2019 - Coolant in Swiss Lathe

This question comes up every once in a while, and I like to get some up to date input.

I have a Star SR20R II.. The issue is machining 304 and 316 or N60. These materials don't really take well to oil. The heat just stays in the material. The only way around it with oil is to use high pressure coolant to take as much heat out of it. It also cooks the oil and needs to be replaced often when doing this type of work.


What are your thoughts of using coolant in a swiss lathe? I am thinking of switching back to straight oil when the tough stainless jobs are done. Some say you cannot go back. Why? The water just sinks to the bottom and stays there.


My idea is to switch over to Hocut 8640 and have all machines in the shop run the same stuff. HOCUT(R) 8640 – Houghton International
I'm thinking of running a 20% concentration.
This has zero synthetic oil, so it should not rust anyting. Have been using it for two years on a lathe and it has not rusted anything at all.

The benefits are:

1 - faster cycle time - tons of heat removed
2 - Machine stability - machine does not heat up
3 - zero fire risk for overnight ops
4 - cost
5 - better tool life (10X more)

Downsides:
1 - more maintenance
2 - risk of bearing or electrical damage.


let me know if I am overlooking something silly. I don't really see a reason to use neat oil in a modern Swiss. This one has air constantly blowing through the bearings. Also bearings are super cheap for these machines, they are so small.

The benefits seem to well outweigh the risks. I want to be cautious the machine is expensive and not easy to replace with another one.

As I recall, when we added a Star Swiss machine about 5 or 6 years ago it was using water based coolant. And I do believe the bigger Swiss machines (Tsugamis?), and all the multiaxis lathes used water based coolant. Only the old, smaller Swiss machines were running oil. I know I ran the coolant very rich because it was rusting the table and vice in the mills, but I couldn't tell you much more about the turning machines, that wasn't really my department. I think they ran normal ratios, I know we switched from Blaser to Fuchs due to foaming issues.

Star's say the machine is suitable for water based coolants http://starcnc.com/wp-content/uploads/2016/08/SR-20RII_PDF.pdf ……..which is a good start ………...Me? I think I'd ask Star what brand & brew they recommend.

I have experience with Stars and still own one, but it was made in 2002. Unless something has changed the revolving bushing assembly has a set of angular bearings that are not totally sealed. They also may not have connections to the auto lube system and even if they do it is easy for water based flood coolant to get inside the bearing races. That is why they recommend not using coolant that you cut with water. My solution has always been to dissemble the revolving bushing assembly every 6 months and repack with white lithium grease.

Limy Sami said:

Star's say the machine is suitable for water based coolants http://starcnc.com/wp-content/uploads/2016/08/SR-20RII_PDF.pdf ……..which is a good start ………...Me? I think I'd ask Star what brand & brew they recommend.

Click to expand...

I do believe it is all about the design of the bushing assembly dictating whether a water based coolant is acceptable.

avongil said:

The benefits are:

1 - faster cycle time - tons of heat removed
2 - Machine stability - machine does not heat up
3 - zero fire risk for overnight ops
4 - cost
5 - better tool life (10X more)

Downsides:
1 - more maintenance
2 - risk of bearing or electrical damage.

Click to expand...

I've never heard of coolant getting better tool life than oil.
???
Always the opposite.

However you should be able to run faster and not have all the smoke!

.. and not have to have 2 rags in your pockets at any one time. (rougher/finisher)
.. and go through WAY less rags...

You've already covered the fire issue, but that is worth bringing up 2wice.

They still demo the new machines in oil tho.

And way lube won't bother the oil like it would the coolant.


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Think Snow Eh!
Ox

We use Qualichem Extreme Cut 251C in our Swiss. I was getting pretty far into mission creep on the purchase and decided to skip the oil and associated fire suppression system. We run mostly <1000 part runs so I didn't think we'd realize the tool life benefits.

It doesn't care for brass - corrodes the copper therein and turns things green LOL. Otherwise we're getting great tool life on several of our inserts so I would do it again.

Ox, about the tool life -

I have always seen way better tool life in my cnc lathes than in the swiss. I have always heard that too, but I just don't get it. I suspect its the material that is run.

