Feed, Speed, IPM, Depth of Cut

[Lookin4help (Mark Roberts)]

I am wondering if anyone can help me with a 1/16, 2 flute, end mill. A few days ago I snapped my bit. Obviously, I must have been using some wrong settings. Is there some sort of math formula that will help me figure out what my settings should be.

My software only allows me to input tool diameter, number of flutes, pass depth, step over, spindle speed, feed rate, and plunge rate.

Is there some formula I can use to get these setting so that I don’t break another mill?

Thanks

[Tod1d (Tod (with 1 'd'))]

There are many variables, and no one simple formula to consider them all.

I think a good place to start is the default tools in Carbide Create. They are conservative & should not break a tool if you select the appropriate material.

I also use FSWizard, but their values are aggressive, so I usually adjust down a bit until I get the required horsepower down to about 1.0 or lower.

There are a bunch of other good sites out there with speeds & feeds info. Note that a site centered on commercial CNC machines may be way too aggressive for a shapeoko. Those machine are a lot more rigid, accurate & have quite a bit more horsepower.

Tool manufactureres usually give some guidelines, but they could be in SFM / Surface Speed for a given part material. You would need to convert that to spindle speed. They may also recommend “chipload” which can also be converted into feedrate.

Which software are you using?

[Lookin4help (Mark Roberts)]

I am using Vectric V Carve Pro. I also have Carbide Create and I will open it to see what setting they recommend. I have looked at some some online tools and even an Excel spread sheet and they are all so far over my head that they leave my head swimming.

[WillAdams (William Adams (Carbide 3D))]

There is a bit on this at:

Origin/consistency of chipload recommendations

I’ve been going back to the basics of the whole feeds and speeds thing for a minute, and this time I want to focus on chipload values only, not the infinite number of associated RPM/feed combinations. I collected a small sample of feeds and speeds below from: usual recommand values from 3 or 4 different web sites what CarbideCreate uses the Shapeoko feeds and speeds chart for the #201, 1/4" endmills Will’s [Tableau] (https://public.tableau.com/profile/willadams#!/vizhome/Carbide3DCNCFeedsand…

and

Feeds & speeds

and

#MaterialMonday on YouTube

@wmoy has begin a series of YouTube videos on #MaterialMonday. For the full list: https://www.youtube.com/hashtag/materialmonday A central tenet of this series is an acknowledgement that the hobby CNC routers need different numbers for different sorts of paths. Thus far he has done: Aluminum: Shapeoko 3: [Aluminum Feeds and Speeds for the Shapeoko - #MaterialMonday] [Machining Aluminum with the 278-Z on the Shapeoko - #MaterialMonday] Nomad 883 Pro: [Sing…

[Tod1d (Tod (with 1 'd'))]

Try not to let it overwhelm you. The truth is… I’ve been doing this for 30+ yrs and there are no exact numbers. There are just too many variables, including the HP & rigidity of your machine & workholding, in addition to stepover & depth of cut, material, tool material, tool coating, temperature & humidity, tool lead & rake angle… ET.AL.

Don’t look for absolutes, look more for “rules if thumb”. i.e. If a plastic is melting, slow down the spindle and/or bump up the feedrate to take slightly larger chips.

Formula for SFM to RPM is: rpm = sfm ÷ diameter × 3.82
Formula for chip load to feedrate is: feed Rate = RPM * chip load * number of teeth