Calculating the RPM for your machines

Here's how to calculate the proper RPM of your machines for a given material and diameter. I explain how cutting speeds are represented (in both Surface Feet per Minute and Meters per Minute), talk a bit about the materials and cutting tools, and show examples of the equations.
If you like my videos, please consider supporting my channel on Patreon. You'll get access to gag reels and I'll give you a shout out in my videos.
/ stuartdeharo

[@robertoswalt319]

Thank you so much for this wonderful explanation. I have been frustrated trying to figure out sliding calculators and the machinery handbook. Now I understand and have written this down on and prominently displayed in my shop. Your students are fortunate to have you as an instructor.

[@andrewdashgdotcom]

Brilliant introduction to an arcane topic. Very glad to have found your video - gets me started from a point of my ignorance! Thank you so much.

[@cristianilie8857]

I've been watching a lot of videos lately for better learning how to use the lathe and mill and this is my favourite so far! Thx for the info and keep up the good work! All the best from Romania!

[@StuartdeHaro]

I'm glad you like it. Thanks for watching!

[@joeydubbs763]

Thank you! Just chewed up an insert & figured it was cause of going too fast. This was nice, simple, straightforward & much appreciated. Have a good1 bud.

[@engelbob8402]

Nicely done. It is disappointing to see so many viewers and so few likes. You deserve more recognition for your effort.

[@seabeckon]

Thanks for the metric calibration of RPMs very helpful.

[@mikekeele1533]

Since i was an auto shop major before electronic ignition was on the shelf, i appreciate instruction that is very simple. You do a wonderful job. The highest accolade we could give a teacher in those days was to call him coach. Thank you, "coach."

[@StuartdeHaro]

Awesome. Thanks, Mike!

[@danmccurry3810]

Thanks for speeds and feeds in a nutshell, I have learned through the years working at various Manufacturing companies, most machinist pic speeds and feeds from tribal knowledge on the machined parts history, memory or trial and error. It's more costly so this technical information will be helpful at any level or skill! It's great that you noted the suppliers of cutting tools and production expectation speeds verses nonproduction or manual time. Thanks for posting this helpful Gem!

[@sheldonbrooksugarhouse7612]

Just found this tutorial. Thank you, they are clear concise and very helpful.

[@johanvantongeren82]

Great video! I was about to go and convert these weird imperial measurements to proper metric, but then you saved me a lot of time in the end 😬 thanks!

[@CaptainSwoop]

Excellent presentation. Thanks from Australia

[@NOOne-im5vg]

Excellent explanation and use of examples.

[@StuartdeHaro]

I aim to please. Thanks for watching!

[@GcVoct]

Very good presentation.Thank you very much.

[@alexpaumen3937]

My high school teacher actually used your videos for a quiz. It certainly worked well.

[@StuartdeHaro]

That's awesome. Tell your teacher they have impeccable taste!

[@tivnator]

Wonderful, merveilleux, so clever and simple thanks

[@travisgowen6594]

Great explanation. Thank you!

[@markdobson4505]

Excellent explanation!

[@waltrichardson3246]

Really like this explanation, I also teach machine shop math and this is much better than what is in the book. The book recommends rpm= fpm x 12 over Pix D but I also prefer the use of sfm x 4 over, much simpler, but I guess I had never taken the time to discover why the use of 4, had just been advised to use that by another machinist. Thanks again.

[@regb8535]

Thank you, very clearly explained

[@MrAllanwinks]

Very well done , thank you.

[@PALM311]

Thank you,Thank you,Thank you! There is a light!

[@ducluong8482]

Great video to learn 👌 Thank you, hope to see your next video, thanks again 😀

[@sergeykochubey630]

Thanks man, my respect. nice explanation. Please continue.

[@Butterbean00]

This was very good teaching. Wish I could take the class. Thanks.

[@hiiitek9053]

Just got into a tool and die maker apprentice program at my job of which there’s manual mills and lathes and only one CNC machine and a big problem I had was understanding the speeds and feeds your video helped a lot wrote it all down and posted it in my Toolbox at work for reference 👍

[@StuartdeHaro]

Well good luck! Let me know if you have any other questions. I'm happy to help.

