Toolholder for deep pocketing?

I sometimes need to finish a fairly deep (2-3") pocket in aluminum. I have been trying to use a reduced neck end mill (Helical 46361) for this -- it's a 0.500" dia, 0.625" LOC, 3.375" 3-flute.

The toolpath is a simple circular pocket. Speeds & feeds are 0.500-0.625" DOC, 0.020" stepover, 1700 SFM (13K RPM), 0.0026 IPT (100 IPM) in 7075. (These are straight out of the Helical calculator.)

The machine is a new Speedio, BT30 (not BBT). I am holding the tool in a Kaiser MEGA13 chuck with an on-size collet (<0.0001" runout).

But the surface finish on the walls isn't great. It's a little chattery and I get some witness marks and a clear horizontal line at each pass.

I can definitely back off the SFM and see if I can get it to behave... but I have been considering trying this with a hydraulic holder -- maybe a little more dynamic stiffness would help. Any advice?

What's the gage length on the mega13 chuck you are using? You are close to the limit for it's collet range. I prefer other holders for roughing. Do you have any of MariTool's super stubby (1.2") end mill holders? Or his 52 mm ER32 with on size collet? Keep it as short as possible. What diameter are you starting at? Spiraling out? If you are starting at 1" Dia. Your chip load is actually double initially. If you are starting at .75" Dia., your chip load is triple initially. Probably should back off some on the SFM due to the longer stickout.

BROTHERFRANK said:

What's the gage length on the mega13 chuck you are using? You are close to the limit for it's collet range. I prefer other holders for roughing. Do you have any of MariTool's super stubby (1.2") end mill holders? Or his 52 mm ER32 with on size collet? Keep it as short as possible. What diameter are you starting at? Spiraling out? If you are starting at 1" Dia. Your chip load is actually double initially. If you are starting at .75" Dia., your chip load is triple initially. Probably should back off some on the SFM due to the longer stickout.

Click to expand...

It's a 60mm gage length chuck. Normally for roughing ops I use a 0.375" or 0.500" chipbreaker end mill in a Maritool 1.2" side lock holder. As long as I can keep chips moving that works great.

The pocket is about 2" diameter and has already been roughed out with 0.020" of stock to go.

I'd use a side lock, as short gauge length as possible. A long stick out in a collet won't be as happy. (I used to always use collets, but my last few years I've come to prefer side locks if possible) I'd slow down the rpm, and the feed - My gut feel is there is a harmonic, but that's where I would start. I'm at home right now, but I'd look at what HSM advisor says. They are often pretty good for a solid starting point, and good at including rigidity of the tool/holder/machine in the numbers.
BrotherFrank is pretty good at solving problems too.
Good luck!

eaglemike said:

I'd use a side lock, as short gauge length as possible. A long stick out in a collet won't be as happy. (I used to always use collets, but my last few years I've come to prefer side locks if possible) I'd slow down the rpm, and the feed - My gut feel is there is a harmonic, but that's where I would start. I'm at home right now, but I'd look at what HSM advisor says. They are often pretty good for a solid starting point, and good at including rigidity of the tool/holder/machine in the numbers.

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Thanks for the advice. I'm on a Mac, so I don't have the full version of HSMAdvisor handy. I do have the version on my phone, which gave a pretty similar SFM but double the chipload per tooth (0.0062 IPT). Maybe I'm being overly cautious but my instincts tell me this is not going to be a 265 IPM toolpath...?

If you dont want a blend line from multiple stepdowns I use a UOP LFF cutter, 12mm with 75mm of flute.
I found the trick was to use very light radial stepover, so normally I rough to 0.2mm stock left on and the run 2 0.1mm passes to bring to size, this stops any chatter and give a very nice finish.

so maybe try taking multiple lighter radial passes to clean up sometimes even a spring pass can yield good results.

I am running this in a 40 taper Albrecht APC chuck , which I've found to be much nicer than hydraulics or milling chucks for this application.

