Best spindle for Low RPM

[gerryv]

Hi,

I've seen a number of comments suggesting that (some/all?) spindles get pretty growly and rough below 3000 rpm. I'm wondering if some are better than others at low (say 600 to 1500 rpm.)

Beyond the usual benefits of a spindle, I'm thinking about the practicality of using one (a) to occasionally double as a drill to conserve travel on my Buddy 32, and (b) so that I could use the broad range of milling bits available to machinists when I'm doing soft metals and plastics.

Speeds and power are not important in my case as it's not a production machine.

Thanks much,
Gerry

[bcammack]

Power does drop off as the RPM falls. A 5hp Colombo spindle doesn't make much more than 2hp between 7k and 9k RPM.

Because that's where our material and tooling dictates that we run, we had to order a custom-made, 480v three-phase Colombo that makes 4.5hp in that range. Made all the difference in the world.

Discussing spindles, we have some big CNC routers for cutting out and profiling granite and engineered quartz countertops. The tooling is water-cooled as is the spindle itself. The Omags are a bit of a nightmare because they must combine the tool grabber, the motor, and the coolant passages in a single unit. The grabbers and motors are always failing because some seal cuts loose and suddenly there's water flowing through things it ought not to.

What I'm leading up to is that the Northwood CNC router such as we have in our Granite shop takes a different approach. Instead of an exotic, Italian spindle unit, they use a separate gearbox that contains the coolant passages and tool grabber. The spindle is a simple, off-the-shelf Fanuc unit. It's an inspired solution because it simplifies the engineering and lowers the cost of replacing the motor.

What I'm trying to postulate is that reduction-geared head unit that has a regular ER25 collet and accepts an off-the-shelf router or a low-powered spindle motor would be a really nice option to have.

I looked for such a beast when researching a solution for our under-powered issue before settling on the custom-ordered spindle.

[gundog]

I have thought about mounting one of these heads but the HP is fairly low.
Mike

http://www.littlemachineshop.com/products/product_view.php?ProductID=1663&category=

[knight_toolworks]

I bet it has enough power if it can handle a 5/8" end mill. it takes a fair amount of power to mill metal.