Cutting thin aluminum sheet

Hey guys. Been reading through several posts & finding a lot of good information but want to check a couple things.

We’re building a 4’ clock for our wall. Looking to make these clock hands since I can’t find them for sale anywhere! Good thing I own a shapeoko :+1:


Picked up a thin aluminum sheet from HD for the hands. .019" thick.

Having only cut wood before, do I need a"O" single flute bit? Or can I get by with a downcut/upcut/compression bit that I normally use?

I saw this bit referenced in another post, so if I NEED to, I can pick it up.

I’ll be workholding with tape & CA Glue as recommended by others.

Do I need to worry about cooling the meterial while cutting?



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No need for O flute for aluminum but you need a ZrN coated bit for best result. A two flute will also cut faster than one flute. The endmills from Carbide like the two flute 1/8in - 102Z are very good but you can get good ones from Drillman1 on EBay also. Use a F&S Calculator like the ones @Julien and @gmack have created to ensure you do not break or damage the bit trough overloading or feeding at the wrong speed.

If you need a baseline to start from for your feeds and speeds, I documented a similar usecase here (#102Z 1/8", profile cut in 0.08" thick 6061 aluminium)

I wouldn’t use a downcut or compression bit for cutting Al. Downcut endmills provide poor chip clearing and in aluminium that’s a sin. Compression only makes sense when cutting through a given thickness in one pass, and that’s not likely to be the case in metal. You can get away with any upcut carbide endmill, but ZrN coated are less likely to stick indeed. Spray some WD40 on the surface before the cut, and with correct feeds and speeds you should be fine.


Thank you. Great info. Ordered a zrn bit, ill upload a pic when its cut

Certainly try some things out before you commit to cutting the big parts.

hey guys checking the feeds and speeds. Looking at your example Julien. You used the formula:

“* to achieve the 0.0005” chipload at 12.000RPM with this 2-flute endmill, the feedrate needs to be 0.0005" x 2 flutes x 12000 RPM = 12ipm = 300mm/min"

For mine I purchased a 4 flute 1/8" ZRN endmill, so I have the 0.0005 x 4 flutes x 16,000 RPM (setting 1 on my dewalt) gives me 32 ipm

Going to keep the plunge at 4ipm, and keep the depth of cut the same as yours at .012"

Look correct?

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Yes, your adjustement to take the 4 flutes into account and higher RPM is correct. However please note:

  • in the example I documented, I mentioned that I eventually used +50% feedrate override during the cut, because my 300mm/min was a tiny bit to slow for comfort. 450mm/min ended being better for my cut.
  • you will be using a 4-flute endmill, that will bring higher ridigity of the endmill, but also poorer chip evacuation, so if you are going to be slotting, keeping a small depth per pass sounds like a good idea (at 0.012" you should be fine). If you can use a little lubrication (drop of WD40) and/or a blast of air, that will put the odds of a good cut in your favor.

So what I would do if I were you is start the cut with those settings you mentioned, have your mouse over the feedrate override button, and increase up to +50% by increments of 10%. If it cuts fine (normal sound/vibration) at +50%, keep it there as it will lower chances of melting the aluminium.

EDIT: it seems to me that setting 1 on the Dewalt can just as well be 16500RPM, so you can easily round up that initial feedrate to 35ipm

Also keep your endmill stickout to a minimum. And do let us know how it goes !

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Thank you, will do. Going to start cutting now

Ok, all went well. As suggested , zrn endmill, sprayed the sheet with some wd40. Cheated it up to 130% speed. Kind of gnarly sounding when cutting metal compared to wood, but I suppose that’s to be expected.

Heres a pic of the aluminum cut out:

And a couple of the finished clock. Made entirely on the s3xxl, with exception to the 48" out ring which wouldn’t fit so it was cut by hand


I really, really like that clock.


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Did you design yourself or are there plans available somewhere?

I drew up each compnent in aspire, using the top picture as a reference.

I am fine with sharing the files, gotta upload them to my google drive though if you’re interested


Well it is a very nice piece, you are talented! I would love to take a look at the files but I have VCarve not Aspire. If you are willing to share, maybe you could also put on Cutrocket.

Yeah however I can get it for you to access. I’ll get them up in the next couple of days!


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