practice materials

[Rayanth]

Another weekend, another newbie question from Ryan ;D

I'm a firm believer that one can never do too much planning in advance. While I still have no shop, and am settling on the machines I want to populate it with, I am looking at my (lack of) skills, and realizing I will probably waste a lot of metal if I just dive into a project without brushing up on skills and learning the machines first.

In the interest of saving money, what is a good cheap material to practice with? I have reasonably easy access to scrap wood (usually pine), but not sure if the properties are even remotely similar enough?

Anything else that is cheap, or readily available as scrap, that would make good practice material?

- Ryan

 

[nfk]

Hi Ryan,
I think for general turning practice wood would be ok to maybe gather some practice about the required steps for a specific piece.
I believe you would need to try sooner or later the actual material, and you`ll find a very different situation than with wood (or delrin, which is quite cheap also)
Different materials require different techniques, at least different cutting speeds and in most cases different tool shapes.
It`s not the same to turn brass than 4140 steel!
I`ve learned the hard way and now i feel comfortable with any material i`ve tried.
Maybe i`ll say otherwise when turning stainless

my $0.02

Norberto

 

[Lakc]

While on occasion we do turn wood, it only teaches you to turn wood, and unless cleaned throughly it can turn acidic and eat you new machines.

Turning scrap metal will teach you all about blood pressure medication. Its hard enough to get a feel for a machine but when one piece cuts ok and the cutter destroys itself on the next part, its just frustrating. I wasted more cutters on garbage steel and gummy aluminum then I ever saved in material costs.

6061 is the cheapest of the good cutting aluminum, and 12L14 is the same for steel. You already dont know your machines cutting ability, or your tooling, try and keep your material from the known good pile.

 

[Tin Falcon]

When I was trained by the U.S. Air Force we were given class time to teach the basics of a particular block of instruction . Then given a written test to make sure we "Got it" then to the lab. The instructor would give a 20 minute to 1/2 hour demo on the machine then we would be handed a piece of aluminum and a print and expected to make the part Initially the tasks were simple like take a piece of 1" aluminum round stock and face the ends on the lathe to make it 6 inches long +_ 1/64 of an inch. then turn down one end to 3/4 inch withe a shoulder of a given size. A simple project was a hat bushing. The material we used was all all aluminum. There was supposed to be one steel item but for some reason my class never saw it.
My suggestion is read all the books you can on basic machining Also learn to sketch and free hand draw and a bit of mechanical drawing manual and cad can not hurt. Take a set of plans for an engine you want to make and redraw each piece onto a file cars 3X 5 or 4X 7 does not really matter but it will give you an understanding of each part.The card will be handy next to the machine when making a part. A lot of "practice pieces" occur from lack of blueprint reading skills rather than lack of machining skills. Also learn part processing sequences this will take time and is really only gained fully by experience. But most new folks will look at a part cut a piece about an 1/8 bigger and go at it this may be an ok approach but in many instances say with that hat bushing you are better putting the whole 6"- 13" piece in the lathe and machining the part on the end of a big piece.

You will not waste a lot of material. You may have to make a part 3 times before it is to you liking. but each piece you make whether usable for an engine or not you will have learned something. I tell folks repeatedly you shop is like a University laboratory no mistakes just learning experiences. just consider the cost of a few pounds of aluminum your tuition for the semester. Aluminum can always be recycled.


CNC learning labs sometimes will use machinable wax to test g Code programs . this can be purchased or you can make your own and you can remelt the chips and unwanted prototypes the wax parts can also be used for patterns for castings.
Recipe for machinable wax here.
http://igor.chudov.com/manuals/Homemade-Machinable-Wax.pd
I second the opinions on wood turning nothing wrong with it but it will not teach metal properties. and the same with scrap. part of this game is learning the properties of various metals . And mystery metal will not each you much but patience , perseverance and a few colorful metaphors that were never in your vocabulary.
Tin

 

[mklotz]

As others have said... Practice on the materials you will eventually use - aluminum (6061), brass (360) and steel (12L14) (in about that order). Order some lengths from one of the many online metal sources. Given the investment in machines you've made, the price of a few bits of metal is negligible. The post-practice leftovers (if there are any) can always be used to make legitimate parts.

I'll also suggest that your practice should consist of actually attempting to make some simple part, not just randomly cutting on a piece of metal. If you have children, try making a small top from each of the three materials. Later, when you've gained some expertise, try making a nut and bolt from each material - extra points if they're all interchangeable.

 

[Tin Falcon]

I'll also suggest that your practice should consist of actually attempting to make some simple part,

What Marv said.
When you get your first lathe you will want to chuck up a piece and face it and turn it and that is fine . But beyond that have a goal of making something useful. I can be a toy or a candlestick or an engine part. If it does not turnout as you like do it again. but in my opinion it is hard to motivate just making chips .
Tin

 

[Maryak]

IMHO,

The most common metal used is steel and it's probably one of the cheaper metals. When you can work with a range of steels from mild through drill rod to stainless and cast iron, the non ferrous pretty well falls into place.

As an aside this was the sequence used during my apprenticeship 50+ years ago, things have probably changed a little since then ;D

One other thing I would add is; start out with your 4 jaw chuck and learn how to centre round stock using a piece of chalk.

As others have said try for something simple but useful. (My 1st was machine washers for a set of calipers).

Hope this helps

Best Regards
Bob

 

[Rayanth]

Thank you all for the words of wisdom. I suspected wood would be too...nonmetallic for practice, but as I have ready access to it it was briefly considered. I think I will end up starting off with aluminum, and just working on what looks like the simpler parts of an engine before doing the harder parts. I have experience, although atrophied, and more with a mill than a lathe. I was just looking for input on keeping materials costs low while I regain the basics, but all of your input will certainly be kept in mind!

