Thread: Chatter when using 50mm face cutter

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

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.

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

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

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....

Simon

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.

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

Originally Posted by Dave J

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

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

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.

Thanks Brendan,
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

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


Stuart

Don't worry, my mistake,

Dave

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.

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!!

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