End mill chatter?

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Hukshawn

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This is a piece I'm working on, it's in the vise for the picture.
I've noticed this in the past and just wrote it off. However, this time I'm actually trying to make a nice looking piece.
It seems I get some kind of chatter in my end mills without my machine actually chattering.
I'm the picture, you can see it in the last pass on the northeaat side of the picture.
Little gouges. This was with a 1/4" 4 flute roughing end mill in mild steel, but I've also seen it in aluminum with a 1/2" 2 flute end mill. Both are relatively new, fairly sharp, and not chinese. I've even seen it in my carbide fly cutter.
I don't feel I'm feeding too fast, or running too high of speed, I try to keep the chips somewhat clear, but the consistent pattern doesn't make me think chips.
The machine is a busy bee mini mill, don't ask me the exact running and feeds speeds cause I have no way of knowing what they are.
The only thing I can think of is slop in the x axis, but I'm power feeding, and it's all fairly tight...
Could a Ben's in the lead screw cause that? How could I detect that? I don't think the table surface is smooth enough to run a dial test indicator accurately.
Thoughts?
 
Are you locking the Z axis, both the head & quill? I haven't played with a mini mill before but I suspect you may get results like that if the Z is not locked with moderate cuts since the head doesn't have a lot of weight.
 
The z is always locked during a cut. That's how I broke the gears the first day I got the mini mill. Lol.
 
Your vice jaws remind me of a bench vice, not a machine vice, could it be moving/vibrating under load?
 
1. Are u climb milling or conventional? Climb milling can get grabbie and pull the work into the cutter. 2. Does it happen more when u go from left to right or vice versa? If your heads out of tram the cutter will travel across the workat an angle instead of flat , this would be especially noticeable with a fly cutter. 3. A bent lead screw shouldn't cause it , as troubling as that sounds. And certainly would help to know how fast things are going
 
Your vice jaws remind me of a bench vice, not a machine vice, could it be moving/vibrating under load?
That is indeed my bench vise. I put it in there for the pictures sake. I have a toolmakers vise in the mill.
 
1. Are u climb milling or conventional? Climb milling can get grabbie and pull the work into the cutter. 2. Does it happen more when u go from left to right or vice versa? If your heads out of tram the cutter will travel across the workat an angle instead of flat , this would be especially noticeable with a fly cutter. 3. A bent lead screw shouldn't cause it , as troubling as that sounds. And certainly would help to know how fast things are going
To take a guess on speed, as the dial is not labeled very well, maybe 900-1000 rpm. Feed speed I'd have to actually measure and calculate as I made the power feed.

Tram COULD be an issue... I trammed the head when I got it but not since, maybe 6 months with mild use... I have a fly cutter that I use at about 1.25", it does sometimes take a very mild cut on that back spin, or whatever you want to call that second pass as the cutter circles around.... more so going right to left than vice versa. But really only maybe .0005-.001" over that 1.25" diameter.

I usually try to conventional mill, but when I'm using the end of the end mill, I sometimes get mixed up. I will have to run a test and see which is worse, if at all.

I had to cut the same flat on the other side of the bar. I ran at quite a bit higher speed, went 1500rpm, (could have gone faster but I didn't want to change the pulley (lazy)), did notice the cut was a bit smoother... so, maybe just not going fast enough? But that potentially seems like a bandaid. The patten in the cut almost lines up with the turning of the lead screw... the table is small enough... I wonder if the weight of the hand crank spinning on the other side of the table is causing it to move as it spins... the gib is relatively tight. Any tighter and the x doesn't move...
 
I would recommend picking up an optical tachometer. A lot of my early problems came from not using the correct speed (usually too fast). That ruins cutters quickly. Knowing the actual RPM (and using the right RPM for the materials and operations) will make a big difference.

The attached is the chart I made up some years ago and one I still use for milling. Not the final word in speeds, but it works for me.
 

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Out of tram would not cause that issue. And if just facing with an endmill without deep cuts, convention or climb milling should not matter. I'm thinking something is loose or it's a rigidity issue. How deep of cuts were you taking? And is it steel aquired from a local hardware store?
 
Cuts were max .020" deep. The steel is unknown, it was an old rusty bolt. I did not pay attention to the grade on the top... So, might potentially be something a bit tougher than the mild steel I previously mentioned. But it doesn't lathe or cut like something hard. Cuts kind of nice.

If there are rigity issues in the table, they are light enough that I can't see them.
 
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