Hello all, this is my first post, but I have been following this forum for some time. I'm fairly new to CNC, and excited to finally have my mill working. Anyway so my question, what does everyone do here about removing material from their workpiece. I'm currently trying to drill through a 0.253 inch piece of alluminum. I'm using a 1/16 inch 4 flute endmill. On each cut I'm only going down 0.2 inches, and a feed rate of 0.3 IPM @ 2000 RPM. So at this rate it takes me over a couple hours to make a complete circle that is 2 inches in diameter. I was hoping to start the mill spread some oil over the piece and come back in a few hours and find it done. Oh I also tied a vacumm to the side of the mill to try and get excess chips out. So my predicament is, when I left the mill and came back my bit was broken. It looked like when I almost got to the bottom of the piece that my vacuum wasn't sucking any of the peices up and it overheated and died. So my question is what do you guys use to stop this problem, should I always just stick around and suck up what I can with a vacuum. Do you think I should switch to a system where I spray vegetable oil on it to push out the pieces?, (can I use vegetable oil?). Any help is greatly appreciated. BTW, I"m using a base sherline mill converted to CNC, and MACH 3.
Thanks for the help guys! I have learned alot from this forum, and if anyone is in the cincinnati area let me know.

~Brian

Hi Brian,

I'm not going to quote you cutting tables or chip loading etc, but I can tell you what I have found works.

I've done some engraving on 6061 aluminium with a 2.0mm endmill with 0.25mm per pass @ 100mm/min (2000 rpm). The problem with aluminium is it tends to weld itself to the cutter, leading to a rough finish and ultimately a broken cutter.

The above is probably conservative, but I only had the one endmill left, and couldn't afford a broken endmill. I've been using a cheap alternative to WD40 to lubricate and blow out the chips after every pass. I've also using kerosene 10:1 with motor oil, and turpentine neat, both are a little hard on the nose after a few hours though.

I do a lot of profiling in aluminium using 3 flute carbide bits, 1.0mm per pass @ 150mm/min (2000 RPM spindle) I can cut all day without a broken bit.

Try taking a shallower cut 0.2" = 5mm you shoud be looking at a cut in the order of 30% of the cutter diameter, so I'd be looking at 0.015" per pass at say 3 IPM @ 2000 RPM as a start. You'll need to get those chips out of the trough left by each pass too, either by blowing them out or washing them out with some form of flooding.

Hope this helps

Pat

Hi Brian,
Are you "milling" a 2" circle thru the alum?
If so .200" is WAY to much of a depth of cut for a 1/16 end mill. I'm not sure what your max rpm is, but dial it up to max, go with a .030" depth of cut (or less) and up the feedrate. At .3 IPM you're only getting the aluminum hot and "welding" it to the cutter. Thats why it broke.
I'd try max RPM (I see on the website that the Sherline is limited to 2800 RPM) If you have more, use it. Try a feed rate of 6 IPM. That will give you a "cut" of .0005" per tooth with a 4 flute end mill. If it "complains" slow it down. Not sure about the rigidity of your setup. You may be able to go faster.
A flood coolant system would be best, a spray-mist coolant good, or just give it a shot of good ole WD-40 once in a while and if you have a supply of compressed air, give that a shot once in a while too.
Aluminum is easy to machine, but it does like to stick to the tools. Anything you can do to get the chips out of the work area and lubricate/cool the work will help.
Hope this helps. Let me know if you need more.

Mark

Definetly need to keep your bit cooled. Ya can,t just throw oil on it and leave and hope for the best.

yep .2 is way to deep of a cut as a rule of thumb pass should be half the diameter of the mill so in your case 1/16=0.062 so your pass should be 0.031 deep as for your feed rate at 2000rpm with a 1/16mill 4 flute lets assume a chip load of .0005 per flute wich gives .002/rev so 2000 x .002 = 4"/min feed but make sure you supply it with a constant amount of cutting fluid and make sure that each time you go down .031 you wipeout the chip or else you are going to break the mill also try to use a mill that as flute that are not to long, so .100 to .200 longer then the total depth as the longer it is the more its going to try to flex wich is a nono on a mill that size
also you said drilling some mill, like 2 flute most of the time, can drill but lots of 4 flutes arnt made to take drill cut

I'm confused on what you are trying to machine:

1) a 2" circular groove partially through the stock?
2) a 2" circular groove through the stock to leave a 2" hole and a 1-7/8" circular cutout?
3) a 2" flat bottomed circular pocket?
4) something else?

