CNC Router Aluminum Drilling Advice

[juchong]

Hi everyone,

I'm looking for advice on what drill bit material/coating I should purchase for use on a high-speed CNC router. I'm currently running an OmioCNC X8 capable of 24k spindle speeds, so any advice on whether cobalt, TiN, HSS, etc. would be appreciated.

98% of the time I'll be cutting 6061 Aluminum, 3/8" or thinner. Most holes drilled will be smaller than 1/4". A WD40 mist will be applied while drilling (and machining).

I'm pretty sure that the "best" solution for drilling using a CNC router is going to be carbide drill bits, but I'm trying to stay away from that for now due to the very high cost of carbide tools. The machine will cut about 100 holes per week as it's main purpose is prototyping, so tool life is important, but not critical.

Thanks in advance for everyone's help!

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[ger21]

You need to run the spindle as slow as possible to get decent tool life.
Quality HSS bits should work fine, if you can keep them cool. I use them at 5000 rpm on my router, with no issues.

[KH0UJ]

On my opinion if it`s a 24K RPM spindle and a 1/4 holes to be drilled, a 1/8 carbide single tool flute tool bit will do the job all day without resharpening the bit, ramp up the spindle speed to 24K and you can drill all day with it. 24K rpm spindles does`nt have enough torque to run at slow speeds Boss Gerry, tried it once and it sucks, I also tried the 12K version spindles and it rocks but the CNC bed sometimes shakes a little bit because of the torque @ slow speeds, personally I like the 24K spindles, it`s smooth to work with in cutting and drilling, does`nt have to be a rock solid frame to cut or drill metal works. the spindle`s high speed setting will just pulverize the metal chips in small bits so even if your CNC frame is flimsy you can still do the job nicely.


Here`s my sample of cutting / drilling 50mm Aluminum with a 24K spindle and only one tool bit

[dharmic]

I tried a bunch of things with normal jobber bits on my X6 and pretty much gave up on drilling ali with this thing once I got bigger than about a 5-6mm hole. Too high RPM and you burn bits - even worse if you reduce the plunge feedrate because the tool then just rubs. Too slow (I'm really hesitant to run lower than about 8000RPM because of this) and you can hear the spindle bog down, down, down and stall.

In the end, for wider stuff (7mm+) I'll do a helical bore using a 6mm two flute and that seems to work really nicely.

For the really little stuff where I can keep the RPM up, it drills just fine.

For the in-betweenies (3-8mm?) it depends on how many holes I need to do. If it's only a couple I just spot drill the hole centres to a couple mm and then, when the routing's done, I manually drill the buggers on the drill press. If it's repetitive work it's worth either helical boring with a smaller two flute or tweaking and tuning feeds and speeds with a decent bit to get it done on the router.

If you're like me and using this mostly for aluminium, do yourself a favour: stop being such a tightarse on tooling. I switched to carbide a while ago, just cheap Chinese bits from danyazhan0 (Klot tool store) on eBay, but they deliver quick and the tooling is a dream to use. For a lot of stuff it's cheaper than HSS bits because although it costs $5 instead of $1 for a 6mm cutter, it lets you run a heap more aggressively (saving time) and lasts a million times longer. Of course, the $50+ 6mm cutters from Sandvik et al are another world again but hey, if we're only using an Omio then let's face it - we aren't expecting that crazy level of accuracy anyway.

HSS still has its place - I use HSS bits for cutting MDF forms and foam, and it was nice and cheap when I was getting started and regularly plowing the tooling into the side of the job, the fixtures, the bed, the wall of the shed etc by being an idiot with the CAM, MDI or even just jogging. But I like to think I'm past that now (mostly, anyway) and even the cheapo carbide stuff makes running ali on these machines quicker, quieter, less cringing-at-the-howls-of-pain-from-the-machine and overall a much happier experience.

I also installed a $20 from ebay dual nozzle mister setup which I run from a gravity fed bottle of 20% methylated spirits, 80% water mix and it's worth a go if you have compressed air. Getting a stream of air to the cutter blowing chips out to prevent re-cutting makes a big difference to tool life and finish on the cuts, adding that mix of alcohol and water (pretty much what the Datron machines use IIRC) keeps things cool and lubricated without the residue of WD40.

[pugsly]

So for prototyping it sounds like speed is not a priority. I'll echo what others have said - don't drill the holes, mill them with a small (and relatively inexpensive) carbide end mill.

