Cutting speeds

[mike4517]

Does anyone know of a computer program for working out cutting speeds


Mike

 

[mklotz]

Take a look at SPEED and DIAM on my page.

 

[rake60]

Little Machine Shop offers a chart of recommended speeds. LMS Cutting Speeds

The listed speeds for carbide are a good bit higher than I would run.
On 1018 cold roll steel I run carbide at 300-400SFM
The chart recommends 800-885SFM

For HSS tools on the same material I'd run 150SFM
The chart recommends 125-215SFM

If you know the SFM you want, it can be calculated with a very simple formula.
SMF / Dia X 3.82 = RPM

To achieve 200SFM on a 3" Dia work piece:
200 / 3 X 3.82 = 254 RPM

 

[John S]

Problem with many programs for sppeds and feeds are they are geared to industry.
Ok for the guy with 22 horsepower at the spindle but not much good for the average X1 /X3 machine.

Marv has put forward on of his very good programs.

I'd like to point to a cheap program called Machinist's Mate from http://www.wadeproco.com/

Usual no connection other than a satisfied user.The speeds and feeds module in this are aimed at the home shop guy. Also has trig modules, measurement over dovetails and even a small program to draw sprockets.

.

 

[mklotz]

If you know the SFM you want, it can be calculated with a very simple formula.
SMF / Dia X 3.82 = RPM

To achieve 200SFM on a 3" Dia work piece:
200 / 3 X 3.82 = 382 RPM

sfm [surface ft per minute] = { (d [in] * pi) / 12 [in/ft] } * rpm [rev/min]

sfm = { d [in] / 3.82 } * rpm

rpm = (3.82 * sfm) / d [in]

(200 * 3.82) /3 = 764/3 = 255 rpm

Since cutting speed is seldom hyper-critical (most sfm suggestions are given as a range, anyway), 3.82 is generally rounded off to 4, which makes the calculation easier to do mentally.

One of the advantages of my program is that all the SFM specs are included in a data file. As you converge on the surface speed that works best for your material and your machine(s), you can edit the file to use that number, thus producing a program tailored to your needs.

 

[rake60]

Sorry I did it a worng button on the caculator when I made
the original post. The correct answer to the example would
be 254.66666 not 382

Rick

 

[Rog02]

Sorry I did it a worng button on the caculator when I made
the original post. The correct answer to the example would
be 254.66666 not 382

Rick

Sheesh, and I thought you were going metric on us Rick. :big:

 

[rake60]

Sheesh, and I thought you were going metric on us Rick. :big:

Na, somedays my hands work faster than my head.
Yesterday was definitely one of those days.

 

[BobWarfield]

I like Mike Rainey's MEPro. Does the trick for lathes, mills, drill presses, and has a bunch of other functions as well. Several nifty features including calculating how many HP are needed, and letting you tell it your max spindle speed so it can do the tradeoffs.

http://www.cncci.com/products/mepro.htm

Best,

BW

 

[shred]

I use AutoEditNC. Free and with a little de-rating, the numbers work well for my tools.

 

[Mcgyver]

i'll go even simpler than Rick.

rpm = 4 * CS/ dia

that's all there is to it. mill, drill, lathe, whatever....cutting speed is the speed the work travelling past the tool....and it is not an exact thing, rounding from 3.82 to 4 is fine. It's a number someone picked looking at where, as speed is increased, tool wear starts to accelerate. its not an exact thing, for example if the answer is 600 it'll still work at 580 or 620.

look up and memorize a few cutting speeds for stuff you commonly cut. For instance HSS on steel is 60-100 (tougher ones like tool or chrome moly toward the slow end), brass is 200, AL is 400 or there abouts. Then using the simple formula you can do it on the fly in your head or with a $5 calculator. the 5% of the time when its some other alloy, then you look it up.

There is no disadvantage in going slower and often with light home machines its more in keeping with what the machine can handle. If you're in production maxing out speed might matter, but not for us. Error on the slow side and you'll be fine and no need to over complicate imo.

 

[IanN]

Hi,

I agree with Mcgyver - the information you read about cutting speeds, tool angles etc is based around production requirements (removing the maximum amout of material in the shortest time and at the minimum cost) and factors in things like machine down time for tool setting and the cost of sharpening and regrinding tooling (or the cost of replacment tips if cheaper).

You should experiment and see what works best for your kit.

Also, I find that the cutting speed data is usually presented the wrong way, there is no point in calculating an optimum speed if your machine cannot run at that speed. My lathe has three speeds (OK, six with backgear) I have a chart marked FAST, MEDIUM and SLOW and against each category the material/diameter range that I have found give the best results.

Ian.

 

[rake60]

I agree with Mcgyver - the information you read about cutting speeds, tool angles etc is based around production requirements (removing the maximum amout of material in the shortest time and at the minimum cost) and factors in things like machine down time for tool setting and the cost of sharpening and regrinding tooling (or the cost of replacment tips if cheaper).

Ian.

Very good point here!
If you go to an industrial insert suppliers index and look up a cutting speed, be very
careful to read the fine print. They all advertise their designs can be run faster and cut
deeper than ever before. Those speeds are based on an estimated tool life of 10 minutes.
Not very practical but it does look impressive in print!

Rick