Finishing UOP LFF on DMG Mori Aluminum 7075 - YouTube

srp61 said:

If you dont want a blend line from multiple stepdowns I use a UOP LFF cutter, 12mm with 75mm of flute.
I found the trick was to use very light radial stepover, so normally I rough to 0.2mm stock left on and the run 2 0.1mm passes to bring to size, this stops any chatter and give a very nice finish.

so maybe try taking multiple lighter radial passes to clean up sometimes even a spring pass can yield good results.

I am running this in a 40 taper Albrecht APC chuck , which I've found to be much nicer than hydraulics or milling chucks for this application.

Finishing UOP LFF on DMG Mori Aluminum 7075 - YouTube

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Using a cutter with a small corner rad will also reduce your witness marks. Sometimes when I have to go really deep with a toothpick for a cutter I will take a finish pass and then a spring pass at each z level/stepdown.

And it's helpful to have a CR on each end, can fudge the one on top where the flutes are larger diameter than the shank if that makes sense. If cycle time isn't an issue you can vary your finish depth passes as well. Say .500 deep first time stepping down, then maybe .400 for a spring pass stepping down.

I've been wrong before, but I seriously doubt you will get an increase in performance going from a good Kaiser holder to a sidelock.

FWIW I have been very unhappy with the 40 deg Helical tools. We ordered them in half a dozen sizes, and have been fighting harmonics like crazy in both hydraulic and shrink fit holders on our CAT40 Dual Contact. I am slowly switching over to 35's which have been good performers in the past.

I think the tool is the limiter, not the holder.

I'd helix down at 0.080 per rev rather than stepping down 0.500.

I'd also leave 0.002-0.003 for finishing.

boosted said:

I've been wrong before, but I seriously doubt you will get an increase in performance going from a good Kaiser holder to a sidelock.

FWIW I have been very unhappy with the 40 deg Helical tools. We ordered them in half a dozen sizes, and have been fighting harmonics like crazy in both hydraulic and shrink fit holders on our CAT40 Dual Contact. I am slowly switching over to 35's which have been good performers in the past.

Click to expand...

I felt that way for a long time. I had used a name brand SK collet and holder, torqued to spec, with both a 1/2 and a 3/8. (also lots of various ER, etc) Based on what someone on this forum said, I tried a couple with side lock. Now I use sidelock whenever possible. They are usually shorter gauge length too.
Either way, do what works for you.

eaglemike said:

I felt that way for a long time. I had used a name brand SK collet and holder, torqued to spec, with both a 1/2 and a 3/8. (also lots of various ER, etc) Based on what someone on this forum said, I tried a couple with side lock. Now I use sidelock whenever possible. They are usually shorter gauge length too.
Either way, do what works for you.

Click to expand...

Fair point, experimentation can yeild surprising results. I occasionally like side locks for for hard metals, but in aluminum all of our tools that small are running at (or near) spindle max, and I'm not spinning a sidelock anywhere close to 15k or 20k.

Orange Vise said:

I think the tool is the limiter, not the holder.

I'd helix down at 0.080 per rev rather than stepping down 0.500.

I'd also leave 0.002-0.003 for finishing.

Click to expand...

Absolutely this. Ramping 'er down is gonna take a while longer but if you're after surface finish that will get you where you want to be with the setup you already have.

The limiting factor here is the BT30 rigidty. I'd do as suggested above and get a lower helix tool like a 35-37* and I'd get a big corner radius on the end (.060+). It will create scallops instead of steps.

trochoidalpath said:

I sometimes need to finish a fairly deep (2-3") pocket in aluminum. I have been trying to use a reduced neck end mill (Helical 46361) for this -- it's a 0.500" dia, 0.625" LOC, 3.375" 3-flute.

The toolpath is a simple circular pocket. Speeds & feeds are 0.500-0.625" DOC, 0.020" stepover, 1700 SFM (13K RPM), 0.0026 IPT (100 IPM) in 7075. (These are straight out of the Helical calculator.)

