[mrcodewiz]

I want to do a small production run of parts which involves doing a few countersunk holes and a profile around a 2"X6" aluminum plate that is .75" thick. The holes don't take too long but the profile does. I am running at probably 3K rpm with a .5" HSS end mill (2-flute) doing 5.5 IPM or so with a DOC of .5. It works OK but I get some chattering and my finish pass of .015 leaves some nasty marks unless I come over and turn the RPMs down just before the finish pass starts (which is too slow for the profiling). Would switching to a carbide end mill allow me to increase the feed or DOC and get a good finish? It currently takes 45 minutes or more for one piece and I would really like to lower that as much as I can but I don't want to spend $50 on an end mill that will be no improvement over what I have.


thanks,
Kevin

[Robin Hewitt]

IMHO carbide doesn't take such a nice edge as HSS, but it can handle much higher cutting speeds. OTOH, why are you having to drop the rpm to get a fine finish

Presume you are using high helix tooling and teh right lubes?

[dertsap]

carbide is far more rigid and holds the edge much longer
carbides aren t necessarily much more expensive for a half decent tool to do the job
http://cnctoybox.com/shop/category_5...ram=cid%3D7%26

[ataxy]

i am trully found of carbide aspecialy in steel and i dont know if its only my experience but i feel that aluminium as a tendency to stick more to hss tool then it does on carbide, they also definitly tend to keep there edge much longer

[mrcodewiz]

IMHO carbide doesn't take such a nice edge as HSS, but it can handle much higher cutting speeds. OTOH, why are you having to drop the rpm to get a fine finish

Presume you are using high helix tooling and teh right lubes?

I am using an 'aluminum cutting end mill' but it is some sort of import. I don't know why I have to slow it down. maybe the .015 finish is too deep for the speed I'm going?

[mrcodewiz]

I guess I should also mention that this is on a Sieg X2 (HF variety)

[ataxy]

I am using an 'aluminum cutting end mill' but it is some sort of import. I don't know why I have to slow it down. maybe the .015 finish is too deep for the speed I'm going?

i would keep my finishing pass to a max of 0.01 x,y and 0.05 z

I guess I should also mention that this is on a Sieg X2 (HF variety)

an even bigger reason to user smaller finishing cut

[Stepper Monkey]

Carbide is awesome for most stuff, especially if you can keep the spindle speeds up high enough for it.
HSS is cheaper and has some advantages where the sharpness of the tool is important, but only in work where you aren't going to lose the edge quickly. I actually prefer it for wood and plastic. It can also do better on some type of cut on machines with slower spindles as the feed/speed equations are very different (and not as demanding) as carbide.

[ataxy]

definitly it is really important to remember like ceramic insert carbide is more brittle then hss so dont expect to run it at low speed this is really the domain of hss, carbide and in particulare ceramic will have better result at high speed and both do prefer harder material, under presurre hss will snap carbide will shater

[mrcodewiz]

Is the 4K top speed of my mill too slow then?

[ataxy]

it all depends on the mill, the tool not the machine, size and the material you are milling

for example to figure out the rpm you need for a type of material the formula is:
rpm= (4xsfm)/D
so for instance lets say a 1/4" hss endmill and a 1/4" carbide endmill in brass
hss sfm will be ~300
so
rpm= (4x300)/.250 so roughly 4800
you would be allright with 4000 but on the other hand
carbide sfm will be ~650 or roughly twice the sfm of hss
so
rpm= (4x650)/.250 so normaly a carbide cutter would need an upward of 10000 rpm
now when all this is said and done you wow 10k that is fast in deed it is but not all machine are made equal so basicly for big cutter you could use carbide with a max of 4000 but for smaller one you would be better off with hss
for instance 1/2" carbide cutter
rpm= (4x650)/.5 = 4600rpm at 4000 you would do
but this is brass when steel comes into play that is a whole new game
so for instance
a steel with a rockwell hardness of ~30 would have roughly a sfm of 80 with hss and roughly 450 with carbide
so again
rpm= (4x80)/.25 = 1240
and carbide
rpm= (4x450)/.25 =7200 still way off your machine spec
now this does not mean that you could not use a .25 carbide endmill at 4k it just mean you would not use it in its optimal range and basicly you dont want also to run your machine at 4k continuously you would just burn you motor to fast so in the end i would definitly go hss for anything 3/8 and under and carbide for over ~1/2 and more in between it can vary depending on what is available.

but thats just to give you an idea

ps: good coated hss tool can give you a good compromise in between carbide and hss but remember the coating on tool is really thin and ounce the sharp edge of your cutter looses its coating the performance will go south with it

