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Will my new slant bed have enough torque for stainless cutting?

ondori

Aluminum
Joined
Apr 30, 2019
I'm getting a new slant bed lathe (either a Doosan Lynx or Haas ST-20).

Both have 20 HP. But they are direct drive and higher speed than I am used to.

Right now I use a geared flat bed CNC lathe. It only has 10 HP, but I always run it on low gear, never need to go past 450rpm.
At low gear, this flatbed produces a lot of torque. I don't have the exact values (its an old machine), but I can assure you it has more torque than what either Haas or Doosan list as their max torque. And at lower RPM too!

For example I have 8.625" OD SS316 part that I turn down to 7.975"
Using Kennametal cutting force calculator; 0.15" DOC, 0.013 ipr, 170 rpm = 202ftlb...

Clearly a slant bed can't do that heavy of a cut at low speed. So I definitely will need to change my feeds/speeds.
I'm not too familiar with "high speed, low DOC cutting" so I used Sandviks Toolguide as a starting point, this what they recommend:

0.08" DOC, 0.009" ipr, 332rpm = 125ftlb

That is still quite high. The Doosan lists 93ftlb max torque at 1125 rpm and the Haas is 150ftlb at 500 rpm.

I'm now beginning to realize that I can't have my cake and eat it too... I want the versatility of a slantbed, but it seems that I have much to do on my feeds/speeds and any high torque low speed slant bed is +$$$
 
Not stainless so I don't know how much that affects the cutting forces.

I ran an SL30 that we turned 4140 at about .15" doc .02"ipr with an LMNX insert/holder. The ST20 is smaller, and a new design so not sure if that helps...
 
If you are doing 8" parts, you won't be doing them in a Lynx. The Lynx 2100 only comes with a 6" chuck. These are meant for smaller parts. If you want to machine 8" part, you want a Puma. Plenty of torque there, 264lb/ft. Still only an 8" chuck though unless you go up to the Puma2600 with a 10" chuck. How about specing a machine for your work instead of your pocket book.

Paul
 
If you are doing 8" parts, you won't be doing them in a Lynx. The Lynx 2100 only comes with a 6" chuck. These are meant for smaller parts. If you want to machine 8" part, you want a Puma. Plenty of torque there, 264lb/ft. Still only an 8" chuck though unless you go up to the Puma2600 with a 10" chuck. How about specing a machine for your work instead of your pocket book.

Paul

Bah! (lol) :D


I have routinely run parts bigger than the machine 'envelope'. That is what we do, right? "Well boss, I only have 20" of travel and the part is 25" ---Boss- "Figure it out!":D

edit: less snarky- We made jaws for our 10" chuck to hold 12" parts and didn't have any problems. Don't see why you couldn't do that with a 6" or 8" chuck...
 
.....We made jaws for our 10" chuck to hold 12" parts and didn't have any problems. Don't see why you couldn't do that with a 6" or 8" chuck...

Sure you can get away with it, but you won't be running the part as fast or well as a machine with a 15" chuck for a 12" part would do.
 
Sure you can get away with it, but you won't be running the part as fast or well as a machine with a 15" chuck for a 12" part would do.

I'm sure you are right. But hate to be running 6-8" parts in a 15" chuck too...

edit: I should clarify, if I had to choose I would rather run bigger parts in a "too small" chuck/lathe... Now that said, if you have an even mix of large and small parts...:confused:?? I dunno then. And/or the big parts make alot more money, maybe you need to re-examine the whole situation...
 
I'm sure you are right. But hate to be running 6-8" parts in a 15" chuck too...

edit: I should clarify, if I had to choose I would rather run bigger parts in a "too small" chuck/lathe... Now that said, if you have an even mix of large and small parts...:confused:?? I dunno then. And/or the big parts make alot more money, maybe you need to re-examine the whole situation...

The potential of this lathe is not there for these larger parts. You were just complaining about not having enough torque. You won't have enough torque. And what happens when you want to run a larger drill on those larger parts?

I work for Doosan. I would love to sell you a machine. But not at the cost of listening to the complaining 6 months from now about how the machine can't handle your parts. Pony up and buy a Puma. You will be very, very happy.

Paul
 
Can you only have one machine due to space limitations? Are you willing to buy a used machine? Or two? There are lots of orphan slant beds out there that will do your bigger parts, that can be bought cheap. My big lathe is a 10" chuck Cinturn that I bought and fixed up back when they were still worth something. 30 HP, 3500 rpm, 2 speed gearbox, 2.5" spindle, can swing 18" if you need to. It's favorite tool is a 4" dia. insert drill. We usually rough one side of parts (over 3" dia) on it then finish the second side in a smaller/quicker machine while it's running the first side. It's been zero maintenance/repair other than a lightning strike in the past 10 years. You can buy a twin to it for $10K or less today, or a Mazak or similar for similar money. The previous owner had a barfeed and parts catcher on it, I can't imagine running bar parts on a machine this heavy here.
 
If you are doing 8" parts, you won't be doing them in a Lynx. The Lynx 2100 only comes with a 6" chuck. These are meant for smaller parts. If you want to machine 8" part, you want a Puma. Plenty of torque there, 264lb/ft. Still only an 8" chuck though unless you go up to the Puma2600 with a 10" chuck. How about specing a machine for your work instead of your pocket book.

