Machsupport Forum
Mach Discussion => General Mach Discussion => Topic started by: studysession on December 25, 2010, 01:22:30 PM
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I have seen some posts where people cut aluminum on their machines and it's clean and polished. What bit do you cut with to give it that polished look and no scratched from the cutter?
Thanks
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You get a polished look by polishing using abrasive and a cloth wheel, not by cutting with a tool. And it's a LOT of horrible, messy, unpleasant work, especially if the as-machined surface is rough!
Regards,
Ray L.
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What tool would at least give a not rough but smooth surface on the aluminum? Would a round nose bit be better than a 4 flute end mill?
THANKS!!!!
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What tool would at least give a not rough but smooth surface on the aluminum? Would a round nose bit be better than a 4 flute end mill?
THANKS!!!!
It has FAR more to do with the type of cut, and the quality of the machine, and especially the skill of the operator, than the specific tool in use....
Regards,
Ray L.
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Yo will normally get the best finish IF you follow the basic guidelines for speed feed and chipload for the tool used AND the material it is used on. Then work on when to climb or conventional mill.
Rarely will you end up with NO tool marks on low end machines.
(;-) TP
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Thanks for the replies...
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If milling a surface a single fly cutter will provide a better finish then say one with multiple cutters. Of course other replies apply.
RICH
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My brother has a drag race car. He wants me to engrave his valve cover but wants a really nice polish to the aluminum.
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Assuming your machine is up to the task, as mentioned above, 3-flute carbide end mills designed for aluminium work best. They have very sharp cutting edge and milling on the side I can get very smooth surface seeing my own reflection. Using a good cutting oil helps a lot with aluminium to get a good finish.
Dan
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Not sure if my machine is really up to the task. I am going to practice on a flat piece of aluminum and see how that comes out. next pay day I will order a couple of the bits mentioned here in the thread and give it a go when they arrive....
THANKS
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I've cut my fair share of aluminum, and I've polished a bit too. Your not going to get a fine shine without using abrasive and a cloth wheel. There are strategies you can do to make the buffing task as painless as possible, by using various techniques, and certain cutters, but you will not eliminate the need for buffing. I should also advise you that the buffing task itself is a bit of an art form, and takes a whoooooole lot of practice to even get decent results. I'm not trying to dissuade you by any means, just trying to give you an honest reply from experience. Best of luck to you, it's going to be quiet a learning curve if your as finicky with quality as most of us are. You might find the finishing forums at Caswell useful. http://forum.caswellplating.com/ (http://forum.caswellplating.com/) I certainly have.
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The key factors in a good finish are...
*Rigidity (This is in the machine as well as the tool and the work)
*Speeds and feeds (aluminum loves high speeds and feeds as long as the rigidity is there)
*Chip evacuation (A high helix helps get the chips out of the way so you don't recut them. Recutting chips will kill your finish. Flood coolant and lots of it is a must. We use through spindle coolant when doing finish passes. They aids in getting the cut chips out of the way.
*Harmonics (Every machine will vibrate. This causes chatter. Chatter = bad finish and poor tool life. You need to tune this out of your machine by adjusting the speeds and feeds to get rid of the resonation)
*Cutter geometry (You need to have a high positive rake to give you a good finish from what I have found. We use some exotic variable flute cutters to do this. For a hobby machine I would recommend 3 flute high helix end mills. They will help with harmonics because 2 flutes will more than likely be engaged in the cut. They have good chip evacuation and have the good tool rigidity to evacuation ratio. They also are relatively cost effective.)
Surface finish is a black art. There isn't a one way works for all method. It requires experience and proper equipment. Getting a mirror like finish with a hobby grade machine I feel will be next to imposable. Even with the best equipment it can be a challenge. Most parts we produce go though vibratory tumblers to get the mirror like finish and we use industrial grade Haas CNC machines. I would say stick to multiple progressively finer grits of sandpaper. Wet sand it the best you can and then use a buffing wheel. if you don't have access to a wheel then some good ole mag wheel polish and elbo grease will go a long way.