.

Also, what's an "object cell"?

I've used two methods to get glossy surfaces on cast acrylic. (I never turn extruded acrylic - it's a different animal)

Method ONE: Sand with fine then very fine sandpaper. (I always use Indasa Rhynowet paper, buy in 9x12 sheets, cut into 1"x3" strips.) After dry sanding to remove any tool marks (at a slow speed and by hand with the lathe off) with 400 grit to 1200 grit paper, I sometimes wet sand with 1200 with water. Clean well between grits with a paper towel then damp cloth to make sure all previous grit particles are removed.

Then i use one of several of the polishes on my shelf - I have several sold for plastic and some for metal, but the type doesn't seem to make any difference. I often use Simachrome since it's widely available and I've used it for years. It's advertised for polishing metals but works well on the cast acrylics.

https://www.amazon.com/Simichrome-Polish-1-76oz-1-76-TUBE/dp/B00JDPS7Z8

After cleaning the plastic again with soft cloth and water, I apply the polish with a small piece of cotton "tee shirt" material, usually about 1"x3" strips, start with the lathe running (fast if I remember), then stop and polish by hand. I think I changed to fresh pieces of cloth occasionally. (I should do another one and make sure I'm remembering things correctly)

Method TWO: I can get a mirror gloss with an very old Micromesh sandpaper kit. What I have was a kit made for aircraft windows - it includes more grits and is far cheaper than the cut-down kits they sell today to woodturners. (I used it to restore our aging Cessna 172 windshield, took it from so crazed you couldn't fly towards the sun, to so clear it looked like new!) This kit has grits to 24000. I simply sanded through the grits and the result was polished. Like magic. I used a little polishing compound afterwards but it wasn't needed. I see the Micromesh kits sold now go to 6000 grit but include "micro gloss liquid abrasive" polish, whatever that is.

Micro-Mesh Acrylic Restoral Kit - 30 Square Feet | Aircraft Spruce

Micro-Mesh Acrylic Restoral Kit - 30 Square Feet Use this kit by hand to restore up to 30 square feet of acrylic. NSN#5350 01 290 4002. A favorite window restore kit with military customers.

www.aircraftspruce.com

It would be interesting to see if the new kits worked as well as the old.

One thing I haven't tried is using polish on spinning polishing wheels. These work well on wood and metals, but I suspect it would take the right wheel (quite soft and very clean) and care to prevent overheating which might soften the surface.

BTW, I've also used extremely fine diamond paste made for industrial polishing and it worked, but I don't have much so I only tried it once. I also don't remember what micron sizes I have.

Also, you can buy very fine and super fine polishing "sandpaper" in small quantities. For example, these, up to 8000 grit:

https://www.amazon.com/Tri-M-Ite-Polishing-Abrasive-Assorted-Sheets/dp/B0718STB17

And these, up to 15000 grit depending on which package you buy:

https://www.amazon.com/dp/B07PC3843L

I've tried some of a different brand and it worked well.

Curious, what polishing method(s) have you tried so far? I've never gotten a "cloudy" surface unless I stopped at too coarse a grit.

Also, I haven't even tried to make optically clear surfaces. All I've done has been decorative, like those in the photos below:

(Note that some of the cast acrylics shown below are NOT made to be clear, but internally a little cloudy, such as the yellow and blue, or opaque like the black ornament. Some, for example the yellow, really catch the light. I carried the yellow ornament into a turning club meeting and several asked me what kind I light I put inside!)



JKJ

 

[Jim Grieco]

Just curious, where did you get your clear cast acrylic? What I have is quite clear and polishes nicely.
I understand extruded acrylic is harder to polish to an optical clarity.

Also, what's an "object cell"?

I've used two methods to get glossy surfaces on cast acrylic. (I never turn extruded acrylic - it's a different animal)

Method ONE: Sand with fine then very fine sandpaper. (I always use Indasa Rhynowet paper, buy in 9x12 sheets, cut into 1"x3" strips.) After dry sanding to remove any tool marks (at a slow speed and by hand with the lathe off) with 400 grit to 1200 grit paper, I sometimes wet sand with 1200 with water. Clean well between grits with a paper towel then damp cloth to make sure all previous grit particles are removed.