Paul

The Lynx comes in a 6", 8", & 10" chuck option. Torque output is 93ftlb, 124ftlb, 198ftlb. I will be buying the 198ftlb/3500rpm version. In my above post I incorrectly listed the Lynx 6000rpm version torque. Also upon a further detailed look, I noticed that Haas lists their torque vales at 200% spindle load, so that 150ftlb is actually 75ftlb.

I appreciate the feedback from everyone here. I didn't mean to come off as I did. Here is some background on what I plan to run on this slant bed lathe:

Based on part count over 50% will be made from PVC and mild steel. The remaining 50% will be SS316, 2205, Hastelloy C276, Alloy 20 and once in a while some Ti GR2. On size, 90% of my parts are below 8.625". And if I get the Lynx I do intend to make full use of its 13.8" cutting ability if I need do. But I won't make a habit of it.

The issue is that this is all new to me. I am moving from a shop full of geared flat bed lathes that produce enough torque to twist the spindle of the very slant bed machines I'm looking to upgrade to. I am aware that I can't expect the slant beds at my price point to perform the same cuts as my flat bed. I just didn't realize how big of a difference in torque there was. So now it's got me thinking, what the hell do I do with my feeds & speeds. I'm gonna have to change it all up to accommodate high speed low doc.
 
Can you only have one machine due to space limitations? Are you willing to buy a used machine? Or two? There are lots of orphan slant beds out there that will do your bigger parts, that can be bought cheap. My big lathe is a 10" chuck Cinturn that I bought and fixed up back when they were still worth something. 30 HP, 3500 rpm, 2 speed gearbox, 2.5" spindle, can swing 18" if you need to. It's favorite tool is a 4" dia. insert drill. We usually rough one side of parts (over 3" dia) on it then finish the second side in a smaller/quicker machine while it's running the first side. It's been zero maintenance/repair other than a lightning strike in the past 10 years. You can buy a twin to it for $10K or less today, or a Mazak or similar for similar money. The previous owner had a barfeed and parts catcher on it, I can't imagine running bar parts on a machine this heavy here.

I would love to get a beefy used one! but in my area they are hard to find. I've be looking all over Canada for some decent slant beds. Additionally I don't have much service/support in my area. We've been lucky with our current machines and can maintain them ourselves. Even our CNC stuff is old and generally quite easy to troubleshoot. But I wouldn't know where to begin on your Cinturn.

The volume of work on this unit will be high, so I can't really risk downtime. So a brand new unit made sense. If however I come across a nice deal, I'd jump on it! have yet to come across it though..
 
My Lynx 2100LB had an 8" chuck, Flex-C 65 lives on it now as I've not put anything bigger than 2.5" in it.

Get a bigger machine if you want to do 8-9"+ Dia work. I'd want a 10-12" chuck for that stuff, I just put those bigger parts in my manual machine.
Look into Okuma, they have some models with dual wound spindles for much higher torque. They are a lot more $ though.
Puma has more power than the lynx. The new LC might be interesting though, and with 10 station turret instead of 12 clearance may be ok enough but its not a huge machine.
 
While a Lynx can be fitted with an 8" chuck, if you're going to be cutting work in that size range regularly, you will probably want a Puma GT2100. Box ways, large spindle, larger turret and specifically made for heavy cutting in hard and tough materials. The Puma "GT" series (Global Turning - not the sport model) was designed and built for that type of duty. The castings are very beefy and "squat" with a low center of gravity and the spindle strategically placed within the triangle of the ways for max stability.
 
The potential of this lathe is not there for these larger parts. You were just complaining about not having enough torque. You won't have enough torque. And what happens when you want to run a larger drill on those larger parts?

I work for Doosan. I would love to sell you a machine. But not at the cost of listening to the complaining 6 months from now about how the machine can't handle your parts. Pony up and buy a Puma. You will be very, very happy.

Paul

Wrong guy.
 
Bah! (lol) :D


I have routinely run parts bigger than the machine 'envelope'. That is what we do, right? "Well boss, I only have 20" of travel and the part is 25" ---Boss- "Figure it out!":D

edit: less snarky- We made jaws for our 10" chuck to hold 12" parts and didn't have any problems. Don't see why you couldn't do that with a 6" or 8" chuck...

ive run a 12" chuck with custom jaws to hold a 14" 4 jaw chuck to turn 2" square parts...chuck size really doesnt limit your part size, only the distance between the door and the chuck limits you :D
 
If you are doing 8" parts, you won't be doing them in a Lynx. The Lynx 2100 only comes with a 6" chuck. These are meant for smaller parts. If you want to machine 8" part, you want a Puma. Plenty of torque there, 264lb/ft. Still only an 8" chuck though unless you go up to the Puma2600 with a 10" chuck. How about specing a machine for your work instead of your pocket book.

Paul

The Lynx 2100 LB comes with an 8" chuck with an optional 10" chuck. I just had one quoted a few weeks ago. So, yes, the parts will fit in a Lynx, but I do agree that if this part is typical of the type of work that the OP does, he would be much better off spending the extra money and buying a Puma or something in that class. The extra money spent on the heavier machine will pay off in the long run.
 
Clearly a slant bed can't do that heavy of a cut at low speed. So I definitely will need to change my feeds/speeds.

Find a used Mori NL or NLX with 10" chuck.

300 ft lbs continuous, 450 ft lbs at 25% duty. Bomb proof machines. A mid 2000s model will keep chugging for another 25 years.
 








 
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