As others have mentioned, you usually want to limit depth of cut to 1/2 the cutter diameter or even a bit less for small cutters.

What sort of end mill are you using? HSS or carbide? Centercutting?

Cooking oil is not the best cutting oil for aluminum - try WD40, Tap Magic Aluminum or some other oil designed for aluminum.

Mike

sounds like to me its option #2.. the way i read it he wants to have a 2" hole clear through the 1/4" thick plate... and so yea that would leave a dropout slug.. i dont know the machine that he's using, but it would seem to me that it would be more efficient (timewise) , make sure its end cutting, and feed it faster and less deep, just like everyone else has said... but i was thinking about useing a larger endmill....... change the offset acordingly.. what about going that route.. i just dont understand using such a small bit...

Yep, if it is option 2, I'd elect to use a larger diameter bit as well unless some unknown spec precludes that option. However a 2" circle has a circumference of 6.2 inches and at 0.3 ipm and 2 passes would only take 45 minutes or so to complete, not the "hours" the OP talks about, so maybe he is making a 2" flat bottom hole.

Maybe he'll pop back and let us know <g>.

Mike

I'm currently trying to drill through a 0.253 inch piece of alluminum. I'm using a 1/16 inch 4 flute endmill. ~Brian

well the way i read it, its all the way through.. tho i was wondering about the math of duration.. maby it just seems to take hours at .3 inches per min...

oh, wait, i got it... run the math on this one... pocket a 2" circle all the way through, instead of just cutting the permiter.. that might account for the time...

thats the only explination i can come up with... ofcourse i love the part about the vac burning up....

Hey guys thanks for all your help, it comes painfully obvious that I should have just been going faster with shallower cuts. You guys rock, I hope to come close to the mastery that is shown in this forum, I have a long way to go though.

It would make alot of since to just use a bigger endmill, but I'm actually making a part for my robotic lawnmower. This part will connect my large tires to my keyed dc motor. Basically I have a pipe extruding out the side of the rim, and I'm making a part to press fit into it, and in this 2 inch circle will reside another 0.75 inch hole with a key way. So thats why I need the smaller endmill for the keyway. I guess I could use an 1/8 endmill up to the keyway, then use the 1/16 for just for the keyway, but I'm still learning how to do such things in mach 3/lazycam, and seeing as this is the very last piece I have to make for my lawnmower (all electronics are done and I just need to bolt on the motors and a little more software), I just wanted to get it done.

I appreciate the help again, I have my cnc machine at work right now so I could work on it after work. Hopefully I'll get a chance to try the faster feed rates and lower depth cuts. Should speed up my time to.

Quick question, not to make this too long, but what is the advantage of a 2flute versus a 4 flute endmill. Seems like you would always want to run a 4flute bit becuase you can have faster feed rates. what application would I use a 2flute endmill.
PS. I'm using a carbide tialn coated 4 flute endmill
( www.lakeshorecarbide.com ) < seems to be the best place I found so far.

Hey guys thanks for all your help, it comes painfully obvious that I should have just been going faster with shallower cuts. You guys rock, I hope to come close to the mastery that is shown in this forum, I have a long way to go though.

It would make alot of since to just use a bigger endmill, but I'm actually making a part for my robotic lawnmower. This part will connect my large tires to my keyed dc motor. Basically I have a pipe extruding out the side of the rim, and I'm making a part to press fit into it, and in this 2 inch circle will reside another 0.75 inch hole with a key way. So thats why I need the smaller endmill for the keyway. I guess I could use an 1/8 endmill up to the keyway, then use the 1/16 for just for the keyway, but I'm still learning how to do such things in mach 3/lazycam, and seeing as this is the very last piece I have to make for my lawnmower (all electronics are done and I just need to bolt on the motors and a little more software), I just wanted to get it done.


I need to get my terminology right, sorry I meant mill out the circle, not drill out the circle, and I didn't kill my vacuum I just meant the bit, and I'll be using WD40 for now on.

another newbie question, what is the difference between a 2flute vs a 4 flute, why wouldn't everyone just use a 4 flute endmill? what would be a good application for a 2flute.

.2" is way too deep of a cut.

