Feed and speed rate for milling g10, micarta, brass, and copper?

[JG Custom Metal Works]

I’m finally getting after it with my manual mill(Bridgeport/clone J head vertical knee mill) and am having a little trouble finding what speed to run my end mills at when milling g10 and micarta. A lot of the charts that I’m finding don’t have any listings for those materials. I went ahead and mentioned brass and copper just for kicks. Currently I’ll be using a 1/8” end mill, but will also be using 5/32”, 3/16”, and occasionally 1/4”.

I know feed rate is just kind of a “feel” thing with a manual mill, so I’m not so much wanting an answer on that. But any advice would be appreciated. From my understanding, a lot of guides say to mill small amounts of material with smaller end mills. I planned to drill through with a smaller twist drill bit and then open up the hole to the desired size with an end mill. For instance, the one I’m working on now needs to be opened up to .158” x .288”. I was going to drill in twice with a 1/8” twist drill and then get in there with a 1/8” end mill and hog the rest of it out. Maybe 1/16” per pass. Does that sound reasonable? I rounded my tang on top and bottom to match the rounded end mill as much as possible.

I do have an auto feed, but haven’t hooked it up yet. It does NOT have a variable speed, so I’ll be somewhat limited on speeds. But of course I can change belt position on the step pulley for different speeds and have a RPM gauge that’s pretty accurate.

The main thing I’ll be doing is milling guard slots. All the end mills I have are carbide(lakeshore), and most are 4 flute.

This thread is mainly in regards to milling g10 and micarta, but if you had info for brass and copper as well, I’d take it. Hell, if you had a good speed feed chart for steels too, I’d appreciate. There’s a lot of feed/speed charts out there and it’s honestly a little confusing. It doesn’t help that I’m using these small end mills that break so dang easy. Again, any advice would be appreciated. Thanks!

 

[JG Custom Metal Works]

So, I found this chart, and it has G10 listed(see page 285). It says the following:

1/16” - 1/8” 8,000rpm-31,000rpm
Chipload per tooth .0015”

Am I misunderstanding something? IIRC my mill gets no where near that rpm rate. I’m not sure, but I think mine maxes out around 4000rpm. Maybe not even that. It’s not an ancient machine, but it’s not new either. IIRC my mill is 30-40yrs old.

I’m also, not really understanding the whole chipload per tooth thing. Does that have to do with the number of flutes?

As you guys can tell, I’m pretty green with machinist equipment. I’m more of a tactile guy. Hands-on. I can design it or look at it, and then make it. But I’m not that great at taking measurements and creating a formula to mill it out or whatever. In other words, I hate math lol. When I was in college I could write a 20 page paper in a day or two and get an A. No sweat. But math killed me. Lol.

I’m rambling now, sorry. Here’s the chart I’m referencing above. The info I specifically cited is on page 285

https://www.garrtool.com/doc/pdf/TECHNICAL.pdf

 

[Busto]

Since you plan to "Fly by the Seat of your Pants" don't over think the process. The high speeds are for CNC programmed machines. Smaller cutters prefer higher speeds so the 3K-4K RPMs on your machine are fine for 1/8" end mills. Buy a handful of HSS end mills and take notes on cutting some sacrificial materials to get a feel for speeds/feeds. If you want to learn about chip loads and other machine terminology purchase the Machinery Handbook (Machine shop tool room Bible) it will certainly be handy once you discover all the nice jigs and fixtures you can make with the Mill.

 

[butcher_block]

i have a high speed Jhead BP top speed is jsut over 5K rpm (i could over drive it with the VFD but dont thing its a good idea)
HHS will be much more forgiving when ham fisting the smaller cutterrs even if they dont last as long cause of G10 being as abrasive as it is. as for speeds and feeds i have FSWizard on my phone for that and its been handy. it does not havev G10 in there but it will let you gauge other stock to help get you in the ball park. note liek was said for us hand crank guys you just have to get close to right. CNC are specing max tool life along with max cubic feet of swarf

 

[HSC ///]

Currently I’ll be using a 1/8” end mill, but will also be using 5/32”, 3/16”, and occasionally 1/4”.

I planned to drill through with a smaller twist drill bit and then open up the hole to the desired size with an end mill. For instance, the one I’m working on now needs to be opened up to .158” x .288”. I was going to drill in twice with a 1/8” twist drill and then get in there with a 1/8” end mill and hog the rest of it out. Maybe 1/16” per pass. Does that sound reasonable?

As someone who started as a cad/cam programmer years ago and managed aerospace CNC machine shops, IMO respectfully you are overthinking this. I mean it's fine that you want to know how to calculate all these things and get the best performance. But we machine little soft stuff... for knife-making. I never change the spindle speed on my BP, I just don't need to, and I cut everything you mentioned just fine. I machine all the materials you mentioned with the same parameters.

anyway, let me approach what you are asking differently.
In general you want to use the largest diameter end mill that will fit your slot and the shortest in length, stub length.
I would not drill with an 1/8" drill and them mill the slot with an 1/8" . I would get a 5/32" end mill (center cutting) or a 9/64" end mill.
I would plunge mill the first thru hole, feed slowly the quill by hand and listen to the sounds and watch how the chips come off.
Also Lakeshore Carbide are fine tools but perhaps you don't need to spend on premium at this point...just a suggestion.

