End mill chatter?

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View attachment 235290

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?

I think you have something somewhere that is ether
Loose or not tight . A chip between something somewhere, vice to table . A bur somewhere
A taper that is not setted right . Or drawbar not tight . A bent arbor or A cracked collet . I hope you are not running your end mill in a Jacobs Chuck
That would surly cause this .

 

[4GSR]

What kind of taper does your spindle have? If it's a morse taper, them this could be your problem. Could be a badly fitted arbor in the taper. Look for dull marks toward the small end of the taper shank.

 

[Hukshawn]

It's an R8 collet and I snug the draw bar up not super tight, but a good 1/3 turn past snug. Just not so tight that I have to wail on the draw bar to dislodge the collet.

 

[Hukshawn]

I'm convinced now it's that chip I put in that one flute.
And it just so happens that the other 1/2" 2 flute that I had seen this with has one full flute as well. Because I tend to baby my cuts on this mill and stay away from anything that is excessively loud, I don't use dull cutters so I am unfamiliar with what a dull cut looks like.

 

[T Bredehoft]

Grind two other tips and the three flutes off and use it for a boring bar.

 

[Hukshawn]

I have so many boring bars. Lol. I'm sure I'll think of something to use it for. It's not a total waste yet. I don't think I've ever used anything but the end of the mill, so the sides are pristine.

 

[mikey]

I'm convinced now it's that chip I put in that one flute.
And it just so happens that the other 1/2" 2 flute that I had seen this with has one full flute as well. Because I tend to baby my cuts on this mill and stay away from anything that is excessively loud, I don't use dull cutters so I am unfamiliar with what a dull cut looks like.

Shawn, just something to consider. End mills can wear excessively at the tips if you "baby" your cuts. That is, if you take multiple shallow cuts instead of one or two larger cuts then the cutting tips will wear faster. This is especially true of finishing end mills but also applies to roughers. When the tips wear the end mill will vibrate and your accuracy and finish will suffer. It is better to use them as intended.

Remember those tables from Niagara Cutter that I sent you? Look at those tables and choose a cutting speed based on the amount of radial and axial depth of cut you need, then look at the suggested feed rate. Those tables are trying to take the chipload into account already so set the speed and feed and dial in that depth of cut and make the cut.

As a general guideline, try to keep the radial depth of cut for a profiling cut no more than 1/2 the diameter of the end mill. For example, if using a 1/4" HSS end mill, a max radial depth of cut would be 0.125". You can, of course, take a lighter radial depth of cut if you like so choose a cutting speed for that amount of radial depth of cut from the table. I would also limit the axial depth of cut to </= 1 to 1.5 times the diameter of the cutter. So, for the 1/4" end mill, you can lower the cutter to a max of 3/8" below the surface of the material and take a side cut into the material by a max of 0.125". You are not likely to have digital control of your feed rate so chip loads and inches per minute may not mean anything to you but you can still feed manually and get a good cut. Start the end mill at a steady rate and feed so that there is a slight positive resistance to the cut and try to be as consistent as you can.

Over time, you will come to learn what your mill can and cannot handle but if you don't use the end mill to its potential it will wear prematurely, and usually at the end.

 

[Hukshawn]

I think I'm going to order 3/8" and a 1/2" Co8 4 flute. That 1/4" had done quite well before I bumped it into the jaw. The other 1/2" 2 flute I had purchased for aluminum. I'll leave it to just that and get some better ones for metal.

I once again learned a lot here. This place is invaluable!