View Full Version : Drilling holes on cnc
dfox1787
22-05-2018, 07:48 PM
Are there special drill bits needed for a cnc?
I know my spindle has certain collet sizes so standard bits are unlikely to fit.
Get good quality bits and get your speeds / feeds right.
If you have the typical 24K RPM low torque spindle, its more difficult. Small holes are OK, large ones you will struggle.
dfox1787
22-05-2018, 10:10 PM
Get good quality bits and get your speeds / feeds right.
If you have the typical 24K RPM low torque spindle, its more difficult. Small holes are OK, large ones you will struggle.
how about fitting them in the colet? Are you talking about bog standard drill bits or do they have special bits for cncs?
magicniner
22-05-2018, 10:13 PM
I know my spindle has certain collet sizes so standard bits are unlikely to fit.
You could throw us a bone and tell us so we don't have to guess or assume?
dfox1787
22-05-2018, 10:13 PM
You could throw us a bone and tell us so we don't have to guess or assume?
lol ok max collet size 12mm. Im only asking if there a special drill bits for cnc
Drill bits are not specific to CNC, however you do get lots of options which may suit a particular application far better.
Have a browse of the Phantom Drills website, and try finding a copy of their catalogue if you want to see just how many options are available.
>I know my spindle has certain collet sizes so standard bits are unlikely to fit.
Why not - you're using an ER system, aren't you?
Anyway, as m_c said, there are plenty of options out there - a cursory search brought this up:
https://www.cadem.com/single-post/cnc-drill-helix-angles
Not a bad place to start. As per Chaz's advice - yep, it can be a bit hit and miss with the 2.2kw Chinese spindles - you don't want to go too fast and burn up the drill, but you really don't want to drop much lower than 9krpm as you risk stalling the spindle...
One thing I would say: make sure you spot drill first..! If you're using standard drill lengths then you can expect a bit of a squeal on the first peck, but that should disappear once the drill gets a bit deeper... Here's a vid of my machine drilling out a section so that I wouldn't have to deep slot (fast forward to about a minute in). I'm sure I could've gone a bit quicker, but you know - when you find something that works you tend to keep it that way..!
https://youtu.be/uwDesJPd6a0
Good luck.
Wal.
For general purpose drilling, I'll normally get Cobalt drills. More durable than pure HSS, but typically slightly more brittle (not as brittle as pure carbide though!), and can handle higher speeds than pure HSS (but no where near as high as pure carbide).
Polished ones for aluminium, and suitably coated ones for steel.
Key thing is to ensure you are within the speeds/feeds specs for the drill, and as Chaz/Wal say, with Chinese spindles that can be a problem. You'll likely get better results on larger holes by either pre-drilling then milling to size, or just helix milling.
Spot drilling depends on what you're doing. I generally only use stub drills with split point (or whatever the manufacturer wants to call their self-centring drills), which I'll never spot drill first. However anything I need to use any longer a drill on, I'll generally spot first.
wiremonkey
23-05-2018, 02:15 PM
Hello,
Drilling accurately placed holes is not easy. I strongly suggest screw length bits, the shorter the better, to eliminate deflection. I'm fairly new to cnc and posted a video of my experiences drilling holes here: https://www.youtube.com/playlist?list=PLGCSTLxY_4w0FlLy1hZjVPFZmTCBEeF2y
I should add that I bought an old 3/8" Jacobs chuck off of ebay and a straight 1/2" shaft for it. I chucked it up in a precision collet on the router and damn if it doesn't work perfectly. For drilling operation, no more changing collets or needing collets for every different size. I highly recommend it. I show it in the video I linked to above.
Cheers, Tyler
routercnc
23-05-2018, 07:15 PM
I use a mix of 3mm HSS twist drill in a standard 3mm collet to pilot holes (no spot drill), and then finish on the drill press. Or interpolate holes using a 6mm end mill ideally with a spiral toolpath. Fusion is great for this.
These end up being very accurate although for bolt clearance holes I often go for bolt nominal diameter plus 0.5 mm to give some allowance in assembly.
See examples in my videos here:
4:40 and 10:40
https://www.youtube.com/watch?v=wqff3IZZWvw
dfox1787
23-05-2018, 07:24 PM
>I know my spindle has certain collet sizes so standard bits are unlikely to fit.
Why not - you're using an ER system, aren't you?