[@GunsWithGage]

Thank you! About to buy my first real machines. Practicing with a mill drill right now

[@trebornirtus6514]

I’m learning a lot from your channel thank you just picked up my first mill yesterday

[@StuartdeHaro]

Congrats on the new mill! What did you get?

[@trebornirtus6514]

Stuart de Haro nothing fancy mill/drill from grizzly GO758 it’s a starter rig

[@plebe791]

Thank you, very helpful tutorial,

[@brianwarburton4482]

Thanks for another excellent video

[@StuartdeHaro]

I'm glad you liked it. Thanks for watching!

[@bambiluong9759]

the best explain sir ,thank you.

[@iamjustaguy9777]

Amazing video thanks so much.

[@Petrolhead66]

Great video, to clarify for metric. Say I have a 1” (24.4mm) dia alloy bar. The calculation would be 45000/(3.142x25.4)=564rpm. If I was working in imperial it would be 150x4/1=600rpm

[@StuartdeHaro]

The difference is because the 4 in the imperial formula is an approximation of 3.82. If you do the math with that it comes out to 573rpm

[@tectopic]

Excellent informative video. Thanks. And a plus for using a HP RPN calculator!

[@StuartdeHaro]

You know, I have absolutely no idea where or when I got that calculator. It seems like I've always had it. It is a great calculator though. I wouldn't trade it for anything. I use a TI-30Xa at work. Also great and very reasonably priced. Thanks for watching!

[@zjtr10]

Most Excellent! Thanks

[@terrypickford627]

Thanks. You make this so easy. Couldn't quite get it from reading a book.

[@StuartdeHaro]

You're very welcome. I'm glad it helped.

[@darrenhoffmann7114]

Thanks mate, just the info I was after, and thanks for the metric for the rest of the world

[@hilltopmachineworks2131]

Good tutorial.

[@velcrodreams178]

Thanks man !

[@prasadjoshi9614]

Really informative... Please upload more,if with program possible... thanks.

[@marcovazquez4986]

You are right!

[@geckoproductions4128]

THANKS!

[@landar1862]

You mention to double the sfm for carbide tools. Would you recommend even faster speeds with carbide tools with high heat coatings (i.e. 1700F+)? 3X the SFM listed? Great videos by the way.

[@EvoKeremidarov]

Thank you

[@petergregory5286]

Hi, Very watchable as are the rest of your videos. One question however, what SFM would you use for cast iron, bearing in mind the varying qualities of that material. Regards

[@StuartdeHaro]

I usually use 100 for cast iron. Cast gets a lot of grief for being dirty to machine, but I personally love working with it.

[@peterbrockley]

@@StuartdeHaro I've used 70 in the past, but that was before the outer skin from casting was removed, then 90

[@krishansharma3957]

And thanking you very much for both matric and inches.

[@userwl2850]

For the metric folks 🤣 most of the steels I cut HSS wouldn't even scratch it. Excellent informative video 👏🏻

[@StuartdeHaro]

You really have to love those metals where your SFM with high speed steel is 10 or 15, or they're just flat out harder than HSS tools. I figured that was a rabbit hole I didn't want to fall down in this video though. Thanks for watching!

[@dileepgatkhane8719]

Nice video bro

[@hmservicemayihnin7339]

Thanks

[@selvakumarant3076]

Dear sir,can you tell me which book teach me basics of CNC and which book would you like top refer to find the formula as you mentioned above.

[@Richierich582]

could you post the information where I would be able to copy it? Thanks, Bill

[@Cpl.Cadaver]

Thank you.

[@StuartdeHaro]

You're welcome.

[@kittiesletsgo]

Hello guys, I want to know the force needed to cut a pipe. May I ask where to start from there? For example a 4" PVC pipe. Using a 2" circular blade.

[@najimuddin-1170]

I'm from Bangladesh. nice explain. 🥰😍

[@theartman410]

Thanks for the schooling.

[@StuartdeHaro]

You're very welcome! Thanks for watching!

[@billmacfarlane4083]

That's going to be so helpful figuring out approprate speeds for my lathe. Thanks for that. Would these speeds equate to bandsaw blade speeds? How would you work that out?

