Cutting tool preference for Aluminium

Paco,

Beautiful finish on those billets. I'd like to achieve something similar.

The type of tool that holds those inserts are usually 20x20mm or the smallest I've seen on the net are 16x16. I have an AXA tool post so just a bit big but would there be any detrimental effects if I get the blokes at work to machine the tool stem down to fit the AXA?
 
Boris Ludwig said:
Paco,

Beautiful finish on those billets. I'd like to achieve something similar.

The type of tool that holds those inserts are usually 20x20mm or the smallest I've seen on the net are 16x16. I have an AXA tool post so just a bit big but would there be any detrimental effects if I get the blokes at work to machine the tool stem down to fit the AXA?
Click to expand...

Boris,
I don't see an issue with reducing the tool holder shank size to fit a AXA. HSS works just as good with a sharp cutting edge. I use inserts for convenience . I run a CXA tooling and for a time the tool holders where inexpensive on eBay all day every day, not so much now.
If you want a dedicated insert cutter for general aluminum work, I would consider modifying the holder. I don't know whats available for AXA as I never owned one.
Paco
 
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Well, I tried the recommended method and the polished CCGT AK inserts and SCLCR1212H06 holder. The outside is better but still very slightly ridged.

The internal was woeful and made a ringing noise. I checked everything was tight and it was so I gave the boring bar some angle and had the carriage feed out from the chuck. And it improved. But it still shows a slight 'w' patterned cut as you can see how it reflects light. On both surfaces I used WD40.

So it's better but I've got a long way before I can say they look like what I see in your photos.

Any other ideas?

BTW thanks for your contributions so far, it's great being helped by all here. Cheers.


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BTW, external cut speed was 620 and feed was .051mm.

Internal improved at reduced speed 530 with the same feed.
 
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Used diesel as cutting fluid for aluminium with good results.
 
Boris,
Make sure you only have enough tool sticking out as need. Choke up as much as possible wherever possible. This also applies to chucked material. Rigidness is paramount to reduce chatter. If you notice the turning operation in my second photo (post #18), The cutting tool is clamped in against the holder with no excess stick out and I'm using a CXA. Point being even with larger tooling, I still choke up as much as possible that the operation allows. On boring operations, again only as much stick out to reach your target depth with the compound locked (if possible) and centered with no overhanging. Every machine is different, I been running my lathe since 2001 and know her very well. The other advantage I have is the ability to change the speed on the fly via VFD and rheostat. If you hear, feel vibration then something is off resulting in a poor finish. BTW, your finish doesn't look bad to me considering how it was chucked up. Order of operations can make a big difference in how you end up chucking a piece. When ever possible, you should avoid chucking with more material hanging out like in your second photo. If your at the limits of your chuck, then thats the only choice you have but lite cuts might be in order.
A quick touch with steel wool would polish it up with minimal reduction in material. I keep 00,and 000 steel wool handy when working with alum. Heres what those hand wheel dials look like after polishing with steel wool. No measurable difference after polishing. Just be carful when polishing a bore as it could result in injury.
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Keep on keeping on Boris, youll find your machines sweet spot on different materials.
Paco
 
Boris, which insert are you using for external work? If it is a CCGT 32.51, you can improve the surface finish by trying a 32.52 insert(next larger nose radius) and increasing speed. You can also try angling the tool maybe 5 degrees toward the tailstock and that will improve the finish with your current insert.

For boring, that looks like a 1/2 diameter steel bar so you have a max extension of 2". If I had to guess, the first pic with the chewed up bore suggests the tool is not on center height, the tool angle may be off or the insert may have been damaged. You want to keep the shank of your bar parallel to the ways with these inserts and only cut going in so you don't break your insert. Feed fast enough to produce short coils, not tiny chips, and do not pause or stop on entrance to the bore.

By the way, that ringing noise is chatter. To resolve it, you need to have the right cutting speed for your diameter, adequate feed to produce coils and sufficient depth of cut to bury the nose radius in the cut when roughing and a depth of cut greater than 1/3 the nose radius when finishing (cut feed by 1/2 when finishing).

The AK insert is a good one. Check the box or consult the manufacturer's literature for the required cutting conditions and you'll be fine.
 
firestopper said:
Boris,
Make sure you only have enough tool sticking out as need. Choke up as much as possible wherever possible. Paco
Click to expand...

^^ what he said ^^

I like the continuous shank boring bars because you can minimize stick-out to the depth of bore & not much more. Just be careful of toolpost interference & small gaps seem to attract swarf getting up in there. I noticed my cheapo thicker/continuous section shank (16mm) boring tool cuts a bit better & defers noise than my thinner shank (13mm) tool which necks down from the clamp part to the tip. Its intended for smaller minimum bore entry but I'm just saying there is less material to resist bending & torsion. The bigger tool is an AliExpress special, I suspect something made of 4140 type steel mixed with tuna cans judging by how it cut with a saw when I modified a similar one fo boring head.

Some other things to ponder

- those same uncoated inserts come in a host of variable nose radius. Larger radius makes for better finish (but require a bit more oomph 7sometimes don't like minimal skim cuts)

- if you are hearing harmonics, experiment with the rpm and/or feed. maybe I missed, but how much in-feed? Boring tends to favor less & ringing can start to happen on thinner remaining shell. Ive heard some people apply things to dampen but Ive never been brave enough to have a wad of putty fly off in my face :)

- boring bar work inevitably involves deflection, so lock the cross feed when turning and do a spring pass (or more) ideally at different fed rate settings so the cutter doesn't feed into its prior track so to speak, rather you want it to cut across the previous hill tops

- so many cutting fluids to choose from, but just make sure your edge does not hav ealuminum welded on the tip or even chipped tip. Harder to spot on the uncoated ones, I need my magnifying glass

- look for any debris under the insert, all it takes is a whisker & the geometry is off. I wash mine in a thimble of thinner before assembling.
 
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