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jgourlay
07-08-2007, 10:34 AM
Gents, I'm a real newbie to metalworking on the lathe, but I have done a fair bit of woodworking on it. My son (6) has an interest in watching me work on the lathe as I teach myself the metal part.

My *primary* interest in getting into the metal side of lathe work is as an adjunct to our homeschool program. I want my kids to actually understand how one goes from idea to reality, and how math, logic, and effort go into that equation. My 6 year old, obviously, has the attention span of gnat. So, its important that I hold his interest by making interest projects fast. By "interesting", simple machines will do: threaded rods and nuts, "little kid blowing through a plastic tube" powered "steam" engines, etc.

Steel, however, while relatively cheap and very durable, is a 'slow' material. I'm wondering if there is a good alternative to steel from the perspective of still being cheap enough for a learning material, but much faster to cut, that cuts using basically the same process of metal (this lets wood out), and is available in round or square stock suitable for turning? Of course I don't expect it to be all that durable: if a device works 2 or 3 times then breaks, that's fine. If it breaks and he gets all upset, I'll use that motivation to build another from steel or brass or something.

lazlo
07-08-2007, 10:58 AM
Aluminum machines like butter, and it's usually around $2/lb at your local dump.

SGW
07-08-2007, 11:02 AM
Delrin (acetal) plastic is really easy to machine and pretty durable. It's not exactly "cheap," but maybe you don't need a large quantity, anyway.

Aluminum might be a possibility, but you have to pay attention to what alloy you get. Some of the softer alloys are very gummy to machine, and no joy at all. There are free-machining alloys that are really nice to machine though, and the ubiquitous 6061 is not too bad.

Check out the metals section of www.mcmaster.com

lazlo
07-08-2007, 11:11 AM
Delrin (acetal) plastic is really easy to machine and pretty durable.

Delrin is way more expensive than common aluminum alloys or steel, and to me it machines more like wood than metal.


Aluminum might be a possibility, but you have to pay attention to what alloy you get. Some of the softer alloys are very gummy to machine, and no joy at all.

6061 is just about the easiest metal to machine. That's why I was suggesting going to the dump -- 99% of the aluminum scrap you'll find there is 6061.

Swarf&Sparks
07-08-2007, 11:14 AM
Acrylic is relatively cheap and readily available in rod, tube and sheet.
It machines easily and has the advantage of "see-through" final model.
It will need polishing where machined if you need the see-through.

Evan
07-08-2007, 11:27 AM
Delrin (Acetal) is easy to machine but poses unique problems that metals don't. It has a low melting point that is particularly evident when drilling. It's a good material to make small demonstration projects but it isn't metal and doesn't behave the same.

I agree with Lazlo that 6061 aluminum is probably the best bet but the dump isn't a good source. Not much of the aluminum there is in a good machinable form and even less is in a T-6 temper which is necessary for good machining properties. Also, the dump here is not the place to find aluminum. It's at the scrap dealer. You are better off using a known alloy instead of mystery metal.

The biggest advantage of aluminum over steel for what you wish to do is that the swarf and burrs don't cut the skin like steel does. It can cut but not nearly as easily. The overall speed of machining isn't that much different.

lazlo
07-08-2007, 11:37 AM
I agree with Lazlo that 6061 aluminum is probably the best bet but the dump isn't a good source. Not much of the aluminum there is in a good machinable form and even less is in a T-6 temper which is necessary for good machining properties. Also, the dump here is not the place to find aluminum. It's at the scrap dealer.

Sorry Evan, agree completely, but I need to clarify:

The dump here in Austin is the scrap dealer: CMC Recyling. So when you walk in the yard, they have a building right inside the entrance with scrap bins full of CNC machining drops filled to the brim with 6061. On a lot of these drops/cutoffs you'll still find the certs printed on the stock.

Evan
07-08-2007, 11:48 AM
So when you walk in the yard, they have a building right inside the entrance with scrap bins full of CNC machining drops filled to the brim with 6061. On a lot of these drops/cutoffs you'll still find the certs printed on the stock.

I wish. Only in my dreams.

lazlo
07-08-2007, 11:51 AM
I wish. Only in my dreams.

Not metrology certs Evan. I'm saying the stock is stamped "6061-T6", so you know exactly what you're getting.

Evan
07-08-2007, 11:53 AM
I understood that. We don't have any real scrap dealer here. The scrap from the job shops is loaded up and trucked out of town.