[@StuartdeHaro]

Bandsaw blade speeds seem to be a bit higher, probably because each tooth is contact with the material very briefly. You can find charts all over the interwebs with blade speeds. I'd recommend using the one provided by your blade's manufacturer.

[@genuzz]

#Cerritos college here I wish you were my MTT class teacher!

[@Petrolhead66]

Another question, is this for HSS or carbide

[@selvarajandrew4282]

OK sir. I don't no English. But I understand.

[@krishansharma3957]

sir from where you got that data of SFM . different site say different SFM that is why i am confusing so please tell .

[@StuartdeHaro]

These are the numbers I use for my students at the local community college. They are meant to be used for high speed steel tools and are very conservative to make sure their tools last through the class. Also, that minimizes the number of crashes. You can plug in any number you would like into the formula, but make sure the cutting speed you use corresponds to the material you are cutting and the type of tool you are using. You really don't want to use a carbide cutting speed with a high speed steel tool. Thanks for watching!

[@douglaspierce316]

I give you A+ thank you

[@joemariollosa9497]

Thnx

[@ezeobisochima9944]

A nice tutorial, Please which of the diameters, is it the diameter of the cutting tool or the diameter of the work piece you used in that formula.

[@StuartdeHaro]

It depends on the machine. On the mill, it's the diameter of the cutter. On the lathe it is usually the diameter of the workpiece unless you are drilling or boring a hole. Then it's the diameter of the hole.

[@vorapobautomation9760]

How to control tension of winder roller of warper machine ?

[@Doug_Edwards]

If you were using an end mill with multiple flutes how do you calculate? Thanks for the video.

[@StuartdeHaro]

The RPM is not affected by the number of flutes, only by the diameter and the material being cut. Flutes do have an effect on feed rate. I have a video on that subject.

[@jeetenderkakkar7570]

Which pulley is used in sugarcane machine and belt

[@mitchelle05]

Stuart, sir Do you have a video that discuss about feed rate in lathe turning?

[@StuartdeHaro]

No I don't. It isn't as clear cut with the lathe. There are a lot more variables. Generally, if you keep the feedrate less than the radius on your tool you should get a nice finish, but don't get too aggressive. I usually get good results with .002-.004" (.05-.10mm) per revolution. You'll find that you need to adjust on the fly to get the chip to break, especially as the diameter gets smaller but your speed stays the same. You will have to play around with settings to see what works on your machine with whatever material you are using.

[@mitchelle05]

@@StuartdeHaro thank you for the reply sir, your videos are big help,

[@chesitojlf]

Hi Stuart D Haro Great info, i recently started at a smaller machine shop. They have me run a old turret lathe for drilling parts. The machine seems to run speeds 56-265, ¿is that the rpm? Ive been drilling 1018, 1215, 1045, 4140, 4140 HT, 410, 17-4 ph, 316, duplex 2705. I use both carbide tips (they call it a spade). Also use a regular drill (i imagine its a high speed drill). I've been having a problem with chipping and breaking the tools recently even though I've used those speeds a few times for the same material. Do you know where i can get a more specific or larger list for sfm on different metals?

[@StuartdeHaro]

I'm sure that would be the RPM. Depending on the size of the drills, that may be really slow and that could explain your breaking and chipping issues. At slow speeds, it is really easy to take too heavy a feed on the drill and break it.

[@chesitojlf]

@@StuartdeHaro Oh ok, i was running 17-4 ph at 88 with at new carbide spade and it was really noisy, but they said noisy is ok for that material, but the spade broke. Do you know where i can find a chart or list for more specific types metals.

[@chesitojlf]

@@StuartdeHaro i imagine theres somebody kind of equation to find rpm using the brinnel hardness of material. Do you know of one?

[@StuartdeHaro]

@@chesitojlf I do not. Sorry.

[@oh8wingman]

So do these numbers change for carbide or carbide insert tooling?

[@StuartdeHaro]

Yes. Generally carbide can be run 2 to 3x faster than high speed steel. Of course, manufacturers of inserts will have their own sfm numbers, so check that information. Keep in mind that those numbers are geared towards production with rigid machines, so they may not work on smaller machines or where tool life is more important than short cycle times.