I have found it better to take shallower passes at a higher feed rate for roughing out. I leave about 5 to 10 thousanths for the finishing pass Finish passes at the same feed rate but because there is not a severe amount of material in the way you can go deeper.

I ran into your situation when I started out.

The fact that aluminum is sort of gummy in nature does not help.

Pweter is even worse gummy wise, although not as hard as alum by any rate.

With deep plunges like that the chips are larger and need to go up the flute to clear. The swarf left in the way to clog becomes as much an issue as the material you are cutting through. The flutes can clog and the cutter will stop cutting and....snap.

I cut some aluminum and alot of pewter and foud that .005 - .010 passes at 10 - 15 ipm work far better. You will need to experiment here.

I would also be wary of the vacuum thing.

It should be well grounded.

I think I read this on the xylotex yahoo forum but someone started a thread there about there controller burning up from a static discharge from the vacuum that ran through the machine and into it.

Not sure of the validity of this but it has always made me wary of using a vacuum while running. Id rather not test the theory.

Sherline also makes a retrofit pully kit which will increase your RPMs on your spindle. It think to 10000???. Take a look on thier site

Markc,.....ALUMINUM???????....there aint no such animule, it's alluminium, I know the Yanks say it different 'cause they can't spell, but spelling it different is like reinventing the wheel.
Ian.

BTW, if you're using a vacuum to remove the swarf, just make sure you're not using kerosene or any other combustible fluid as a coolant, otherwise the vaccy motor, which passes some of the air through it from whatever is sucked up, will catch fire.
The same goes for sucking up any damp material with an ordinary vacuum cleaner, the motor can short out if there is any water present.
I think the Aqua Vac differs here as it does not have this method of cooling the motor, and is designed to lift wet material.
Ian.

Markc,.....ALUMINUM???????....there aint no such animule, it's alluminium, I know the Yanks say it different 'cause they can't spell, but spelling it different is like reinventing the wheel.
Ian.

If you're going to be pedantic, you really should use a spell-checker:
In English English, it's aluminium - pronounced Al-you-mini-um (I wouldn't dare to presume how it's pronouned in Scotland or Wales) ;)

Though what I can't tell you is how I should spell it when it's been mined in Australia, smelted in the USA and then milled in the UK :)


However you spell it, if you're going to mill it, you really need to use some decent coolant.

Allo Digits, aluminium it is, you're right about the coolant, but on the other hand the material is probably the cause for concern.
If you've ever worked with bright mild steel you'll know why they use free cutting and leaded steel for machining, that is production machining, when the bird's nest of swarf cannot be tolerated.
Aluminium comes in many forms and if you're using the stuff that has been rolled or extruded you can practically forget about the machining properties, as it's too ductile to break up the chips and if you're speeds and feeds are wrong you'll just smear the material instead of cutting it, especially when it sticks to the tool.
Ian.

http://www.fileden.com/files/2006/5/29/42142/my%20speed%20and%20feed%20calc.rar

try this speed and feed calc ,it s something ive been poking away at , its not complete or 100% correct
but it should give you a a guideline to work from
you will need to have microsofts netframework 2 in order to make it workwhich is free from their website
right now it only covers hss endmills
a bit of feedback would be great

Hey guys, so I tried a more shallow cut with a faster feed rate and I broke another bit. I think this time I was able to see my problem. It looks like at the faster feed my system is binding (I guess its just not rigid enough? ) and it actually starts trying to cut off the path, breaking the bit. I did have success using an 1/8" bit, I filed down the keway. I ran this 1/8 at 1IPM with a plunge rate of 0.0615, and a depth of 0.02, and I seem to cut fine. It takes awhile, mostly becuase I'm waiting for the cutter to plunge, I need to figure out how to make lazycam go rapid to the depth of the previous cut, then plunge down slowly. Right now it always makes the cutter go to 0.1 and plunge slowly from there.
Yeah I can't spell, aluminium, there we go. Maybe I will type it right next time. Thanks for the help guys.
oh yeah why would I use a 2 flute vs a 4 flute?

Oh yeah i tried the program dertsap, but it keep giving me a feed rate of 9 IPM. here were my numbers, I probably put something in wrong,

4 teeth
100 sfm
0.125 dia
0.0007 removal/rev
3056 RPM

I had to manually put in the 100sfm because everytime I selected aluminium it would force it to 300.


Has anyone made their sherline more rigid, any tips on what i should go do?