- Ryan

 

[bentprop]

Ryan,I think you will find pine is absolutely useless for turning.It's stringy,splintery stuff only good for shelves.
If you are near any car wreckers,see if you can get a couple of old back axle half-shafts,car or even better light truck/pickup.These are usually a form of alloy steel,and should be reasonably cheap.
Also,as far as plans,etc. goes,here's what i do:
I copy each part of the plan onto A4 sheets,using a common computer 3-in-1 printer.Then i use these copies in the workshop,and keep the original plan pristine in a folder.
An added advantage of this is you are able to enlarge any part that's difficult to get your head around.I find making such a part larger often makes things much clearer.

 

[Rayanth]

regarding plans, most likely I will end up rebuilding them in my preferred CAD program anyway, which gives me a better visualization of the parts and process, and will let me make digital measurements with ease

Regarding scrap... I've never been particularly good at asking for that kind of stuff. Always feels like begging, and that goes against my upbringing

- Ryan

 

[Mainer]

What the others have said...get known metals and experiment with them. Presumably you're talking about relatively small parts, and parts that turn out to be "learning experiences" won't waste a lot of material. Even if you do mess up, the material cost per hour of shop time is low. I can spend several hours working on $2.00 worth of aluminum before I give up and throw it away. ;D

You can try to use free "mystery metal" but if it turns out to be terrible to work with be prepared to give up on it promptly...starting out, you don't need the aggravation.

BTW, the steel stock from a hardware store is dreadful stuff. Don't bother with it.

Your idea of redrawing parts in CAD is IMO excellent. I do it all the time, adding extra dimensions to make the machining easier.

 

[Tin Falcon]

There is noting wrong with "scrap" if you know what you are dealing with. And no one mentioned begging or scrounging.
I have had the good fortune of liberal scrap privileges at several places I have worked I have collected cherry wood , corian , some aluminum sheet a bit of steel Lucite etc. Nothing wrong with it at all it saves me money and less stuff in the dump.
But like it has been said mystery material can case frustration some plastics will suck in a drill bit and hold on for dear life you may not get it back at least not without a fight no joke.
Tin

 

[Captain Jerry]

I think it interesting that machinists talk as if wood is wood. This is no more true than to say metal is metal. There is a huge difference in the characteristics between do-it-yourself aluminum and alloy steel and there is a huge difference in characteristics between a piece of construction grade fir and a piece of walnut burl.

There is one thing that is constant in machining any of the above. EDGE! To improve your result with any of the above materials, learn to produce a sharp! edge. You can get a nice finish on gummy aluminum and 12L14 with the same tool if it is sharp. Tool shape is important of course but the most important is sharp.

I think you can prove this to yourself on almost any material.

Jerry

 

[n4zou]

Machinable Wax. You can make it yourself for little cost and reuse it.

If creating your own design you can produce a prototype in machinable wax.
This includes casting parts in wood molds because the temperatures involved are low.

It produces no wear on tooling and if you "crash" a tool into it no damage is done.

http://www.machinistblog.com/make-your-own-machinable-wax/

 

[radfordc]

Search on ebay for cheap metal. I bought 20 lbs of 12L14 1.5" round cut offs for about half the going price. I've also found bargain brass and aluminum.

 

[jdsackett]

If you're looking for practice material, nothing beats a local scrap yard. If you have any. I go to a couple of them here locally. One is better for aluminum and brass, the other steel. I can buy scrap aluminum for a buck a pound. Square, flat in various thickness and width, short round stuff. Not much long round stuff. Most the aluminum is marked 6061, some is unmarked, but all of it will make chips. I can go spend half a day and 20 bucks at a scrap yard and it keeps me out of trouble for weeks. Steel is harder for me to find for some reason and unknown alloy. Most the stuff i do, it doesn't need to be any specific alloy. If it does i buy it at a local steel yard or ebay. Have gotten some good stuff off of ebay for good prices. Check the yellow pages for some local scrap yards and let your fingers do the walking till you find someplace good. Good luck. Regards, j.d.

 

[shred]

Another source (the good scrap place here quit selling to people a while back) is the places that sell new metal-- often they'll sell 'drops'; the cut off ends of bars that are shorter than their customers want (they used to give them away, now not so much). The good thing about those is they often have the markings or color code still on them so you know what you're getting and the sizes are convenient for small machines. If you have any metal suppliers in the area, call them and ask if they sell drops.

 

[Tin Falcon]

Machinable wax was mentioned
http://www.machinablewax.com/machinable_wax_cylinders.htm
tin

 

[Maryak]

Another source (the good scrap place here quit selling to people a while back) is the places that sell new metal-- often they'll sell 'drops'; the cut off ends of bars that are shorter than their customers want (they used to give them away, now not so much).

"GIVE THEM AWAY." ...........Locally we have a company who charge like a wounded bull for the "drop" or as we call them "offcuts." e.g. a piece of phosphor bronze 32x75mm $AU36.00, ($US38.00)

They make an absolute killing, there is no cutting and it's take or leave it.

On the other hand we have another who will sell a metre of drill rod 5/8" dia for $50.00. Compare that to a price on Oz EBay of $50.00 for 100mm + postage.

Adelaide is a provincial city, so there is little if any competition for non ferrous and specialised steels.

Best Regards
Bob

 

[Tin Falcon]

If you have any srew machine shops in your area they make be able to sell you some short pieces.
Tin