# Cutting tool preference for Aluminium



## Boris Ludwig (Jan 28, 2018)

Just wondering if HSS as opposed to carbide is the prefered tool for cutting aluminium on a lathe?

I've tried carbide but seem to get a "gritty" or "torn" surface finish on the part. I've tried faster speeds up to 1200 rpm and slower feeds but can't seem to get it to work well. This has been true with boring internal surfaces too. 

I've used HSS and I seem to get a better result but I'm wondering if I'm overlooking something with carbide tool use. 

Any comments that might be helpful are appreciated.

Cheers


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## benmychree (Jan 28, 2018)

I(f you use carbide, use uncoated inserts, they have a sharper cutting edge than coated; HSS is good too, using a ground in chip breaker to curl the chips; the most important thing as to finish is using a cutting fluid, traditionally kerosene was used, but light cutting oil works too (non sufurized) or I use Tap Magic, applied with a brush, water based coolants also work, but oil is best for finishing.


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## wrmiller (Jan 28, 2018)

Some 6061 just looks like crap, no matter what I cut it with. 7075 on the other hand... 

I use carbide exclusively on my lathe, and have found that the polished 'aluminum only' inserts work really, really well. Careful with them though as they are near razor sharp as I soon discovered when I ran my thumb down the edge of one! 

They also work really well for steel, but I only use them for finishing passes so as not to damage the cutting edge.


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## mikey (Jan 28, 2018)

Boris, if you want to stay with carbide, try the SCLCR tool holders with a CCGT AK insert. They are ground, polished, have a chip breaker that actually works and will give you the ability to rough heavy while also producing a fine finish with lighter cuts. The same holders will also take CCMT inserts for use with most other materials. For aluminum, this is one of the best inserts I've seen. I tend to run these AK inserts as fast as my lathe will go and have had very good results.

A well ground HSS tool will do as well or better (better in my opinion) if you get the geometry right. 

I use both kinds of tools but 90% of the time, I reach for my HSS tool.

Hands down, the best cutting fluid I've seen for aluminum is Relton's A-9. WD-40 works pretty good, too.


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## Hawkeye (Jan 28, 2018)

I often use Crisco to lubricate aluminum. Brushes on with an acid brush and stays in place, until it gets hot, then flows like oil.


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## wrmiller (Jan 28, 2018)

I recently received PM's lathe tool and boring bar setup (BXA) that takes the CCGT/CCMT 300 series inserts. Set comes with inserts for aluminum and steel. And I only have to remember one size/config of insert when I need more. Those insert charts make my brain hurt...


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## Boris Ludwig (Jan 29, 2018)

Thanks, that's all helpful. I'm going to try those suggestions and report back with my results in case I'm doing something wrong.



Hawkeye said:


> I often use Crisco to lubricate aluminum. Brushes on with an acid brush and stays in place, until it gets hot, then flows like oil.



Isn't Crisco a blended vegetable oil for deep frying potatoes?  LOL
"......many ways to skin a cat"  still holds true!!


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## Z2V (Jan 29, 2018)

I guess the garage shop would smell better like french fries than kerosene


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## wrmiller (Jan 29, 2018)

Boris Ludwig said:


> Thanks, that's all helpful. I'm going to try those suggestions and report back with my results in case I'm doing something wrong.
> 
> 
> 
> ...



I have Relton's A-9 in my fogbuster and it works well for aluminum, and even mild steel. I guess any cutting fluid is better than none.  

Prior to that I kept a small spray bottle of WD-40 on the mill and lathe which works good as well.


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## coherent (Jan 29, 2018)

Any end mills, bit or inserts that are coated generally don't work the best for aluminum.  The better chip clearing the cleaner the cut. Cut your tool or buy inserts with a high rake angle.  Aluminum is soft and sticky. Coatings tend to grab and gum up the tool bit.  I cut a lot of aluminum on a cnc mill and higher speeds and bits with a higher helix that clean the chips make a huge difference.  It sounds like you already have but test a few different speeds, especially for the finishing pass. A sharp tool/insert is a must, the duller it is the more it will grab and spall the surface. I also get a better finish when using at least some type of coolant and/or lube. Even air will help some.


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## Robert LaLonde (Jan 29, 2018)

I preferentialy use uncoated carbide for aluminum.  Sometimes I have no choice but to use HSS.  Then I take the time to stone the edges as sharp as I can make them.


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## cg285 (Jan 29, 2018)

my go to for turning/facing most metals is a ccmt 3251. i get a good finish with 6061 (flood coolant). if i'm picky i go to a komet w00 34360.0203
(google it). i got stuff to do so i don't have time to grind hss all the time like my grandpappy did. i only grind for special jobs


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## cg285 (Jan 29, 2018)

and although some people may fry food with crisco i think it is really meant as a bore butter for cap and ball revolvers


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## Hawkeye (Jan 29, 2018)

It's interesting to note that the stuff is found on regular store shelves (not chilled) and has no 'best before' date. Better to use it for machine and black powder shooting than eating.


