Cutting Speed and RPM on the Lathe and Mill
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- čas přidán 20. 08. 2024
- Proper rpm on the lathe and mill increases tool life and productivity. This lesson discusses how to determine the proper cutting speed for various metals and how to convert that cutting speed to the correct rpm for the tool or part.
As far as a clear demonstration, this is the best and most straight forward on CZcams.!!!
This is by far one of the most informative to the point videos I have seen. I appreciate that you kept it simple and showed how it's done. I am new to metal turning and this is a fantastic jump off point!! Thank You!
I copied your comment.... It was so good, so well written.... Thanks... Paul I am new at the Milling machine !!
I don't know how many times I have come back to this video. I am a hobbyist and don't use this every day, having these resources is great. I am grateful to you Tom and many others out there providing us this educational material.
Steve S
Thanks Steve. It's good to hear that the video is being used.
Tom
Yet another video that has taught me something I didn’t know in as many minutes as the number of other videos I’ve watched.
I was reading the comments and Wow some people really do come straight from the classroom books and calculator in hand looking for someone to critique. As for the rest of us we do appreciate these helpful videos.
I know this is an old video but I just found it and I wanted to thank you for it because this one video has (I believe) solved my premature cutter wear problem. I've been running my tools at way too fast an rpm and have been wearing out end mills much too rapidly. I also am making normal sized chips in steel now instead of a bunch of tiny needles that I'm not sure I'll ever get out of my hands completely. Priceless info for me!
I am new to using a lathe and mill and I am appreciative of all information that helps me to gain new skills. It was helpful when you showed the math that determined the relative rpm for various metals. Thank you!
Hi Dan,
I make these videos for guys like you. It's good to know they are appreciated.
Tom
Hi I'm new to the hobby, just bought a mini mill. I worked in a machine shop, over 50 years ago. Always wanted my own machines, have a mini lathe. Enjoy watching all the. videos.
It's a fun hobby, Bob.
Thanks for watching.
Tom
Thanks, I'm glad to have you on board.
As soon as I get my website up and running, the videos will be better organized and there will be project tutorials to help you learn even more.
Tom
Second time through this one. Very informative. I also enjoyed Rex Walters' explanation in the comments which answered a question banging around in my head, "Why four?" Let the sleepy viewers fall asleep: we awake ones are interested in both the how and the why. I'm looking forward to a productive new year and you'll be a part of it. Thanks.
Thanks Jim, glad you are enjoying the videos.
Tom
SFM =RPM * pi * dia (inches)/ 12. [12 inches per ft]. Pi is 3.141... or just round to 3. Circumference of bit = Pi * dia.
so
RPM = SFM * 12 / (3 * dia) or SFM * 4 / dia
Thanks Tom, for this very basic and easily understandable explanation. There are a lot of newbies for whom this is brand new stuff and what is obvious to the experienced machinist may be mystifying to the beginner. Thanks!
That's who these videos are made for. It's good to hear that they are helping.
Thanks for watching.
Tom
I've learned a great deal from these videos from Tom. I can now sharpen a lathe bit and run it at the right speed. I've had an old South Bend "Junior 9" for almost 50 years and it's high time I improved my skills. Thx Tom!
Good to hear!
Tom, I got my intro to RPN in 1970 when I started with computers. Most of the guys in the class just rolled their eyes and shook their head. I loved it, made so much sense. It was sometime in the mid 70's when the $100 simple/stupid algebraic calculators came out but no RPN. Got my HP 41CV in 81 along with a few modules and memory. I used the navigation module to replace the multiple books required for celestial navigation. I was going to answer the question.but you beat me to it😊.
+Scott Burrous
I would be absolutely lost without a RPN calculator. You nailed it saying that it makes so much sense. I' all about the logical approach to solving a problem.
Sorry if I stepped on your response. :)
Tom
To tell you the truth i was going to watch it later, but you made it easy to understand and i didn't want to stop watching it. Thank you for taking the time to share your knowledge.
I also saw your "square up stock video" and i applied it at work and works great! Thank you Tom sincerely.
