Depth of cut with an 1/8" end mill (cnc router)

Hey guys,

I've been using some cheap eBay end mills for the past couple of weeks with varying success. They don't seem to last as long as I had hoped, even though they are they inexpensive kind.

I purchased GWizard awhile back so that I don't have to worry too much about figuring out the proper feed rates, or spindle speeds. The only real question I have is with the depth of cut.

GWizard actually gives you numbers based on your parameters, but I'm wondering if the depth of cut I'm using is even worth it. The deepest cut I've tried with an 1/8" end mill is 0.030. This seems
to go just fine for awhile, and with a brand new end mill, the cut is almost perfect. Depending on the feed rate, I can get a decent finish, but I'm worried that I'm digging into the material too deep and wearing
out the end mill too fast. The numbers I'm going with are - (17ipm feed rate / 15400RPM spindle speed / 0.030 DOC)

Is that depth fairly common? Should I be trusting GWizard's parameters when I enter in my depth of cut?

I should point out that my biggest problem right now is heat. I have a dedicated air blasting line that directs air right onto the end mill, but I currently use a dust boot that's trapping the heat from the router + end mill. I'm
using this dust boot to keep the chips from going all over the room. Unfortunately, I don't have a dust collection machine yet (it's on order), so I can't really tell if this will remove enough of the heat. I'll know more about
that in the next week or so. The opening for the dust collection is plugged up with some paper towels, just to keep the chips from blasting out the top. This will all be corrected later, once the dust collection machine arrives.


I'm cutting aluminum. I should have specified this above. My apologies.

So you're wondering why you're burning up endmills while you're cutting through an ever growing pile of chips that is trapped inside a dust boot?

I'd wait until the dust collection arrives before trying to solve your problem. You might want to mention what material you're cutting, I'm assuming wood or plastic...

Set your end as far up as the holder will allow and with out being into the flutes. Keep the chip/dust whatever cleared then post again with your results. I suspect they will be much better.

Aluminum, plastic, wood???

How about a material spec to start!

Depth of cut can often be one diameter when slotting.

That's a very light chip load, which will wear out a cutter due to rubbing rather than cutting. You can probably safely double your feed rate and possibly increase it by 2-3 times with a decent cutter. You'll get better tool life and less heat.

General purpose geometry endmills designed for steel are a poor choice. I like endmills designed for aluminum, though the helix can lift your work on a router. The Onsrud router bits and MSC Accupro copies work well. I've slotted phenolic and G10 and carbon fiber 3/8" deep with a 1/4" cutter with two and single flute cutters fed .004 per revolution. The machine needs a little grunt for this to work, obviously.

I'm assuming you're not trying to cut steel here...

TheCook said:

So you're wondering why you're burning up endmills while you're cutting through an ever growing pile of chips that is trapped inside a dust boot?

I'd wait until the dust collection arrives before trying to solve your problem. You might want to mention what material you're cutting, I'm assuming wood or plastic...

Click to expand...

Chips aren't the problem. As I said, I have an air blasting system that is getting rid of the chips just fine. The chips are actually making it outside the boot, they just aren't going all over the room like before.

706jim said:

Aluminum, plastic, wood???

How about a material spec to start!

Click to expand...

Aluminum. I should have specified. My apologies.

I'm a little confused by your first post there, cheap eBay end miss that don't last long? Who would have thought.

Have you tried quality alu specific end mills?

What type of mill is it? LOC? Shank size? I use a lot of spiral O flutes for sheet Aluminum. Also what router do you have?

CAPCNC said:

What type of mill is it? LOC? Shank size? I use a lot of spiral O flutes for sheet Aluminum. Also what router do you have?

Click to expand...

CNC router by cncrouterparts.com (Benchtop Pro). Router is a Bosch 1617 variable speed. Shank size is 1/8". I'm using 2 flute end mills. LOC is 1/2". I'm also using special collets from PreciseBits.

Semus said:

but I'm worried that I'm digging into the material too deep and wearing
out the end mill too fast.

Click to expand...

You're not wearing it out too fast.
Heat is your enemy in aluminum, can you use a coolant mister?
Can you go faster on the RPM's?
Is the endmill breaking due to feedrate? or is it loading up because of heat and then busting off?

air blast useless for your application. you need a mist type lube spray. the mist can be tuned surprisingly lean, such that the dust collector system should be ok with it. I liked a shop vac with a 3m goretex hepa cartrige and a simple cyclone or at least an in-vacuum diverter to keep the chips from blasting the element.

Mtndew said:

You're not wearing it out too fast.
Heat is your enemy in aluminum, can you use a coolant mister?
Can you go faster on the RPM's?
Is the endmill breaking due to feedrate? or is it loading up because of heat and then busting off?

Click to expand...

Heat is definitely an issue here. I'd say that this is more than likely the reason I'm having problems. The cheap eBay end mills works surprisingly well in certain cases where I don't have to mill a whole lot at once. Once I start to do things that take an hour or so, then it becomes a problem. I can't even touch the aluminum plate because it gets too hot. As others have suggested, a good dust collection setup can help here, and I tend to agree. A misting system is also a great idea. I didn't initially go with one because I wanted to keep the wood fairly dry so that I can repeatedly maintain a certain uniform height across the entire backing plate (birch plywood). Still, I don't think a misting setup would cause too much of a problem, especially leaned out.

I am able to spin the router up to 25K RPM's. That's probably more than I'd need with an 1/8" bit. In fact, the highest that GWizard tells me to cut with is 18K or so. The chips are actually being blasted away, so chip buildup isn't really an issue.