Anyway, as m_c said, there are plenty of options out there - a cursory search brought this up:
https://www.cadem.com/single-post/cnc-drill-helix-angles
Not a bad place to start. As per Chaz's advice - yep, it can be a bit hit and miss with the 2.2kw Chinese spindles - you don't want to go too fast and burn up the drill, but you really don't want to drop much lower than 9krpm as you risk stalling the spindle...
One thing I would say: make sure you spot drill first..! If you're using standard drill lengths then you can expect a bit of a squeal on the first peck, but that should disappear once the drill gets a bit deeper... Here's a vid of my machine drilling out a section so that I wouldn't have to deep slot (fast forward to about a minute in). I'm sure I could've gone a bit quicker, but you know - when you find something that works you tend to keep it that way..!
https://www.youtube.com/edit?o=U&video_id=uwDesJPd6a0
Good luck.
Wal.
Hi Thank you for this.
Ill take a look into those bits. My spindle is the ER system. The min rpm i can get is 10000.
The link you sent me takes me to the video edit part on my youtube. Id love to see the video though
The link you sent me takes me to the video edit part on my youtube. Id love to see the video though
Ah - I copied link from my creator page - here you go (not that interesting, to be honest..!):
https://youtu.be/uwDesJPd6a0
All the best.
Wal.
wiremonkey
24-05-2018, 01:05 AM
Wal, what are you using for coolant and how are you catching it? Would be cool to see a wide shot and overall setup view of your CNC.
Wal, what are you using for coolant and how are you catching it? Would be cool to see a wide shot and overall setup view of your CNC.Here's a link to a handful of pics on an old thread. Added a couple of extras since, but the machine itself remains the same...
http://www.mycncuk.com/showthread.php?p=55068
Sent from my HTC One M9 using Tapatalk
Oh - and coolant wise: WD40
I do my best to avoid it like the plague nowadays. Useful, but once it atomises and hangs in the air it's nasty stuff. Instead I try to plan better, use decent materials that cut well and as much air as I can get on the part...
Wal.
Sent from my HTC One M9 using Tapatalk
A_Camera
24-05-2018, 08:04 AM
dfox1787,
Perhaps I missed something, but I don't see any reference to the material you want to drill. That is very important in my opinion. The fact that you have ER collet is not a problem, you just need to buy a set of collets since those are not like a drill chuck, you need a number of those. I have ER11 so I can't drill anything larger than 7mm with drill bits, which is OK for my needs, but of course, even I must have a large number of collets. I am drilling holes from 0.3mm up to 6mm with different drill bits, depending on the material I need to drill in, which can be PCB, aluminium or plastic. Of course, wood and similar is also OK. I also don't know why you feel you are limited to 10k rpm. The recommended lowest rpm for high speed 24k rpm spindles is 6k rpm but I have absolutely no problems to go below that as well.
Drilling starts at 2,5 minute mark.
https://youtu.be/p2BCw1ORcxQ?t=2m46s
In that clip I am drilling with different, standard (I think Cobalt) spiral drill bits, from 1.5mm to 5mm and in that video the lowest rpm is 5800rpm, but in aluminium I went as low as 3800 rpm also and that caused no issues at all. What is important is to use sharp and good quality bits. I use no liquid cooling at all and have no issues with welding, but if I have to drill many holes I let the bit to cool now and then.
dfox1787
24-05-2018, 08:24 AM
dfox1787,
Perhaps I missed something, but I don't see any reference to the material you want to drill. That is very important in my opinion. The fact that you have ER collet is not a problem, you just need to buy a set of collets since those are not like a drill chuck, you need a number of those. I have ER11 so I can't drill anything larger than 7mm with drill bits, which is OK for my needs, but of course, even I must have a large number of collets. I am drilling holes from 0.3mm up to 6mm with different drill bits, depending on the material I need to drill in, which can be PCB, aluminium or plastic. Of course, wood and similar is also OK. I also don't know why you feel you are limited to 10k rpm. The recommended lowest rpm for high speed 24k rpm spindles is 6k rpm but I have absolutely no problems to go below that as well.
Drilling starts at 2,5 minute mark.
https://youtu.be/p2BCw1ORcxQ?t=2m46s
In that clip I am drilling with different, standard (I think Cobalt) spiral drill bits, from 1.5mm to 5mm and in that video the lowest rpm is 5800rpm, but in aluminium I went as low as 3800 rpm also and that caused no issues at all. What is important is to use sharp and good quality bits. I use no liquid cooling at all and have no issues with welding, but if I have to drill many holes I let the bit to cool now and then.
Drill aluminium mainly. However i would need collets that would fit say 2.5mm drill bits so the hole can be tapped. Myabe i just need some high quality bits for the cnc. Its just the high speed of the spindle that concerns me.
