what aluminum has the smoothest cutting properties

[metlmunchr]

"Posted by person another another forum The statement about the nature of Fortal vs. 7075 (i.e. chemistry) is essentially correct. Like the QC-7, Fortal is basically off-spec 7075, but if I recall correctly, Pechiney has a process to manufacture a product with high properties that are essentially the same throughout the plate. In thicknesses over 4", this is very important, as 7075 tends to get "gummy"
towards the center of the plate.""
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That could very well be the case. The sole US importer of Fortal stresses its dimensional stability and consistent machining characteristics for use in short run molds as a cost saving effort compared to mold steels. Mold use would obviously imply heavy sections. Mold steels are far from cheap, and an aluminum material fine tuned for mold use would command a premium price and still be cheap based on time savings. I suspect it performs as stated. However, I seriously doubt all the hundreds of "Fortal" cutoffs of rounds, flats, plate, and every other imaginable shape peddled over the internet have ever spent even a moment of their lives in France. I just can't envision metal warehouses across the US filled with a premium priced 7075 variant, whose specialized properties aren't even applicable at common thicknesses, shipped in from 6000 to 9000 miles away, in the hopes some shop owner with money to burn will happen along and buy the stuff. I'd guess most of these drops are run of the mill 7075 being peddled by the typical less than honest internet clown. The company who imports Fortal will sell it to anyone who wants to buy it, in cut to size sections, so there's no reason other metal distributors would be selling or processing it to generate these drops.

[sendkeys]

Originally posted by metlmunchr " seriously doubt all the hundreds of "Fortal" cutoffs of rounds, flats, plate, and every other imaginable shape peddled over the internet have ever spent even a moment of their lives in France.

rofl didnt think about that very true

[mineralman]

I have been turning and milling 6061 hobby stuff for about two years. It machines okay. For some experimentation, I ordered some 2011 aluminum. Machining the same parts I've been making for two years, the 2011 is head and shoulders above the 6061! The chips from holes peel off so easily and machine so smoothly. It machines so nicely that it's worth the little extra 2011 costs to machine some of the more difficult parts.

BTW, I machine everything dry except when threading (Tap Magic for that). Lubricants just don't seem to help aluminum.

Larry
New Orleans

[metlmunchr]

Yep Larry, 2011 screw stock is nice stuff to work. You just have to pay attention to the final application of the part, since 2011 doesn't have nearly the corrosion resistance of 6061. Most of the metal suppliers' catalogs will have a table listing how each of the common alloys rates in various categories such as strength, corrosion resistance, and machinability. I mentioned 6262-T9 in an earlier post. It's got the corrosion resistance of 6061 and the machining properties of 2011. Why it's so damn hard to find is beyond me. Using aluminum specific inserts can be a big aid to getting good results regardless of the alloy being worked. Like is often the case with tooling, some of them look real expensive until you actually try them and realize the results you're getting make the tooling cost per part seem cheap in comparison to tooling that may initially cost less.

[svenakela]

I was making a pretty uge mould once and couldn't get the cuts nice at all, until my working friend poored his soda on it, the surface went from terrible to mirror polished in a second. All I had to do was to add some water and then it was the best cut ever. Since then I've been using water with a little bit of soap when I've been cutting aluminium with very good result.

Cheers,
Sven

[mineralman]

[QUOTE]Originally posted by metlmunchr
>I mentioned 6262-T9 in an earlier post.
I've not heard of 6262. Is it a new alloy? Actually, I'm looking for something that machines like 2011 and costs like 6061--- in other words, cheap! The application is nothing that requires strength or corrosion resistanct.

>Using aluminum specific inserts can be a big aid to getting good results regardless of the alloy being worked.
I'm looking into getting some insert tooling for my lathe. What's a good insert shape/style for turning aluminum?

LarryO
New Orleans

[metlmunchr]

Larry, 6262-T9 isn't a new alloy. When I've managed to find it now and then, it's typically priced about the same as 2011, or a little higher than 6061. Like everything else, the price is directly tied to the volume produced.