[@vorapobautomation9760]

How to control 2 roller winder and rewinder which speed setpoint and diameter calculate from PLC ?

[@StuartdeHaro]

Sorry. I can't help you with that one.

[@arunvishwakarma5414]

Aapse mera ek question ❓ hai Hamara roll daya 272mm hai Gear ratio 1.62 hai to Hamein stand ke rpm nikalne hai to kaise aayeag

[@santopezzotti730]

great Video. But how do you calculate the feeds

[@StuartdeHaro]

I happen to have a video on that as well. kzbin.info/www/bejne/npDOiZqtgspgf7c

[@SaleCNC]

For CNC, you get 1600rpm for aluminum, then how to calculate Feed rate?

[@StuartdeHaro]

RPM x flutes x chipload = feedrate. Flutes is the number of edges you have on your cutter. Chipload is the amount you want each flute to remove. Generally the most you want for chipload is 1% of your cutter diameter. Use less chipload for a better finish on your finish cuts. I have a video on this as well. I hope this helps. Thanks for watching!

[@SaleCNC]

@@StuartdeHaro Can you kindly do a sample for us? We just want to use CNC Lathe to cut steel. Don't know how to calculate feedrate.

[@StuartdeHaro]

Lathes are a bit different. The feedrate is given in inches (or mm) per revolution of the spindle. Your insert manufacturer probably has recommendations for the feedrate, but as a rule, I start around .004"/rev (.10mm/rev) and then start playing around with it until I get the finish I'm after and the chip is coming off cleanly. Sometimes the chip won't break or curl. It depends on the material, but if your finish is good, then no worries. I always start conservatively and then keep bumping it up to see what I can get away with.

[@Valkaneer]

What sfm for hardened steel around 58-62 Rockwell? 30ish?

[@StuartdeHaro]

For something that hard I would use a carbide endmill. With that, I'd start in the 90-100sfm range and make adjustments as necessary. Slow it down if it squeals or throws flaming chips. If the chips are brown or deep blue, you're fine. Pale blue means the speed is too fast and you should slow it down. I hope this helps. Thanks for watching!

[@binobyslar]

Please what's your recommended SFM for woods

[@StuartdeHaro]

I'm not sure, sorry. I never work with wood.

[@sushantkumar2631]

sir how can we use it in metric valve ..if tool dia is 25 mm and material is mild steel....pls tell me the formula

[@StuartdeHaro]

I show how it's done in metric starting at 9 minutes and 19 seconds. Here's the link: kzbin.info/www/bejne/iYuXgn9sab-Gr7M

[@whoareyou221]

How did you get 150 for aluminum and 90 for mild steel?

[@StuartdeHaro]

Like I said in the video, these are the numbers I use for my classes at the local community college. They are meant for high speed steel tools and are pretty conservative numbers to keep the students from crashing the machines. You can find a lot of SFM charts online with wildly varying numbers. You just have to be aware of the cutter material the chart is for (HSS v. Carbide) and the fact that most of those charts give production oriented numbers that are meant to maximize productivity and not tool life.

[@josemane4497]

How do you calculate this sir you have to machine an 18-8 stainless steel shaft with an external diameter of 76 mm.what speed in Rpm would you set the lathe to if you're using a a) high-speed steel tool b) brazed-tip carbide tool What does that 18-8 means

[@StuartdeHaro]

I go into how to do the metric calculation starting at 9:20. For a high speed steel tool, your RPM would be around 50. For brazed carbide, you are probably safe to double the cutting speed to 24 meters/minute, so your RPM would also double to 100. 18-8 is the alloy of stainless. It is made up with 18% chromium and 8% nickel.

[@brianhamilton6123]

1600.8675309 RPM, HAHA, IDK if anyone else picked up on that but I got your number lol

[@StuartdeHaro]

3 years and 169k views and you're the first to mention it. Kudos to you and to Tommy Tutone!

[@nilashahul1066]

SS 316 metril parting tool spindle speed Or feed rad ?