Then i use one of several of the polishes on my shelf - I have several sold for plastic and some for metal, but the type doesn't seem to make any difference. I often use Simachrome since it's widely available and I've used it for years. It's advertised for polishing metals but works well on the cast acrylics.

https://www.amazon.com/Simichrome-Polish-1-76oz-1-76-TUBE/dp/B00JDPS7Z8

After cleaning the plastic again with soft cloth and water, I apply the polish with a small piece of cotton "tee shirt" material, usually about 1"x3" strips, start with the lathe running (fast if I remember), then stop and polish by hand. I think I changed to fresh pieces of cloth occasionally. (I should do another one and make sure I'm remembering things correctly)

Method TWO: I can get a mirror gloss with an very old Micromesh sandpaper kit. What I have was a kit made for aircraft windows - it includes more grits and is far cheaper than the cut-down kits they sell today to woodturners. (I used it to restore our aging Cessna 172 windshield, took it from so crazed you couldn't fly towards the sun, to so clear it looked like new!) This kit has grits to 24000. I simply sanded through the grits and the result was polished. Like magic. I used a little polishing compound afterwards but it wasn't needed. I see the Micromesh kits sold now go to 6000 grit but include "micro gloss liquid abrasive" polish, whatever that is.

Micro-Mesh Acrylic Restoral Kit - 30 Square Feet | Aircraft Spruce

Micro-Mesh Acrylic Restoral Kit - 30 Square Feet Use this kit by hand to restore up to 30 square feet of acrylic. NSN#5350 01 290 4002. A favorite window restore kit with military customers.

www.aircraftspruce.com

It would be interesting to see if the new kits worked as well as the old.

One thing I haven't tried is using polish on spinning polishing wheels. These work well on wood and metals, but I suspect it would take the right wheel (quite soft and very clean) and care to prevent overheating which might soften the surface.

BTW, I've also used extremely fine diamond paste made for industrial polishing and it worked, but I don't have much so I only tried it once. I also don't remember what micron sizes I have.

Also, you can buy very fine and super fine polishing "sandpaper" in small quantities. For example, these, up to 8000 grit:

https://www.amazon.com/Tri-M-Ite-Polishing-Abrasive-Assorted-Sheets/dp/B0718STB17

And these, up to 15000 grit depending on which package you buy:

https://www.amazon.com/dp/B07PC3843L

I've tried some of a different brand and it worked well.

Curious, what polishing method(s) have you tried so far? I've never gotten a "cloudy" surface unless I stopped at too coarse a grit.

Also, I haven't even tried to make optically clear surfaces. All I've done has been decorative, like those in the photos below:

(Note that some of the cast acrylics shown below are NOT made to be clear, but internally a little cloudy, such as the yellow and blue, or opaque like the black ornament. Some, for example the yellow, really catch the light. I carried the yellow ornament into a turning club meeting and several asked me what kind I light I put inside!)

View attachment 68338

JKJ

Thank you for all that info - nice work on the acrylic!

Extruded means there is a line in the tube and casting doesn't - is this correct? If yes then what I was using was cast. I found acrylic tubes on Amazon and I also have ordered thick sheets and then cut a square the size I needed and turned out the inside on the lathe.
I dry sanded to 800 using mess sandpaper and then used a wet sanding kit up to 6000. The only other differences were that I used a couple different polishes. Some were acrylic polish and a couple were headlight lens polish which was suggested to me.
Again, I am sure it was user error!

 

[Richard Newman]

Thanks for the writeup John, some great information!

My experience is kinda the opposite of yours, I first started turning wood on a little 9" Southbend metal lathe. I was a furniture and banjo maker, and needed some turned details and parts. Made some scrapers from files, and ground form tools from HSS square lathe bits and figured out how to get what I needed. Later made my own scraping tools by silver soldering pieces of Tantung from cut-off blades onto mild steel bar. Tantung is easy to grind, but lasts much longer than HSS, especially on ebony and other exotics. I'm embarrassed to say I never learned how to turn wood properly, maybe some day...

I also turned a lot of 360 brass freehand, using scrapers held to get negative rake. Worked great, and so much easier and fun than grinding a form tool.