Tin Falcon
07-08-2007, 12:43 PM
JG:
The primary materials used for small simple steam engines and such are aluminim and brass. Steel for shafts and bronze for bushings. 6061 aluminum machines well and is weldable. 360 brass is easy to machine and easily soldered. I typicaly use O-1 for shafts all these materials available from enco. Some people say Aluminum is too light for fly wheel material. I have several engines with aluminum fly wheels and they run fine .
You will also learn that it is recomended to use diferent matals for parts that run together ie a steel piston in a brass cylinder or a brass piston in an aluminum cyinder.

By Swarf&Sparks :Acrylic is relatively cheap and readily available in rod, tube and sheet.
It machines easily and has the advantage of "see-through" final model.
It will need polishing where machined if you need the see-through
Acylic makes great edutaional "toys" because of the see through feature. I have built and showed several, kids of all ages love them . You will notice the stair step display with the see through models top shelf this is because retired guys were just about standing on there heads to see how lucy works at my first show. She was just on the table as waist height then.

Here is some of my collection:
http://i78.photobucket.com/albums/j108/Tin_Falcon/CF2006-55.jpg
As far as durability all engines pictured have run for 8 hours at a time at the shows x two days x several shows. Sometimes a screw will back out and an engine will fall apart but a drop of locktite and you are back running.
Corian machines nice. Great material if you can scrounge scraps. My son and wife have built there own engines.
Tin

Mike Burdick
07-08-2007, 01:15 PM
jgourlay,

Others have answered your question about a material, but I'm going to address the "learning" part, which to me, is the "jest" of your post.

If you have a decent lathe then cutting a part out of steel will not be a big deal. If you browse thru the posts here on a daily basis, you'll find that most concern the properties of materials..."How do I stop this chatter..."The finish looks horrible, how do I fix it?"..."How do I grind a bit for cutting brass?"... etc, etc, etc. You'll never learn this unless you work with many different materials. Why limit your education from the start!

By the way, once you understand the turning process and what tools are needed, steel will cut like butter.

Mcgyver
07-08-2007, 01:49 PM
agree with Mike, steel is cheapest and you need to learn to work it. Plastic or AL will give a higher removal rate, but why would you want that if you're learning? two cuts on something that's easy to get a good finish on, or 8 cuts trying different feeds, tool geometry, learning how much flex there is, turning to dia, learning where the machine is off etc etc - you'll get more out doing it 8x than 2x and if you don't learn to cut steel (not that its hard to do) you will hobble yourself on future projects

besides, turning down a bar to dia will wear very thin in no time.....mostly what dictates material is the project at hand. imo you'd best to pick a simple one and learn to deal with the challenges it presents, material and otherwise

Tin Falcon
07-08-2007, 02:14 PM
JG:
I will throw another $.02 in
Mike and McGiver are right. You need to learn to work all common materials. I will also add that when I was in US Air Force tech school we only machined Aluminum. I am shure there was a good reason for this. I do not realy know what it was.
But learning to thread aluminum and making an aluminum tap is useless if you only can machine aluminum. steel and brass are much stonger fasteners. Aluminum fasteners are rare and the uses limited. Some project require special screws and threading is a basic skill.
An aluminum tap is useless. If you make a tap out of O-1 as a learning project and heat treat it you will have a usefull tool when done not somthing only good for show and tell and the scrap pile.
Tin

BadDog
07-08-2007, 02:35 PM
He wants the fast removal rate so he can quickly go from raw stock to a finished something. Remember, he's talking about a 6 year old. About the third tool/parameter change seeing nothing but diameter changes (i.e. “nothing” to a 6 year old) and that attention is long gone. The experimentation and additional materials can come once the attention is captured, and more maturity added so that not only patience and goal setting are more evident, but also additional safety issues (like avoiding stringy razor swarf) can be grasped. Our erstwhile student/teacher can work with steel on his own without the child/student to pick these things up after class.

Joel
07-08-2007, 03:27 PM
It depends on what one is teaching - lessons can easily be obfuscated by other factors not relevant to the task at hand.
For example, when first teaching someone to thread, I typically use 6061 so that full attention can be paid to learning the settings, motions, etc. Getting a good finish, dealing with chatter or work hardening and the like, are best left until the basics of the skill are understood and practiced.

darryl
07-08-2007, 04:06 PM
I've been using lathes and power tools for decades now, so I'm no stranger to turning different materials. About ten yrs ago I discovered PVC in the form of pipe discards. Having read that you can form it with heat, I cut some up, heated in the oven to 280 or so F, then flattened it between boards. It can be cut with a jig saw or table saw, or hacksaw, and is my material of choice to make prototype parts or finished parts. It's easy to work with, machines fast, and can handle being machined without distorting significantly. It's easy to break the edges with a scraping tool, it can be drilled and tapped easily. It does tend to catch a drill bit somewhat, so that's something to be aware of. Heating it is also something that you have to pay attention to- it won't hurt the oven or leave a smell behind, but don't get it so hot that it starts to bake. There are material safety hazards involved, but mostly that involves heating it beyond its forming temperature.