For metric multiply the cutting speed by 25.4 , surface mm per minute. eg mild steel = 2540 , and use the same formula.
5/8" = 15.875mm
4* 2540/ 15.875 = 640 rpm.
Some rounded off number for the other metals.
Tool Steel 1800
Cast Iron 1500
Aluminium 6400
Brass 7500
+Jack O'Toole metric cutting speed is measured in m/min. The formula for figuring out the rpm is (cutting speed x 1000)/(pi x tool/workpiece diameter)
+Espen Andre thanks, I agree, the above is just a means of using a cutting speed quoted in feet per min with metric sized tools. Tom has a simpler answer which I overlooked before.
cutting speed fpm x 100/ tool size mm
+Jack O'Toole
I meant to post that in the video but completely forgot. Guess there's no time like the present. :)
Tom
Toms Techniques a
Toms Techniques a
Tom, thank you very much for this tutorial. I'm sure I speak for many of us who have not commented.
Thank you, very concise, to the point, very simple to understand. No stupid over loud or annoying background music or dramatic video shots.
I am looking to make my own mill, but was unsure of max spindle speed I needed to do this, you have answered this question perfectly. Now I subscribe and look forward to watching your other videos
Thank you sir.
Thanks for watching. I'm considering building a gantry type CNC mill myself.
Thanks Tom
Was trying to cut a 3mm deep oring groove in a manifold today, got it half done and broke end mill, was running way too slow 1300rpm, after seeing this vid i know i was miles off the speed, will have another crack tomorrow
Thanks
Rob
Extremely well explained. Any simpler than this just isn't possible
Well done, Thank you
Thanks!
This is right up there with the most useful info us new hobby machinist could possibly get.
THANK YOU!
Thanks for watching
The trusty HP reverse notation calculator...had one in college and still use 25 years later. Nice video. Thanks for sharing.
+djhoosier
Thanks.
Bought it in the 80's and it's still going strong. Don't know what I'll do if it gives up the ghost.
Tom
I was waiting to see the cutting saw in action! That was a big chunk of steel!
Thank you sir ! I burnt up a 1/8 endmill today because my journeymen toolmaker told me to run at 800 rpm !???? Thanx again I am a apprentice toolmaker will be watching you're videos!!
Not sure what you were machining, but 800 rpm is about a quarter the rpm you should have been using for mild steel. Was the material hardened by chance?
@@TomsTechniques no 8620 basically cold roll
Cool tutorial Tom. Reminds me of the way my Dad used to explain things to me as a kid. My Dad was old school machinist. I never took to the trade but love watching all the videos. Puts a smile on! :)
Thanks Allen, I'm glad you enjoy them.
Tom
Thank you very much, the results of my milling have greatly improve after watching your video.
+Marco Sandoval
That's good to hear.
Most people tend to run an end mill too slow because they are afraid to burn it up, but that often results in breakage. Proper rpm is critical.
Thanks for watching.
Tom
Tom, I cannot thank you enough for the compendium of knowledge that flows from this instructional video! Like you, I am dedicated to the art (or science) of manual machining, and usually rely upon intuition when setting speeds and feeds, but you clearly give me a more full understanding of the ratios that work best. Nice to know you Tom, I'm subscribed! Thanks again!!!
Thanks Eddie.
Tom. Thank you for taking your time to make these vids. I'm just a rookie at this , but am learning fast.
Thanks for watching.
Tom you are my new best friend, I have looked at the charts and tried to understand the written explanations (few and far between) but you have nailed it on the head. I was completely sold when the impact ran to loosen and tighten the tool holder a man after my own " get it done" attitude, I hate tightening and breaking loose the collets' and you have given me the proof that that is a good idea as well. Thank you so much and I look forward to your other straight forward videos. I realize this is basic to you but for those of us starting it is invaluable. God bless the internet, you-tube, your new website, and you as well.
Getting the basics down will pay off in good looking and precise parts later on.
Thanks for watching.
Tom
thank you tom Thats the simplest explanation of cutting speed. Real basic topic I know but the basic things are the most important.