BTW, if you're using a vacuum to remove the swarf, just make sure you're not using kerosene or any other combustible fluid as a coolant, otherwise the vaccy motor, which passes some of the air through it from whatever is sucked up, will catch fire.
The same goes for sucking up any damp material with an ordinary vacuum cleaner, the motor can short out if there is any water present.
I think the Aqua Vac differs here as it does not have this method of cooling the motor, and is designed to lift wet material.
Ian.


Ever watch mythbusters? modern shopvacs dont pass load air through the motor.. they suck air in from around the base of the motor and the 2 airstreams dont mix... and even if they did, you'd have to get the "fuel" air mixture just right for it to burn.. and what are the chances of that, and what are the chances of sustaining it even if you were to hit it momentairly?

now i will give you that a common house vac passes the load air around the motor, but not through it.. the air comes in from the suction head, passes through the trap(bag, canister, vortex, basically where the dirt lands) then through the veins of the disk attached to the motor and then is expelled..

sorry, had to put in my 2 cents worth...

Oh yeah i tried the program dertsap, but it keep giving me a feed rate of 9 IPM. here were my numbers, I probably put something in wrong,

4 teeth
100 sfm
0.125 dia
0.0007 removal/rev
3056 RPM

I had to manually put in the 100sfm because everytime I selected aluminium it would force it to 300.


Has anyone made their sherline more rigid, any tips on what i should go do?


removal/rev should have been removal/tooth ,something i forgot to change

100sfm is pretty slow for cutting aluminum with a carbide tool
there should be no real reason not to be able to run at 300 sfm , the numbers i have used are fairly conservative for hss cutters ,provided the cutter is cutting at the recommended depth of cut

Two flute will cut faster with less clogging.
Four flute will give a smoother cut but cut slower and clog easier.

Similar to tires in a vehical.

A knobby motor cycle tire is very agressive and will not plug up with mud and leaves a very agressive pattern(cut) on the ground it grinds.

I smoothe road tire from a road bike will give a much smoother ride and leave very fine marks when ridden on dirt but it will clog easy and will not attack the terrain as agressively

Allo Digits, aluminium it is, you're right about the coolant, but on the other hand the material is probably the cause for concern.
If you've ever worked with bright mild steel you'll know why they use free cutting and leaded steel for machining, that is production machining, when the bird's nest of swarf cannot be tolerated.
Aluminium comes in many forms and if you're using the stuff that has been rolled or extruded you can practically forget about the machining properties, as it's too ductile to break up the chips and if you're speeds and feeds are wrong you'll just smear the material instead of cutting it, especially when it sticks to the tool.
Ian.

Hi Ian - I haven't played with steel at all yet. I have cut what is supposed to be 2012, 6082 and C250 on my little mill, and I'd agree the drill swarf is crazy - I make my own aluminium 'Brillo-pads' in the process and quite literally end up polishing around each new hole! The C250 is also sticky enough to actually stall my bandsaw unless I keep applying WD40 - I've never had a problem with the 6082-T6 - is that to do with the heat-treatment?


P.S. I don't think your user name translates too well to the UK, but then again, isn't 'spunky' a compliment on the upside-down end of the planet too? ;)

Hey guys, so I tried a more shallow cut with a faster feed rate and I broke another bit. I think this time I was able to see my problem. It looks like at the faster feed my system is binding (I guess its just not rigid enough? ) and it actually starts trying to cut off the path, breaking the bit. I did have success using an 1/8" bit, I filed down the keway. I ran this 1/8 at 1IPM with a plunge rate of 0.0615, and a depth of 0.02, and I seem to cut fine. It takes awhile, mostly becuase I'm waiting for the cutter to plunge, I need to figure out how to make lazycam go rapid to the depth of the previous cut, then plunge down slowly. Right now it always makes the cutter go to 0.1 and plunge slowly from there.
Yeah I can't spell, aluminium, there we go. Maybe I will type it right next time. Thanks for the help guys.
oh yeah why would I use a 2 flute vs a 4 flute?

1 IPM seems a little slow to me - I usually run a 4mm mill at about 600mm/min / 24IPM at 0.5mm/0.02" depth of cut and 2,000 rpm (which is all my mill can manage) with good results.

why 2 flute more then 4 well because 4 will tend to pack more as the flute are closer together

seems to me the best way to go about it is to rough it with a 2 flute, move most of the material, and then do a finishing pass with a 4 flute.. less material to move and all...