[@StuartdeHaro]

You want to run parting tools slower than normal tools because you have a lot of flexibility in the tool and a lot of it sticking out. The most important thing is to make sure the center height of the tool is perfect and the tool holder is square to the part. Otherwise you are asking for trouble. Feedrate can be kept the same as turning, however, if you are parting solid stock on a manual machine you probably want to finish it by hand, not under power feed. That last bit in the middle is when things like to go badly, so having some feel in that situation is very good.

[@esachan_]

Do you have, like, a reference book for this? Thank you.

[@StuartdeHaro]

Not specifically for this but it's covered in pretty much every machining textbook.

[@ahmershiraz4713]

Can you upload video for how to calculate cycle time for milling in excel for cost estimation?

[@StuartdeHaro]

Sorry. That one is a little out of my wheelhouse.

[@bollywoodindiamasti909]

Nyc video

[@20MaRk23]

Somethings wrong here Milling (Metric) Mild steel (material thickness 20mm)(1000×27÷3.14×20) = 171,974.52... sorry I don't know what I missed here, is it 171 RPM, if so that's seems really slow 🤔 or is because it should be the thickness cutter tool in Mill not material thickness like lathes??

[@sonuverma2796]

Sir that formula applicable for cnc router for portrait designing Engraving on iron

[@StuartdeHaro]

It should work on any rotating cutter. You just need to know the cutting speed for the material.

[@sonuverma2796]

@@StuartdeHaro sir I have several portrait designing stl file whom I want to engraving on iron but I have no idea about spindle rpm,step over, feed rate and plunge and step down, so how to calculate it, my cnc is chaina made and it's mach3 controller have RJ45connector

[@StuartdeHaro]

@@sonuverma2796 It’s a bit out of my wheelhouse, but with most engraving you'll be using a very pointy cutter. That point is not moving very fast, even at high RPM, so you’re usually going to be cutting at the max RPM. Check with the cutter manufacturer to see what they recommend for speeds and feeds.

[@robertchiscop3282]

Can I applying this for metric units?

[@StuartdeHaro]

Yes. I cover that at 9:18.

[@pemandu_nikoseptian5062]

Sorry sir, could you like to share with me how the rpm for threading can be calculated?

[@peterbrockley]

We threaded drill collars for the oilfield with carbide at 600 sfpm.

[@jeetenderkakkar7570]

Hello sir How to calculate rpm of activa and car

[@razaahmad7633]

is this same for flutless tap RPM calculation???

[@StuartdeHaro]

No. In general taps are run slowly since they will self-feed once they engage. They can be run faster on CNC machines with rigid tapping since you can program the feedrate to be the same as the pitch, but you still don't want to go too fast.

[@Scorpio888]

Sir i have 29 hp d engine 2200 rpm with 6 inch pulley. Tell me water fan pulley size? Because i have 8 inch water fan pulley. In this position tube well water though is best but engine on some fast speed?

[@sc1999]

silly question, im in the Uk and just learning. does this still work or how does it work in Millimetres ?

[@sc1999]

lol forget that, just need to watch more :)

[@StuartdeHaro]

I was scratching my head thinking, "Didn't I cover that?" Thanks for watching!

[@sc1999]

@@StuartdeHaro yeah lol, just as you finished the working out I paused and posted, then 3 seconds later you said “don’t worry haven’t forgot you metric boys” serves me right. But thank you very well explained.

[@sc1999]

Just to check my maths (I’m completely new to lathes, basically just at the turning it on stage) RPM = for mild steel is 27, so 1000 x 27 divided by 3.14 then times diameter, say 25mm ??

[@StuartdeHaro]

@@sc1999 (27 x 1000)/(3.14 x 25) = 27,000/78.5 = 343 RPM.

[@jw200]

Hello Stuart de Haro So im metric guy I have 10mm brass rod. With metric formula i got 1432 RPM. 1000x45 = 45000 PI x 10 = 31.41 45000 / 31.41 = 1432 I didnt know the formula, im beginner with lathe. I did my work with 600 RPM on that brass piece. So that means i did my cutting completely at wrong (too low) speed? I thought that 600 is enough. Just now i started looking around what the actual speed must be and found the videos and formulas. Im using chinese mini lathe, if that matters. So with correct speed i could and should get much better surface finish?