Thanks Tom, one of best most informative video for a newbie like me, thanks for the time you put in for these videos
Thanks for watching.
Tom, very helpful. SFPM is easy to understand by watching your 'show and tell' method! EXCELLENT!
Thanks....13
Glad to be of assistance.
Thank you for this clear explanation. I have printed out a chart of the cutting speeds and the rpm formula. My antique Vernon Mill has no electronics, so my first task is to measure the rpm of the spindle for every belt setting. With that info I can set my rpm to fit my bit and material. Thank you again!
It's good to hear that the material is getting used.
Thanks for watching!
Tom
I appriciate your vids, they're so simple, informative and very easy to be understandable. Thank you, Tom!
Thank you.....
This is so much fun and Soothing cutting parts and puzzling making accurate pieces ..... I never knew there was a job like this
I'm so glad you taught me what speed to run my tool.
Thank you for this! I'm going on 3 years of experience in a tool and die shop (no schooling). We mainly work with tool steel and cold roll steel.
Thank you! As a hobby fitter/turner, it gives me a starting point. The rest is up to me to feel the feed rate.
I just wanna say 1000 thank you for your simple information 🙏
Chuck,
I'm not a big fan of carbide in the hobby machine shop, so all of my cutting tool videos will be HSS oriented. To answer your question, carbide is generally run around four times the cutting speed of HSS and at much higher feed rates. Well beyond the capability of most hobby type machinery.
I will be covering feed rates in a future video.
Tom
If your measuring your stock diameter in mm, use equation "rpm=97*SFM/SD" instead of 4.
Getting my mill working later this week. Thanks for the info.
RPM and feed rate determine chip load so yes, it does have to be taken into account. But that's another video. :)
It's good to hear that you are getting some benefit from my videos.
Thanks,
Tom
Awesome video there. I've been going to college training in turning and fitting, but a lot of information has been left out in thin air, making it a little risky. Thanks for the tutorial. Its gonna make life a little safer in the workshop!
Thanks Wayne
I seem to be under speeding most times, then I gradually speed up in following cuts. I never break an endmill but I take to long. Sometimes I don't have a clue what type steel I'm cutting, Hence underspeeding. I've always watched the chips to get a feel for the cut. Thanks for the videos, I'm picking up alot!
Too slow an rpm is quite common, but it does waste time and increase tool breakage. There is nothing wrong with going by the color of the chips and feel of the cut, the formula just gets you in the ballpark.
Thanks for watching!
Tom
Exactly what I needed to know.
Thanks for the video! Very informative for someone with two new machines.
It's actually a DoAll mill. When I bought it in the 80's, the Bridgeport/Textron mills weren't the quality they once were.This one has served me well over the years.
Tom
I can't thank you enough Tom for this video! I've been doing some milling for awhile now, just fumbling along. It's been on my mind to learn the proper feeds and speeds to make jobs go faster, and I now know that I have been running my mill WAY to slow. I had no idea you could remove metal that fast on a vertical mill. Thanks again!
Be sure to download a copy of my cutting speed and rpm chart from the website (tomstechniques.com). That will save you even more time.
Thanks for watching.
Tom
Thanks for that. Never understood it until I watched your video!
Thanks Tom, cut a new bit today very slight rake and used air for coolant , back gear on the BP little faster on the travel speed , all went well .
Good job.
Thank You. Just used my first end mill. Like how you made it easy to understand and follow along. Sure going to save you in my files of help.
That simplified formula is super handy. It really gets you in the ballpark in a hurry!
Thanks for watching!
I'm one year in on a Clausing. Love coming across videos like this.
What model Clausing?
@@TomsTechniques I dont know the model but they bought it new in 2016. I'll let you know when I go in tomorrow. I also operated their Vectrax and Bridgeport. I'm new to this field. Milling is different from running a turret.
@@TomsTechniques It is a standard knee though.
