High rpm face mills

[colinbParticipant @colinb]

Hoping for a bit of advice. I’m tooling up for a new-to-me Alexander Master Toolmaker (= Deckel FP1). I will have the luxury of the high speed vertical head, but won’t have the regular vertical head. In a vertical setup then, my slowest rpm is 1900.

Where does this leave me in terms of viable/reasonable facemills and flycutters for surfacing parts? All the feeds/speeds calculators seem to indicate that, for example, a 100mm diameter indexable facemill with 45° lead angle needs to go much slower than this head can manage. Am I really limited to approx 50mm inserted cutters with 1mm DoC?

I completely understand I could use the horizontal spindle to access the slower speeds, but I’d like to try to understand where the theoretical limits of this vertical setup lie.

 

[SillyOldDufferModerator @sillyoldduffer]

I think Colin will have to experiment.  Online calculators and books all recommend maximum economic industrial cutting rates, which are generally generally faster and deeper than a hobby workshop is capable of.   So our experience is more of dialling back than going much faster.   I guess experience of Colin’s too-fast problem will be thin on the ground!

HSS is probably out, but carbide and the right material might work well enough.  In ordinary machining, free-cutting metals do well because less energy is needed to cut them and they resist tearing, resulting in a good finish.   When I ran a fly-cutter too fast on free cutting steel the finish went to pot, I think because the metal tore rather than cut.   With carbide a deeper cut often fixes tearing, provided the machine has the necessary power, torque and rigidity, which mine doesn’t.   A high-speed head might do better with a more difficult metal, one tough enough to resist tearing at high speed.  Dunno.

High-speed heads are for spinning small diameter cutters doing delicate work.  Most desirable I reckon, but a specialist tool that will struggle with face cutting and any other general purpose milling for which slower speeds are needed.  (Usually much slower than 1900rpm!  My mill gets down to about 150rpm, and that’s too fast for some jobs.)

Feels like a lot of pratting around.   Like taking a Formula 1 car to Tescos, could be done, but more trouble than it’s worth.  My gut feel is the best answer is to find a slower head for rough work, and get the high-speed one out only when needed.  Sorry!

Dave

 

 

[John HaineParticipant @johnhaine32865]

I don’t know what motor drives your mill but a 3 phase type with a VFD with flux vector control would allow it to run with full torque at low speed, though a separate cooling fan on the motor may be needed.

Or you could convert to CNC so the control will take the tedium out of long facing cuts using a smaller cutter!

[JasonBModerator @jasonb]

No need to experiment I have done it for you ramp it up rather than dial it back.

63mm insert face mill with inserts intended for non-Ferroius will spin happily at 2000rpm on all the common model engineering metals. So if you come down to a 50mm head then you could run at 2500rpm for iron and steel and if you have more available then use it on non ferrious. Go for a 5 insert rather than a 4 insert then you can feed a bit faster for the same given chip load.

See the copies of my MEW articles here and here.

You can also wind it up with solid cutters too.

An insert lathe tool in a flycutter will also run at similar speeds but you need to have it well blanced, downside is your feed rates will be slow a sit only cuts once per revolution

I’ve run the 80mm at 5000rpm on the CNC so not sure where Dave gets his idea high speeds are only for small solid cutters, I’d be running them at a lot more if I did not max out at 5000rpm.

All at 2000rpm with a 50mm dia head, feeds upto 400mm/min

[mark smith 20Participant @marksmith20]

Is the high speed head capable of handling  large diameter cutters,  i assume it probably is ok with a 63 mm facemill but not sure. Unfortunately my Alexander didnt come with the high speed head . Heres the manual page for it.

[JasonBModerator @jasonb]

If you are going to be limited to a 12mm straight shank arbor in a collet as the above suggests then 50mm would be about as big as I would want to go on steel and iron and shallow cuts too.

Speed is not going to be the issue, it’s that small diameter mounting so VFD to drop the speed may not help as you will still have a less than rigid setup.

[JasonB]

On JasonB Said:

No need to experiment…

…

I still recommend experimenting.  Jason’s experience is of a different machine.  Though he’s experimented successfully on his particular box of tricks and it worked (though what machine and alloys were tried we haven’t been told) , but that doesn’t mean Colin’s Alexander head also has  “the necessary power, torque and rigidity”.

I’ve run the 80mm at 5000rpm on the CNC so not sure where Dave gets his idea high speeds are only for small solid cutters

I didn’t say ‘only’.  Perhaps I should have typed  ‘Deckel high-speed heads are for spinning small diameter cutters doing delicate work’ and referenced lathes.co.uk who explain what heads are available, and what they are for.  Jason generalises from experience, I looked the Alexander up and read the blurb.

Again gut feel, but thrashing tools by persistently running them outside their design intent feels wrong to me, especially when the tool is posh, rare and costly.  Therefore I suggested Colin find out for himself by experimenting.  The result he gets will be correct for his machine on his range of materials.  Could be Jason and I are both wrong!

