Problem with DT-2 Spindle

Hi All,

I need a sanity check. I have a 2018 DT-2 Mill with a 20,000 RPM Spindle. We use it mostly for endmills and drills under 0.125" in aluminum. There is one operation that we did that required a 0.375" 3 flute endmill with a 37 deg. helix. The cut parameters are 13,250 RPM at 180 IPM. Ap is 0.800" and Ae is 0.056". The operation is milling a hole thru the part with an adaptive stratagy. A starter hole is already drilled in the center. Material is 7075 T6 Aluminum. The issue I am having is really nasty fretting on the tool tapers. I checked the pull studs, pull stud torque, Tool runout, and changed to a different holder. Results were the same. I decided to check the taper with some Dykem Hi-Spot blue and I really think that this machine has the taper ground like crap. This is a brand new machine and there are 46 hours on this spindle. I know im a bit heavy with my blue but the results are pretty clear in my mind. At least I think. I contacted my HFO and they think that I am being too aggressive with a BT30 Machine. I call BS.

Any advise on this would be appreciated.

you do know what 7075 T6 is harder to machine that a lot of steels? Also when your milling out a hole your programmed feed is the center line of a cutter and not the OD of the hole ... so depending on endmill size to hole size your feed rate could be way off ...

Calculate your feed by hole Dia X 3.1416 ... then subtract your tool dia ( two times the Rad ) from the hole size and you well see were your off on your feed rate ..

I`m not a Fan of 30 taper but I would say your pushing that cute little thing to hard . most 30 taper machines I have seen only have like 200 -250 LBS of retention on the pull stud and with long engagement and a Heavy cut with a Hi spiral flute endmill your pushing it .

How much torque are you using for your pulllstuds? Not an expert, but it looks from the bluing like your pullstuds might have been overtightened, and bloomed out the small end of the taper.

Regards.

Mike

Finegrain said:

How much torque are you using for your pulllstuds? Not an expert, but it looks from the bluing like your pullstuds might have been overtightened, and bloomed out the small end of the taper.

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My thought exactly. First thing I would do is remove a pull stud, clean and reinstall just past finger tight and re-blue to rule it out. We've been running our pullstuds this tight for years with zero issues.

I agree about checking the mate with a minimally torqued pullstud, but it might also be worth looking at different tooling and speeds/feeds to get the cut dynamics acceptable. Maybe going up to a 7/16" endmill in a stub solid holder - anything to improve stiffness will help you.

On the spindle taper mate, you could also try a few other brands of tooling to see if the blue pattern stays the same.

Matt@RFR said:

My thought exactly. First thing I would do is remove a pull stud, clean and reinstall just past finger tight and re-blue to rule it out. We've been running our pullstuds this tight for years with zero issues.

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Agree that looks like tape bulge from the stud. Matt do you guys Loctite your holders, do they tend to stay in on their own?

We blued up about a half a dozen holders. All with the same result. Also, the holders we blued were spread across different brand holders as well. I didnt want to take a chance with a bad batch from one supplier. Swarf is no issue and we have little to no re cutting. I understand the issue with interpolation on the centerline of the tool. I have run tools like this much much harder. We torque all of our pull studs to the recomended 25 ft/lbs. and monitor them regularly. Haas specs out 675 - 775 Lbs of draw bar force for the 20K DT Spindles. This should be more than enough to hold a 3/8 endmill in there solid. We checked tool runout to verify that it was not causing issues. Also, the bottom of the pockets are 0.002 to 0.003 larger than the top. This is with the tool runout dialed in to 0.0001 TIR. That is way out of normal. All of our tool holders are showing a polish near the pull stud. One of the reasons I started to check with blue. One of the tool holders has a 0.0625" drill and has done nothing but drill little holes 0.04" deep and it has a polished band around the pull stud about 0.400" wide and no contact at the wide end. This particular machine has had its history of down time. I have had about 5 warrenty service calls on it already with issues spanning from way cover wipers that were 1/4" from touching the slide on the sides while overcompressed in the middle, (came like that from the factory), to bad prox switches to software issued that almost caused crashes if not for the operator hitting e stop. It took a week to fix the bad prox because this is a new version of the machine and haas didnt properly document what parameter went with what. It took the factory 3 days to figure it out with the service tech on the phone with them. Hell, no one knew which version of this DT I was getting until 1 day before is showed up. I was waiting with a drill to install concrete anchors and finally got the proper hole locations about 3pm the day before delivery. This machine does this fretting with 0.25" endmills cutting at 20,000 rpm, 0.08" doc, 0.003" IPT and and Ae of 0.190". Takes longer for the fretting to show but still. I could continue. The amount of time this machine has on this tool that is showing the most fretting is about 5 hours total since new. Since my original post, the people at my HFO reviewed the results and are sending a new spindle and a tech to install it this week. I also had a few tool makers that I know with at least 30 years experience each review what I am doing to check the taper and they agree the grind is off as well. I have been machining professionally for about 20 years now, ( I have calipers I purchased new that can vote), so I have a pretty good feel for when something is not quite right but I value outside sanity checks. I always learn something new.