The machine is a new Speedio, BT30 (not BBT). I am holding the tool in a Kaiser MEGA13 chuck with an on-size collet (<0.0001" runout).

But the surface finish on the walls isn't great. It's a little chattery and I get some witness marks and a clear horizontal line at each pass.

I can definitely back off the SFM and see if I can get it to behave... but I have been considering trying this with a hydraulic holder -- maybe a little more dynamic stiffness would help. Any advice?

Click to expand...

maybe try slowing down the 100 IPM, maybe 50-75 IPM, or am I washed up.

If I'm after the best finish and cylindricity I usually run a 0.015-0.030" radius end mill in a helical bore path like others have said.

I had similar issues running with nearly identical parameters and that holder.

Without the BBT spindle, you’ll find more success with the stubby side lock from Maritool. The great runout and grip on the Mega doesn’t mean much when it has almost 2” of extra stick out and no face contact behind it. Otherwise, your cut parameters look pretty good, though the advice on ramping the finish is solid.

Once I upgraded to BBT? The Mega holder is the clear winner for these situations.

gkoenig said:

I had similar issues running with nearly identical parameters and that holder.

Without the BBT spindle, you’ll find more success with the stubby side lock from Maritool. The great runout and grip on the Mega doesn’t mean much when it has almost 2” of extra stick out and no face contact behind it. Otherwise, your cut parameters look pretty good, though the advice on ramping the finish is solid.

Once I upgraded to BBT? The Mega holder is the clear winner for these situations.

Click to expand...

I guess I'll plan on converting this sort of application to short side-locks. That's a bit of a headache because Helical doesn't put Weldon flats on most things standard... ugh.

How bad was the BBT upgrade?

trochoidalpath said:

I guess I'll plan on converting this sort of application to short side-locks. That's a bit of a headache because Helical doesn't put Weldon flats on most things standard... ugh.

How bad was the BBT upgrade?

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BBT upgrade itself is simple, but the tool wash down option that's required with it is not particularly simple (keeps chips off of the contact faces). 2outof3 or BROTHERFRANK would be able to give you better numbers, but I'd expect $6-8k for the entire upgrade and half a day's work for the tech. (This is based on my memory of how long it took for those things to be installed on my machine when it was delivered.)

trochoidalpath said:

I guess I'll plan on converting this sort of application to short side-locks. That's a bit of a headache because Helical doesn't put Weldon flats on most things standard... ugh.

Click to expand...

You can get away without the flats in this application (I did). You are not putting a lot of pullout force on the tool (or running it near the top of the book parameters) - you're putting lateral leverage on it, which is causing the issues.

I did start throwing a little flat on my tools with a basic green grinding wheel. IDK if it makes much of a difference, I've never had much in the way of pullout with end mill holders (though I do have Destiny put a Weldon on all my Diamondback roughers, which is a different matter).

How bad was the BBT upgrade?

Click to expand...

Annoyingly, I was in the middle of the rough spot on a rough job at a customer's plant when Yamazen installed it, but he was done in 4 hours. The spindle is an hour of that, the washdown system is the other 3.

It is an expensive upgrade, and that is because Brother insists that all Big+ machines get their face wash system. Having worked with Speedios (Face Wash) and Robodrills (No Face Wash) in a production environment, I can confidently say that Brother is 100% correct in their requirement. I've seen a whole day worth of production out of an automated Robodrill cell get binned because the Op2 machine ran for about 14 hours with a chunk of 17-4 stuck on the spindle face. Normally, the in-stream QC checks would catch that earlier, but as is usual, stuff was getting hectic and the CMMs were all dedicated to more critical tasks at the time because real life is not a book on Lean.

In the end, all BT30 machines should be Big+. In fact, I think Yamazen US is importing all of the Speedio X2 machines as Big+ from the factory, so that should bring the price down.