Chatter when using 50mm face cutter

[19brendan81]

I was using a 50mm face cutter last night in a HM40 mill drill at a local tafe. This mill is fairly old and I have always got a lot of chatter/noise when using it...it sounds really bad, almost like the spindle is rattling around in the head.

i was using a 50mm 6 flute indexable cutter with positive rake inserts (that were all in good condition) very similar to this one...

M530 | 3 Piece Universal Milling Kit | machineryhouse.com.au (http://www.machineryhouse.com.au/M530)

A bad rattling noise was evident at any DOC over .5mm (i was mainly doing 1.5mm or 2mm cuts). Job was a 30mm mild steel round bar 125mm long that was secured in a vice for its entire lenght. I was machining the length of the bar to produce a large flat. Feed was prob around 100mm a minute. Slower or faster feeds wouldnt stop the noise.

Would I have been pushing the limits for a face cutter like this trying to take off 2mm? I am trying to work out if operator error was the cause for the racket or if the machine is in need of attention.

[Stustoys]

Hi Brendan,
My first guess is you didnt always have a tooth in the cut so the spline rattles as the load comes off and on it. I've been know to run my fingers on the draw bar to keep a little load on it and keep the noise down, oil can also help.

Stuart

[Dave J]

Keep the cutter over hanging about 2-3mm on the in feed side since it's a 50mm cutter doing 30mm, this will help with chatter. Also what speed where you running? My 65mm one likes to run around 1300rpm and gives a nice finish. The shaving coming off should be a blue colour.

Dave

[simonl]

Hi Brendan how's things!

I hate that spline blacklash sound! It sounds like somethings about to go kaput! I keep thinking of Davej mod he did and think I should give it a try. Hi Dave!

So, 1300 rpm Dave? I've got a 63mm 4 flute and have been running it at 700 approx. I get the impression I should be running at a little higher?

Hey Brendan, I was wondering if the mill is trammed the correct way. I mean so as to not create back cutting? I have this issue with my mill. I usually aim for a tram of 0.05mm and always make sure the that it favours milling in the direction so that the numbers on the dial increase. This involves the table moving right to left and front to back (for my mill). I bring this up because I still manage to get back cutting circles when I shouldn't. I assume this has been one of the reasons I get a poor finish?

Then again, maybe has nothing to do with your problem, I dunno.... :doh:

Simon

[pipeclay]

First question should be what advice did your instructor give?

Was there chatter evident in the workpiece,or are you reffering to machine vibration?

Your feed rate can be increased to between 350/400mm/min,depending on the ridgidity of your machine and setup.

2mm depth of cut should not of been a problem.

Speed wise I would look for something in the 700/900 rpm range.

Were the tips turned prior to machining?

When you inspected the tips were there any shiny spots on them.

[Dave J]

Hi Simon,
If you can keep the cutter in contact with the job it will help eliminate the chatter, this is why you only have it over hanging 2mm or so.

If you do a test run, running the table either direction you should see which way gives the best finish, as you can never tram it perfect. I never run mine out of tram and I tram it on a 400mm+ diameter, but even then, there are variables like quill/bearing flex/play that will always make it work better in one direction for finishing cuts where surface finish is important. Just remember when changing direction to move the job in the Y direction to keep the in feed side 2mm or so off the job.

Dave

http://www.woodworkforums.com/attachment.php?attachmentid=220690&stc=1&d=1345693855

[Stustoys]

If you can keep the cutter in contact with the job it will help eliminate the chatter, this is why you only have it over hanging 2mm or so.

But then it doesnt look as pretty.............. sometimes pretty matters, even for me, so I put up with the wear on my finger tips lol
Stuart

[Dave J]

It also helps your cutter with not hammering on the side of the job coming in at near 90 degrees. I also use the technique when using standard end mills.

If you really want the pattern to be centered on the job it would matter, but then you can always come down in cutter diameter to help out.

Dave

[19brendan81]

Thanks for the input fellas. Re the questions raised...

1) chips were coming off blue
2) RPMs were allegedly 1250 rpm (max for machine) but it certainly didnt seem that fast to me.
3) Tips had no flat or shiny spots on them...they looked pretty well new.
4) i was using the mill informally, there was no instructor there.
5) surface finish didnt have evidence of chatter (although it wasnt perfect either).

Re point 5, what I did notice on one pass was as the front part of the tool left the job, suddenly the surface was scratched up by the rear portion of the arc as the pass was finished.

P.S Go Dave - 5000 posts - all of them helpful.

[Dave J]

Thanks Brendan,:2tsup:
This is where Stuart was talking about having the mill out of tram slightly. If the job is only a cosmetic surface and is not mating with a another, the slight concave this produces would not be noticed as it is only very small.