DethloffMfg said:

Agree that looks like tape bulge from the stud. Matt do you guys Loctite your holders, do they tend to stay in on their own?

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We put a little bit of loctite on for saftey and always torque to the recomended spec. BT30 is 20 - 25 ft/lbs. The blue results are so far off that I dont think it would matter even if the studs were german tight (goot nd tite).

DethloffMfg said:

Agree that looks like tape bulge from the stud. Matt do you guys Loctite your holders, do they tend to stay in on their own?

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We clean the pull stud and tool with acetone, apply some light oil, install by hand and then give the pull stud an "ehh" with an endwrench. Probably 5-10 ft/lbs. No problems with loosening. Remember, the drawbar is rotating with the spindle; there is no rotational force on the pullstud.

amctony said:

We blued up about a half a dozen holders........... INSERT A WHOLE SHITLOAD OF TEXT HERE.........I always learn something new.

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Dude. Paragraphs. Pretty please.

amctony said:

We put a little bit of loctite on for saftey and always torque to the recomended spec. BT30 is 20 - 25 ft/lbs. The blue results are so far off that I dont think it would matter even if the studs were german tight (goot nd tite).

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Please don't be "that" guy that solicits advice, and then shrugs said advice off. Bluing another holder with a finger tight pullstud is free and will take 2 minutes of your life, and the whole community can learn from it.

Matt@RFR said:

We clean the pull stud and tool with acetone, apply some light oil, install by hand and then give the pull stud an "ehh" with an endwrench. Probably 5-10 ft/lbs. No problems with loosening. Remember, the drawbar is rotating with the spindle; there is no rotational force on the pullstud.

Dude. Paragraphs. Pretty please.

Please don't be "that" guy that solicits advice, and then shrugs said advice off. Bluing another holder with a finger tight pullstud is free and will take 2 minutes of your life, and the whole community can learn from it.

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-5-10 ft/lbs is not correct. The tapers were meant to match at proper torque values.

-We did clean with acetone and checked for embeded chips. No oil, Hi-spot blue was used for contact checking.

-Im a machinist and business owner, not a damn english major. You want paragraphs, read a book.

-"........... INSERT A WHOLE SHITLOAD OF TEXT HERE........" is information I have about what I'm doing and the history of the situation.

-I learn from things when someone points out something valid that I missed. Hence the original post where is state "I need a sanity check"

-I'm glad I never hired you at my facility. "Ehh" does not cut it when the repair is 10 grand and the down time is much more.

Thanks for you input

amctony said:

-I'm glad I never hired you at my facility. "Ehh" does not cut it when the repair is 10 grand and the down time is much more.

Thanks for you input

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Matt's one of our best, most helpful members, giving him attitude is not the best way to go forward. We're almost all machinists here. Some with twice or three times your work experience. While that's not a immediate indicator of competency, it's still going to trend (the weaker guys will wash out).

Since this is mostly a text medium, good spelling, sentence structure, syntax, and reasonable paragraph length really help with reading and understanding the questions at hand. Don't knock it, pay attention to how others write for clues.

BTW, most Loctites work by expanding a little while curing, so excess use can result in swelling even if initial torques were lower.

