Clicking Noise When Cutting Aluminum Sheet Metal

[lukemackaman]

I'm getting some weird clicking noises while trying to machine some 6061 aluminum sheet metal (1/8in thick). It sounds like something is wrong but I'm not sure what it could be. This is the bit I'm using. Perhaps my stepdown is too extreme? (It's 1/16in and my bit is 1/4in diameter) or an issue with the chip load. See video and pic below.

(Don't mind the bottom height offset being too short, and the accidental drag in this pic)

[seth.madore]

It sounds like that slug popping around in the pocket. Couple bits of advice:

1) Lubrication. Cutting aluminum dry, without any air-blast (at minimum) is a recipe for disaster. The melting point of aluminum is really low, and it won't take long to weld it all to your shiny new endmill.

2) Find a way to restrain the slugs so they don't get knocked around, or turn it all into chips and eliminate any waste pieces. However, that goes back to point 1; don't run dry

[lukemackaman]

Thanks for the advice, I'll try using some sort of lubricant next time. As for the slugs - I don't believe that's the cause of the clicking noise, as that happens within the first 5 seconds of the cut.

[Anonymous]

I loaded your file in Fusion, ran it with speakers volume all the way up and I didn't hear any clicking noise 🤣.

Then I ran the video, as pointed out, running dry is a bad idea, on top of that you are using single flute end mill and running it at fairly aggressive rate of speed and feed.

My guess is that you are generating fused chunks of chips that are separating from tool after weight of accumulated and melted bal of material can no longer stay attached to tool due to centrifugal force.

These chunks of arbitrary shapes of half melted half disfigured chips are then bouncing around that broom covering the tool.

Some years ago an "expert programmer" produced similar art effects in turning deep groove where back of the tool was crashing into material at start of each pass, we took a picture of chips and used it as screensaver on shop floor computer for about a month to honor the artist.

Get it wet, slow down and use 3 flute end mill, that would be my start point.

[Stuart-H]

is it the entire plate lifting ie. flapping about and slapping the spoil board by any chance

if I was doing that job I would find some pints that could be used to fix down the plate and try WD40 as a cutting fluid works well and take it easy on feed/speed better to slow down and get it done than flat out and make a mess up

[lukemackaman]

I don't believe so, it's clamped a decent amount. I'll try slowing it down and adding WD-40

[johnswetz1982]

WD-40 is not a lubricant. It is a Water Displacer (formula 40) for preventing rust.

[seth.madore]

@johnswetz1982 pfft...WD-40 is awesome in aluminum! Another great option (with some major safety concerns) is kerosene. I've used both on manual machines, so granted, the speeds were MUCH slower. I reckon that using either in high rpm situations would likely result in smoke and eventually fire.

So yeah, get a coolant mist system 🙂

[johnswetz1982]

I just looked on Wikipedia and it does state it is a lubricant. Though Kerosene sounds way more fun and high stakes. If you are going to be doing a hobby, make it an extreme hobby. (cause you might start a fire).