If you are breaking end mills on a manual feed, I'm going to speculate you are a little too firm/aggressive in your feed rate.
And you are taking too much in one cut. I would say "Maybe 1/16” per pass." is too much too take for an 1/8" end mill, also depends on the depth of cut, is it full depth of the slot or a partial depth ( and you take it in steps...)

Lastly, if you are breaking tools, is your setup rigid?

so to recap
1) is your setup rigid?
2) use largest dia tool and shortest length
3) don't be too aggressive on side load cuts, take multiple passes to widen the slot to your final size requirement

regards
Harbeer

 

[JG Custom Metal Works]

Thanks a bunch guys. I have a complex about getting too complex at times. I just checked my mill and top speed says 2720 :/ . Eventually I might try to upgrade that somehow, but is where I’m limited to at this point.

 

[JG Custom Metal Works]

As someone who started as a cad/cam programmer years ago and managed aerospace CNC machine shops, IMO respectfully you are overthinking this. I mean it's fine that you want to know how to calculate all these things and get the best performance. But we machine little soft stuff... for knife-making. I never change the spindle speed on my BP, I just don't need to, and I cut everything you mentioned just fine. I machine all the materials you mentioned with the same parameters.

anyway, let me approach what you are asking differently.
In general you want to use the largest diameter end mill that will fit your slot and the shortest in length, stub length.
I would not drill with an 1/8" drill and them mill the slot with an 1/8" . I would get a 5/32" end mill (center cutting) or a 9/64" end mill.
I would plunge mill the first thru hole, feed slowly the quill by hand and listen to the sounds and watch how the chips come off.
Also Lakeshore Carbide are fine tools but perhaps you don't need to spend on premium at this point...just a suggestion.

If you are breaking end mills on a manual feed, I'm going to speculate you are a little too firm/aggressive in your feed rate.
And you are taking too much in one cut. I would say "Maybe 1/16” per pass." is too much too take for an 1/8" end mill, also depends on the depth of cut, is it full depth of the slot or a partial depth ( and you take it in steps...)

Lastly, if you are breaking tools, is your setup rigid?

so to recap
1) is your setup rigid?
2) use largest dia tool and shortest length
3) don't be too aggressive on side load cuts, take multiple passes to widen the slot to your final size requirement

regards
Harbeer

Thanks for the info. I’m fairly sure my setup is rigid. I suppose I could take some pics of it here in a few and get your opinion. My vise is an import, but it seems sturdy, and it trammed easily. Very accurately too from what I can tell.

As far as using a short stubby end mill. I think the cutting length is around an inch. I imagine it’s not good to clamp down on the sides of the flutes, otherwise I could just push it further up in the collet and only leave a 3/8” or so sticking out.

I’ll snap a pic or two here in a min

 

[JG Custom Metal Works]

Here’s my mill. It’s a Bridgeport clone. It accepts all Bridgeport parts and is pretty much exactly the same. Of course genuine Bridgeport mills are probably a tighter, and nicer. But this mill seems to have reasonably tight tolerances from what a couple of my machinist friends tell me. One said it was just as solid as his genuine Bridgeport. I can’t complain too much, it ended up only costing me $100 for the mill, DRO, and a power feed.

 

[Drew Riley]

I'm gonna guess the feeds and speeds will be somewhere between steel and aluminum. Cutter life will probably be your biggest obstacle, as g10 tends to dull things pretty fast.

You might google "Feeds and Speeds for Garolite" or something like that, as that's another industry term for micarta. Some types are harder/tougher than others, so you'll have to wing it to some extent, until you make a few chips.

Brass will depend on grades too, as some brass machines very easily, and other grades are very gummy and hard to work with.

 

[JG Custom Metal Works]

Would I be better off, economically, to just use a HSS or Cobalt end mill for milling g10? Rather than carbide that is. Would high speed steel or cobalt cut just as well on g10? If I’m going to be ruining a end mill by using it on g10, then it might as well be a less expensive, non-carbide end mill. That’s what I’m wondering. Or will carbide still be the way to go? I’m actually thinking about switching to brass(from USA KNIFEMAKER) for milling my first guard. As far as what kind of brass it is, I imagine it’s whatever is most conducive for knifemaking. Being that it’s sold by USA KNIFEMAKER that is.

When you guys have a tang that is 1/8” wide, do you just use the next step down in diameter for your end mill size(to mill out the guard slot)? Or do you just try to buy slightly oversized stock and just use a 1/8” end mill? I ask this because, a lot of times, stock that is sold at a certain thickness is often a little thicker.

Thanks again for all the info everyone. I really appreciate it.

 

[Nathan the Machinist]

Carbide is the way to go in G10 and Micarta. Your speeds can be high (though don't have to be), 600SFM+, similar to what you would use on aluminum and your feed rates are probably double, .004 FPT on a 1/4" endmill.

the goal, especially with G10, is to keep it cutting, not stewing. These materials especially G10 are very abrasive.

Copper is also machined with carbide at high speeds and high feed rates, with a low depth of cut. The high surface feet per minute reduces built up edge, and the high chip load per tooth reduces smearing.

Brass has a wide processing window and can be machined pretty much any way you want with pretty much anything.