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Need Help Breaking chips in Aluminum

p3446

Plastic
Joined
Jun 17, 2024
Location
Sunnyvale
Hi, I'm od turning a 12" part aluminum 6061-T4 and I'm unable to break the long chip. I'm using a ccgt 120408-af insert(link) with a chip breaker specifically for aluminum. The depth of cut is 2mm and I have tried feeding it as low as 0.25mm/rev( 0.01in/rev) and as high as 0.425mm/rev( 0.017in/rev) but the chip doesn't break. The max recommended feed for that insert is 0.3mm/rev(0.012in/rev). Do you have any recommendations? would a different kind of insert help?
Thanks
 
Most inserts made specifically for Ali suck at breaking chips...........too many of these inserts are just a big "dish" and the chip just gets pushed up and outa the way but never snaps off............you gotta find an insert with a shallower and shorter breaker so the chip actually gets curled up enough to break. I have a CNMG insert I use.....I'll have to go look at the exact style.
 
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I had to look it up because I don't think I've never used it, but T4 is very soft compared to T6/651.

65HBn vs 95 HBn.

The cutting data you've posted would fairly reliably break a chip in T6 with the insert you linked. I usually have .4mm/r as a base minimum when roughing T6. I generally use CNMG alu. roughers, but that's only because I have a big lathe that can take a big cut. At 2mm DOC the insert you linked is probably optimal. You could try a sharper nose radius as 0.8 is a bit big for a 2mm DOC and that might hinder chip formation.

In your T4 I think it's going to be a struggle no matter what... If you push the feed too far you'll get a big blob built up on the cutting edge followed by a crunch, but I strongly suspect you're going to need to be up around .7mm/r to break a chip. It will be a fine line to tread, and it might simply not work.

Does your lathe have any interrupted feed function? Live tools such that you could notch it for an interrupted cut or even turn mill it?
 
I also use a CNMG for my alu cuts. I do about 2200 SF .200" DOC and .012" per Rev . on a 1.0" mclnr tool holder. I use a CNMG 432 H13 for non Ferrous metals insert. I don't really use the for aluminum inserts that much.
 
Whenever I'm needing to break a chip in aluminum I use a steel roughing insert and then switch to an aluminum only insert for finishing with another tool when using a CCxx insert. Spent too much time in the past fighting stringers.
 
I had an aluminum job recently where I couldn't break a chip with a high-positive CCGT insert made for aluminum. I switched to a high-postiive CNMG (CNGP?) insert for aluminum, and it broke the chip just fine with the same cutting parameters. It surprised me. Something about that negative angle of the tool that broke chips better.
 
I had an aluminum job recently where I couldn't break a chip with a high-positive CCGT insert made for aluminum. I switched to a high-postiive CNMG (CNGP?) insert for aluminum, and it broke the chip just fine with the same cutting parameters. It surprised me. Something about that negative angle of the tool that broke chips better.
Yup.........that's been my experience too.
 
The best way I know to break 6061 chips is to use a polycrystalline diamond insert with laser-machined chipbreaker. I use these, but I think Becker and maybe Sumitomo make the same kind of thing:

https://www.ranitool.com/RTC_DTS_PCD_WEB.pdf

They still need some DOC and feed to break chips like 0.5 mm DOC and 0.05 mm/rev works well for 6061-T6. I expect T4 will need more aggressive feed and DOC.

Breaking a 6061 chip with a carbide insert is difficult unless you feed the heck out of it. And then you can't get a fine finish. Seems like nobody has figured out how to mold as an aggressive of a chipbreaker in carbide as can be laser-machined in diamond.
 
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I have had luck with using stainless specific inserts in Aluminium to help break the chip.
I don't have exact specs but last time from memory I used a variation of Taegutec and Widia stainless specific inserts in a negative CN shape.
 
Can you cut this operation without coolant?
We have some high standards for finish quality on our aluminum parts and have always suffered from stringy chips because of that. Using PCD inserts we could never run fast enough to break a chip (limited to 2000RPM due to workholding/part size) so there would always be a rats nest gumming up the conveyors. After trial and error I found a recipe that works pretty well, using much cheaper carbide inserts by running finishing passes dry. The extra heat makes the chip more brittle and help it break apart.
 








 
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