[dertsap]

definitly it is really important to remember like ceramic insert carbide is more brittle then hss so dont expect to run it at low speed this is really the domain of hss, carbide and in particulare ceramic will have better result at high speed and both do prefer harder material, under presurre hss will snap carbide will shater

i dont understand how it would be an advantage to run hss instead of carbide at low speed , i have never heard that before , the only advantage hss has in comparison to carbide is that it has give to it , it will deflect a great distance before it breaks and at times it is necessary to have that give , but this is also a major disadvantage because of the deflection that occurs you can face tool wander ,chatter, gouging , tapered walls ultamitely poor finish , typically standard 2 and 4 flt hss tools must be run at lower speeds ,feeds , less tool engagement and lesser depth of cut ,than carbide . there is a reason that hss is cheap , it is no longer desirable in manufacturing due to the fact it is such an inefficient tool ,carbides can handle a great amount of cutting force before they break at any speed , hss was a choice tool for plastics but the high end micrograin carbides being produced have the same sharp cutting edge as the hss tools and lasts far longer
hss has its place but it very limited and its mostly to sloppy machines

[MonoNeuron]

I don't think anyone has taken into account the rigidity of the machine. You have to make sure all your Gib keys are adjusted for the minimum play because any lash will be reflected in the cut finish and it won't make any difference how sharp or what type of cutter material you are using. Smaller mills tend to chatter a lot more due to less mass of the machine as a whole and it's why they make production mills very heavy to absorb the cutting stresses and not just for the overall accuracy.
It's a bit of a tricky situation with a small mill as to what you can use, so you will probably have to try a few different feeds and speeds and work out what is actually suited to your particular machine.
Make sure you have the machine on a solid table or surface and that it can't wobble all over the place as well (for safety's sake, too.) .
Rich.

[ataxy]

i dont understand how it would be an advantage to run hss instead of carbide at low speed , i have never heard that before , the only advantage hss has in comparison to carbide is that it has give to it , it will deflect a great distance before it breaks and at times it is necessary to have that give , but this is also a major disadvantage because of the deflection that occurs you can face tool wander ,chatter, gouging , tapered walls ultamitely poor finish , typically standard 2 and 4 flt hss tools must be run at lower speeds ,feeds , less tool engagement and lesser depth of cut ,than carbide . there is a reason that hss is cheap , it is no longer desirable in manufacturing due to the fact it is such an inefficient tool ,carbides can handle a great amount of cutting force before they break at any speed , hss was a choice tool for plastics but the high end micrograin carbides being produced have the same sharp cutting edge as the hss tools and lasts far longer
hss has its place but it very limited

no you are right but i think that at low speed were there are less heat generated by the tool cut the expense, mostly in a hobbiest point of view, does not justify the expense of carbide over hss again not in a production situation in a production situation i would say hey go carbide all the way the tool will last you longer and all but ounce you start producing part the cost of the tool can becomes profitable so you pay more but you get a more constant cut but when you do small work and the tool dont get abuse then paying twice the price may be more properly invested but hey again its only my two cents and i am not the god of knowledge, just a guy with a point of view.

by the way nice price on those carbide endmill what made are they.

I don't think anyone has taken into account the rigidity of the machine. You have to make sure all your Gib keys are adjusted for the minimum play because any lash will be reflected in the cut finish and it won't make any difference how sharp or what type of cutter material you are using. Smaller mills tend to chatter a lot more due to less mass of the machine as a whole and it's why they make production mills very heavy to absorb the cutting stresses and not just for the overall accuracy.
It's a bit of a tricky situation with a small mill as to what you can use, so you will probably have to try a few different feeds and speeds and work out what is actually suited to your particular machine.
Make sure you have the machine on a solid table or surface and that it can't wobble all over the place as well (for safety's sake, too.) .
Rich.

absolutly.

[dertsap]

i understand your point about justifying the expense but carbides can be had at a fraction of the cost they were a few years back which for me personally is a no brainer , ive got my hobby diy router table out back , i started off trying hss to cut aluminum but i quickly crossed over to carbides because the benefit was far greater , this is on a machine that doesn t have the rigidity of the mills you guys are running

i am not the god of knowledge either , just a guy with a point of view same as you

as for your question they are oem , you may want to take notice of the hss tools as well

[ataxy]

no actually ill put a bit of shame on me i have like 200 carbide mill in my shop and about 20 hss and they are used on a need to need basis

yeah those are some inexpensive hss mill even your carbide as a nice price tag

[dertsap]

most time it boils down to personal preferance and where our comfort zones are , i think we are all guilty of that shame

[ataxy]

thx at least i am not alone do you carry face mill

[dertsap]

yeah those are some inexpensive hss mill even your carbide as a nice price tag

thanks , ya i'm happy they are all pretty decent tools but whats really floored me are the gorillas that ive taken on , bit pricey for a hobby tool but they've definitely impressed the crap out of me for industrial use


no facemills yet , i've been looking at a swiss made company but i'm not sure if i'm going to pusue it at this point , this was only meant to subsidise my hobby , little did i know that i was going to push it further

but thats as far as i will say on the subject i posted the link to proove a point more so than anything

[HackMax]

Quick question here. I have an X3 and the max rpms is 2000 and I have to plow through aluminum quite a bit with a 3/16 end mill. What should I use in this situation? Thanks

Rick