Posted: 1/4/2008 12:08:43 PM EDT
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For you machininst types out there... I do just enough metal work to be dangerous. For milling, I use my drill press and a cross slide vise. It works well for simple things like milling slots in flat metal. Well I was building a mount for a cable box the other day, using soft aluminum. I was milling a 1/8th inch slot in the aluminum with one of my good carbide end mills and the end mill got "gunked" up with the soft aluminum and quit cutting well. Attempts at removing the material from the end mill with a steel wire brush were unsuccessful. Any thought on cleaning up/ restoring my end mill? or is it just caput... TIA, - AG |
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Since you are endmilling using a drill, you probably were not running coolant (unable to). Due to aluminums properties, you should run flood coolant if possible. If you cannot run flood coolant there are spray mister systems on the market that use vegetable based oils so they are safe to inhale. That will help in the future in the prevention of aluminum welding to the tool. Not as effective as flood coolant but will help. Another thing that will help is to reduce the RPM (SFPM-surface feet per minute) on the drill motor. Running the endmill slower will generate less heat. Only do this if you cannot run flood coolant. Also, if you do this you can buy a commercially offered liquid tapping fluid and squirt on the endmill ocassionally. This will also help prevent the welding. As for the tool once the aluminum welds to it it will be very difficult to remove. Pulling or scraping it off can result in micro shipping to the cutting edge of the endmill. The edmill will still be useable but not as effective as a new one. You could have someone locally resharpen the endmill. All you lose is the diameter, it will change. You are probably using a smaller diameter endmill and resharpening would not be cost effective. Probably cheaper to purchase a new one. Sorry I can't help more. BS |
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Aluminum will gall just as you have seen. You can try scraping it off the end mill with a steel pick or dentist tool or something, or you can purchase another few end mills. Chances are that one was getting dull. Another poster mentioned coolant. For light cuts a 50/50 mix of Automatic Transmission Fluid and Kerosene is a great homemade cutting fluid. Using compressed air to blow the chips away might be another option that could help a little or a lot depending on the type of cut. 300 surface feet per minute is a target for aluminum removal with HSS end mills in a real mill. You are using carbide which likes to run faster and I also don't know the diameter or the stoutness of your setup so you could be higher or lower. |
| WD 40 can also be used as a coolant. From the Machine Tool classes that I am taking that was one of the suggested coolants. While you are cutting use short bursts directed at the end mill and part. I had a problem like this awhile back when drilling holes in a lower receiver. I changed out the drill bit that I was using and added more coolant and haven't had it happen again. But I to am wondering if your setup is rigid enough for milling. Anyways, Good luck! |
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Since you are using a carbide bit and machining aluminum, your drill press likely cannot go fast enough with enough power to prevent what you are experiencing without some sort of coolant. Something that does work for lower speeds and soft aluminum (6061 T6 is likely what you have) is to coat the endmill with bee's wax. This works better than WD 40 and the other mixtures posted above. ETA: Quick calculation on the rpm needed to avoid gumming up while machining dry with an 1/8 carbide cutter: 28,000 rpm. At this speed the chips will fly out and not get stuck. Air flow is needed to help cool things a bit too. |
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Don't waste your money on carbide, high speed steel is good enough for aluminum. A pretty good lube/cutting oil for aluminum is baby oil/mineral oil, gives a nice finish too. To save money on mills check out Travers.com they are very well stocked and have different grades of mills, drills, taps etc. Travers is like the Midway for machinists. |
WD40 is NOT a cutting fluid. While it may help keep the aluminum from sticking to the tool, it is not helping the cutting but actually hindering it. People use it because it's always available. Carbide normally resist aluminum welding to the tool if you can clear the chips good enough. An air compressor works good, blow air on it while your cutting. Kerosene by itself is a great cutting fluid for aluminum. If you want to mix it with tranny fluid, fine, it just helps it stick better but isn't necessary. And lastly, you shouldn't be milling with a drill press. 
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