What is causing these machining marks ?

[tq60]

For aluminum soapy water or anything slippery will work.

Atf really well.

For finishing cut climb mill, slower motion too and it should come out nice.

Very light cut until you determine what your mill can do..

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[mikey]

Interesting. I would have expected there to be less rigidity in X, which makes me wonder if your Y-axis gib is adjusted well. You might want to re-evaluate those gibs and see if you can eliminate any play.

By all accounts, the FB-2 is supposed to be a good machine. The Y-axis table is a big slab of cast iron and if Emco stayed true to form then they use gib screws along the length of the gib, not the crappy tapered gibs commonly found in Asian mills. If this is so then you should be able to dial out all play in that gib.

 

[compact8]

If this is so then you should be able to dial out all play in that gib.

The Y axis gib has been adjusted before the test. Thats why I suspect that the poor finish is due to the vibration of the mill head.
In the past I didn’t notice the difference between the X and Y axes in this regard because all the side milling was done along the Y axis. I guess I will need to rotate the vise by 90 degrees so that side milling can be done along the X axis. But then the freedom in positioning the vise on the table will be reduced.

 

[Ken226]

The Y axis gib has been adjusted before the test. Thats why I suspect that the poor finish is due to the vibration of the mill head.
In the past I didn’t notice the difference between the X and Y axes in this regard because all the side milling was done along the Y axis. I guess I will need to rotate the vise by 90 degrees so that side milling can be done along the X axis. But then the freedom in positioning the vise on the table will be reduced.

In my previous reply I mentioned that I see that type of finish when my head gibs are loose. At the time, I didn't realize that you have a round column machine.

What does that type of machine use in place of gibs, to tighten the head?

When my head gibs are loose, I see worse finishes along the Y axis than the X as well.

 

[compact8]

What does that type of machine use in place of gibs, to tighten the head?

The rear end of the head is a steel block that slides along the round column. There is a vertical slot on the block that can be squeezed down by tightening a bolt.

 

[Ken226]

The rear end of the head is a steel block that slides along the round column. There is a vertical slot on the block that can be squeezed down by tightening a bolt.

Doesn't sound like there's much you'll be able to do to increase it's rigidity, assuming the bearings are good and the gibs are tight.

A machine of that size and design is going to be limited in the feeds, speeds and depth of cut it's capable of.

Perhaps try multiple passes along the side, stepping down Z axis in smaller increments until you figure out what it can do. Then perhaps some deeper z axis passes, with less stepover depth.

Is it possible that the mill is fine, and your just taking a bigger bite than the little machine can do?

 

[compact8]

Is it possible that the mill is fine, and your just taking a bigger bite than the little machine can do?

The depth of cut is 0.1mm or 4 thous on 6061 aluminium so its already the lightest cut I think.

 

[mikey]

I just don't buy it that an FB2 should chatter in Y with such baby cuts. Something is definitely wrong when a Sherline mill will outdo an Emco mill.

I strongly suggest you join the Model Engineer forum and post this issue there. There is a fellow named Graham Meeks there who is one of the gurus for Emco machines. He owns an FB2 and if anyone can sort this out, Gray will be the one.

 

[Ken226]

The depth of cut is 0.1mm or 4 thous on 6061 aluminium so its already the lightest cut I think.

Yea, there's definitely something weird going on. A .004" cut is tiny, and the chatter marks in your first pic look nearly as deep as your entire depth of cut.

 

[compact8]

Yea, there's definitely something weird going on. A .004" cut is tiny, and the chatter marks in your first pic look nearly as deep as your depth of cut.

The chatter marks shown in the photo is kind of misleading because I intentionally adjust the lighting to maximize their visibility. The depth of the marks is definitely not that much. I have tried to indicate the marks ( ball diameter of the indicator = 2 mm ), the TIR I get is about 0.003 mm or about one tenth.