I have seen posted here before a formula or ration for machining speed. I
didn't understand it at the time, and still don't but a metal working guy I
know rattled it off to me the other day, and I was finally realized that
this is something I probably need to know. That and where to look up the
machining speed for various metals. Until I have just been guessing.
Probably cost me more than a few cutters and certainly has cost me time when
I set something up to run slowly so as to be sure not to break cutters.

Can somebody please point me in the right direction? Not just the
ratio/formula, but some basic guidelines in how to apply it. Thank you.

Bob La Londe wrote:
I have seen posted here before a formula or ration for machining speed.


(...)


Some feeds and speeds:
http://en.wikipedia.org/wiki/Speeds_and_feeds

Have a look at chapter 8, pages 8-19 and 8-20 of:
http://metalworking.com/tutorials/AR...524-index.html

--Winston

--

Don't *faff*, dear.

"Bob La Londe" wrote in :

I have seen posted here before a formula or ration for machining
speed. I didn't understand it at the time, and still don't but a
metal working guy I know rattled it off to me the other day, and I was
finally realized that this is something I probably need to know. That
and where to look up the machining speed for various metals. Until I
have just been guessing. Probably cost me more than a few cutters and
certainly has cost me time when I set something up to run slowly so as
to be sure not to break cutters.

Can somebody please point me in the right direction? Not just the
ratio/formula, but some basic guidelines in how to apply it. Thank
you.


(4xCS)/D = RPM is the formula.
4 = A constant (been too long for me to remember how it's derrived, but
there is a formula for that also)
CS = Cutting Speed (Surface Feet/Minute = SFM): You find this in tables
for the material you want to machine.
D = Diameter: Diameter of the workpiece at the tip of your cutting tool
(not the OD of the material) in inches
RPM = The RPM you should be turning the work (lathe) or cutter (mill).

So, say the CS for an aluminum alloy is 3000 SFM

You are turning it on a lathe to a diameter of 3.0", the material is
3.125"
so:

4 x 3000 = 12,000

12,000/3 = 4000 RPM
You should run the lathe at 4000 rpm
If the lathe won't run 4000 RPM, then you just run it as fast as it will
go.
Note that this is IF you have the part clamped properly.

Note 2: SFM, surface feet per minute is the distance of material passing
by the cutting tip in 1 minute. This has _absolutely nothing_ to do with
feedrate so do not get the two mixed up.



--
Anthony

You can't 'idiot proof' anything....every time you try, they just make
better idiots.

Remove sp to reply via email

Anthony wrote:

(4xCS)/D = RPM is the formula.
4 = A constant (been too long for me to remember how it's derrived, but
there is a formula for that also)

Anthony:

I believe it comes from:

CS X 12
------- = RPM 12/3.14 = 3.82 then rounded to 4
D X Pi

CS is in surface FEET per minute. Multiplying it by 12 changes it to
surface INCHES per minute.

Diameter in inches X Pi of course gives the circumference in inches.

--
BottleBob
http://home.earthlink.net/~bottlbob

On Apr 14, 12:53*am, BottleBob wrote:
Anthony wrote:
(4xCS)/D = RPM is the formula.
4 = A constant (been too long for me to remember how it's derrived, but
there is a formula for that also)

Anthony:

* * * * I believe it comes from:

* * * * CS X 12
* * * * *------- = RPM * 12/3.14 = 3.82 then rounded to 4
* * * * * D X Pi

* * * * CS is in surface FEET per minute. *Multiplying it by 12 changes it to
surface INCHES per minute.

* * * * Diameter in inches X Pi of course gives the circumference in inches.

--
BottleBobhttp://home.earthlink.net/~bottlbob

How about meters/minute
3.28 X SurfaceFeet/Minute=Meters/Minute (3.28 feet per meter)
FYI: dont get the 3.82 mixed up with the 3.28!

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