In Stainless 304, 316 and N60 jobs I have, the tool life is 10X better with coolant.

I can give you a coolant through drill example:
F drill - N60 - .9" deep. Same speeds feed. .0038"/rev & 1200 RPM.

Swiss:
2000PSI Oil (three types tried)
40 parts.

CNC Lathe:
300psi coolant
500+ parts

Even when I hand sharpen the drill it still lasts 200+ parts.

Maybe its because with oil everyone runs slow. When you run slow with water based the tool life is better in my experience.


The water just takes the heat right out of the material. The evaporation also cools the machine. On the swiss with oil it just keeps getting hotter and hotter...

I'm done worrying about fire. I switched to Hocut 6840 at about 15%. Emailed a chemist and he told me there is nothing in the striaght concentrate that will degrade plastic so I am replacing the ISO 100 oil in the bar feeder with straight up concentrate. Free coolant maintenance!

thanks for the suggestions - will clean rotary. I thought I was going to get a good beating.




https://i.imgur.com/0kC7VxJ.jpg

I would expect you to git better drill life than that, but then I'm not familiar with N60.
I have ran 2.5" deep or more with smaller drill in 310 and was told to expect 225/240 parts, and that's exactly what I got.
HP coolant.

On the small through drills, I would expect that not much oil makes it through compared to coolant.

I believe that it's usually turning tools that are expected to git so much better life, and as you say, S/F could have something to doo with it too, but I'm gunna say that the lack of chatter is likely as much to doo with it.

If I get a newer Swiss, I will be tempted to go your route too.
???
I just don't like walking out the door with oil slingers running ...
I've had multi-spindles lit up before, and it's not hard to see how so many screw machine shop's have burnt down over the years.


--------------------------

Think Snow Eh!
Ox

I feel so much better now. It was a real source of anxiety that I did not know was there!
Burning down the house is bad thing. Very bad thing.


Here is my spreadsheet I made when I was running the part on the Star. I made it because I was spending a fortune in tooling.
https://i.imgur.com/ZKN76hp.png

If I remember correctly, the drill lasting 600 parts was with me resharpening it about 4x before sending it out to titex for resharpening. so it really only lasted 150 parts.

OD tool lasts about 60 parts now.
The thread mill is on part 600 now.
the cut off lasts about the same.
the 1/4" about the same
the boring bar I don't use anymore.
The supermill is on part 600 and not wearing so its on target for at least 1000. It seems like its going to last the full run of 2,000 since I have not had to use wear comp.

So I am once again mistaken, not 10X longer. For some operations 2x or more life but not less on this job at least.




AG

in regards to drill life. Check this out:
https://i.imgur.com/iUPnbSq.png

A Walter apps guy calculated 175 holes with coolant. I got about that with oil and making sure I had full coolant pressure.

The hole I drill now is only half way, so I will know tomorrow at some point if the coolant performs better on this particular drilling operation in this material

Just ran a 316 stainless steel job overnight. Slept like a baby!

Thanks for the post. Made me switch right away. For brass, I have been running it dry because the oil clogs up the holes. I need to remember to keep running it dry!

Here are my initial conclusions about oil vs modern coolant:

1- 100% mineral oil based water soluble coolant can be of high quality and will not go bad if the concentration is kept above the minimum (6%). This is a far cry from what was around 20 years ago. Synthetics degrade plastic and promote rust.

2- tool life when cutting slow and with HSS old fashioned tools will be higher in oil.

3 - tool life when cutting soft materials with be similar

4 - tool life when cutting difficult materials that produce heat will be significantly higher with water if high pressure coolant is not used. If used it must be super high pressure. It might even be necessary to swap the oil for something thinner.

5 - the fire risk is high with oil. the 2-4 K in fire equiptment plus refills when it gets discharged adds up. Failure of the system when running lights out is a real possibility. Difficult to cut material produce heat, and then you have an oily hot mist inside the machine. Not having a mist collector and running difficult materials unattended is a recipe for disaster.

6 - revolving guide bushing machines are good candidates for coolant. In my opinion, even if the machine is not designed for coolant I would try to inject some dry oily air to places that need it.