If Colin’s machine had come with a standard head , he wouldn’t have had to ask! The standard head, also posh, is tailored for ordinary cutting speeds, plenty of torque, job done!  The problem here is Colin’s machine is fitted for intricate cutting with small diameter tools spun at high speed, higher the better.  For speed the motor is geared up, but small diameter tools don’t need much torque.  Asking a geared up head to drive a big face cutter though is questionable because they do require torque.  I don’t know how well Colin’s head will perform and neither does Jason – we are both joining the dots.

Fortunately, the question can be answered by experimenting.  Whilst Jason’s experience is reassuring, Colin might prefer not to hack metal with a high-speed head specially made to do delicate precision work: might be silently taking years off the life of the bearings!  He certainly won’t persist with high-speed cutting if his machine complains or he can’t get a good finish.

Dave

 

[mark smith 20Participant @marksmith20]

Dave, i like your use of the word “posh”.

[JasonBModerator @jasonb]

Once again Dave I assume you have not even  looked at my articles or the videos as your comment “though what machine and alloys were tried we haven’t been told” is a figment of your imagination as what I put clearly gives the alloys “From Left to right the samples are 6082-T6 aluminium. 070M20 (EN3) steel. CZ121 Brass and GR17 cast iron.” and numerous times it is mentioned that the Sieg SX2.7 is being used.

There are no gears in that head so again how you can say “Asking a geared up head to drive a big face cutter though is questionable” make what you say more questionable.

My suggested use of inserts meant for non ferrous significantly reduces the amount of torque needed as these inserts are far sharper so don’t need to be pushed through the metal. Most will say the imported machines lack torque but my suggested methods are a way to use these tools without the need for much in the way of low speed torque.

What facemills do you use Dave and what speeds and feeds to you run them at?

Things have moved on, some of the posters here need to do the same too.

Often it is said that carbide can be run at 3 times the cutting speed of steel. So now that High speed head has a max of 6000rpm which in my book is about 3 time sfaster than the usual top speed of around 2000rpm found on many an industrial or hobby machine. I’d like a 20K rpm head for using small carbide cutters when doing things like engraving and fine 3D finishing paths, so 6K is not really that fast these days.

So that 1/4″ HSS screwed shank cutter that was being run at 2000rpm back in the day can now be replace with a reasonably priced plain shank carbide one and run at 5-6000rpm on steel or more on non ferrious.

Cutting speeds don’t change in the industrial tables it is only the feed rates and depths of cut that may need to be reduced for hobby use.

 

[not done it yetParticipant @notdoneityet]

Is there any opportunity to replace the motor with a 1425rpm version?

 

If so, would that work?

[David SeniorParticipant @davidsenior29320]

At work we use 63mm face mills with aluminium specific tips, and usually run between 4000 and 6000 rpm, depending on whether the machine has enough torque. Then we got a bigger 5-axis machine with a 20,000 rpm spindle, so thought we would go a bit faster. 15,000 rpm on the face mill worked well, until a tip/screw broke and shattered the door glass. At over £700 to replace it we gave up on that experiment!

Dave

[colinbParticipant @colinb]

Thanks Dave.

I reckon making a new “low speed” vertical head is in my future – a nice project to target my skill-building at. A spindle, gears, castings – no shortage of things to learn!

In the meantime, I shall play

[colinbParticipant @colinb]

It’s a single phase 0.5HP motor, so VFD out of the question without a motor swapp – and I don’t have a spare 3 phase at the moment. Definitely not impossible

[colinbParticipant @colinb]

Thank you Jason, I will carefully read your articles.

The analogy to CNC spindles is why I was thinking running a facemill on this head isn’t necessarily an impossibility.

I do plan to play extensively with the horizontal spindle and its arbor too

 

[colinbParticipant @colinb]

How would I establish whether the head is “capable of handling  large diameter cutters”? Other than trying, and destroying the bearings to establish that it’s not capable…

[colinbParticipant @colinb]

Could do, but at that point I’d just go 3 phase and VFD

[colinbParticipant @colinb]

Just to check – Al tips but cutting steel? Rpm range appeals, will have to look at the torque topic

£700 for a window?! Ouch. On the other hand, a helluva lot cheaper than the alternative costs if it had flown out and hit something else or, worse, someone else

[colinbParticipant @colinb]

Sorry all, just realised “Reply” doesn’t auto quote!

Thanks for the input, it’s made some focussed experimentation more viable

[colinb]

On colinb Said:

Just to check – Al tips but cutting steel? Rpm range appeals, will have to look at the torque topic

£700 for a window?! Ouch. On the other hand, a helluva lot cheaper than the alternative costs if it had flown out and hit something else or, worse, someone else

£700 is I should think the going rate for a properly toughened glass window. Some years ago near me a young lad was killed when a CNC lathe workpiece flew out of the chuck straight though the viewing window and hit him in the head. The original glass had been replaced with a Perspex sheet!! The cowboy company went bust before they went to court and the young lad never got to attend his wedding which was scheduled for a couple of weeks after the incident!

Tony

[JasonBModerator @jasonb]

Yes the non ferrous inserts cut steel and Cast Iron and put less load on the machine.

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