Most of the time you will find running in one direction will give this effect as you can never have the tram perfect on these smaller mills as they flex. My mill is the next step up and I still get flex.

If your really going for surface finish you cant beat the old fly cutter, or better still leave a bit on it and grind it on a surface grinder after woods if you have access to one.
I have done plenty of jobs where I will finish up a cosmetic surface on the belt sander after milling, if your careful you don't round the edges over.

Dave

[Stustoys]

Hi Dave,
Sorry I meant the cutter centered on the work, not tram.


Stuart

[Dave J]

Don't worry, my mistake,:doh:

Dave

[pipeclay]

When you say the rear portion scratched after the leading cutting edge cleared the job,are you reffering to a slight cut or roughness of the finish at this point?

Were you able to feel any roughness/difference in the finish,this sometimes can be an indicator that swarf is not being thrown clear of the job and it catches on the cutter leaving a trailing mark or slight surface roughness,similar to when turning and swarf drags along the job after been caught by the tool.

It would seem that there is no real problem with your machining method apart from possably feed or speed.

Has this noise from the machine been a regular event or is it something that only occured when last in use?

If only when last used it would be advisable to either write a report or give a demonstration to whoever is responsable for allowing you access to the machine room so as maintanence can be carried out on the machine.

[Burner]

I would say a cutter that size in a mill drill would need a spring cut and a small finishing cut to get a real good finish at an accurate size. I haven't used mill drills much, mainly worked with larger mills. If your spring cut doesn't remove anything you weren't pushing the machine hard!! If the back of the cutter removes something then spring cut in the opposite direction before measuring to take a final finishing cut, it's not a problem. I have used large bed mills that would need that practice.

Daves drawing explains well how the work piece needs to be positioned to cut well and avoid that annoying noise and help the tips survive.

Don't ever climb mill in a drill mill, I don't think they would have a backlash eliminator and that will destroy things!!

[pipeclay]

Climb milling on these machines is possable,but limited by the amount they can cut by there ridgidity.

[simonl]

Thanks for the info Burner.

I have performed climb milling on my machine but only light cuts low feed rates and I nip up the gibb screws. Only done it out of interest not necessity to see what happens and how it goes.

Simon

[Col2310]

Quote

Would I have been pushing the limits for a face cutter like this trying to take off 2mm? I am trying to work out if operator error was the cause for the racket or if the machine is in need of attention.[/QUOTE]


Brendan
Some good information on this page as to the application of milling cutters

http://www2.coromant.sandvik.com/coromant/pdf/metalworking_products_061/tech_d_1.pdf

[Big Shed]

Good info there, just in case people want to see or download the rest of these guides, here is the link where they can be found

The Metalcutting technical guide contains quick and adequate information for trouble-free and productive machining using Sandvik Coromant products. (http://www.sandvik.coromant.com/sandvik/0110/Internet/I-Kit1/se02673.nsf/Alldocs/Information*Material*2ADownload*catalogues)

[19brendan81]

Thanks for the tips fellas. Will read up on those links before I use the machine again.

Brendan

[Retromilling]

Quote

Would I have been pushing the limits for a face cutter like this trying to take off 2mm? I am trying to work out if operator error was the cause for the racket or if the machine is in need of attention.




2 mm is too much cut for a HM 40 . It lacks rigidity and HP . Also the spindle speeds being touted in this thread are too high for steel .
For soft steel at 100 SFPM a 50mm x 6 tooth face mill should only be spinning at 200 rpm . My machine is way more rigid than a HM40 and I only run mine at 240 RPM and I get grumbling at a 2mm cut . It will do it but it don't like it , Chinese machines are not very rigid.
You have to find the right Surface Feet per Minute of the metal you are cutting first then work out the correct spindle speed for the cutter .
Here is some common SFPM speeds .
300-800 for aluminium
200-400 for brass
100 mild steels
40-70 for high carbon steel
30-80 for stainless steel

I work out the spindle speed by SFPM x 4 -;- diameter of the cutter in inch.
Mild steel = 100 x 4 = 400 -;- 2 inch cutter = 200 Rpm.
There is more complicated ways but that is simple and works for me.
Adjust the depth of cut according to feed , rigidity and the HP you have available and the needs of the work being done .

[Stustoys]

Hi Retro,
I think you'll find that table is for HSS.

Stuart

[Retromilling]

Hi Retro,
I think you'll find that table is for HSS.

Stuart

It does not matter it still works for indexable inserts even though you can speed it up in some cases . However for general hobby workwithout flood coolant it works ok for me and 200 to 250 RPM on a 2 inch face mill is about right for 100 SFPM .
The trouble is if you run the face mill too fast , it will cut but gets very hot and you burn your inserts early without flood coolant .
Run slower and you can do a lot of milling without coolant .

