# How To Calculate Speeds and Feeds (Inch Version) – Haas Automation Tip of the Day

Articles . Blog

– Hello and welcome to

this Haas tip of the day. In today’s video, we’re gonna talk all about speeds and feeds. We’ll show you the path that we take to reach starting speed and feed values that we can trust, that will work with any tool and material combination. We’ll be using inches in this video, but we’ve made an entire other video for those of you that are

using the metic system. A few key concepts, a formula, and we’ll reach the RPM

that our program needs. Another quick calculation (bell chime) and we’ll establish our feed rate. And have you home in time for supper. As we jump into one of

the coolest concepts in CNC programming, Speeds and Feeds, I’ve got a question

for you, are you ready? If our tractor is moving

along at an amazing one mile per hour, that’s

88 feet per minute, which tire is moving faster? Our small front tire,

or our larger rear tire? (folk string music and engine purring) Everything for me begins

with my set-up sheet– So, check this out, I’ve

got a block loaded up– You’re tidying up those tools by hand– (marker scratching) That’s it, pencils down, answers? I know, it’s kind of a trick question. It depends on what I mean by faster. If what I am asking is how fast the tires are moving across the surface of the ground, where the rubber meets the road, then both tires are traveling

at the exact same speed, 88 surface feet per minute (cow mooing) See, both tires travel the same distance, where it matters, along the tire’s edge. Now, if we’re talking about

revolutions per minute, RPMs, then that’s a different story. While both tires cover

the same amount of ground, the smaller tire had to

make more revolutions per minute to get there. If we want to calculate how much ground a tire will cover with each revolution, then we’ll need to come

up some kind of ratio between a tire’s diameter

and its circumference. Well, it turns out, someone

has already figured this out for us, and they’ve even

given this ratio a name. Pi. The ratio between a circle’s diameter and its circumference is pi, no matter what our diameter our tire is, the distance around the

outside of that tire, where the rubber meets the road, is always 3.14 times greater. This tire has a diameter of 3.82 inches. 3.82 times pi is 12. Now this tire, come on. This tire has a diameter of 40 inches. 40 times pi, about 126

inches circumference. Okay, that’s great, get out

of here (backing up beeping) If we were to run out tires too fast, too many surface feet per minute, they would overheat, blister and fail. Our end mills work in the same way. There’s a limit, a maximum cutting speed, that a specific tool can

go on a specific material. Any faster, and it begins to

overheat quickly wears out. In machinist talk, if

we’re talking about speeds, like speeds and feeds,

we can be talking about one of two different things. We’re either talking about

cutting speed or spindle speed. Our cutting speed, our Vc, our

surface footage per minute, is the speed our tool is turning at where the rubber meets the road, where the tool meets the part. And our spindle speed is

simply our revolutions per minute, our RPM. Now we get our cutting speed,

SFM, right from our catalogs. But the control, the Haas machine, needs to know the RPM

value, our spindle speed. That’s our S code. To get from here to here,

we’re gonna use a formula. And that formula’s gonna make use of pi, and our tool’s diameter,

to convert our SFM that we got from our catalog into a spindle speed, an RPM value. Now once we’ve got that RPM value, we can calculate our feed

rates: speeds and feeds. Here is our formula to calculate our RPM. Now, I’m gonna start using some symbols, some notation, because

those are the symbols being used by all of

the tool suppliers now. And you’ll need to recognize them. RPM equals cutting speed times 12, all divided by our diameter times pi. N is our RPM, our spindle speed,

the S code in our programs. This is what we’re trying to solve for. V-C is our cutting speed, that is, our surface feet per minute. D, also sometimes listed as D1

or DC, is our tool diameter. This is the long version of the formula. The 12 in this formula is there to convert feet to inches,

there are 12 inches per foot. We already know what pi is. Now we’re gonna simplify this formula. by dividing 12 by pi, that gives us 3.82. This new simple formula is

the one we’re gonna use today. Before we open up our catalog,

and get our cutting speed, before the tractor even leaves the barn, we need to know exactly what

cutting tool we’re gonna use. And we need to know exactly what material we are gonna be cutting. Now in the good old days,

all we really needed to know was whether our end mill

was high speed steel, carbide, PCD, or CBN. Those days are gone. Today’s tools have coatings on them that might double their

allowable cutting speeds. So we really need to know

what tool we are working with. Otherwise we’ll have to

use really generic values which are pretty wimpy. With our exact tool number in hand, we can go to our tool catalog. We can download the manual from any tool manufacturer in PDF form. Once that catalog is opened up, we’re gonna search for the

material group section. That’s gonna tell us what material group our exact material falls into. Our materials are color-coded P is for steels, M is

for stainless steels, K is for cast irons, N

is for non-ferrous metals without iron in them, like

aluminum or magnesium. S is for our superalloys,

materials like titanium, and H is for hard cast

irons, or hardened steels. I am working a 41 40 steel. At least that’s what we call

it here in the United States. If you’re in Europe and you’re using EN names and numbers, this

might be called 42 CR MO4. If you’re in Japan, you’ll

call it something different. But no matter where you are in the world, this material is gonna find itself in the P isomaterial class. Now the number that follows

are color-coded isoletter, changes between manufacturers,

so be careful here. Kennametal calls this material a P4. Niagara and Seco, may call it a P5. Sabic classifies it as a P2.1 while Iscar and Widia

might call it a P6 or a P7. Same material, different tool vendor. Now, it’s important

that we get this right. If you don’t choose the

right material group, you are gonna burn up your tools Titanium has a different

machine ability than mild steel. If you try running a drill

or an end mill in titanium, at cutting speeds meant for mild steel, you are gonna melt that tool. It will overheat and