I also would not be using WD-40. I favor Kool Mist, a gallon of it will last you for many, many years. I scored an actual Kool Mist 100F system at an auction recently for ~$20, but before that I was just using the cheap ebay mister.

[Zorbit]

A 4mm single flute carbide mill, at 5k rpm, as ger21 suggests, will work well. WD40 is effective but messy. My method is to place the alloy sheet on the machine and hold it down to MDF backing with vacuum, then put the waste sheet from the previous job over the top so I can see exactly where the tool will cut. I draw a thin line of airtool oil around the cut line, remove the waste sheet, and cut. I drill holes with the same tool, it leaves disks of alloy in the MDF backing but works fine, very clean holes both sides. This surprised me.

[juchong]

Thanks for the feedback and advice everyone!

On my opinion if it`s a 24K RPM spindle and a 1/4 holes to be drilled, a 1/8 carbide single tool flute tool bit will do the job all day without resharpening the bit, ramp up the spindle speed to 24K and you can drill all day with it. 24K rpm spindles does`nt have enough torque to run at slow speeds Boss Gerry, tried it once and it sucks, I also tried the 12K version spindles and it rocks but the CNC bed sometimes shakes a little bit because of the torque @ slow speeds, personally I like the 24K spindles, it`s smooth to work with in cutting and drilling, does`nt have to be a rock solid frame to cut or drill metal works. the spindle`s high speed setting will just pulverize the metal chips in small bits so even if your CNC frame is flimsy you can still do the job nicely.

I usually have to cut holes only slightly larger than 1/8" so using an endmill for everything is a viable - albeit slow - option. For now, I plan on machining everything with an endmill, but I'll start playing with drilling using carbide bits once they arrive from China.

I tried a bunch of things with normal jobber bits on my X6 and pretty much gave up on drilling ali with this thing once I got bigger than about a 5-6mm hole. Too high RPM and you burn bits - even worse if you reduce the plunge feedrate because the tool then just rubs. Too slow (I'm really hesitant to run lower than about 8000RPM because of this) and you can hear the spindle bog down, down, down and stall.

In the end, for wider stuff (7mm+) I'll do a helical bore using a 6mm two flute and that seems to work really nicely.

For the really little stuff where I can keep the RPM up, it drills just fine.

For the in-betweenies (3-8mm?) it depends on how many holes I need to do. If it's only a couple I just spot drill the hole centres to a couple mm and then, when the routing's done, I manually drill the buggers on the drill press. If it's repetitive work it's worth either helical boring with a smaller two flute or tweaking and tuning feeds and speeds with a decent bit to get it done on the router.

If you're like me and using this mostly for aluminium, do yourself a favour: stop being such a tightarse on tooling. I switched to carbide a while ago, just cheap Chinese bits from danyazhan0 (Klot tool store) on eBay, but they deliver quick and the tooling is a dream to use. For a lot of stuff it's cheaper than HSS bits because although it costs $5 instead of $1 for a 6mm cutter, it lets you run a heap more aggressively (saving time) and lasts a million times longer. Of course, the $50+ 6mm cutters from Sandvik et al are another world again but hey, if we're only using an Omio then let's face it - we aren't expecting that crazy level of accuracy anyway.

HSS still has its place - I use HSS bits for cutting MDF forms and foam, and it was nice and cheap when I was getting started and regularly plowing the tooling into the side of the job, the fixtures, the bed, the wall of the shed etc by being an idiot with the CAM, MDI or even just jogging. But I like to think I'm past that now (mostly, anyway) and even the cheapo carbide stuff makes running ali on these machines quicker, quieter, less cringing-at-the-howls-of-pain-from-the-machine and overall a much happier experience.

I also installed a $20 from ebay dual nozzle mister setup which I run from a gravity fed bottle of 20% methylated spirits, 80% water mix and it's worth a go if you have compressed air. Getting a stream of air to the cutter blowing chips out to prevent re-cutting makes a big difference to tool life and finish on the cuts, adding that mix of alcohol and water (pretty much what the Datron machines use IIRC) keeps things cool and lubricated without the residue of WD40.

I ended up purchasing a few carbide bits from Klot as you suggested. I plan on using an endmill to do most of my "drilling" for now until I receive the bits. Also, thanks for the coolant tip! I've been manually spraying WD40 during my testing, but I'll try this out with my mister before I commit to WD40.