[Ueee]

The iscar tips i buy have the recommended speeds on the box, MS is 80-150 Meters P/M, so i use my 50mm cuter at 760rpm, the next speed up on the HM50's is 1300 and it is too fast at 200 MPM 760 equates to 119 MPM, i find i get blue shavings, and when i have a full or close to full cut it feels almost buttery....
Brendan, if you want i can give you a demo of what it is like on my mill just so you know if the tafe's is in the ball park.
Retro, i was told not to use coolant with my tipped cutters, i have never had lifespan problems and i cut a lot of 5160 in less than 100% rigid situations.

[Retromilling]

The iscar tips i buy have the recommended speeds on the box, MS is 80-150 Meters P/M, so i use my 50mm cuter at 760rpm, the next speed up on the HM50's is 1300 and it is too fast at 200 MPM 760 equates to 119 MPM, i find i get blue shavings, and when i have a full or close to full cut it feels almost buttery....
Brendan, if you want i can give you a demo of what it is like on my mill just so you know if the tafe's is in the ball park.
Retro, i was told not to use coolant with my tipped cutters, i have never had lifespan problems and i cut a lot of 5160 in less than 100% rigid situations.

I agree 1300 is too fast for most hobby situations . I have run mine upto 700 rpm on K245 steel but it gets too hot without coolant . Now I just use 250 to 400 depending on the steel . If I use flood coolant the SFPM can increase quite a bit .
I don't know what kind of cutters you have but most coated carbide inserts are designed to run with flood coolant that is how the professional machine shops work .
Keep the heat down and they can run at much higher speeds and will last longer . Heat is the killer of coated inserts quicker than abrasion .
Some professionals forget that the average hobbiest will not be using flood coolant or a $50 000 machine or the top grade cutters . So they can't run at the max cutting speeds and feeds that the pros use .

[Dave J]

I just put up some shields to stop getting burnt, and then let the chips fly.
Carbide likes speed and feed and up around that range I quoted (1300 rpm) for my mill (HM52) is just about right. I have tried lower speeds and found it just takes a lot longer and get no better results (actually worse at a lot lower speeds).
For a smaller mill I would just recommend a bit less depth of cut, Pipe Clay could tell you what a bench top mill is capable of, as he has one and has used it extensively.

These are the colour I get off the face mill.

http://www.woodworkforums.com/attachment.php?attachmentid=221523&stc=1&d=1346239968

PS
I chased up this thread on the same subject
Carbide question (http://bbs.homeshopmachinist.net/threads/28908-Carbide-question)

Dave

[Retromilling]

I produce blue chips also but not as much as that. I feel you are just hardening up the steel as you cut . Carbide inserts will do it but the extra heat will reduce their life .
For the hobbiest time is not the big factor but expense is .
If you are getting paid for a job it's different as the tooling is factored in.
I have slowed down a bit and find my latest set of carbide inserts are lasting way longer than before . That makes it worthwhile for me . If I run coolant it's different .

[Dave J]

I don't run coolant on carbide as the speed they run at just spray it around to much. Those chips where ones I took making the 40 odd tool post holders recently, and the feeds and speeds helped get through them a lot quicker. It would have taken an awful lot longer if the speed and feed where reduced.

With the heat in the steel, the chip carries the heat away from the job and I have not noticed any reduced life out of the inserts.

Have you done the top taper bearing mod to your machine. I not I would recommend it as it does seem to make a difference to the surface finish.

Dave

[Retromilling]

I don't run coolant on carbide as the speed they run at just spray it around to much. Those chips where ones I took making the 40 odd tool post holders recently, and the feeds and speeds helped get through them a lot quicker. It would have taken an awful lot longer if the speed and feed where reduced.

With the heat in the steel, the chip carries the heat away from the job and I have not noticed any reduced life out of the inserts.

Have you done the top taper bearing mod to your machine. I not I would recommend it as it does seem to make a difference to the surface finish.

Dave
No Dave I would not know how to do that mod . I am sure better bearings would help heaps . That is one of the reasons I run a bit slower to help control the coolant but if I put up coolant barriers then I can run much faster but most of the time I don't bother . Time is not a big issue .
I don't want to spend too much money on this mill as I want to sell it one day and buy a better quality one. If the bearings fag out then I might think about it.
I don't have big issues with surface finnish , infact I get good surface finish even when not using coolant . I make the last cuts to size very light . Your machine may be more cappable of taking a heavier cut than mine after all the mods you have done.
However the HM40 in question is a very light machine .

[eskimo]

so its not just the HM52's and clones:oo:

[Clubman7]

Coolant can actually shorten carbide life by causing edge fracturing due to heat and quenching of the cutting edge.
I would try about 1000 rpm and reduce the depth of cut to about 1mm.
Seems your problem is mainly machine rigidity though.