Chatter problems with carbide tooling

[levelzero]

I've had my machine for about 2 years. I've always had a lot of chatter with carbide tooling, but becasue I don't use it very often it hasn't been a big issue.

Right now I'm doing a run of parts and need to use a carbide cutter I have for a few of the operations. It's screaming like a .... well something that screams a lot.

The part is 1.5" X 2.5" X 6" 6061 held in a 6" vice. The cut that's giving me the most problem right now is dead center in the part. It's roughly 3"x0.75" pocket 0.65" deep.

The cutter is a 0.500" solid carbide 4 flute with a .125 Radius. DOC is 0.050", full width (small pocket). 4450 rpm 48ipm. The cutter is held in a 0.500" TTS holder with the cutter sticking out 1.300". This should be a relatively easy/light cut but it's still screaming, although sometimes worse then others. I've tried more feed as well as less rpm but nothing has made the chatter go away.

I recently faced my spindle and it made little difference. I'm stumped and looking for any ideas of suggestions anyone might have.

Thanks

[Geof]

Originally Posted by levelzero ... This should be a relatively easy/light cut but it's still screaming, although sometimes worse then others. I've tried more feed as well as less rpm but nothing has made the chatter go away....Thanks

How much more feed? Many times you can correct chatter by increasing feed but on a lightweight machine this may not work.

A drastic approach is to slightly dull the cutter. There are different ways to do this and one is to wad up some Scotchbrite abrasive felt (the purple stuff I think) into a ball and stroke it down the cutting edge. Do this carefully otherwise you might learn how sharp the edge is from the slice in your finger tip. Using the Scotchbrite is a shade below drastic.

[skip56uk]

Originally Posted by levelzero I've had my machine for about 2 years. I've always had a lot of chatter with carbide tooling, but becasue I don't use it very often it hasn't been a big issue. Right now I'm doing a run of parts and need to use a carbide cutter I have for a few of the operations. It's screaming like a .... well something that screams a lot. The part is 1.5" X 2.5" X 6" 6061 held in a 6" vice. The cut that's giving me the most problem right now is dead center in the part. It's roughly 3"x0.75" pocket 0.65" deep. The cutter is a 0.500" solid carbide 4 flute with a .125 Radius. DOC is 0.050", full width (small pocket). 4450 rpm 48ipm. The cutter is held in a 0.500" TTS holder with the cutter sticking out 1.300". This should be a relatively easy/light cut but it's still screaming, although sometimes worse then others. I've tried more feed as well as less rpm but nothing has made the chatter go away. I recently faced my spindle and it made little difference. I'm stumped and looking for any ideas of suggestions anyone might have. Thanks

Easy fix m8
the reson for you scream is simple!!! you are useing a 4 flute cutter.

swap it for a 3 flute and your sceam will go away

[skip56uk]

I dont buy or use 4 flute carbides EVER! there nasty, and the fact that you cant make a cut useing full width of the cutter should be writen on the box! lol

[levelzero]

Originally Posted by Geof How much more feed? Many times you can correct chatter by increasing feed but on a lightweight machine this may not work. A drastic approach is to slightly dull the cutter. There are different ways to do this and one is to wad up some Scotchbrite abrasive felt (the purple stuff I think) into a ball and stroke it down the cutting edge. Do this carefully otherwise you might learn how sharp the edge is from the slice in your finger tip. Using the Scotchbrite is a shade below drastic.

I've tried running the feed as high as 58ipm which is about max for the machine.

I've heard of the dulling trick, although I've heard to use a piece of copper and run it down the flutes. This cutter is used, I'd estimate I've put 3-5 hours of aluminum machining through it.

Originally Posted by skip56uk Easy fix m8 the reson for you scream is simple!!! you are useing a 4 flute cutter. swap it for a 3 flute and your sceam will go away

I know the 3 flute cutters break up the harmonics better and I've tried 1-2 ... lol mostly with poor results due to bad work holding. The problem is going to be tracking down 3 flute cutters with the radius on them.

[dertsap]

with the radius you want i would suggest using a 2 flute 55 deg high helix ,it would be much cheaper than a three flute

[audioandy1762]

Hi

Have a look on here http://www.damencnc.com/damencnc.php...2ba88275cc90d7 the cutting bits are down the page.

Andy

[mc-motorsports]

I would be using a 2 flute, not a 4, maybe a 3.

To dull out a chattery cutter, I run the endmill backwards and use a 600 grit stone and LIGHTLY rub the cutting edge. Or the variable flute endmills will take care of most of that problem.

You should also be cutting at full depth (leaving stock for a clean up pass) and a 20% step over, vs. .050" DOC with a full step over. If will increase your roughing productivity quite a bit if you get the parameters right, plus your tools will last longer because your using more cutting edge than just the tip.

MC

[levelzero]

I'm going to look into a 3 flute as soon as I can get to my supplier, I'm always hesitant to give up flutes especially on 0.5" and larger cutters. I also have a tenancy to avoid ordering anything in and stay with tools I can get within 24hrs.

Unfortunately this pocket is only slightly wider then 0.5" at it's narrowest point so a 20% step over is not an option for this item. I could drop to a smaller tool but that would add a tool change and it's already a short cycle so I'm trying to avoid having to run back and forth from the machine even more.

It's strange how many people recommend honing carbide tools. I haven't tried it yet but I think I'm going to as this endmill is barely usable to me right now. I talked to my tooling supplier and he told me this was an old school trick and no longer necessary on newer carbide tools. From the number of times I've read about this I trust that it works but does anyone have a link to an article that explains why it works?

[mc-motorsports]

2 flute endmills will have larger flutes which will give you more room for a larger chip to eject, and even move, making welding chips much less likely which is the major problem with cutting aluminum. The trade off is the cutting edge is thinner and longer and not as strong which is needed for steel. 2 flute endmills work excellent for aluminum, 4 flute works excellent on steel because you'll be cutting a lighter chip and need that extra streangh.

Depending on how many parts you need to make, you might be able to pocket that hole a lot faster with a smaller tool. But if you don't have a ATC and using a .5" for another opp, I could clearly understand the circumstance.

I've never seen an article about honing tooling to reduce chattering. It was one of the first things I learned 14 years ago. It does work, and yes, variable geometery fluted endmills won't have these problems, the "old school" standard helix and geometery endmills that are still more widely used and more readily available do have these problems.

As far as salesmen, they scare me. They make money running thier mouths. I would take advice from someone who makes his or her living USING cutting tools, or MAKING cutting tools, not talking about them. I always say "if you can do anything with your mouth and nothing with your hands, management or sales is where you need to be". I can totally understand that in some cases, mostly business owners, some will move off the shop floor or away from the actual production process to make more money and increase thier standard of living, so to say. A REAL machinist will always be on the shop floor and or in the production process. I tend to take advice from people who are experienced. What I'm saying is take what the sales rep tells you with a grain of salt, or atleast consult people with REAL WORLD experience. Just my opinion.

MC

[levelzero]

Well I am almost positive now that it's either my spindle or my holder. I was running the part and stop mid pocket due to chatter. I rotated the holder 90* and the chatter went away. I'm sure the tooling isn't helping but this explains why it's been a semi intermitant problem.

[keen]

Hi. The number of flutes is only part of the equation - the cutter geometry is also critical. Yes you may have a rigidity issue with your cutter holder or spindle. You may have a resonance issue with that cutter - have you tried running at slower revs?