@@TomsTechniques Clausing 2VS08
I noticed that RPM can really mess things up if you get it outside the ballpark. I was cutting a sort of oval hole for an exhaust flange in mild steel with a 10mm thickness (just short of 1/2"). I used a 14mm endmill, and managed to completely burn it up to the point where the endmill became miscolored running at about 1400RPM. Turning it down to about 780RPM made it run so much better with a new end mill, and it didn't burn it up.
Too slow and they break, too fast and they burn up. RPM definitely matters.
@@TomsTechniques What I don't understand is, how can they survive in CNC machines running several thousand RPM?
Wow... Tom, I wish they would show videos like these in my inside machinist trade theory classes instead of boring old videocassettes that are noisy, worn out, full of horrible audio, and not as engaging. I learned more in this video about cutting speed and the tools you showed more so than seeing it in a book or watching drab by-the-numbers instructional videos. Not as interesting. Thank you for this. I'm a green, fresh, first year apprentice inside machinist and I need all the 'real world' help i can get. It's a new career and a new path to learning. Would love to see more videos like this!
Thanks.
It's always good to hear that videos are appreciated. I've taken a bit of a hiatus, to get used to this retirement thing, but there will be more to come, once I get my act together.
Very informative. I can also hear the air ratchet on the draw rod, I always wanted to try that.
I works very well, except the cheap Harbor Fright impact wrench leaks air like crazy. I bought s nice Ingersoll Rand impact wrench for it, but haven't had time to adapt it.
Tom
Thanks for the quick reply. I just subscribed to you last night. I already used the tip on squaring the vise in one pass. Works like a charm!
Great Video !!!! This is by far one of the most informative to the point videos I have seen. I appreciate that you kept it simple and showed how it's done. I am new to metal turning and this is a fantastic jump on point!! Thank You! (Copied from Keith B) Thanks Keith B..... Paul
Outstanding presentation. Thanks for teaching me a few things.
Thanks for watching
Mike better use this: rpm x number of tooth's x feedrate per tooth (0.05. = finishing) (0.1 = for removing material) or use that if u want to bake steel and ur mill
OMG thank you for some good information for a change it was very educational I've been looking on CZcams for days trying to come up with what you just told me
Thanks for watching!
Hello Tom, I'm glad I found your site it's excellent viewing. Thanks for the effort you put into making relevant, easy to understand info for us beginners.
3:33 Maths - 4 x [100] over diameter (of 5/8)
= 400....... now, to divide by a fraction [5/8] - flip the fraction......
= 400 X 8 / 5
= 3200 / 5 - now, note 5 is half of 10 = 10/2 but as we are dividing by this fraction, we flip it - so X 2 and /10 ........
= 6400 /10 = 640
Calculator not required.
Thank you very much, finally, me being a novice, got a grip on this 👍
Tom, as I've told you before your videos are very informative. Keep 'em coming.
Ron
Thank You.
I'm hard at work building a website to help organize the existing videos and new ones to come, so stay tuned.
Tom
Thank you I learned quite a bit it's exactly what I wanted to know.
What a good video! Showed me exactly what I needed to know. Kept it simple too. Very nice.
I love your videos, and unlike you I'm an absolute novice at machining, but I (and apparently RVJimD) hate memorizing or looking up "magic" numbers and formulas without knowing where they came from ("Was that 4 x cutting-speed, or 3? Or was it 6?"). It might seem obvious, but it's worth pointing out that the 4 in the formula (rpm = 4 * cutting-speed-in-FPM / diameter-in-inches) comes from rounding pi down to 3 and knowing there are 12 inches per foot.
To be explicit (this has to be the most pedantic comment in CZcams history):
The only magic number and formula you really need is one everybody remembers from primary school:
circumference = PI * diameter
RPM just means revolutions per minute. The linear surface distance traveled by the working edge of the tool in one revolution is just the diameter of the milling-tool-or-lathe-part * pi (or times 3 if you're fudging).