Some thoughts:

For steel turning, I wonder if a leaded steel like 12L14 would be easier to work with, certainly is on a metal lathe. There are other free machining grades often used on screw machines, some with sulfur like 1215. The common cold rolled steel easily found is usually 1018, which is not an easy material to get a good cut or finish with. Years ago I bought an ancient Hardinge Cataract turret lathe at an auction of an equally ancient screw machine shop. It came with a ton of small short bars of steel, and they turned like butter! A caution - 12L14 rusts very easily!

Also, I wonder if the use of a metal cutting fluid would help. Kinda messy, but always used in the metal machining world. Old machinists used bacon grease, easily available and smells great! But attracts mice...

Last, the use of gloves around machines is pretty controversial in the metal machining world. There are all sorts of horror stories about people getting pulled into a machine when a glove or sleeve gets grabbed by a rotating part. The results are grisly, often fatal - DON"T watch any videos of this stuff online! Here's a current thread on the Practical Machinist about this, with the usual PM "give and take".
https://www.practicalmachinist.com/forum/threads/gloves-in-the-machine-shop.432293/

 

[John K Jordan]

Thank you for all that info - nice work on the acrylic!

Extruded means there is a line in the tube and casting doesn't - is this correct? If yes then what I was using was cast. I found acrylic tubes on Amazon and I also have ordered thick sheets and then cut a square the size I needed and turned out the inside on the lathe.
I dry sanded to 800 using mess sandpaper and then used a wet sanding kit up to 6000. The only other differences were that I used a couple different polishes. Some were acrylic polish and a couple were headlight lens polish which was suggested to me.
Again, I am sure it was user error!

Jim, There shouldn't be a line in an extruded cylinder, but I don't know about a tube - never had any tubes. I buy 1.5" diameter colored cast acrylic rods for turning.

Thanks for the writeup John, some great information!

My experience is kinda the opposite of yours, I first started turning wood on a little 9" Southbend metal lathe. I was a furniture and banjo maker, and needed some turned details and parts. Made some scrapers from files, and ground form tools from HSS square lathe bits and figured out how to get what I needed. Later made my own scraping tools by silver soldering pieces of Tantung from cut-off blades onto mild steel bar. Tantung is easy to grind, but lasts much longer than HSS, especially on ebony and other exotics. I'm embarrassed to say I never learned how to turn wood properly, maybe some day...

I also turned a lot of 360 brass freehand, using scrapers held to get negative rake. Worked great, and so much easier and fun than grinding a form tool.
...

Richard,

If you get down this way sometime, stop in for a woodturning lesson! My fee is a good story or a good joke.

And if you want haven't, try watching the Clickspring videos. In his series making an entire wind-up clock (just... amazing) he mentioned at one point how much he enjoyed turning some small pieces freehand on the metal lathe - he called the tool a "graver" but it looked like a scraper. If he thought that was fun, he should try woodturning!

I once had a woman come to the shop for me to make a "magic" wand she wanted for a friend. She had never seen a wood lathe but had a lot of experience with metal-turning lathes while making equipment needed when working her Phd. She was amazed that the tools were held in the hand - she imagined we turned cranks to move the tool. I'd quit today if I had to use "etch-a-sketch" controls to turn wood!

As for steel in the wood lathe, the only time I did it was to turn down some Nova chuck jaws. I did it on the wood lathe instead of the metal lathe to easily insure the cut surface would be concentric when the chuck was threaded on the wood lathe spindle. I don't want to do it again. I love the woodturning, but I'd hate to do without my metal lathe and mill.

I agree about the gloves. I don't even use them when my hands are assaulted by smokin' hot wood chips when using a gouge - the chips seem to be channeled down the gouge flute directly towards my fingers. I did find a good solution, though - instead of a gouge I use one of the Hunter tools and the chips go sideways instead of towards my hands.
Another thing about safety - when someone wants a turning smock I give them a disposable paper jacket like they use in my dentist's office, but with short sleeves.

JKJ

 

[Richard Newman]

Thanks for the invite John, might just take you up on it if I get down your way. Everyone around here is tired of hearing my stories and jokes!