fail, so if you can’t find what material group

your stock should be in, then give your tooling

representative a call. They would love to hear from you. How many tooling reps out there would love to hear from one of our

viewers and talk tools? (cheering) Yeah, that’s what I thought. From the section of the

manual for our tool, under the row for our material type, we’re gonna find out

cutting speed, Vc, our SFM. Now if your manual gives you a range like 2 to 300, then base your choice on your tool length and your set up. The more rigid the set

up, the faster we can go. But remember that tools

tend to live longer, they have a longer tool life, when cutting speeds are slower. For my tool and material,

our cutting speed is 300 SFM and I’m using a

three-quarter inch diameter tool, so we’ll use .75 in our formula. We’ll do the math and come

out with an RPM value of 1528. That’s an S code of 1528. We now have a cutting speed, an RPM value that we can use, without

our tool (explosion) Exactly. We now know how fast to

spin our tool, our speed. The control now needs our table feed, our F code, a feed rate. The feed rate is how

far the tool will travel in one minute along

the tool’s center line. That inch per minute feed rate is how far the tool will travel

along the machine’s axes. Here is our feed rate

formula for end mills. We’ve got out table feed

equals our feed per tooth, times the number of teeth, times our RPM. So, what’s a tooth? This is a tooth! It’s just a cutting edge

along the outside of a tool. An insert is also a tooth. For most tools, the

number of teeth matches the number of flutes. This tool has three

flutes and three teeth. This tool’s got six teeth,

and this one’s got four. We want our tool to take

a very specific sized bite with each tooth. This our feed per tooth, in inches. Just like our cutting

speed, the books, or PDF, will give us that feed per tooth value. The catalog says that

for my tool, material and type of tool path,

three thousandths of an inch per tooth is a good starting range. 0.003, our feed per tooth, times four, our number of teeth, times 1528, our RPM, will give us our inch per

minute feed rate, F18.336. Some manuals will just

give out a single feed rate for all cutting conditions. But most will give us at

least two possibilities. One for slotting and

one for slide milling. Our A-E is our width of

cut, that’s our step over, that’s our radial depth of cut. And our A-P is our axial depth of cut. How deep the tool’s moving in the z-axis. Most times, if you’re slotting, your bite is gonna be about 25% less than

if you’re just sidemilling. With the popularity of

optimized tool paths like dynamic, adaptive, volume-mill type high speed machine-y tool paths, the tool manufacturers are

getting more and more specific with their speed and feed recommendations. So you’ll often see charts like

the one we’ll show you here listing all different kinds of tool paths. You’ll choose one, and then

match your speed and feed to the path that you’re using. Now, if you’re dealing with

drills and not endmills (laughs) our feed rate might be

listed in our catalogs as a feed per revolution,

and not a feed per tooth. We just multiply the inch

per revolution chip load, from the book, times our

RPM, to get our feed rate in inches per minute. Now watch out for, and

know the difference, between inches per tooth, F-Z, which we typically use for milling tools, and inches per revolution, F-N, which we often use for drills. Here is that completed legend, and the formulas we typically use for calculating our speeds and feeds. We’ve got our cutting speed

formulas, spindle speeds, we’ve our feed rate formulas, for both end mills and drills, and we’ve got all of the notations, all these symbols, that you’re

gonna see over and over again in your tool catalogs. With all of that said,

there’s a big shift happening with tooling catalogs in general. A lot of these tooling catalogs are just giving us our

feed rate and RPM values. No formulas needed. You may open up your manual and find that you don’t have to do any math at all. (cheering) In the past, we used to have to rely on slide rules to calculate

our RPM and feed rate. I still like these, I think they’re great. But today, we’re more likely to use an app on our phone, or a piece of software on our computer or the

speeds and feeds calculator right on the Haas control. On machines with next-gen controls, you can reach the milling calculator by pressing current

commands and navigating to the milling tab. We’ve made some videos that help you calculate those tabbing feed rates. We’ll link to those in the description. Well, that’s it, let’s go home. You can call your tooling

rep in the morning. Well, thanks for letting us be a part of your success, and for watching

this Haas tip of the day. (piano riff)

##### Written by Brian Rohrer

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how do you calculate the cutting data if:

1: the tool (endmill) is old, has no discerning markings on it

2: the company provides you with NO cad/cam software

3: the cnc machine is centurys old (80's okuma)

4: the only documentation you have is the material code and its hardness

smaller tire turning faster when biger

Wow, I need to watch that a 2nd time.

Where can I find the tables of cut values and tool advances, the one you mention at 13:20?

Why doesn't everyone just use feed/revolution (G95)? You have that info and then put it into your formula to come up with inches/minute. With feed/rev, the feed stays constant even if you raise or lower the rpm.

Excellent video.

that rock guy ,two thumb up

I like how you are holding overheated drill bit in your hands (I know its special effects) but that bit will be hot all the way around.

What bit is best for engraving on stainless steel 1/32" deep and 1/32" wide?

Cool animation🤗

Can anyone recommend some good apps for Android?

So at that f/s is -.25, really a good depth to cut at??

Sir you r great

I asked sir i want 2d programmings pocket n interpolation

….for drills also give ..

Wonderful

What about the lathe version? Thanks!

Why you are not mentioned mapal

Here is the updated link to the bonus content:

https://www.haascnc.com/video/Video-Bonus-Content.html

Thanks for watching!

Call Nates Industrial Tools in Los Angeles!

There's a mistake in the video, everybody knows that 12/pi=4

metric units please

How do you determine depth of cut once you have done this? Do you assume you are using the entire cutting depth of the flutes? I know he said about ap and ae and that slotting should 25% less. But 25% less of what calculation?