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Chris Lina
07-22-2006, 02:39 PM
Hi guys,
I am new to this thread and hobby. I have been researching milling machines for many months now in preparation for purchasing one. I am a total rookie as far as maching is concerned but I want to learn.
My main question is concerning spindle speeds (rpm's) of various machines. Some mills advertise speeds 80- 2720 rpm's and others 120-1550 rpm's, I will be milling aluminum, mild steel and stainless. Is there a rule of thumb as far as spindle speeds are concerned? Is more low end better than high top end? The machines I'm referring to are the Jet 836 and the Jet JTM-2What are the advantages of higher or lower spindle speeds? Thank You.

Millman
07-22-2006, 03:13 PM
Go for the lowest RPM's. You can use more tooling that way, the cutters will last longer,......

tattoomike68
07-22-2006, 03:13 PM
I would want the greatest range of speeds, the upper end for small hole drilling and the lower range for milling and tapping.

80- 2720 rpm sounds good.

BadDog
07-22-2006, 04:09 PM
As already said, widest range is almost always preferable to more limited range; as long as it is not too granular in increments. But obviously there are also many other things to consider such as rigidity, work envelope, intended use and so on that may make the other with smaller range a better choice.

SGW
07-22-2006, 06:19 PM
Speed range can be fixed by getting the machine with a 3-phase motor and adding a VFD. In fact, speed range questions aside, I'd suggest you do that anyway, just to get the speed control flexibility a VFD gives you.

You are looking at two very different-size machines there. I'd choose the machine you have room for. While a lot of people argue "bigger is always better," and that may be true from a strictly functional point of view, us home shop guys have to think about moving the thing into our shop -- and possibly out, if we move. Even the JVM-836 is no lightweight, at 1500 pounds or whatever it is.

That being said, slow speeds are necessary for things like slitting saws and boring heads. A 4" diameter slitting saw is about 1 foot in circumference (to a rough approximation), so to get a cutting speed of 75 feet per minute, a reasonable guess for cutting steel, you'll need about 75 rpm.

You'll need high spindle speeds for tiny cutters. If you have a 1/16" diameter end mill, that's a fraction of an inch in circumference, so to get any kind of reasonable feet-per-minute cutting speed, you need to really whizz it. But since in a home shop one isn't concerned about production rates, a slower than ideal speed can be lived with. It will just take longer to cut.

What you can't live with is too fast an rpm for the size of the cutter; you'll burn it up in short order.

JRouche
07-22-2006, 09:37 PM
I would go with the slower speed machine. You can get a spindle speeder if you want higher speeds. JRouche