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## petertha (Jan 29, 2018)

Totally agree with the (uncoated) CCGT AK inserts. I have not had a bad finish from 6061 but I would say I get a slightly different finish depending on the source of material for some reason. Also note they come in different nose radius so experiment. Even the larger radius don't build up too much heat on aluminum & leave a mirror finish. I agree with cutting fluid rec, personally use Tapmatic (aluminum) mostly because I have it & not quite as strong an odour or fumes under heat as others. I think the big thing is it helps aluminum from coating the nose.

I've purchased majority of inserts from Ebay, Korloy for the most part (assuming they are real Korloy). I just cant tell the difference between these at $2 a pop vs. the $8 ones from tooling suppliers. At the price I'm pretty sure the cost of HSS blank + electricity to grind them works out higher than an insert  But hard to replicate the insert chip breaker  - well maybe not breaking but more manageable swarf,

The other thing is you can get a complete boring bar selection which uses these exact same inserts so all your ID cutting will similarly benefit. I've even seen face mills that use the opposing 2 edges.


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## Boris Ludwig (Jan 30, 2018)

Hawkeye said:


> It's interesting to note that the stuff is found on regular store shelves (not chilled) and has no 'best before' date. Better to use it for machine and black powder shooting than eating.




You're probably right... 
I'm a fan of cold pressed olive oil or wild animal fats!


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## ch2co (Jan 30, 2018)

I'm a fan for using Canola oil which has one of the highest smoke temperature ratings. Used  on steel and aluminum.
I tried just about everything I could find and Canola oil worked best. I got that idea from someone on this site several
years back and I thank him whatever his name is. Typically I grind all of my own HSS tool steel cutters. Ive used a few 
replaceable cutters but I don't find them easier to use and I still have to hone the cutting edge to make them work as
well as the home made cutters. Back to the canola oil, the wife never gets annoyed when I steel it from the kitchen
I brush it on usually with an acid brush.


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## Firestopper (Jan 30, 2018)

I use uncoated WNMG inserts for aluminum and WD-40 (sparingly) for deeper cuts with pretty good results. These cutters can be flipped/rotated providing six cutting edges before discarding. I'm only on my second edge after 1.5-2 years and have turned a fair amount of T-6 aluminum. I am a fan of inserts and only use HSS for custom grinds. The biggest difference is these cutters have a much sharper point than my go to insert for turning steel.

I took .060"-.080" DOC (on first of two wheels) last week at at 650-750 RPM and feed rate of .0090/rev  the surface finish was excellent.






Used 00 steel wool to finish off requiring fast a few seconds. The second hand wheel was turned at .100" DOC and did produce a little smoke with WD-40 but I like the smell. Mark (mksj) turned me on to the WNMG inserts  for aluminum and has saved me considerable time by eliminating sanding/polishing.
Hope this helps.
Paco


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## Eddyde (Jan 30, 2018)

For aluminum, I like the brazed carbide tools as I can grind them if necessary. I also use HSS if I want a mirror finish or need a special profile. WD-40 or WD & Kerosene blend for cutting, but I'm gonna try Hawkeye's Crisco trick for sure.


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## jbolt (Jan 30, 2018)

CCGT inserts are my goto for non-ferrous metals and plastics. Second choice would be HHS but I generally only use HHS for specialty tools.

50-50 mix of Kerosene/WD-40 for aluminum. Straight kerosene works well on stainless. Not a fan of the sticky residue from bio oils.


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## Boris Ludwig (Jan 30, 2018)

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?


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## petertha (Jan 30, 2018)

Machining examples using inserts & re-purposed boring bar in boring head using same insert


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## Boris Ludwig (Jan 30, 2018)

Nice sample pics Peter. Hope one day my samples will look similar.


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## Firestopper (Jan 30, 2018)

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?



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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## Boris Ludwig (Feb 1, 2018)

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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## Boris Ludwig (Feb 1, 2018)

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

Internal improved at reduced speed 530 with the same feed.


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## cascao (Feb 1, 2018)

Used diesel as cutting fluid for aluminium with good results.


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## Firestopper (Feb 1, 2018)

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.



Keep on keeping on Boris, youll find your machines sweet spot on different materials.
Paco


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## mikey (Feb 1, 2018)

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.


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## petertha (Feb 1, 2018)

firestopper said:


> Boris,
> Make sure you only have enough tool sticking out as need. Choke up as much as possible wherever possible. Paco



^^ 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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## Boris Ludwig (Feb 1, 2018)

Cheers guys. This will take me a while to subsume the info.... 

Much appreciated.


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## mikey (Feb 1, 2018)

Boris, I re-read my last post and I can see how it looks like Greek to someone who doesn't work with inserts. Let me try to clarify some of my comments.

