What lathe to turn 12" O.D.?

[Frank_S]

I'm finish machining a 12.250 inch O.D. part made from either alum 6061-T6 or acrylic so I want a HAAS lathe that will be able to turn the O.D. and face it as well. The part is 3 inches thick.
I currently rough it out on my VF-2 and finish it on an engine lathe. I locate the part on a 6 inch spud which is held in a 3 jaw chuck.

I already contacted the HAAS factory and spoke with an app. engineer but he has not returned with an answer yet. The machine must be fully enclosed and I don't need a tailstock. Your help would be greatly appreciated.

[Geof]

TL-2P, the full enclosure version with the 3500 rpm spindle option.

[Frank_S]

TL-2P, the full enclosure version with the 3500 rpm spindle option.

Thanks Geof but I think I'd rather go for a machine that will perform auto tool changes. I could add on the turret option to the TL-2 but then it will only turn 8" diameter, plus the price goes up near $40K for both the spindle and turret options. I think an SL or perhaps a GT series machine is my best option, and I'm also leaning toward buying used since there are so many used machines out there. I do appreciate your help.

[JohnJW]

I though small diameter need more rpm but why would a 12" diameter need a 3500rpm spindle instead of the standard 2000 rpm spindle? Not that I am turning anything that large or that I know any thing about turning. . . I'm just curious. . .

Regarding app engineer, Haas_apps referred me to Milton at mramirez@haascnc.com when I had some question on the TL-2 in an earlier thread.

Thanks,

[stucaruk]

I do 13" parts on a HAAS HL1BB all the time. It only has a 10" chuck, so the part overhangs and you can't use a stick tool because there isn't enough clearance outside of the turret. I'm using a KM type holder in a broing bar holder to face, turn and profile the OD. It works just fine.

I turn 14" + parts in my Mazak Integrex with an 8" chuck on a regular basis as well, but the parts only fit on the sub spindle.

[Geof]

I though small diameter need more rpm but why would a 12" diameter need a 3500rpm spindle instead of the standard 2000 rpm spindle?.......

He was facing it as well and working with acrylic and aluminum so when you get near center you need the higher rpm.

[Frank_S]

I'm only finish machining this part on the lathe and holding it with a 6" spud in a 10" chuck but I could also use a faceplate (if applicable). My main concerns are with the part hitting the machine or the turret crashing.

[JohnJW]

He was facing it as well and working with acrylic and aluminum so when you get near center you need the higher rpm.

I think facing is very common on a lathe right? but if it's common, how do people face on standard TL-1 or TL-2 with a 2000 rpm? Is 3500rpm generally better for facing aluminum or acrylic regardless of part diameter? and worth the extra cost of upgrading to a higher rpm spindle? The answer is probably very obvious but I'm like a blind person in machining. . . .

btw, I remember seeing a image of your turned acrylic rod/case and that cool.

thanks again,

[HuFlungDung]

Keep in mind that you need a lathe with some sort of gearbox reduction to achieve the necessary torque for serious metal removal on large diameters. This requirement usually goes hand in hand with seriously oversize spindle motors, because high horsepower motors are low on horses when they are not turning near nameplate (rated) rpm for that horsepower. Running the motor through a gearbox gets it running faster again, so it is able to provide more horsepower and boosts the effective torque so it can cut real chips.

[Geof]

I think facing is very common on a lathe right? but if it's common, how do people face on standard TL-1 or TL-2 with a 2000 rpm?.....

I did phrase things a bit sloppily; I said 'you need' when in fact it is really more correct to say things go faster at higher rpms. With carbide you can machine aluminum at something like 3000sfm which means that under CSS your spindle is up to 2000 rpm at a diameter of just over 5" so the extra speed saves time.

[JohnJW]

I did phrase things a bit sloppily; I said 'you need' when in fact it is really more correct to say things go faster at higher rpms. With carbide you can machine aluminum at something like 3000sfm which means that under CSS your spindle is up to 2000 rpm at a diameter of just over 5" so the extra speed saves time.

If feed has to be lowered due to the 2000 rpm limitation are there any advantage to using carbide vs hss for aluminum? As a general rule when cutting soft material should I generally try to keep my rpm as high as possible?

[Geof]

Second point first: Just because a metal is soft does not guarantee that you can cut it at a high surface feet per minute so you cannot safely generalize and say soft equals go fast. I am thinking about metals such as brass and copper which are soft but which cannot be machined at the same speed as aluminum.

Regarding the advantage of carbide over HSS for aluminum when you do not have a high spindle speed available? That is a good question; if you could get pre-ground HSS tools with all the shapes available for carbide insert tools, at a cost less than carbide quite likely if your maximum rpm was 2000 it would be sensible to use the HSS. If it is a case of having to grind your own HSS tools I think it is much easier to use carbide.

Of course as soon as you consider machining cast aluminum then carbide is the way to go because high silicon aluminum alloys are very abrasive.