Thanks a million guys, I was just being stupid. Once I was putting enough cutting oil on, I ramped it up to 3IPM at a depth of 0.02 per pass and everything went great. I've finished one complete wheel to motor connection, and now working on the second. It makes sense about 2 flute vs 4 flute, what kind of feed rate difference should I expect between the two? Can I run the 2 flute twice as fast?

Ok look the idea is the following base cutting speed for aluminium is somewhere 600 and 800 so lets say 700 so the formula is the following:
rpm=(700x4)/cutter diameter.
So a 1/8 cutter would be:
(700x4)/.125= 22400rpm
Now most mill wont reach those speed so keep it at around 2000 or the max rpm and it should be fine, now for the feed rate the formula is the following: rpm x teeth load x # of tooth
Or in the current case most .125 end mill can take .0005" per teeth so:
2000x.0005x2 if its a 2 flutes mill
and
2000x.0005x4 if its a 4 flutes mill
so 2"/min for 2 flutes and 4"/min for 4 flutes

can you not drill out the hole first (with a regular twist drill bit), have a tool change then go back in with your end mill and true up the hole. You could do this with out any plunging of the end mill as well and just come in from the middle to do side cutting? If there are multiple holes to be drilled in one part, have the drill bit start all of the holes, have a tool change set in there and finish them up with the 2 flute.

I am not sure if i have missed what the purpose of these holes are going to be used for (ie: press fit ect) but I would imagine either way you will get a fine enough finish with a 2 flute after you have pre-drilled.

You may be finished this project now so not sure if this info will even help...lol

Ataxy that was very helpful, thanks for the post!!

Lose the vegi-oil and PLEASE get some aluma-tap. No thick oils for cutting aluminum. I used to use WD 40, but the alumatap works bettter.

Rob kindly steps down from the soap box :drowning:

"aluma-tap"

Where can I find it, I'm interested in trying it?

Ataxy that was very helpful, thanks for the post!!
glad it helped you

Hi Digits, wot's inna name? the handle wotsit bit is a slang term for a turner, from the workshops I served in, while in UK, and being a fitter and turner I thought I'd have a bit of humour.
I suppose Doodlebreak would raise a few eybrows.
One of my workmates there was called shagnasty, he smoked a pipe with some of that "wayside mixture", hand rolled baccy stuffed into it, the stuff commonly called "horsesh#t and bus tickets".

Back to the alloominum, I used to use kerosene, diesel fuel and on one occasion milk as a lubricant and coolant.
Some of the older guys swore by turpentine.
They all stunk bad, and you usually got to smell like an old oilrag after a while.
One potent mix I was given the "secret" of was made from coconut oil, that came in a solid form like candlegrease, and was mixed 50:50 with paint thinners untill it dissolved.
Pretty damm potent when you got a lung full of the fumes.

As long as the speed and feed is right you'll get results, using any of this stuff mentioned, but on that soft rolled ally stuff if you didn't keep the bit wet then you were in trouble.
I made some castings once, using old gearbox material, the stuff that looks like it's gritty and porous.
I think it is silicon alluminium.
It's ok for machining, and is the stuff if you don't want your tools covered in festoons of swarf, but it is a b##gger to get a good finish, not like the rolled stuff, don't know the grade or type.
I melted a lot of old ally washing machine bodies down and added some offcuts of the rolled type for some castings to make bearing housings for a bandsaw.
Despite a lot of tales that you shouldn't use iron near molten ally, we melted the stuff down in a steel ladle with a Propane burner in a small firebrick enclosure, and poured the melt into steel moulds formed from pieces of steel bar, tack welded together for the occasion.
Result, we got blocks of cast ally about 3" X 3" X 4" long, without any problems and they machined up well, no blow holes, hard spots or the like.

I will state that this material is poor for machining as it is so ductile and doesn't chip up well, so you have to clear the swarf from the drills and boring bars as you go along, but if you want to have a lovely smooth finish that you can polish if required,and don't have to worry about the material getting tangled up in the tools, then that's the stuff to use every time.
I wouldn't advise the old gearbox stuff even if it is plentifull, as it is as rough as, and doesn't leave a good finish, but if you only want a casting for say a bearing plumber block then it'll do.
Ian.