If you switch to aluminum specific inserts, chances are you'll be able to do your parts from 6061 and most likely get far better finishes than you're getting now with 2011. Travers Tool handles a Korloy brand of insert that I've found to work great. It's a micrograin, uncoated, super high positive rake with surfaces polished such that they look like they're chromed. I'm using a CCGT 32.52 for normal turning and boring. The C shape(80 degree diamond) has excellent strength. For profiling which requires more clearance I use their DCGT 32.52 (55 degree diamond). Either of these inserts retail for about $5 each, but Travers has been running them on sale for about 3 months now at less than $3.75 each. For some reason, similar inserts from most any of the other carbide makers run in the $12 to $14 range each. I've been using the Korloys for about 6 months now and their life is very good. I've found JTS machine supply (on Ebay) an excellent source for boring bars for these types of inserts. For example I bought a couple of 1" bars for CCGT's from them for $33 each, brand new, and they're great. Similar bars from the major manufacturers are in the $160 range. JTS usually has these listed in various diameters from 1" down to about 3/8 or 5/16. The smaller ones are under 20 bucks. For turning toolholders, U S Shop Tools is a good source at decent prices. They list them under Swiss type toolholders. They sell direct, but generally not on Ebay. Most all this tooling will be listed as using CCMT inserts (or DCMT or whatever) which is a steel cutting variety with a molded chipbreaker. The CCGT's also fit the same tooling. The main characteristic of the tooling is a neutral rake seat made to use screwdown inserts with 7 degree clearance. Try some of these and you'll throw rocks at anyone who suggests you go back to the old methods of turning aluminum One caution: run these or any insert turning tooling either flooded or dry, but don't attempt squirting a little coolant on them now and then. They can stand heat, but thermal shock will fracture the edges in a heartbeat.

[BT1]

We were talking about this recently and an interesting point was made about alluminium purchased that was virtually sitting there for twenty to thirty years, full large size plates varied thicknesses grades etc.

Machining this is absolutely beautiful, zero warpage. Guess time cures all.

[metlmunchr]

Originally posted by BT1 We were talking about this recently and an interesting point was made about alluminium purchased that was virtually sitting there for twenty to thirty years, full large size plates varied thicknesses grades etc. Machining this is absolutely beautiful, zero warpage. Guess time cures all.

That would certainly make sense. Certain heat treatable alloys of aluminum such as 6061 are "solution heat treated and artificially aged". The artiificial aging means the metal is brought to some elevated temperature after the solution heat treatment to achieve the same state that the material would achieve over some long period of time at room temperature. It seems reasonable that a chunk of plate sitting for 20 to 30 years would undergo some further aging past its as-produced condition. Sometimes aluminum is "over-aged" intentionally to produce a more stable form, although this additional stability comes at the expense of some loss of strength. Certain alloys will age fully at room temp in 4 or 5 days. In some instances it's desirable to fabricate them into some structure and let the aging take place after the structure is complete. Fabricating 2024 sheet is a good example of this. In the aged condition 2024-T3 sheet will break like glass if you attempt to bend it in a brake. To facilitate this, the aluminum is stored at -50 to -100 degrees F until ready for use. The age hardening then takes place after all necessary bending etc is complete.

The two tempers we most often encounter as machinists are -T3 and -T6. T3 is solution heat treated, cold worked and naturally aged. If a material carries a T3 treatment, such as 2024, then you know its one of the alloys that ages quickly at room temperature. T6 is solution heat treated and artificially aged at room temp. A material with a T6, such as 6061, would indicate its one of the alloys that does not age quickly at room temp. Further number designations, such as T6511 which is commonly seen on extruded 6061 shapes, are just further refinements of the process indicated by the first number in the string (the 6 in this case) and are generally not of significance to us as machinists.

[BT1]

metlmunchr,

Interesting man.

I was told the Japanese leave machine housings - castings outdoors, painted throughout, for periods of time as a curing, aging type process thus making them more durable etc. Before they finish building the machine etc.

Then came the topic about Chinese machines!!!

[metlmunchr]

Cast iron will definitely walk around if its not aged prior to machining. Heat cycling in an engine where the block wasn't fully aged before manufacture will cause significant movement. I've re-bored some large diesel engine blocks for oversize sleeves in a horizontal boring mill in the past. In a dry sleeve block where the sleeve bore looks much like the cylinder bore (long and straight), you can take a light initial cut and see all the places where the bore has changed shape over time. This is not from wear, as there is no movement between the sleeve and block. If you go back to a service manual and check the bore spacing spec, you'll generally find its off as well, indicating movement of the entire casting. I've seen variations in excess of .010" in where the bore is as compared to where it should be. In doing this work, the goal is to use the minimum oversize sleeve, but if the goal is to correct the bore spacing as well as correct deviations within individual bores, it becomes a tedious process where all bores have to be indicated true and their positions recorded, and then the amount to be machined out of each cylinder is calculated based on the cylinder whose position is furthest from its specified centerline. The real fun part of work like this is when you go thru all the process of determining where everything is and how much to bore, and then, on the last cylinder, the boring process shows up a crack the magnaflux failed to detect. You now have a large chunk of scrap iron that just happens to look like an engine block