Milling aluminum slots

L

Littlebriar

Registered
Registered
Joined
Dec 28, 2018
Messages
21
I know there's similar threads out there but I'm still a bit confused on the best approach. I have grizzly mill/drill and using cheap HF bit set. I need to create 1/4" slot, 1/2" long in 1/4 inch thick aluminum. I have tried to plunge a 1/4" bit, then feed for the 1/2" length. First off, the bit chatters as I make the plunge cut, even if I modulate the quill. Then the slot is ragged when I make the cut.
Researching this, it seems like I need a smaller diameter bit and mill down the center, then do a climb cut on both sides to get a smooth wall. So I have a couple questions:
  1. Should I drill a hole on both ends with a drill bit to start?
  2. Are there end mills that plunge well.
  3. What's the best mill type for making this slot in aluminum?
  4. Any other tricks I need to know about?
 
Yes, you should drill a hole. Yes there are different types of end mills. You need a center cutting EM if doing it your way.
 
When doing a slot you will get a better quality cut using the smaller bit and do what you said climb cut the slot to get your width. When using the same diameter endmill as your slot I usually move the z axis while traversing the slot so your going deeper as you go left to right. It eases the cutter in.
 
Apologies if I'm belaboring the obvious, but you also need to make sure your work piece is clamped solidly and not moving.

As a newb, I mention this because it's bit me on the derriere...
 
I agree with the posts above. Drill holes. Also, I find I get best results with slot cutting in aluminum with a two flute end mill vs a four flute. Better chip clearance. You can also use cutting fluid, spray mist, etc. for best results. I use a mister, but something like WD-40 works too.

Ted
 
Cutting a through slot watch out on your clamping pressure. When your about to break through the bottom you might want to let up on the vise pressure so it doesn’t try to collapse the slot when em breaks through.
 
I haven't seen it mentioned but I assume that you are locking the non-moving axis?

David
 
Use a 2-flute end mill for plunging. I did a similar slot in steel recently, using the Taig mill, and went about it as you described - plunged in one end, then milled through to the other end of the slot without retracting the cutter. Came out great, and the Taig is a much less solid machine than your mill-drill. I had to feed pretty slowly of course.
 
Yup, what he said, a 2 flute bottom cutting endmill. Plunge once to start, cut slot, retract, and plenty of WD40. I would do this at 6-700 rpms.
 
Littlebriar said:
... I need to create 1/4" slot, 1/2" long in 1/4 inch thick aluminum...
Click to expand...

This is about as easy as a milling job can get. You should be able to plunge the bit through 1/4" aluminum and mill the slot in one pass. I would never buy HF bits.
 
You must log in or register to reply here.
Back
Top