different bits, different speeds

[Bented]

This is a nice starting range of speeds for different tooling and materials, many home shop machines lack the spindle speed to implement these numbers using carbide tooling.

Carbide tooling does not require high speeds but will handle them and also produce improved surface finishes. Speed also aids chip control.

[Black Forest]

Hey, when I'm standing at my grinder with a HSS bit, 'removing metal' is exactly what I AM doing! But I get your point.

I stand corrected!

[Doozer]

Bented, This is not CNC central.
Your chart is nice to look up a number and plug it into the computer screen.
But with manual machine tools, you just look at the chips color.
For a guy starting out in manual machining, a chart with numbers like that
is just a source of frustration and a buzz kill. I have never calculated
speeds and feeds on manual machines. Been using manual machines
for 30 years (gosh, wow, time flies). Keep it fun, just look at the chips!

--Doozer

[SVS]

A friend blew up and laminated this chart for me. 10 seconds for a sanity check on speeds isn’t enough to wound my machismo.

[Doozer]

That chart is about as attractive as looking at pictures of naked dudes.

-D

[SVS]

Sorry it doesn’t meet your high standards……you don’t use’em any how though right?

[Bob Engelhardt]

[pic]
A friend blew up and laminated this chart for me. ...

Yikes! I just posted my mill speed controller, the whole point of which is to do away with charts like that.

[SVS]

That’s great Bob. Which is more useful, TODAY, to a novice without a clue?

[Doozer]

Sorry it doesn’t meet your high standards……you don’t use’em any how though right?

Just being funny. Come on.

-D

[Bented]

Bented, This is not CNC central.
Your chart is nice to look up a number and plug it into the computer screen.
But with manual machine tools, you just look at the chips color.
For a guy starting out in manual machining, a chart with numbers like that
is just a source of frustration and a buzz kill. I have never calculated
speeds and feeds on manual machines. Been using manual machines
for 30 years (gosh, wow, time flies). Keep it fun, just look at the chips!

--Doozer

I always calculated a speed to start a job 25 years before ever touching a CNC machine.
The same principals apply, cutting speeds remain the same on manual and CNC machines, the same tools and materials.

Nothing could be more simple than the "suggested" speeds in that chart.

Low carbon steel with HSS tooling, 120-170 SFM.
Uncoated carbide, 400-450 SFM.

Exactly what is confusing about this?

[polaraligned]

Just being funny. Come on.

-D

And it was funny.

[Bob Engelhardt]

That’s great Bob. Which is more useful, TODAY, to a novice without a clue?

Fair enough.

Here's a much better idea, though:



The diagonal lines represent constant FPM for various diameters & speeds. The horizontal lines represent the speeds for all the belt & gear settings (e.g., the line labeled HLB is 140 RPM when the motor pulley is on high (H), the jack low (L), and in back gear (B)). To use, for example, you start with the diameter (1-1/2) & go up (red) to the line for the FPM wanted (125 - green), then the nearest horizontal line (blue) is the belt/gear setting to use (motor on low & jack on medium - 340 RPM). You don't actually use the RPM. You can't set your speed to a specific RPM anyhow, so that level of accuracy is over kill.

The horizontal RPM lines are, of course, specific to my lathe. But the FPM lines are universal, depending only upon the 4xFPM/Diam formula. The chart can be easily made for any lathe.

[eKretz]

Suggested speeds in any chart or table are only starting points. From there you need to dial in speed by watching the chip AND the tool edge. No speed recommendation is going to be accurate unless you have a material (including hardness if it's possible to vary that much) a depth of cut, and a feedrate suggested along with it. All of those things affect the best speed to be used. Watching the chip color can be a decent indicator of appropriate speed. Watching the tool edge (under magnification if necessary) is the most accurate and reliable indicator. When using carbide, whether you get a highly reflective finish can also be a good indicator. The thing you're trying to achieve is proper tip temperature. You don't want too cold (built up edge and chip weld issues, both leading to earlier than ideal edge failure) and you don't want too hot (rapid tool wear/edge failure). All of those factors form a sort of triangle, with your ideal speed being in the middle. Change any of those factors and your ideal speed changes as well.

And I definitely don't agree that cutting speeds will be the same on manual and CNC machines. Manual machines generally do not have the high pressure coolant that CNC machines do, nor do they have the advantage of the tool never dwelling in one place and rubbing. They also generally take much heavier cuts at higher feeds than most CNC machines (talking big industrial machines here, not home shop). All of which mean they need to run lower speeds for the same workpiece materials.

[polaraligned]

In the distant past I had looked for blue chips in carbon steel as internet rumor has it that the chips are then taking the heat from the cutter. I found that this killed my carbide life. I now look for straw colored chips. Aluminum is a lot more difficult to find the sweet spot as going too high on the SFM just causes aluminum to weld to the cutter and it becomes a PIA once that happens. I find that about 400 SFM has worked well for me with carbide in aluminum using WD-40 and air blast. Take a good size cut at a lower than "max" SFM seems to work for me.

[SVS]

Doozer,
You can make fun of my chart and my Chippendales calendar but don’t EVEN start on my Starrett tap and drill poster……

Bob,
When my buddy showed up with this chart I was probably lukewarm in my thanks. It grew on me, but I’m not evangelical about it.

Your chart reformats the data to allow machine specific lines. As a fpm chart alone I don’t see an advantage beyond personal preference, and likewise, I don’t see utility in the horizontal lines for my particular machines. (All gear heads with speed change plates.)