SFPM and feed rate

M

Mutt

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So How does one determine SFPM using the chart on the side of the lathe ?
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Gearbox Levers; Feed Rate Chart - Grizzly g4003g Owner's Manual [Page 31]

Grizzly g4003g Manual Online: gearbox levers, Feed Rate Chart. Notice Never Move Levers While The Lathe Is Run- Ning, And Never Force Any Lever When Shift- Ing. If The Lever Will Not Engage, Rotate The Chuck By Hand While Keeping Light Pressure On The Lever. As The Chuck Rotates It...
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A guy on Youtube sent me this chart also.
speed rate.jpg
How are the 2 combined to tell ya where to put the gear box handles
 
The chart is based on the RPM of the spindle and the cutting diameter of the material, it has nothing to do with the feed gearbox levers. If you don not have variable speed, then you would set the spindle RPM to the closest RPM for the material and tooling being used. As you turn down a material the spindle RPM would increase to maintain constant SFM. Published SFM (SFPM) are typically for more rigid machines so for carbide I dial down the SFM a bit on my 1340. The gearbox sets the feed rate of the cutter into the material (IPR), which is different then the SFM. You also need to consider the type of cutter/insert profile, DOC, if you are removing maximum material or doing a finishing cut, etc.

Turning Formula Calculator - calculates automatically for surface feet per minute (SFM), revolutions per minute (RPM), inches per revolution feed rates, inches per minute feed rates, and cubic inches per minute metal removal rate

Turning Formula Calculator for SFM, RPM, inches per rev, inches per minute, and metal removal rates
www.carbidedepot.com
 
Enter RPM
spacer.gif
Enter D
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600X1.00X
pi.jpg
/12
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=157.080
so like this . how does this determine what long. feed rate I should use?
 
It doesn't. Feed rate depends on a lot of factors, Hp, roughing, finishing, depth of cut, nose radius etc. On my lathe I like to rough one half of the dial or .1 off the OD. I don't have enough Hp to pull a decent feed rate so my feed rate is down in the finish category. If your finish passes are like a phonograph record = too much. On roughing I try and pull as much as I can without bogging the motor.
 
Mutt said:
So How does one determine SFPM using the chart on the side of the lathe ?
Click to expand...

I don't bother. I listen to the machine, if it is complaining, I choose a different RPM or a different DoC, sometimes change the machining lubricant.

For parting off, I like slow speeds (70 RPM) and lots of lube
For turning, I like 360 RPMs
for polishing, I like 1000 RPMs.
For threading, it's back to 70 RPMs with light cuts.

How are the 2 combined to tell ya where to put the gear box handles
Click to expand...

For roughing, I generally use the B-2 slot in the Norton gearbox.
For finishing, I generally use the D-2 slot.
For threading, I use the setting for the thread I want to cut.

But these are all things you will work out for yourself. The trick is to listen to what the machine is telling you.
 
that's what I've been doing for the last 20 years. Just figure I might try logic
 
Mutt...I do not have your answers and I occasionally have issues, saying that I can say I have calulators, charts, watched videos and I can't get a straight (or understandable) answers. Having a few types of material test bars has been the most helpful. I played around with rpm, feed rate (power feed) and depth of cut. I know they'll be debate but, I've given up on HSS. I can have beautiful finish on SS, aluminum and some sort of tool steel (A60 I think it is) With Carbide I have just done away with any cutting fluid and don't be afraid to take deep cuts (up to .500mm) that's where I found I need to balance RPM and power feed until it looks good. Two more things to gauge that on is, are you getting rats nest chips or small chips? (You want to stay away from the nest in favor of chips) and watch the color. Bigger bites help get you there,but I imagine if you play with RPM and feed rate you can replicate...good chip color. Again, there maybe variation due to material, but straw color to blue would signify your chips are taking the heat with it rather than your tool of work piece.
Again, just a laymen looking for answers myself just sharing where I got to after much frustration (I still have it trying to decode inserts! And yes, I have all the deciding charts!) It really is difficult to have folks that do this stuff second nature, try to explain to us green horns.
Good luck,best wishes.
 
so long strings are not what is wanted, just small silver chips?
 
Yes, and depending on the material....silver may not be ideal. I think for the first year, i was turning too slow, or afraid to take a bigger bite. Are you using carbide inserts? What was the last metal you cut? As finding an easy formula for this wasn't happening for me, changing rpm, feed and D.O.C, really help pull it together. Wish I had an easy answer, as you probably already found, it doesn't appear to be out there.
 
I cut use my lathe everyday. Various kinds of mild and medium carbon steel and aluminum, I don't mess with stainless much. Yes, I use carbide inserts on almost every lathe tool I have.
 
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