Milling aluminum slots

Thanks for the advice all. This is a great forum. Yeah, I know HF bits are trash but I just wanted to get started and over time discover what tools I would use on a regular basis. Then buy quality stuff that I find I will use regularly. This strategy how worked for me on my woodworking tools.
 
You will use endmills 90% of the time in a mill. Their like the saw blade,router bits,or chisel to woodworking. You need good quality ones of various sizes a flutes for machining. Buy good ones now And save the grief.
 
End mills from first rate U.S. companies such as Niagara and Atrax can be purchased on ebay for 5 or 10 dollars with a couple bucks shipping on a regular basis. They make all the difference. Also, there is a cnc routine called ramping moves that allows a non center-cutting end mill to plunge into the work with minimum stress. It involves (in the case of a straight slot) moving back and forth along the cut center-line while slowly dropping down in the Z axis.
 
If you plan to do a lot of these, learn to use roughing end mills. They will hog out a slot very quickly and save your finishing end mills. Plus they last forever, even the HSS ones. Coarse pitch works best for slots.

You can mill a slot with a non-center cutting end mill if you drill a hole first, then drop the end mill into the hole. You only really need a hole on the end that you are starting on. Best to have stops on the milling table so the cutter stops in the same place on either end of the slot for each pass. Another option is to use a drill mill instead of an end mill; this has a drilling point on the end to drill the hole and sharp flutes like an end mill to cut the slot.

In aluminum, a high-helix end mill works best and you will have a better finish with a 3-flute high-helix end mill. These end mills pull the chip out of the slot and make milling aluminum much faster with better finishes and tool life.

If the slot has to be accurate, it is best to use a 3/16" high-helix rougher to hog out the center of the slot and then switch to a 3/16" high-helix finishing end mill to finish the slot to size. You can conventional mill the sides and then leave a thou or so for a climb cut if appearance is important. Conventional milling the sides is preferable unless your machine is rigid; even a 3/16" end mill can move a milling table if it catches.

I'm with the others in that it really doesn't pay to use junk end mills. Find odd sized Niagara Cutter end mills on ebay and slot with those - they work fine for this application and are cheaper because they are an off size.
 
3 flute for slots . No overcutting because only 1 edge is in contact . For milling keyways it's important . Drill out both ends undersize and mill it out to size . No problem . :)
 
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