March 14, 2013
Again sorry for my beginner questions.
I went to the scrap yard the other day to get some aluminium for a job, found a crappy looking old piece of 39mm round stock which was perfect. After getting it home and putting it on the lathe I was absolutely amazed at how well it turned, couldnt make a bad cut. Then I had a piece of 10mm steel bar in there and its horrible to turn, very grabby and binding a lot.
So I was wondering what metals are good to turn and which are bad? I want to make my jobs look good with out filing and sanding all the time.
Thanks in advance,
July 23, 2010
Hi, Symesy. As you progress, you'll find that "aluminum" or "steel" just aren't descriptive enough to tell you how well it machines. You need to know what alloy you are working with. Some aluminum turns beautifully, whereas other alloys are gummy and can form a crust on your cutting tool. 6061 and 6063 are not supposed to machine terribly well, but end up machining well enough. Alloys with more silicone in them, which are used for castings machines really, really well.
As for steel, I would go so far as to say that no other metal varies in its machinability as much as it (jump and correct me if I'm wrong here, guys ;) ). Not only do you have to worry about which alloy you have, you need to know if it is hardened or not, how much it's been hardened, etc. When I was starting out, I made the mistake of grabbing a bar of scrap from the local dealer, thinking that it would be perfect for practicing on. In my ignorance, I grabbed a piece of structural steel! The stuff was so tough that it just tore through my tool bits rather than the other way around! Of course, I bet that I could machine the stuff a little better today, but it probably would be hard-going nonetheless. Another thing to avoid is ground shaft (very high surface hardness). The best machining steel that I have ever worked with is 12L14, which has a little lead in it that makes if cut super smoothly. 1018 is a good all-round alloy, I fined. If you google. Finally, if you have a tool bit that is ground properly, brass can be a joy to turn, but can get a little pricy for "practice work" :)
The last thing that I will say is to watch your speeds and feeds. Each material has cutting speeds specified for it, and if you follow those guidelines, you will find that your cuts will be much nicer and your tool bits will last longer!
January 9, 2009
Never apologize for beginner questions. There are plenty of forums out there that get snippy with beginners. This (proudly) isn't one of them. This site was started for amateurs by an amateur (me). I still learn from beginner questions. So keep asking them!
I can second Chris's recommendation on 12L14. I just turned my first piece a few days ago and it wasn't gummy at all.
OnlineMetals.com has a metal buying guide that talks about different alloys and their machinability. They also sell bar stock sets in different diameters for aluminum and steel in 3' lengths. It's a relatively inexpensive way to get a variety of sizes of the same material.
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