At any rate, it's mostly free material since it can be picked up as scrap from construction companies, etc. My fav is water pipe- I've found lots of that in the 24 inch diameter range, and when flattened it's a little more than an inch thick. I can consistently turn clean round bar over 1 inch diameter from strips cut from the slab, so that also becomes a useful starting material.

You can also, with some care in table sawing, cut strips out of the pipe pieces themselves, without having to heat and flatten the material to begin with. These raw strips can be chucked up and turned round, though you won't be able to get quite as much diameter out of it. This is because PVC tends to become thicker as it relaxes once at forming temperatures.

You can bandsaw it, but it will load up the teeth very quickly, and get on the wheels and guides. That's a pain.

Turning and milling it is fun, but it does tend to dull a cutting tool quickly. Very sharp works best for me, so that usually means HSS.

It's easy to make build-ups because is welds ok using the available cements. I think that's my worst problem with it- the smell of the cements is nasty. At any rate I'd recommend good ventilation regardless of what operation you'd be doing on it. I don't suppose that's much different than using cutting fluids for metal turning- you would still want to ventilate properly.

jgourlay
07-08-2007, 07:39 PM
Gents, thanks for the outstanding discussion!!

Materials: you all told me everything I wanted to know, plus a lot!

Education: I completely understand I need to work different materials with a focus on steel. What I am trying to teach, at this stage, is nothing more than a single lesson: You Can Make It if You Try!

Once that sinks in, then I worry more about really learning something. I started him in woodworking, and he can use in very rudimentary manner chisels, saws, and planes. If we wants a toy gun, car, axe, or something of the sort, he'll drag a board and his tools over to me, "daddy, can you help me make this?"

I want to move that desire to the next level. Thanks again for all your great lessons and suggestions!

Tin Falcon
07-08-2007, 08:32 PM
Education: I completely understand I need to work different materials with a focus on steel. What I am trying to teach, at this stage, is nothing more than a single lesson: You Can Make It if You Try! I Am not sure the focus needs to be on steel. It is a part of the puzzle. At this point you need to light the fire then feed with the details.Like I said Aluminum is used by the Air force to learn on.
Here is a simple little engine you may want to build with your son
http://i78.photobucket.com/albums/j108/Tin_Falcon/Newton.jpg
http://i78.photobucket.com/albums/j108/Tin_Falcon/Newton1.jpg

it is an altoid tin with a simple hat bushing in the bottom it has several small holes evenly spaced on the perimeter and vectored. just punch with a nail and turn sideways for the jets. Seal the can with electrical tape. the base is just a piece of aluminum with a 1/4" nipple to fit the bushing. the hole on the side is drilled and tapped for 10-32 then a barb fitting to hold plastic tube and fed with compressed air. The block was held down with double sided tape. The buterfly box just happened to be handy and somthing to stick the base to. Folks at the shows love the simplicity.
Tin

jgourlay
07-09-2007, 12:53 PM
Sweet!!!! I really like that and looks about the perfect scale and complexity!

oldtiffie
07-09-2007, 02:24 PM
Deleted/erased-out

DR
07-09-2007, 03:31 PM
A material that's really excellent for machining is ABS plastic. Of course, being plastic it may not be the cheapest stuff in town.

Over the years we've used this in all sorts of prototype parts. It paints well, and can be shaped and sanded by hand.

One of the best features of ABS is it glues easily. Make a mistake and just cut the bad part away and glue in a new replacement section. Super glue is what we used.

Tin Falcon
07-09-2007, 10:05 PM
Oldtiffie:
That sounds like fun. When I worked on the military range we sometimes had to "Dispose of surplus" One time we were given 500 rounds of 40MM Practice grenades for the M203 launcher. Another time we got a case of hand grenade simulators. You know how some folks will launch a 1 lb coffee can with a firecracker or cherry bomb. We were launching 55 gallon drums 50 ft in the air with the simulators. you could only do it a couple of times as the force of a couple bangs would start to tear the bottom out of the drum.
Tin

Paul Alciatore
07-10-2007, 02:53 AM
Not wanting to restare any debate, but if steel is desirable, the 12L14 alloy is very easy to machine.