Milling Aluminum with a Router?

[John Stevens]

I'd like to mill a 1/4" wide slot into 1/8" x 3/4" aluminum bar. Can I do it with a router and straight bit? Carbide or HSS? What RPM? Any type of lubricant needed? Thanks in advance.

[Michael Ballent]

Milling anything that small would make me worry especially with a power tool. Carbide can cut into aluminum, but the little bits of aluminum flying off might hurt both you and possibly the tool...

[Keith Outten]

John,

You can machine aluminum with your router but be carefull. Start by purchasing an end mill, router bits aren't designed for metal cutting. You can use end mills on wood though and I prefer them to straight router bits and they are cheaper, less expensive and more accurate.

You should make sure that the aluminum is secure, use multiple clamps as necessary. Take very light cuts, just a few thousands deep with each pass and the aluminum will cut like butter. Like any new technique start with a piece of scrap and do a few practice cuts first. Drill a starter hole if necessary but don't try to plunge in metal. Use the slowest speed on your router, 20,000 rpm will work but slower is better.

[Lewis Mills]

John,
If the stock is only 1/8" thick, your 1/4" wide slot can't be very deep. Depending on the length, this might really be easier to do with a file. But to answer your question, yes, you can work aluminum with a router.
For what you are trying to do, I would start by cutting a dado in a piece of hardwood exactly the size of your aluminum stock. Then you can "trap" the aluminum in the wood (I would also add some good double-sided tape), and use it to carry the aluminum over the bit in your router table and cut the slot.
Lewis

[Glenn Clabo]

Everything Keith said and ....
There is a formula to calculate RPM for a 1/2 in diameter High Speed Steel end mill machining aluminum but here's what the result is -
The cutter should revolve at about 2400 RPM (in other words get your router to go real slow) with a feed rate of 24 inches per minute but if you feed slower it will cut fine. You are going to use a hand held or table mounted router...so start shallow (like Keith said) and don't be in a hurry and you'll be fine.

[Dave Moran]

John, When I was a locksmith, way too many years ago, we used a router to cut the opening in narrow style doors, the brown ones you see on stores. They are Au and with a way overpriced fixture they made a perfect opening in the door.

[Hoa Dinh]

Soft metals such as brass and aluminum can be cut with carbide cutters. Assuming the it's a "through" slot (not like a dado), this is what I'd do:

Draw the slot you want to cut on the bar. Drill an 1/4" hole at one end of the slot.

Use a jig saw and a fine metal blade, rough cut the slot as wide as you can without cutting into the lines.

Chuck a 1/8" carbide bit in the router table.

Set up the RT fence 1/2" from the further cutting edge of the bit.

With the router power off, put the bar down with the bit going through the (rough cut) slot.

Make sure the bit does not touch the bar, turn the router on, trim the OUTSIDE edge of the slot.

Turn the bar end to end and repeat for the other edge.

Make sure you don't trim the INSIDE edge (near the fence) of the slot. The bar is then trapped between the fence and the spinning bit. It can be ugly.

If you don't feel comfortable doing this, don't do it.

No lubricant needed, just make sure to wear long sleeve shirt, eye & face safety gears.

I have a backup router table top. If I need to cut metal, I do it outdoors.