[David Lee]

Hello, I am David from New York and this is my 1st post. Not sure if I have in correct place in Forum. I am in between jobs here and soon moving to a better location for work. I have CNC Machine Trades School behind me in 2001 and, went 6 years before I gained employment in the field. I have 2 3/4 years experience working on HAAS 3 axis Vertical and EC400 Horizontal mills. I have a long way to go and much to learn.

My school did not teach or have CNC lathes so I am weak in that area. I have been a operator of a few lathes. I love the field of work and hope to return to a good shop soon. Wish I could serve a apprenticeship. With that said, I will get to bothering someone with my first questions here..

OK..of great interest and help to me would be a few examples of usage of the 3.82 constant for calculating speeds and feeds for various cutters. In my trade school, we learned a method more used on manual machine tools and is not so helpful on CNC's. I would like to be brought up to speed on a few different end mills, high speed and carbide, 4 and 5 flute, maybe use of the constant for a drill, a tap..a few examples.

I will just go ahead and post this, if it is not allowed here perhaps a Mod will instruct me or move to correct area. Thank you and, I am pleased to be part of CNC Zone, even if I am a newbie.

[David Lee]

OK Thanks just the same folks. I will find another sorce for learning the use of the constant.

[bobo17]

see if you can find a Feed and Speeed Calculator. most tooling companies have them like sumitomo, valenite, iscar , etc.. they take the guess work out of setting feeds and speeds for cnc's. i use one from valenite and from iscar.

[David Lee]

Thank you bobo17, I will look them up. I really need to get updated on these as I was taught the old method which more applies to manual machines.

[LUCKY13]

Go to CNC CookBook, a forum member has this site and they have some softwear that is made to do this for you. It does some other things also but it apears to be very good from all the other forum members using it. Bob Warfield ( the one with the website) is great guy that post here alot and he will offer a lot of help to get you going when you get the softwear.


ANymore this question has a changin anwser. Mostly becuase of all the new cutters they are coming out with these days. You can get cutters that wil allow you to run twiced as fast, or take deeper cuts than the normal setup. They even have new cutters designed to give high speed milling results out of a low speed spindle machine. And ofcourse they have cutters designed to make the best use out of a high speed spindle machine.


The Feed & Speed calculator at Bobs site seems to be very good and it is getting updated and upgraded all the time so its not something that will get out of date as you grow.

Feed and Speeds is one of the hardest things to get a hold of when running a CNC machine. Its much different than manual milling and there is almost always more than one way to approach a job. WHen buying cutters you will find after you use something like the Feed & SPeed calculator that you can match up cutters that will work best for your machines ability. The three flute cutter are working out very good for a lot of guys cutting aluminum and soft metals on these benchtop style machines. WIth a slow RPM spindle you can get a cutter that has more flutes to give a higher surface speed to help make up for the slow RPM spindle. Bob's softwear explains a lot about all this and afcourse when you punch in the numbers on what your working with it will tell you what to run. It even tells how much horse power is need for a cut if you punch in your own number, or when it recammends a setup.


There are many threads on the site with a lot of info about all this, with others expeirances and more. Its a big site and it might take a bit of searching but I am sure you will find more info than you can go through in any short amount of time. This a CNC Tooling section down close to the bottom of the forum with lots of post and threads about diofferent problems when cutting and how to eleminate it.

CNC Tooling - CNCzone.com-The Largest Machinist Community on the net!


One thing is for sure, even a year after you have been using a CNC machine you will still be learning about this subject.


Good luck, Jess

[slowlearner]

I beta-tested the GWizard software that Bob Warfield sells on his site. I was impressed with the performance.

[davereagan]

David,
The speed charts you get with endmills and drills are good to study. Both vary with different materials. SFM is the "surface feet per minute" and I like to remember the base calculation so I am not depending on a special calculator, chart, etc. From Engineering School, I learned that if I can dervie an equation, I can bring it back ten years from now. If I am running a 1/2" diameter endmill at 1500 rpm, what is my SFM? Well, the circumference of the endmill is Pi (3.14) * the diameter, so that is 1.57" At 1500 revs/minute, the outer edge of the endmill is travelling 1.57*1500 inches per minute (2355 inches per minute) Then you have to divide by 12 inches per foot to get feet per minute, so it's 2355/12 = 196 SFM.
Let's run it backwards to check it. Let's say you have a 1/2" endmill and you want to run it at 196 SFM. 196 SFM *12 inches/foot = 2355 inches per minute. The circumference of the 1/2" endmill is still 1.57", so if we divide 2355 inches per minute by 1.57" per revolution, we get 1500 revolutions per minute again. The constast 3.82 comes from dividing 12 by Pi (3.14)

Roughly, with a TiALN coated carbide endmill, you can cut mild steel at 300-400 SFM with full engagement. Some guys run much higher with smaller widths of cut. Aluminum has no real speed limit except what might make the material gall and melt to the cutter. Coolant with oil becomes really important there. If you go to the cutting tool sites, you find speed and feed charts. www.sgs.com, www.garrtool.com, www.hanita.com