[@StuartdeHaro]

600 is definitely low. Since my numbers are pretty conservative and your stock size is small, you could probably run your machine as fast as it can go and you'll be just fine. With brass you shouldn't have to work too hard to get a good surface finish (at least with alloy 360). You can also try a tool that is totally flat on the top. Brass cuts very well with no rake angle. Thanks for watching!

[@jw200]

Thank you. I will try What about plastic rods? Acetal rods, acrylic rods, etc. I guess much slower because they will melt?

[@StuartdeHaro]

You can machine it about the same as Aluminum, but keep it on the low side of the cutting speed spectrum because yes, they can start to melt.

[@mohammedmal6128]

From where the 3.3 came from?!

[@shankarkulkarni7763]

how you talk .375/.3125/.250 plz tell me sir

[@What-is-thehandle]

3/8 of an inch = 3÷8=.375 1/4 of an inch = 1÷4=.250

[@Valkaneer]

I run manual Bridgeport at my shop. The leader who's been teaching me over the last few years always just gives estimates for RPMs. There has to be two different formulas, you don't run end mills and drills at the same RPMs. The formula given to me for drills was 229.2 divided by the diameter. But they've never given me the formula for endmills. Also, don't the number of teeth or flutes matter?

[@StuartdeHaro]

I'm not sure where the 229.2 came from, probably from an sfm x 3.82 (that would make it 60sfm). You shouldn't use a single number for speeds because the sfm varies from material to material. You can run endmills and drills at the same RPM. You run reamers slower (half the speed as the same sized drill) and I always run countersinks, counterbores, and anything else that has a lot of tool in contact with the part slower than calculated to avoid chatter. The number of flutes comes into play when you're figuring out your feedrate. I have a video on doing that as well. Thanks for watching!

[@Valkaneer]

@@StuartdeHaro Yeah funny thing is after I watched your video I was talking to my leader at the shop and I was telling him what you were saying that he started looking of into himself, and he was surprised to find out that they seem to use the same formula. One of the reasons he really started looking into it was we have a engineer at the shop who thinks he's an expert in programming that was running a Haas CNC (extremely light duty machine). And he was running a quarter inch end Mill at about 6000 RPM's. You could hear it screaming all the way across the shop. We were joking that the machine was vibrating so badly that it was going to walk right out the door.

[@MegaRiffraff]

👍🏻

[@krishansharma3957]

I love you sir. Sir can you tell me something about westermann table book please.

[@KJR1905]

Why do you get different rpm when doing the same values but in metric

[@StuartdeHaro]

Mostly because the 4 in the formula is an approximation of 3.82, as I said earlier in the video. 3.82 comes from 12/pi, so it converts surface feet to surface inches. If you use 3.82 instead, you should get roughly the same RPM, give or take a bit for rounding errors between units.

[@KJR1905]

@@StuartdeHaro thanks for the response. I’m trying this for the first time and my maths is terrible. When I use your example for aluminium (using 3.82) I get an rpm of 1528 When I try to use the metric formula I think I get an rpm of 1364. Is that correct?

[@StuartdeHaro]

You should be getting a lot closer than that. Are you using the same cutter size in each problem (i.e. 6mm = .236")

[@KJR1905]

@@StuartdeHaro Apologies😊 I tried to use the same as in the example 3/8 which I inputed as 9.525mm in the metric example. 1000*45/3.14*9.525

[@KJR1905]

@@StuartdeHaro tried it several times not sure what I’m doing wrong. With imperial I get 1528 With metric 1000*45 / 3.14*9.525= 136,504.4077

[@gasparini76]

What are the SFM values in meters per minute? please

[@StuartdeHaro]

I show them at 9:55

[@trey7778]

What is sfm compared to CS

[@StuartdeHaro]

They're two different ways of referring to the same thing.

[@highstreetkillers4377]

Drill length is the 2nd biggest factor after the diameter. I use a 9/16" longer than my leg in P20. I get using 4 on a manual but that is so wrong, machining is precision, that math should be accurate then round the rpm