A CCGT AK insert is a positive rake insert intended for aluminum. The nose radius (NR) on any insert is the most important feature because it influences your cutting conditions (speed, feed and depth of cut). A 32.51 insert has a nose radius of 1/16"/0.016". A 32./52 insert has a nose radius of 1/32"/0.031". The larger the nose radius the better the finish but the deeper the required cut will be to prevent chatter. It gets a little complicated because the larger the nose radius, the larger the tangential and radial cutting forces are. What this means is that in order to cut well with the least amount of deflection, you have to take a deep enough cut. For roughing, this cut should be at least NR + 0.010" but can go much deeper. For finishing, the depth of cut would be about 1/3 - 1/2 NR at minimum. Speeds vary with diameter but I would think its safe to say you can run your lathe at max speed and still be below optimum for these inserts so I would suggest trying it at the max speed your lathe can run for external turning. Feeds vary with the insert also; what I suggest is to try it at the lowest feed rate you have and slowly increase it until it affects the finish and then back off. 

The guidelines above also apply to boring but you should adjust your feed rate to produce coils, not flakes or chips. Feed manually if you need to (it will be faster than you think). There is a LOT to boring with inserts, much more than can be discussed here, but try messing with your cutting conditions and see how it turns out.


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## umahunter (Feb 1, 2018)

I have a smaller 10 x 22 lathe and I found these korloy inserts on ebay ccgt 32.51 ak the ak is specifically for aluminum and they leave a close to mirror finish I was just trying different things and found these and love them I think I bought and 10 pack for around 40 bucks they've lasted quite a long time


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## Silverbullet (Feb 1, 2018)

High speed and used hydraulic oil , I have it free so I use it oil I mean.


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## Boris Ludwig (Feb 1, 2018)

mikey said:


> Boris, I re-read my last post and I can see how it looks like Greek to someone who doesn't work with inserts. Let me try to clarify some of my comments.
> 
> A CCGT AK insert is a positive rake insert intended for aluminum. The nose radius (NR) on any insert is the most important feature because it influences your cutting conditions (speed, feed and depth of cut). A 32.51 insert has a nose radius of 1/16"/0.016". A 32./52 insert has a nose radius of 1/32"/0.031". The larger the nose radius the better the finish but the deeper the required cut will be to prevent chatter. It gets a little complicated because the larger the nose radius, the larger the tangential and radial cutting forces are. What this means is that in order to cut well with the least amount of deflection, you have to take a deep enough cut. For roughing, this cut should be at least NR + 0.010" but can go much deeper. For finishing, the depth of cut would be about 1/3 - 1/2 NR at minimum. Speeds vary with diameter but I would think its safe to say you can run your lathe at max speed and still be below optimum for these inserts so I would suggest trying it at the max speed your lathe can run for external turning. Feeds vary with the insert also; what I suggest is to try it at the lowest feed rate you have and slowly increase it until it affects the finish and then back off.
> 
> The guidelines above also apply to boring but you should adjust your feed rate to produce coils, not flakes or chips. Feed manually if you need to (it will be faster than you think). There is a LOT to boring with inserts, much more than can be discussed here, but try messing with your cutting conditions and see how it turns out.



Greek.... LOL I not only don't know about carbide inserts but I have no background in machining at all. 

Anyway, on account of your post I read some stuff on the depth of cut and radius relationship on the Sandvik site this morning in the train to work. There are lots of things to remember but I guess I'll make myself a check list so I can slowly build library in my experience.

My lathe top speed is 1680rpm


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## mikey (Feb 1, 2018)

Boris Ludwig said:


> Greek.... LOL I not only don't know about carbide inserts but I have no background in machining at all.
> 
> Anyway, on account of your post I read some stuff on the depth of cut and radius relationship on the Sandvik site this morning in the train to work. There are lots of things to remember but I guess I'll make myself a check list so I can slowly build library in my experience.
> 
> My lathe top speed is 1680rpm



Try turning at top speed; you are nowhere near the speed these inserts require for optimal performance. I suspect your finish will greatly improve.


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## Boris Ludwig (Feb 1, 2018)

petertha said:


> ^^ 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.
> 
> ...




*feed speed was .051mm* that the finest/slowest I have on this machine.

Thanks for the tips.


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## Boris Ludwig (Feb 3, 2018)

Had some better results boring today. No noise and short coiled chips about 3/4" long went slower at 390 rpm with a feed of .051 mm.

It seemed the deeper I cut the better the insert performed and better the cut. Of course it could still be better but on auto feed with no ringing and a cleaner cut I was happy.

Looks worse than it really is...



External was better at 1680rpm and a feed of .051mm and the tool having less overhang.


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## ZSK (Mar 1, 2018)

Replying so that I can find this later.  Thank you for the great info.


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