- Joined
- Jan 10, 2016
- Messages
- 29
Hello folks, my name is Ed, I am a newbie and I live in Canada . I have just got my first milling machine (hi torque 3990 from LMS) and I look forward to learn machining. I have a question about plunge cutting and here is the context: I am installing the DRO and needed to reduce the height of one of the mounting brackets by about 1/2 of an inch (the bracket is made of 0.4 inches thick aluminum)
I used a 1/2 " 2-flute "premium" end mill which came with my machine (HSS / cobalt, made in Korea) and successfully shaved off the metal from one side of the bracket. It took a good 30 min to cut the metal from one side of the braket by shaving a few thousands at a time at about 1000 rpm. But then I grew inpatient and remembered that what I watched a video that clamed that so called plunge cutting was a much better way to remove larger amounts of materials especially when using a non-rigid setup or underpowered milling machines. So I gave it a try on the second side of the bracket. The first two "plunges" were great - the end mill plunged into the aluminium with some chatter but it wasn't excessive. Then on the third "hole" it started developing a very loud screeching sound. The forth plunge I did not complete because the sound is quite loud and there is also chatter. I don't think that this sound is normal and I have tried to change the RPM and lower the feed speed but this made no difference. I have also examined the end mill under the magnifying glass but I seems perfectly fine. Please comment what in your opinion is causing this and what is the best kind of end mills to use for plunge cutting - e.g. would so called roughing end mills be more suitable for the job or is this me who is doing something wrong?
I used a 1/2 " 2-flute "premium" end mill which came with my machine (HSS / cobalt, made in Korea) and successfully shaved off the metal from one side of the bracket. It took a good 30 min to cut the metal from one side of the braket by shaving a few thousands at a time at about 1000 rpm. But then I grew inpatient and remembered that what I watched a video that clamed that so called plunge cutting was a much better way to remove larger amounts of materials especially when using a non-rigid setup or underpowered milling machines. So I gave it a try on the second side of the bracket. The first two "plunges" were great - the end mill plunged into the aluminium with some chatter but it wasn't excessive. Then on the third "hole" it started developing a very loud screeching sound. The forth plunge I did not complete because the sound is quite loud and there is also chatter. I don't think that this sound is normal and I have tried to change the RPM and lower the feed speed but this made no difference. I have also examined the end mill under the magnifying glass but I seems perfectly fine. Please comment what in your opinion is causing this and what is the best kind of end mills to use for plunge cutting - e.g. would so called roughing end mills be more suitable for the job or is this me who is doing something wrong?