Algebraically, where C is the circumference in feet:
SFPM ft/min = C ft/rev * RPM rev/min
or, rearranging:
RPM rev/min = SFPM ft/min / C ft/rev
Since we have the diameter (D) in inches, not feet:
C ft/rev = PI * D in/rev / 12 in/ft
= PI/12 * D
so:
RPM = SFPM / (PI/12 * D)
= 12/PI * SFPM / D
if we approximate pi as 3:
RPM =~ 4 * SFPM / D
All of that said, in practice you'll simply memorize that last line. If you're a newbie like me, though, you'll probably just run the tool too slow most of the time and not remember the formula when you need it. That's when it's useful to know how to simply re-derive it.
(Also, for what it's worth, you've probably heard "PI R square". Pi aren't square. Cornbread are square. Pi are round! :-)
You have way too much time on your hands Rex. ;)
I actually thought about going through all of that on the video, but was afraid that half the audience would fall asleep by the end of it. Maybe I'll add a page showing where the formula came from to the reference page on my website, tomstechniques.com.
Tom
Thanks Tom for keeping it simple!!! Simple is always the best way to Go!
...... Dad??
Ah, twelve inches a foot. That's quirky, I guess. May I interest you in a wonderful alternative called the 'metric system'? ;)
Antonio A.B. How many countries put a man on the moon using metric? 😒
There is a great book, I don't know whether you can get it in the US but, it is called the Engineers little black book. It has all the formulas and charts you could ever need. Mind you I still have my father in-laws old book from when he was an apprentice fitter and turner.
I recognize that confounded RPN calculator of yours! ;-)
thanks for this video. very helpful.
Thanks. I couldn't live without it.
@@TomsTechniques used a TI-59 the last year at DeVry 1982. Never could change mindsets to the HP way. PC versus Mac maybe??
Hi Tom. Great video. Doesn't get easier than that. Another way that I do it is:
FPM / dia x .262 = RPM
The long formula is:
feet/minute=(revolutions/minute)* (Dia. (in.) * pi)/12)
The simplification factor that I used of .262 is pi/12 to convert diameter in inches to feet.
It is easier to understand the practicality if you think about it as this:
fpm=rpm x circumference
agree with everyone here. Thanks for putting this together and understandable for a first timer
Thanks for watching!
Total noob here. Just bought a 40 something year old Jet 16 drill-mill from a friend, and trying to learn all I can before I start my first surfacing/milling project. I understand the surface feet per minute, and the bit diameter, but why 4? Why not 3, or 5, or some other number. Since surface speed must be multiplied by 4, 4 must have a significance? Otherwise if it is always 4, then by default surface feet per minute for mild steel would always be 400. Then could be simplified by simply 400 / 0.625 = 640 ? I must say though your tutorial has explained bit speed better that any other tutorial I’ve seen! I certainly have more confidence to start my project than before I watched this !
I think you are misunderstanding the formula. The 4 is just a constant in an easy to remember formula to provide an approximate rpm for various cutting speeds and diameters. In the case of mild steel, the cutting speed is 100 sfpm (not 400). With your ,625 diameter part, that works out to 400/.625=640rpm. For aluminum, with a cutting speed of 500, the rpm works out to 2000/.625= 3200rpm.
@@TomsTechniques , Thank you for your quick reply. Your formula is very simple and easy to follow. Your formula helps me tremendously! But primarily the question is about the constant # 4. Is the constant always 4? Is it possible to ever be another number? Is there a reason the constant is 4? Or is it one of those things that just is?
very usefull informative video , getting back into machining after years , needed a bit of study , well explained
Thank you sir this was very helpful to me !
No problem, glad you liked it.
Very useful for my report on the milling process, thanks!
Thanks for watching
Great video! Very informative. Thanks for uploading!
Hi, I've used a simpler "no calculator" method for a long time... (40 years) it depends upon knowing a few metric conversions, but you and I came up with a very similar answer to the spindle rate for your 5/8" cutter... (16mm is 0.63" no appreciable difference...)
For a 100 FPM cutting speed, divide 100 by the cutter or workpiece diameter (so it applies to mills, drills, turning) then multiply that answer by 100. So, worked example-
100/16 = 6.25. Multiply 6.25 x 100, you get 625... Not so different from your 645? And the calculator was redundant...
