Help with mill bit speed for cutting aluminum

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DaveHalverson

Well-Known Member
Joined
Mar 9, 2015
Messages
223
Help!

I am fabricating my own engine mounts for 2 riggers and need to cut about 1/8" deep by 5/8" wide out of the ends of the engine rails. I am using high strength 2024 aluminum and using a

High-Speed Steel Three-Flute End Mill for Aluminum in a variable speed drill press to cut the aluminum held in a bench vise. I know my upright heavy duty drill press can develop some good speed but I have now heard there is a chart for such a thing and depending on the type of aluminum determines the RPM needed. Can anybody help with the RPM so I dont burn out the bit? I am not a machinist and dont know the terms really well but I believe I have and end mill for a box or square cut. The mill bit is from McMaster-Carr stock number 2716A62 http://www.mcmaster.com/#catalog/121/2489/=wygjjx
Any help would be appreciated.
 
As a rule of thumb the cutting speed for aluminum is 200-400 sfpm with high speed steel. The formula for figuring out RPM is Cutting speed x 4 / dia. of cutter. That being said a drill press is not designed for using an end mill and can be dangerous if not real careful.

Jim
 
With the Drill press, vibration will be a problem. Standard Speeds & Feeds will not apply. A medium speed setting on your drill should be fine. If it chatters, slow it down.

And as Jim mentioned, be careful, Do not take deep cuts. The tool may grab the part and toss it out of your vise and make a mess of your work.
 
Yes, be very careful. An end mill is designed for use with a firm, and highly accurate machine. The drill press will not be as accurate as an end mill. Take shallow cuts so that the tool does not grab your part and either ruin the part, damage the tool, or fling some pieces across the room. Even a heavy duty drill press will have some variation at the cutting edges.

Al Hobbs
 
I have to agree with being careful, slow and taking small cuts. As already said, a drill isn't designed for taking a side load. A drill press is made with bearings designed for an axial load. This means that it's possible to ruin the spindle and bearings if too much side pressure is applied. I would recommend using a face shield as well as safety glasses just in case the press loses a bearing
 
Thank you all for your advice... I will take all precautions.. The drill press is an old one built like a brick you know what... I have a table vice bolted to the table to hold the stock and I plan on taking only a very small amount off at a time. It is not going very deep but this process will be better than trying to grind it off. Much more accurate and even this way I hope.... I have safety glasses. I will keep the speed around 300rpm then and vary it depending on the outcome....
 
You may want to double that. I know,using my .1 hp Sherline mini-mill, I was cutting at 2500 rpm but was only taking between .005 and .010 per pass using a carbide three flute end mill cutting 6061-T6. What I found was that slower spindle speeds gave me a rougher cut and slower feed rates
 
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