Calculating cutting speeds

Hi out there,
This is something people always quote me formula's.
e.g. Bar dia Divided by 'pi'x FPM. or what ever

Just like 'conceptsmachine' from the speeds and feeds debate.

The F.P.M in the acual speed formula
comes from where.'The manufacturer's' of the tip or tool that you are using.All of who want you to use more tips etc.

I would be rich ,if every time a sales man told me I am running to slow.

If you are cutting at 1000rpm with a .002" feed
it is the same cycle time as cutting 2000rpm with a .001" feed.

With technolagy improving all the time I like to keep abreast of it and often invite these sales people to our workshop to cut steel, proof is what I want.Twice in the last year I must admit that I have been proved wrong.But I am glad of it as this keep me on my toes,and to the fact that we are always learning.

In my game,a cycle time is everything,but the 'correct cycle time' is the one that gives me the most correct components at the end of the day
at the least cost.

The F.P.M in the acual speed formula
comes from where.'The manufacturer's' of the tip or tool that you are using.All of who want you to use more tips etc.

Click to expand...

Sounds a bit too much like a conspiracy theory to me. What percentage of the manufacturer's recommended surface footage have you found to give the maximum productivity AND minimum insert cost?

its my understanding that the materials will dictate the speed.
if your running stainless at aluminum speeds and feeds you will soon learn that it dont work like that, you know that.
the cutting tool companies spend a lot of $$$$ to be competetive othewise they lose market share.
yes 2000 r's and .001fpr is the same as 1000r's and .002frp. is it correct? i would have to check with a applications engineer.
the other day when i mentioned my old Bridgeport feed and speed chart i felt that the recommended speeds and feeds were way to fast, boy was i wrong good finish and fast times.
that was 25 yrs ago.
i wouldnt imagine what todays speeds and feeds would be with diamond inserts and 30,000 rpm spindles.
have the app. eng do a demo then leave yo 10 inserts to test. then you can tweak to your hearts content, at least for 10 inserts...jim

i like to play the speeds and feeds game myself. you would be suprised at the technology in cutters these days as compared to just 15 years ago when i was green. time is money after all and good cutters do pay for themselves. the charts and books of old are way out dated in my opinion. sometimes the manufacturers recomendations are right on and the proof is in the pudding. i feel the same way about salesmen sometimes wanting to push their product to get you to buy more of this and that from them. but if they can show you that it works with the machines and materials your working with why not support them as well.

Cutting speed is figured by the diameter of the work piece in turning & diameter of cutter in milling. Formula is SFM=.262(constant) X diameter(inches) x RPM. In any type of tool remember that speed kills. Wrong grade &/or RPM & you'll struggle all day. Running slow, get a PVD coated old carbide grade & you can cut all day on a manual lathe. The .262 constant is actually pi (3.14) divided by 12 to get the result ro be in surface feet per minute. To find RPM you work backwards, RPM = 3.82 X SFM / diameter. If you are on a manual lathe your sfm is changing after every pass so start in the middle range. Good luck.

Yes your 1000 RPM and .002 rev is AS FAST as 2000 RPM and .001 rev, but in many instances cutting the slower RPM and the heavier feed MAY BE more efficient, in both cycle time and in tooling ware. I believe that someone stated it already, but the material and tooling composition dictate S&F, leaving out work holding conditions.

Any speed and feed chart, or statement by a salesman, is never written in stone. Never. There are way too many variables. If a cutter is advertised to cut material"x" at this rate of speed, this advertisement assumes perfect conditions. What if your cutter needs to hang out from the holder to clear a clamp? It's less rigid. What if your cutter is running out a little? That can compromise efficiency. What if your machine is a little older and worn out? What if you have a Haas instead of a Mori Seiki? What if your set up is not rigid? See what I'm getting at? And by the way, if you run a cutter at 1000 rpm with a .002 per tooth chip load, and then change to 2000 rpm with the same chip load, you will still put more pressure on the cutter than at the slower speed. That's another thing to keep in mind.

Good replys,
The material you are cutting is very relevent of course, but the point i was making is you still have the recommended cutting speed (FPM).

Each supplier will give you a different cutting speed for the same apllication.

As said earlier by others,lots of variables apply when cutting.

What do I use?

I promised not to mention it.

If you want a fast way to play interactive "what if" games with all the elements (SFM, RPM, IPT, IPR, IPM, HP, etc.), try this free program (ME Consultant). The User Guide walks you through the terminology, plus offers some thoughts on other things you need to consider, beyond just the numbers.


http://dl.winsite.com/bin/downl?14500000037133

Hello everyone a new member here so expect some Du mass questions haha. Mrainey I couldnt get the link you posted to work. Could you give me some assistance on finding that page.

I understood everything you guys have said so far on this post except the .001 and .002 feed. I have some machine shop experience but was really taught on a manual machine at by a old cogger that told me what feed rate depth of cut and spindle speed. Trust me there was never any calculations involved. After that I just went with estimations. ( we were machining R&D components at the college not really big on making profit there). But I am wanting to get into some cnc work and was wondering if you could help me with some of the terms I don't yet understand.

Thanks guys I am really excited about finding this web page.

Todd

Don't know what the problem is. Try this link.


Read the Terminology and Using sections of the User Guide first, before you play with the program.


http://bellsouthpwp.net/r/s/rsnmar/MEConsultant20.zip

Thank you Mrainey

That worked alot better