For a cutting speed less than or greater than 100 FPM, just pro rate... 500fpm? 625 x 5 = 3,125 RPM
50 RPM? 310 rpm
1/16" drill = 1.6mm 100 /1.6 = 96, 96 x 100 = 9,600 rpm. As you say, a starting point... But 40 years of using my simple formula tells me it works... And... 100 FPM is 30 metres/min, so you can do a fairly rapid mental approximation from metric to imperial (calculator free)
When I started work, the old guys recommended these spindle speeds for drilling... 1,000, 500, 250 rpm for 1/4", 1/2", and 1" drills, respectively, pro rated for bigger and smaller drills, in mild Steel, run wet. I think some of them started out with high carbon steel drills.
HSS and Super HSS, we could use 1,600, 800 and 400 RPM, wet. 60% of that speed dry...
And none of it needs a calculator... (or pi)
Outstanding as usual. Thanks Tom
Thanks Terry
You bet Earl, thanks for watching them.
Awesome information and very well presented. Thank you!
Great video and simple to understand, thank you.
It’s a very good new knowledge that I got today thank you bro 👍🏻
Wonderful video and very understandable. Thank you . subscribed 💪🤘🇺🇸
Thanks, glad you enjoyed it.
Tom
Great tutorial! Thanks
Love all the info you put out
+Brian B
Thanks Brian. I'll try to get some more out over the next few days.
Tom
Very simply put and useful....
Thanks.
When I get the chance, I'll write up a reference sheet for this video and add it to my website. There have been quite a few requests for one.
Tom
Thanks Tom Jolly good show!
Thanks for watching
very good video Tom!!! Helped me out big time. Glad I found your videos
Thanks.
This is an outstanding video Tom thanks for this.
Glad you liked it. I just realized that I never posted cutting speed chart on my website. I've been working on it and it will be available in the reference section shortly.
Tom
Toms Techniques This type of info is what I and probably alot of other noobs are looking for.all the calculations and what there for.
looks like a bridgeport miller with the R8 collets. built in england. i have 3 of these. great tools.
very informative. Just getting started in milling.
thank you tom for such a helpful video
great job and easy right to the point
Noe Cortez
Thanks for watching!
Thanks for your wisdom. It really helps.
It's bad when 2 years into my apprenticeship, I didn't understand this until I watched this video lol.
It's good to get a grasp on the basics before you get too far along. I'm glad the video helped.
Tom
It was a simple formula, but I didn't know it. Thanks for the great video! I'll go search- maybe you've covered it, but perhaps a followup video on carbide? That would be great!
Thanks.
Carbide can be run at roughly 4X the cutting speed as high speed steel.
Tom
That was quick! Thanks for the response!
Thanks! Even though i'm in my 3rd year of my machine tool class and should know this. I still wasn't quite sure about it. Usually just asked a classmate.
The best way to learn it and remember it is to get out and make some chips. Nothing makes a concept sink in like practical experience.
Tom
Another warped and twisted mind - Didn't know anyone else used RPN,
can't live without it. Use apps for my phone since my HP41-CV bit the
dust.
Oh yeah, liked the video. Sent it to my brother who is just getting started on mill and lathe.
+Scott Burrous
I find it impossible to use an algebraic calculator. Use and RPN at work and in the shop, plus an app on my phone. It's so logical, I can't believe it isn't more popular.
Tom
+Scott Burrous Can you explain what this is? I am unfamiliar with the concept. Thanks.
+GunFun ZS
Reverse Polish Notation was used on engineering calculators starting in the 80's and has developed somewhat of a cult following. It makes quick work of solving expressions containing parentheses because it doesn't require the use of memories or equal signs. For instance, to solve the expression (5-3)*(6+2), you would simply enter 5 3 -, 6 2 +, followed by *. If there are deeper sets of parentheses, you just work from the center out, just like you would do with paper and pencil. It seems a bit awkward at first, but once you get the hang of it you'll never go back to algebraic notation.
Tom