7 - oily rags. I think those too are a fire hazard!

Disadvantages:
1 - Daily maintenance. Water needs to be added twice per day. A hose should be installed next to me machine.

2 -Bar feed contamination. The bar feed ISO 100 will contaminate the coolant. Will replace that with the straight concentrate mid week when I get more. I will post later on how that works.

DON'T ADD WATER TO EMULSIFIED COOLANT. KEEP THE HOSE AWAY FROM THE MACHINE!

Always add a dilute emulsion to top off the machines. We use a $70 mixer off eBay to add 4-5% emulsion to water to dilute to <1% for top off (we fill the buckets 3/4 or more with water then add emulsion from the mixer). Always add coolant to water, never water to coolant. I spent the six years of my life prior to my CNC career treating industrial wastewater, including emulsified coolants, and what the manufacturers tell you about this is true.

Also, Abanaki makes a ~$400 oil skimmer that works great for the barfeed oil and other tramp oil (oil on material, way lube, etc.).

Our biggest problem with insert life was actually not running the SFM high enough. We were using Sandvik inserts in 304, 316, and 416 stainless, and we needed to change the grade for the operations we couldn't run at high RPM. The 1125 grade wanted 600SFM+ in stainless! After fixing some phasing issues at higher RPM we are now getting pretty killer tool life with coolant. I have one of those Sandvik (made by someone else, FWIW) 0.027" wide solid carbide groove tools that made something like 12k grooves before a corner went away!

Rick Finsta said:

DON'T ADD WATER TO EMULSIFIED COOLANT. KEEP THE HOSE AWAY FROM THE MACHINE!

Always add a dilute emulsion to top off the machines. We use a $70 mixer off eBay to add 4-5% emulsion to water to dilute to <1% for top off (we fill the buckets 3/4 or more with water then add emulsion from the mixer). Always add coolant to water, never water to coolant. I spent the six years of my life prior to my CNC career treating industrial wastewater, including emulsified coolants, and what the manufacturers tell you about this is true.

Also, Abanaki makes a ~$400 oil skimmer that works great for the barfeed oil and other tramp oil (oil on material, way lube, etc.).

Our biggest problem with insert life was actually not running the SFM high enough. We were using Sandvik inserts in 304, 316, and 416 stainless, and we needed to change the grade for the operations we couldn't run at high RPM. The 1125 grade wanted 600SFM+ in stainless! After fixing some phasing issues at higher RPM we are now getting pretty killer tool life with coolant. I have one of those Sandvik (made by someone else, FWIW) 0.027" wide solid carbide groove tools that made something like 12k grooves before a corner went away!

Click to expand...

Glad you chimed in on this thread, can you run coolant on older citizens machines(say mid 90s and earlier)?


My tool life is incredible with oil always has been, we run .004 rad sanvik ccmt inserts for finishing and .008 for roughing. our thread tool life is also fantastic.
BTW running a thin bit insert .011 wide .015 width groove .030 deep(303 ) per side standard carbide for grooves corners are still there and were at over 7k parts parts are burr free.

Am I the only person in this thread that has had the revolving bushing assembly apart on a Swiss? Or was I the only one who has worked on for the man and owned Stars that were poorly designed for using water soluble coolant?

Delw said:

My tool life is incredible with oil always has been, we run .004 rad sanvik ccmt inserts for finishing and .008 for roughing. our thread tool life is also fantastic.
BTW running a thin bit insert .011 wide .015 width groove .030 deep(303 ) per side standard carbide for grooves corners are still there and were at over 7k parts parts are burr free.

Click to expand...

My tool life in 303 with coolant vs oil is the same (incredibly long). It's 304, 316, N60 or anything nasty like that.

I can't comment on any of the others or legacy designs but we talked to REM directly about running emulsion coolant prior to buying our Tsugami. We do get a skim layer of the re-concentrated coolant (after the water evaporates out) hanging out in the main spindle housing but no other problems so far. We haven't even had this thing running a year, though.

I always figured my swiss buddies ran oil so when they got tired of being a machinist, they could tweak the feeds and speeds on an un-attended run and let the insurance company help them retire...