A_Camera
24-05-2018, 08:53 AM
I have a set of collets and 2.5mm is one of them. Drilling in aluminium it is important to spot drill first. I normally use a 6mm 90 degree spot drill for that purpose, and after spot drilling (not resetting the machine so that I keep the zero positions) I just change to the right bits and start the drilling. Just make sure the spindle can't start spinning when you are changing bits so that you are safe.
magicniner
24-05-2018, 08:20 PM
Drill aluminium mainly. However i would need collets that would fit say 2.5mm drill bits so the hole can be tapped. Myabe i just need some high quality bits for the cnc. Its just the high speed of the spindle that concerns me.
You don't need to Drill to get accurately sized and positioned holes, you can mill with an interpolated spiral tool path, a 2mm endmill will suffice for a 2.5mm hole, with air and lube it may be the ideal solution with a spindle with only high speed capability.
dfox1787
24-05-2018, 08:58 PM
You don't need to Drill to get accurately sized and positioned holes, you can mill with an interpolated spiral tool path, a 2mm endmill will suffice for a 2.5mm hole, with air and lube it may be the ideal solution with a spindle with only high speed capability.
nice ill give that a go on some scrap aluminium.
A_Camera
24-05-2018, 10:21 PM
nice ill give that a go on some scrap aluminium.
Give it a try, but expect to break many small bits. In my opinion it is better to go out and buy some good quality 2.5mm spiral drills. Drilling is much faster and 2.5mm is not that expensive or difficult to find.
dfox1787
24-05-2018, 10:29 PM
Thank you. I was worried about breaking bits. I thought about spotting and then using bench drill.
Do you know anywhere to get descent spiral drill bits?
Give it a try, but expect to break many small bits. In my opinion it is better to go out and buy some good quality 2.5mm spiral drills. Drilling is much faster and 2.5mm is not that expensive or difficult to find.
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A_Camera
25-05-2018, 09:49 AM
Thank you. I was worried about breaking bits. I thought about spotting and then using bench drill.
Do you know anywhere to get descent spiral drill bits?
Sent from my SM-N910F using Tapatalk
Yes, but that won't help you. I am buying mine locally in Sweden in a shop near me.
magicniner
25-05-2018, 11:27 AM
Give it a try, but expect to break many small bits.
Crikey, you must have issues with your CAM or machine!
I've never broken a milling cutter when using a helical path to cut a hole slightly larger than the cutter up to 5 diameters deep. Provided you use air nozzles to clear chips it's a very low stress job for the cutter, climb milling with a very small step over and DOC, it's a quick process too and ideal if your spindle only does high speed.
This strategy also works well for jobs where it's faster to machine an appropriate starter or guide hole then finish on a manual drill press.
A_Camera
25-05-2018, 12:08 PM
Crikey, you must have issues with your CAM or machine!
I've never broken a milling cutter when using a helical path to cut a hole slightly larger than the cutter up to 5 diameters deep. Provided you use air nozzles to clear chips it's a very low stress job for the cutter, climb milling with a very small step over and DOC, it's a quick process too and ideal if your spindle only does high speed.
This strategy also works well for jobs where it's faster to machine an appropriate starter or guide hole then finish on a manual drill press.
The comment was to somebody who has no experience with it. Yes, I broke a few at the beginning... Anyway, yes, some times it is practical and may even be faster, but most times drilling using drill is faster than through milling. It is also easier to drill deeper holes using spiral drill than milling them using long mill bits. Especially small holes, like he needs to drill, I'd not bother milling. Large holes are different.
I would also recommend that if you need to do anything larger than 4mm or so (with a 2.2KW type spindle), consider milling the holes. If you need accuracy, do them slightly undersize and then ream them.
magicniner
25-05-2018, 10:43 PM
The comment was to somebody who has no experience with it.
I started with no experience, I used HSM Advisor with the good advice to start at 50% of recommended feed and see how it goes, air and lube and I didn't break any bits in Aluminium, it's easy-peasy, try 304 SS, that's more challenging ;-)
A_Camera
26-05-2018, 05:21 PM
I started with no experience, I used HSM Advisor with the good advice to start at 50% of recommended feed and see how it goes, air and lube and I didn't break any bits in Aluminium, it's easy-peasy, try 304 SS, that's more challenging ;-)
That's very good, but I am not that perfect, so yes, it did happen that I broke a bit or two, and in fact, even today it can happen. I don't think there is a shame in that.
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