I'm pretty well equipped with metal stuff: 9" Southbend, 17" Leblond, and Hardinge HSM, plus Oliver 25C patternmakers lathes, Bridgeport mill, surface grinder and tons of tooling.
And then there's all the woodworking stuff...way too much. Just moved to a smaller shop (2000'), had to shoehorn everything in, went vertical with racking, Gaylord's, and a pallet stacker. At age 78, I almost didn't survive the move- never again, next time I call the auctioneer. Or my wife does, after the undertaker.

I try to deal with chips using polycarbonate shields on mag bases. When I turn banjo rims, the 25C wants to shoot a steady, high speed stream of hot long wood shavings directly at my face, the shield saves the day. I make rims for other banjo companies to pay the shop rent, can spend the whole day turning. Need any packing excelsior? Also great for wiping off glue squeeze out.

 

[Darryl Fective]

I haven't turned much metal on my wood lathes. I did modify a set of cheap Hummer H2 wheels so they would fit on my Ram 2500. (center bore was a little small)



Another project was cutting a large hole in my motorcycle's aluminum clutch cover. I turned a piece of polycarbonate to fit as a window. It was a successful experiment and as soon as I posted photos, I had people wanting them. I ended up making and selling about a dozen of them.

 

[Ed Davidson]

These cast acrylic yo-yos were wet sanded to 6000 grit, then Beall buffed...works for me.

 

[stu senator]

Thank you for all that info - nice work on the acrylic!

Extruded means there is a line in the tube and casting doesn't - is this correct? If yes then what I was using was cast. I found acrylic tubes on Amazon and I also have ordered thick sheets and then cut a square the size I needed and turned out the inside on the lathe.
I dry sanded to 800 using mess sandpaper and then used a wet sanding kit up to 6000. The only other differences were that I used a couple different polishes. Some were acrylic polish and a couple were headlight lens polish which was suggested to me.
Again, I am sure it was user error!

Extruded is thru a die, a hole in a metal part and no parting line. A casting will have a parting line where the parts of the mold meet. This may not be visible where flat surfaces meet but will appear on round castings at the widest point.

 

[Jim Grieco]

Extruded is thru a die, a hole in a metal part and no parting line. A casting will have a parting line where the parts of the mold meet. This may not be visible where flat surfaces meet but will appear on round castings at the widest point.

Thanks for the clarification - I guess my tubes were extruded then. But, my polishing challenges were mostly from thick sheets that I cut a hole in. Can never get the inside polished correctly. The inside diameters were around 2.75"

 

[John K Jordan]

Extruded means there is a line in the tube and casting doesn't - is this correct?

Jim, in revisiting this, a couple of things aren't clear:

By "line" in an extrusion, do you mean a surface line or a seam?

And are you working with "tubes", not cylinders? A casting can have a visible line or not, depending on the mold used, i.e., a 2-part mold vs a mold made from tube/hole with smooth surfaces. All the extruded rods/cylinders I bought had absolutely smooth surfaces. (Who knows, maybe they were rough cast then machined and polished!)


For extrusions, I forgot about this before, but now remember reading about different ways to extrude tubes, some might create visible lines and other not. I think I mentioned somewhere that I've never tried turning plastic tubes and I haven't even seen any colored tubes for sale. (I see clear tubes on Amazon but don't see "cast" or "extruded" in the descriptions I've checked.)

I did find this fascinating page that describes a method to seamlessly extrude aluminum tubing, might be an interesting read:

Aluminum Extrusion: Porthole or Seamless Extruded Tubes? - Wiley Metal

Life is full of decisions. Tea or coffee? Pepsi or Coke? Sometimes the answer doesn’t matter that much. Other times it matters a great deal. Take extruded aluminum tube for example. This comes in two forms: structural and seamless. Structural extruded tube is made by the porthole process, and...

www.wileymetal.com

And their guide to "hollow cylinders":

Your Guide To Hollow Cylinders: Aluminum Round Tubing Vs. Aluminum Pipe - Wiley Metal

Know the difference between aluminum tube and pipe for your next metal fabrication project—choosing the wrong one can affect performance.

www.wileymetal.com

For anyone who missed it, this is where I've bought a variety of colored cast rods. (They claim to offer tubes but I can't find them on their website)
Everything I've bought from them has been flawless.