Cool. Stick to what "the book" tells you to do. No sweat off my back.

And asking for paragraphs was so other people had an easier time reading what you write. You know, so you can get better help. But you obviously know much more than I do.

Milland said:

BTW, most Loctites work by expanding a little while curing, so excess use can result in swelling even if initial torques were lower.

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I use just a little dab on the last thread that engages to avoid the swelling issue and keep the area with the loctite as high up as possible. Loctite is applied to the stud. I believe the last thread is above the top of the taper in the spindle.

Matt@RFR said:

Cool. Stick to what "the book" tells you to do. No sweat off my back.

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This is an area where the companies that produce the tool holders and the spindle go from a book that lays out operating specs as assembled. The components that mate need to have a certain distribution and area of contact in use. If i do not torque the stud at all, the resulting measurement tells me nothing especially because I also am not going to run a tool in that condition. That is why I am measuring it as I am.

If I think someones suggestion does not apply or work, I am going to give a reason, and have. Hence explaining my position. It's not personal. I do this all of the time with my employees, colleagues, and customers. I find it works great for solving problems. Maybe I am right, maybe not.

BTW, Never claimed to know more than anyone. I just disagree with your method because this system has to function fully torqued.

amctony said:

-5-10 ft/lbs is not correct. The tapers were meant to match at proper torque values.

-We did clean with acetone and checked for embeded chips. No oil, Hi-spot blue was used for contact checking.

-Im a machinist and business owner, not a damn english major. You want paragraphs, read a book...

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So you haven't blued up a holder with a pull stud snugged up just to validate it's not caused by overtightening?(torque wrenches can be wrong) While I agree it looks like it's not a pull stud issue, it is an easy sanity check.

Calm down twinkle tits. Nobody gives two shits that you're a business owner, how long you have been machining, or who you would or would not hire. We have all seen business owners and machinists with 40 years of experience who don't know their head from their ass. If you're asking for help don't be a prick if the answer isn't what you want to hear. There are a lot of great people here who can help you.

2 tests conducted on another 6 holders. Results are as follows

finger tight....


20 ft/lbs. with a calibrated torque wrench....

BTW, the wrench on the table is NOT my calibrated torque wrench if anyone asks

Thanks for checking with loose pullstud .

I think your spindle taper is horked. The very sudden delineation between blued and not blued, with a loose pullstud, makes me think the taper grind is faulty and they did not relieve the spindle taper up where the toolholder taper ends. On my Speedio, the spindle taper is relieved well shy of the end of the toolholder taper, by like 1/2" or so. Since you are getting lots of blue right up to the very end of the toolholder, I suspect someone missed the step where they relieve the taper, then the finish grind only went as far as it did, leaving extra material farther up the taper which is where the toolholder ends up seating.

That's just a guess though.

Regards.

Splitting hairs, but it looks like the finger tight version might be a teeny bit better, but certainly not the issue. Now, we know, thanks for doing that.

If you are happy with the spindle otherwise, I would think about having it reground in place versus putting in a new one. Haas doesn't have the best reputation for their spindles, so if you have a good one (bearings), you might want to hang on to it. That may be my tin foil hat showing though.

Thanks for all of your inputs, Much appreciated.

Im not trying to be a dick. I can be quite abrasive at times Ill admit. Especially when I have a machine down.

Im going to have Haas replace it. The already sent a new one and the tech is on his way. I have a year and a half left on the warranty so I am going to let them fix it. If the next one fries, Ill call them again. Otherwise I agree with Matt and would just have it reground in place as this one does seem to have good bearings.

Matt@RFR said:

If you are happy with the spindle otherwise, I would think about having it reground in place versus putting in a new one. Haas doesn't have the best reputation for their spindles, so if you have a good one (bearings), you might want to hang on to it. That may be my tin foil hat showing though.

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Ida know, as banged up as that one fretted toolholder is, I have to wonder what trauma the spindle bearings have suffered. It's a 20,000 RPM spindle, after all. If Haas says they'll put in a new spindle, I would go for that option since it likely will be better than what you have.

Regards.

Mike