Speed & feed from Machinery Handbook equation?

# Thread: Speed & feed from Machinery Handbook equation?

1. Diamond
Join Date
Mar 2009
Country
UNITED STATES
State/Province
California
Posts
6,607
Post Thanks / Like
Likes (Given)
131
1275

## Speed & feed from Machinery Handbook equation?

The equation: N = (3.82 x V) / D

N - spindle rpm
D - workpiece diameter
V - cutting speed (fpm)

From Machinery Handbook:

Uncoated cemented carbide tool (probably a ChiComm C5).
V = (520, 13) or (640,7) or (310, 36) or (345, 17). (X , Y) are (speed, feed) from page 994 25th edition.

workpiece is 316 SS 0.4 diameter. Target diameter is 0.375.
V = 310, N = 2960 rpm.
V = 520, N = 4966 rpm.

These rpm numbers are kind of high. Are they correct?
The power feed box has a min to max control. Would it be tacky to paste masking tape with feed rates (in/rev) on the feed box.
That would not be too bad. Just measure the travel for different dial settings. Who would do something like that?

The max rpm of the machine is 3000 rpm.

(In case you wonder why a simple question, I do checks like this once in a while for the fun of it....)

2. Diamond
Join Date
Jul 2007
Country
UNITED KINGDOM
Posts
5,533
Post Thanks / Like
Likes (Given)
3496
2874
The translation of the formula
circumference (in feet) is D(inches) *pi /12

N=cutting speed (FPM)/Circumference (in feet) = V/D *12/pi = V/D * 3.82

Those rpms are right for thise cutting speeds and diameters.

Stand back. The chips will be hot!

3. Diamond
Join Date
Mar 2009
Country
UNITED STATES
State/Province
California
Posts
6,607
Post Thanks / Like
Likes (Given)
131
1275
I am ashamed to say that I run in the 750 - 1000 almost all the time. Without coolant. But with threads oil is used, at speeds in the 300 rpm range.

Wonder why the Machinery Handbook does not have different numbers if you are using coolant or misting?

4. CJD
Aluminum
Join Date
Aug 2019
Country
UNITED STATES
State/Province
Texas
Posts
157
Post Thanks / Like
Likes (Given)
17
24
That's what I have been wondering. Based on my experiences with just air jet cooling, I have to assume the Manual assumes you are using flood cooling so heat is not a factor in the cut. You would think there would be a conversion factor when using mist and dry. I am sure a machinist prior to the CNC days would know how to adjust the rates based on cooling.

5. Diamond
Join Date
Mar 2009
Country
UNITED STATES
State/Province
California
Posts
6,607
Post Thanks / Like
Likes (Given)
131
1275
In the past (and including today) I coat the workpiece with oil and then spin it up.

I would question that assumption a bit. Not al coolants are the same.
On the other hand the coolant factor might only be a variable for surface finish and cutting tool life.

Off Topic:
If the Olympic Games ever make it to Afghanistan there will be a new event: Catch the C-17 taking off.
In the case of a tie winners are determined by who hangs onto the plane the longest.

6. Titanium
Join Date
Oct 2010
Location
Dewees Texas
Posts
3,512
Post Thanks / Like
Likes (Given)
37
1164
First shop I ever worked at that we really paid attention to speeds was a multiple spindle screw machine shop. The owner had one of those paste board slide rule calculators (from La Salle/Quanex) for figuring speeds and feeds. I got one when I started my own shop and have never manually figured speeds. Always knew I could have looked in the Machinery's Handbook but as long as can find the slide calculator I will not need to.

I might make the assumption that the recommended speeds are with flood cooling and machining dry would call for a speed reduction.

In that multi shop the customers would supply hex bars with their individual logos stamped on the flats. He did give them a nickel per part discount if the bars were from Carpenter. We could run them 10% higher than the book speeds and still get very long times between tool sharpenings. Never found the high limit that would give regular time between sharpening tools.

7. Diamond
Join Date
Jan 2007
Location
Flushing/Flint, Michigan
Posts
11,110
Post Thanks / Like
Likes (Given)
665
8879
So a four inch cutter or part and SFM is close to spindle speed and 1:1. IE: Rpm equals surface footage sort of.
One inch part or cutter 1/4 the size so four times the desired SFM at the spindle.n 1/2 inch 8 times.
12 inch 3 times bigger so 1/3 at the spindle and so on.

I have to estimate all the time on a floor so this is how make a to guess as to where it is and where to go.
Not accurate or perfect but close and who is to say 400 SFM different or better than 382.
I find this ratio handy when thinking about surface footage.

Now surface footage to miles per hour as if dragging a cutting tool outside your car........Oh my, cutting tools seem awful slow.
150, where the fun begins is 13,000 SFM which is a whole different range of metalcutting and above this a fair amount everything changes.
Supersonic was a thing at one time.
Bob

8. Diamond
Join Date
Mar 2009
Country
UNITED STATES
State/Province
California
Posts
6,607
Post Thanks / Like
Likes (Given)
131
1275
This is finished at 2400 rpm with a feed rate on a Hardy lathe set to 16 and high/low switch set to low.
Looked at the finish on a 50X inspection scope. No lines. Just small craters. Stainless doesn't look so
hot when looking at it up close.

9. Originally Posted by CarbideBob
So a four inch cutter or part and SFM is close to spindle speed and 1:1.

I have to estimate all the time on a floor so this is how make a to guess as to where it is and where to go.
Not accurate or perfect but close and who is to say 400 SFM different or better than 382.
I find this ratio handy when thinking about surface footage.
Bob
I gave that one to LilRob some years back, he thought it was a hoot. Just slightly over speed.

Matt

10. Cast Iron
Join Date
Jan 2016
Country
UNITED STATES
State/Province
New York
Posts
353
Post Thanks / Like
Likes (Given)
7
96
Originally Posted by rons
The equation: N = (3.82 x V) / D

N - spindle rpm
D - workpiece diameter
V - cutting speed (fpm)

From Machinery Handbook:

Uncoated cemented carbide tool (probably a ChiComm C5).
V = (520, 13) or (640,7) or (310, 36) or (345, 17). (X , Y) are (speed, feed) from page 994 25th edition.

workpiece is 316 SS 0.4 diameter. Target diameter is 0.375.
V = 310, N = 2960 rpm.
V = 520, N = 4966 rpm.

These rpm numbers are kind of high. Are they correct?
The power feed box has a min to max control. Would it be tacky to paste masking tape with feed rates (in/rev) on the feed box.
That would not be too bad. Just measure the travel for different dial settings. Who would do something like that?

The max rpm of the machine is 3000 rpm.

(In case you wonder why a simple question, I do checks like this once in a while for the fun of it....)
For HSS tool bits.
4 x SFM / diameter = RPM

SFM (Surface Speed per minute).
Low Carbon Steel = 60
Brass = 80
Aluminum = 200
Tool Steel = 40
Example 4 x 60 / 2"dia. = 120RPM

Roger