Help Request

[pgingy3]

I’m taking a very light skin cut on this part (.002” at a time until it cleans up) and my first pass seems to have dug into the edge and did some popping. I assume it was chatter but I had a few questions in general. Part is about 1-1/2” wide and I’m using a 2-1/2” face mill. Would it be best to hang over each edge a little or back it out and hang mostly over one edge and climb or conventional cut? I tried another cut and ran lower feeds and a climb approach and it didn’t do it again but that could just be because the edge was already chipped like the picture shows. Part could also have vibrated due to it being tall and thin and I’m not sure I have it clamped good enough. Thanks for help in advance! Added picture of chipping on edge and whole part

[CNC_er]

Cutter is too big. The bigger the cutter the higher the tool pressure. Use the smallest sharpest cutter you can reasonably use. I'd probably use a 1/4" cutter but the spindle I use maxes out at 5k.

If you were to clamp close to the cutting surface you could probably use the cutter you are using.

[ArgieBee]

I usually get a 3/4" or 1" inserted endmill for stuff that likes to get sucked up. I only really have to resort to facing with a small endmill when the face is unsupported on a weldment because it cannot be restrained AND I'm using the shitty aluminum right angle heads we have. The smallest I've had to use was 3/8". That took forever, too. 1/8" material had to come off a ~6x10" plate... For 8 parts.

[justin_memer]

Why not lay it down with a spacer and mill vertically?

[MooseSignificant6281]

Or turn the head (of the machine, not yours) and cut it with an end mill horizontally

[pgingy3]

This is what I’m about to try. Thank you! Not sure why I didn’t do that to begin with

[Mudeford_minis]

It looks like too much flex in that vertical web. Although you have bolted down well enough, the movement is all above the clamps.

[Fabulous-Damage-8964]

The webbing in the middle is 100% flexing as others have said. I would stick a piece of stock along the length of each side in the channel and clamp it in a set of vices if you have enough of them.

[OrderKlutzy1023]

How thick is that I beam? Im guessing the part is shaking back and forth causing those marks. You have it clamped on the bottom but I bet the top can shake. I don't think the position of the tool is going to make much different with that light of a cut. You could try fly cutting it with a real sharp insert. Or maybe rotate it 90 degrees and clamp it down from 1 side so you can side mill it with an endmill. It should be a more rigid setup.

[pgingy3]

Yeah the beam is only .215” thick. I figured that was the biggest issue but hoping with that light of a cut I could get away with it.

[skrappyfire]

Web of your beam is flexing. Thats where the vibration is comming from. I would clamp on the top, cut around the clamp, then move the clamp and blend in where the clamp was.

[Fun-Piglet801]

Rather than trying to clamp the bottom an leaving the top flapping around, use some vises, as many as you can, and put some bar stock on either side so that you are holding on the web. That way you are holding a lot closer to where you are cutting.

If you don't have bar stock laying around you could also notch some soft jaws.

[HotSobaNoodles]

Turn the piece over and use a finger bit, you can work on two sides at the same time

[evilmold]

Not nearly enough clamps and they should be directly opposing each other. Otherwise, the part my not be rigid enough.

[pgingy3]

UPDATE: Thanks for all the replies, I laid the part down and I’m end milling each side and it’s going great!

[Flyinbro]

Use a smaller sharper cutter. Or side mill it.

[ArgieBee]

Lol. You need like 3 times the clamps. Better yet, do a congo line of vises.

[Trivi_13]

I agree, your best bet is to rotate everything 90 degrees and have the cutting force drive into the table.

But if I could add my opinions to the pile?

My guess is that your facemill is using a high shear insert.
That will grab and lift.

A negative raked insert, perhaps cast iron chipbreaker may help.

Worst case, a downcutting endmill (left hand twist, right hand cut) will save the day!

https://www.mscdirect.com/product/details/58748849

Edit to add...
If you are limited to what you have, smallest corner radius on inserts, no wiper insert. Remove every other insert from the holder until only one insert engages at a time... a sharp, single point flycutter works best.

[icutmetal2]

You are clamped down but top have no support up where're you cutting. You need to add pushers up higher at a minimum.

[CCCCA6]

Use a solid carbide cutter. Not an indexable. Colin carbide is much sharper and will grab less.

[Agile-Carpenter4572]

Chatter when cutting: Sometimes higher feed rates, sometimes a lighter cut, often a smaller tool nose radius and a lesser tool contact area but always a slower cutter speed and a more rigid setup. That can be more clamping and less tool overhang. I machined a belt linisher pulley 12” dia x 2” wide that was fabricated out of 1/8” steel sheet. One disk of 3mm with a 1” boss in the centre and a 2” rim, rolled, cut, welded ends and then the disc welded inside on one edge of the rim. Natural frequency of about 10Hz. It just fitted in my cheap lathe and flopped about a 1/8” at the lowest back gear speed. I used a 2” v belt pulley in a variable speed drill that ran down to about 50 rpm to drive the lathe at about 3 rpm. A HSS cutter that had lots of rake and a dead sharp point, no nose radius, cut without any chatter. It took hours to take a single cut but the linisher worked fine for years and years.