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#1
02-27-2008, 09:02 PM
Cutting Speed/Feed Speed

There needs to be a machining area here at the forum.

Anyways i have a question about Cutting Speed. How do i figure out the Cutting speed and feed speed for lathe and milling?

I found a few things.

Steel 50-60 Ft/min
Mild Steel 100-125 Ft/Min

I don't know what they mean by Steel ? Cold rolled? Hot Rolled?

Formula

Cutting speed = k x speed / Diameter

What is k?
#2
02-27-2008, 09:23 PM
 Burnit WeldingWeb Craftsman Join Date: Nov 2007 Location: Out in the Sticks, WI Posts: 1,354
Re: Cutting Speed/Feed Speed

K is for picking how your measuring everything
K=320 for metric K=4 for 'merican (inches)

that way when you plug all the numbers in you get a value that you can use
#3
02-27-2008, 09:25 PM
 Burnit WeldingWeb Craftsman Join Date: Nov 2007 Location: Out in the Sticks, WI Posts: 1,354
Re: Cutting Speed/Feed Speed

What are you cutting? Are your cutting tools HSS or carbide? that makes a big difference
#4
02-27-2008, 09:32 PM
Re: Cutting Speed/Feed Speed

Quote:
 Originally Posted by Burnit What are you cutting? Are your cutting tools HSS or carbide? that makes a big difference
For some reason i think they are HSS , but then again i think they are just carbide.

I know on the lathes , we just use hardened steel cutters. I will find out on the mills.
#5
02-27-2008, 09:33 PM
Re: Cutting Speed/Feed Speed

Quote:
 Originally Posted by Burnit K is for picking how your measuring everything K=320 for metric K=4 for 'merican (inches) that way when you plug all the numbers in you get a value that you can use
Oh , alright then i would use 4.
#6
02-27-2008, 10:01 PM
 backuproller WeldingWeb Tradesman Join Date: Jul 2006 Location: moncks corner, sc Posts: 454
Re: Cutting Speed/Feed Speed

Standard Sizes
Surface Feet per Minute = RPM x .262 x Tool Diameter

RPM = Surface Feet Per Minute x 3.82 / Tool Diameter
example CS is the cutting speed of the material, a property that you can find in reference books. It is measured in surface feet per minute (sfpm). Our shop uses the following values:
500 plastic
300 aluminum
200 brass
100 mild steel
50 stainless steel
D is the diameter of the tool in inches.

Example: If you were using a 3/8”-diameter endmill on mild steel,
you would perform the following calculation
Speed = (100sfpm)*4/(.375") = 1067RPM

Feed Rate (in/min.) = RPM x Chip Load per Tooth x No. of Flutes

Feed is the calculated feed rate in inches per minute (ipm).

ChipLoad is the amount of material that each flute will remove on each revolution. Each material/operation has a suggested value, which you can find in reference books. It is measured in inches, sometimes written inches per tooth (ipt). Our shop uses the following typical values:
0.005” for roughing
0.001” to 0.002” for finishing
n is the number of flutes on the tool.
Speed is the spindle speed in revolutions per minute (rpm).

Example: If you were doing a roughing pass with a four-fluted endmill
turning at 1000 rpm, you would perform the following calculation
Feed = .005" * 4 * 1000rpm = 20ipm

Chip Load Per Tooth = in./min. / RPM x Number of Flutes

in 3 /min = Width x Depth x Inches per Minute

Required Horsepower = in.3/min. / Powerfactor

Horsepower = 1.341 x kW

Metric
Surface Meters per Minute = RPM x .00314 x Tool Diameter

RPM = Surface Meters Per Minute x 318.057 / Tool Diameter

Feed Rate (mm/min.) = RPM x mm per Tooth x No. of Teeth

Chip Load Per Tooth = mm/min. / RPM x Number of Teeth
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#7
02-27-2008, 10:05 PM
 zapster Moderator Join Date: Jan 2006 Location: In A Nice Comfy Chair Posts: 13,803
Re: Cutting Speed/Feed Speed

There is a major diffrence in Carbide vs. Hi Speed..

Most times you just go untill the chips turn blue and then "back off" a bit..
But sometimes vibration will set in..

You need to figure out how fast per diameter vs. feed speed..

Small 2" diameter stuff you can "Buzz Away" in no time...

16" diameter goes way slower...
All a learning curve..

Carbide tools do not like interupted cuts..
Snap Break Shatter every time...
But Carbides will put up with heavy loads if under constant load..
Hi Speed on the other hand will put up with interupted cuts to a certian extent..
Melt usually happens and the melted tool gets in your piece...No good..
How you grind your tools makes a big diffrence also but that can get too involved here now...

Trial and error..
Go by that..
I have been grinding my own bits for 30 yrs..
All seat time..
Just like anything else you want to be good at..

...zap!
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#8
02-27-2008, 10:34 PM
Re: Cutting Speed/Feed Speed

Quote:
 Example: If you were using a 3/8”-diameter endmill on mild steel, you would perform the following calculation Speed = (100sfpm)*4/(.375") = 1067RPM
What if i wasn't using a end mill , how about a face mill.

Its 4-5" Dia with 6 cutters. If i calculate it , it turns out to like 100 RPM which i find is super slow.
#9
02-28-2008, 01:04 AM
 Burnit WeldingWeb Craftsman Join Date: Nov 2007 Location: Out in the Sticks, WI Posts: 1,354
Re: Cutting Speed/Feed Speed

Think about the surface speed of that tool though. How fast the edge is moving. Does that make sense?

like if you swing something on a string, your hand isnt moving that quick but whatever is tied to the end is really movin
#10
02-28-2008, 11:58 AM
 Magnetic Mechanic WeldingWeb Craftsman Join Date: Jan 2008 Location: Arkansas Posts: 1,202
Re: Cutting Speed/Feed Speed

[QUOTE=Bikespot;168031]There needs to be a machining area here at the forum.

Anyways i have a question about Cutting Speed. How do i figure out the Cutting speed and feed speed for lathe and milling?

I found a few things.

Steel 50-60 Ft/min
Mild Steel 100-125 Ft/Min

see attachments

lathe:

mill:
Attached Images

#11
02-28-2008, 04:20 PM
Re: Cutting Speed/Feed Speed

I did some milling today

Face mill 4-5 Dia

At about 300-400 RPM , works good.

1/2" End Mill

I tried at around 800 and 600-700 RPM , i had to be in high speed for 800 , low speed for 600 RPM. I found that at 600-700 RPM it cut better. I think it could be the machine also , because it seemed like it didn't have enough power to cut when it was in high speed.
#12
02-28-2008, 06:45 PM
 65535 WeldingWeb Tradesman Join Date: Oct 2007 Location: Irvine, CA Posts: 291
Re: Cutting Speed/Feed Speed

Start slow and work your way up, don't go any faster than you have to, in order to make deadlines and time costs. Breaking tools is much more expensive than the time you save.

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