Drilling Duplex steel with Kenna DFT/DFSP index drill

Hi,
Earlier, with good help from sales rep, I managed to find the best inserts & feed and speed for making deep Ø50 (2") holes in 316L, but this time around I'm going to do the same in Duplex - going about 170 mm (about 7") deep.
Annoyingly, the Kenna center trigon insert selector for my drill (#5691889) does not come up with any reccomendations for materials in the M class.
Im worried that it's going to be another round of buying all sorts of inserts and finding the feed/speed sweet spot in terms of breaking chips and not making strings.

If any of you guys have any recommendations for best insert based on experience then I'm happy to try the same.
For the square corner insert I've bought HP inserts (they are classified as good for M class), but for the center trigon insert I went with DS again (even though it's not supposed to work well on paper).

The center of the Drill has zero SFM. That's why it's hard to get good recommendations. I've had a lot of good things happen with that Drill. I'd take the speeds and feeds you used with 316 and multiply that by .75. And start there.

litlerob1 said:

The center of the Drill has zero SFM. That's why it's hard to get good recommendations. I've had a lot of good things happen with that Drill. I'd take the speeds and feeds you used with 316 and multiply that by .75. And start there.

Click to expand...

Thanks a lot Rob, that makes a lot of sense - never crossed my mind that it's not really going anywhere when it's in the center.
Will try using the .75 factor and take it from there.

Not related, but read somewhere that I should make fairly deep cuts when turning to get below the surface which gets hardened by machining. In a week or so I'll know how it works out:-)

I presume all machinists do the same, but I'm making a table for experienced best feeds&speeds for all materials and tools/inserts that I use.
I'll post it here once somewhat complete.

Cheers,
John.

If you're cutting it off, it won't work harden. That's the most basic logic. I'm not the best person to ask, because I push Turning centers to their limits. Max depth, max feeds, max spindle--for the job. . Some logic states that Spindle speed is expensive, Feeds are hard but depth of cut is free.

R

litlerob1 said:

If you're cutting it off, it won't work harden. That's the most basic logic. I'm not the best person to ask, because I push Turning centers to their limits. Max depth, max feeds, max spindle--for the job. . Some logic states that Spindle speed is expensive, Feeds are hard but depth of cut is free.

R

Click to expand...

Think the reasoning behind the surface hardening is that with Duplex the heat apparently doesn't go so well into the chip. But I know nothing, this is just some paper of the internet that I read and likely misinterpreted.

In any case, those are wise words you shared.
My only concern with heavy loading is all the "downtalk" I've read here about Haas machines vs. "fancy" machines (Okuma,Mazak,Makino etc..) and that "don't get a Haas if you're going to run stainless all day". Due to this I've been keeping the loads to around 75% more or less to keep things from shaking apart over time.
That being said, my machine has been ploughing through stainless steel all day for weeks on end no problem, so to me it's all BS until I'm proven wrong and the bearings or something are shot prematurely:-)

Schjell said:

.
...........My only concern with heavy loading is all the "downtalk" I've read here about Haas machines vs. "fancy" machines (Okuma,Mazak,Makino etc..) and that "don't get a Haas if you're going to run stainless all day". Due to this I've been keeping the loads to around 75% more or less to keep things from shaking apart over time.
That being said, my machine has been ploughing through stainless steel all day for weeks on end no problem, so to me it's all BS until I'm proven wrong and the bearings or something are shot prematurely:-)

Click to expand...

I've been researching turning centers for the last few weeks/months. While it's true that Haas may hold up okay, looking at numbers is revealing as to why they are less rigid and powerful.

Haas ST-15Y compared to an Okuma GENOS L3000-MY --- (Okuma is 40% more money BTW)

Haas machine weighs ~6000 lbs., Okuma is 11,400.

Haas is 20 HP for 2 min. (15 HP for 20 min.) vs. Okuma is 30 HP for 20 min.

Haas has a belt driven spindle vs. Okuma's integral double-winding motor.

Last but not least, Haas uses linear ball guideways, the Okuma is boxway.


So yeah, Haas might be perfectly fine for some applications but other brands are giving them a run for their money.

ChipSplitter said:

I've been researching turning centers for the last few weeks/months. While it's true that Haas may hold up okay, looking at numbers is revealing as to why they are less rigid and powerful.

Haas ST-15Y compared to an Okuma GENOS L3000-MY --- (Okuma is 40% more money BTW)

Haas machine weighs ~6000 lbs., Okuma is 11,400.

Haas is 20 HP for 2 min. (15 HP for 20 min.) vs. Okuma is 30 HP for 20 min.

Haas has a belt driven spindle vs. Okuma's integral double-winding motor.

Last but not least, Haas uses linear ball guideways, the Okuma is boxway.


So yeah, Haas might be perfectly fine for some applications but other brands are giving them a run for their money.

Click to expand...

I see where you're coming from - I generally believe that you get what you pay for and the Haas machines are relatively inexpensive and probably less heavy duty engineering-wise.
So far, so good though. My Haas has done exactly what the sales rep promised it would do. I've got friends that are struggling with a number of issues on a new (XXXXX ) that's easily four times the cost of my machine, so there are no guarantees. All companies will deliver the occasional lemon; it's inevitable given the complexity of the machines.
If we could justify the cost I would have bought a Mazak though - I spend most my time planning tool strategies for avoiding collisions between chuck, part and the tools in turret. Not ideal when we never make more than ten of the same part

Nothing lasts forever. 2 ways to look at it. Treat the Machinery real nice for longevity. Or run the mother fucker into the ground, squeezing every cent worth of productivity out of it. Sometimes they last 15 years, sometimes not. If I were a Haas owner I'd push it to its limits all day. With the intent of replacing it.

R

On the topic of work hardening---just because the bar you're Machining gets hot, doesn't mean it's getting hardened.

Work hardening DOES NOT HAPPEN if the contact material is coming off. (exceptions are poor practice and OE).
You're probably not going to get a bar of Duplex hot enough to affect the anneal.

R