turning spindle speed

Mutt

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Could some one shed some light on this subject for me please
This is a link to a speed chart for turning (lathe)
,
https://littlemachineshop.com/Reference/CuttingSpeeds.php#Milling

But I am not understanding some thing.
It has 3 inputs. One is the work piece diameter, so that's self-explainatory. But if I type 1.00" work piece diameter and use 1018 plain carbon steel SFM (850) for steel, the rpm comes out to 3250 rpm spindle speed? That can't be right can it?My 1236 lathe doesn't turn anywhere near that fast. What gives? Thanks
 
I tried it, when I put in 100 surface feet and 1.0 inches is showed me 320. When I put in 0.1 it showed me 3280-

850 seems to be pretty fast.

I believe you put the decimal in the wrong place.
 
My end shows different

The chart shows material and HHS sfm and carbide SFM. Using the Turning chart, material 1020 , 1.00" work piece diameter and the chart shows 850 Surface feet per minute. When I hit calculate, the calculator shows 3247 rpm

My lathe goes from 70 to 1400 rpm spindle speed

How does the spindle speed (rpm) relate to Surface Feet per Minute?
 
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The HSS speeds look reasonable, the carbide seems fast to me also- it may be those are correct maximum speeds for industry, to maximize material removal in the quickest possible time
 
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You do not say what cutting tool material you are using, HSS or carbide; for HSS, it would be around 400 RPM, for carbide, about 1200 rpm.
 
I assumed one looked at the chart. The HHS SFM is only 125-215. I rarely use HHS, because I haven't a guided way to grind it. So where can I find a chart that is actually close to what I need for carbide? This one is outta wack....
 
That HSS guideline for HSS is too high. should be 80 - 100 fpm, unless you enjoy burning up tools.
 
If you are using inserts, there should be a sticker on the pack that shows you the cutting speed for steels. If not, go to the insert maker's catalog and look it up. Most of the time, your speed will be faster than 1400 for mild steel when turning a small work piece.
 
I’ve wondered about that chart before. According to it, the smallest diameter of 6061-T6 that my lathe should turn at its max speed of 2000 rpm with an HSS tool is just under 1”. I’m glad my lathe doesn’t know that. :)

The lead in to the turning speeds chart says it is based on a feed rate of .004/rev, a DoC of .040 and a tool life of 180 minutes. The tool life parameter suggests to me that Mark (post #4) is right, the chart is based on maximum material removal rate at the expense of tool life, as in an industrial environment. But, I could be wrong. I was once before. :grin:

Tom
 
Most of the time the suggested speeds on the inserts from the manufacturer are not realistic with the small lightweight machines we have.
The speeds they show are for machines that weigh 10,000 lbs and can spin 8k rpm or more.
I would recommend just chucking a piece of material up and trying different speeds and feeds. Getting the correct tool, either HSS or insert, makes a huge difference.
I use the inserts for aluminium often for almost any material. They leave a nice finish on 304ss. But they are delicate and won't take much abuse.
 
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