Acrylic Rods & Tubes

Shop for Acrylic Rods & Tubes products at Delvie's Plastics Inc., the most trusted name in Acrylic & Plexiglass.

www.delviesplastics.com

IIRC, I think the gentleman who gave me the first samples of extruded colored rods worked in something involving retail displays. He brought a bunch of short offcuts to give away at a turning class - almost no one else in the class was interested so he told me to take the rest. Their loss! (It was a class jointly conducted by the late other John Jordan, the famous one, and the amazing and prolific artist Clay Foster.)

Jim, if you ever jump in the car one day and find yourself near Knoxville, give me a holler and we can play with plastic on the lathe!

JKJ

 

[Doug Rasmussen]

Basically wood and metal lathes are the same, a spindle driving the work piece.

The important difference is how the tools are held. Generally, wood lathe tools are hand held which is a poor way to maintain the rigidity needed to prevent tear out and catches in wood, much less in metal. Metal lathe tools are most often securely and rigidly fastened to an inflexible part of the machine structure. That's why a metal lathe with the correct cutting tool can avoid tear outs and catches even while working against the grain in wood.

IMO, the best way to turn metal on a wood lathe is by mounting a 2 axis cross slide to the lathe bed. Back in the day Delta offered a metal turning slide for their lathes. Shown below is a fairly expensive one I found online. 3rd world versions shouldn't be much over 50 bucks



A cross slide won't automatically turn a wood lathe into a metal lathe since the spindle, bed, etc are not as beefy as most metal lathes of comparable size. Softer metals and plastics are easily turned, hard metals not so well. With a cross slide the basic shape of your metal piece can be roughed near to the final contour. Final finish can be achieved with files and sanding.

 

[John K Jordan]

I really like that cross slide; been casually looking for one for my drill press, I'd like to find one similar to that on my mill but much smaller.

I bought a small cheap one but it's junk.

The important difference is how the tools are held. Generally, wood lathe tools are hand held which is a poor way to maintain the rigidity needed to prevent tear out and catches in wood, much less in metal.

I'd like to suggest a modification to one statement:

Perhaps change
"Generally, wood lathe tools are hand held which is a poor way to... prevent tearout and catches in wood..

to say
"All too often, wood lathe tools are poorly sharpened, held, and controlled which can lead to tear out and catches."

In my experience, tool type/grind/sharpening are critical, but paramount is to learn the fine tool control to eliminate tearout and catches.

I could include examples, but the bottom line includes things, in approximate descending order of importance, like tool presentation, stance/body motion, rest height, grain direction, wood type, lathe speed, and more. Like my piano teacher always said, "Everything's easy once you know how!" Sometimes the hard thing with woodturning is the learning how part. Easiest way I know: find a nearby turner who knows how and is willing to teach in person! (That may be difficult in some areas.)

JKJ

 

[Bill Alston]

Some of the old British Wood Lathes were well equipped to turn other materials if needed. Primarily though for turning things like perfect cylinders etc?

 

[Doug Rasmussen]

Some of the old British Wood Lathes were well equipped to turn other materials if needed. Primarily though for turning things like perfect cylinders etc?

In this country (USA) that type lathe is usually referred to as a patternmakers lathe. They have the tool rests for hand turning plus the carriage for facing and round turning. The compound slide on top of the cross slide can swivel to create tapers and add draft to casting patterns.

Kinda hard to find them much anymore but with the bargains in large metal lathes use one of them as a patternmaker lathe.

 

[Jim Grieco]

By "line" in an extrusion, do you mean a surface line or a seam?

Seam - but it has been a while since my last attempt and I am starting to confuse myself lol. All I know is I could not get rid of the cloudiness on the inside turnings. Anything I had to turn on the outside came out much better with the sanding and polishing.

Jim, if you ever jump in the car one day and find yourself near Knoxville, give me a holler and we can play with plastic on the lathe!

JKJ

Thank you for the invite. Beautiful country over there!

 

[Bill Alston]

A more up to date machine with a saddle. I’d love something similar for some jobs.