Re: [CAD_CAM_EDM_DRO] Re: Machine flex; How much is to much?

>What type or size of a machine can utilize a 1/2"
>mill to its capacity?

The Rong Fu and similar sized machines will run a 1/2" endmill. They will pull a 1" endmill. The rong fu and similar mills will do basically anything a Bridgeport does, just not as well. You are talking a 4" tube column verses 2600 pounds of cast iron. I think you have a misconception of the "capacity" of endmills. If you are removing stock, you need a rougher. And if an roughing endmill is 1/2" diameter and flutes 1 5/8" long doesnt mean it can be buried in the stock 1/2" wide and 1 1/2" deep and expected to remove it all in one pass. It could be done but not for very long. The easiest way to judge your cut is look at the chips. Are they thick? If so, Cut down the feed. If they are thin and brown, the cutter is dull or the spindle is too fast. They should be reasonable thickness and bright. When a rougher is cutting properly it will emit a particular sound that after practice and burning up a few you will recognize when you hear it. A good spindle speed on a 1/2" rougher is about
800rpm and about 3 or 4 inches per minute, a 1/2" finish should be around 1000rpm. Endmills with long flutes such as a 1/2" with 3" flute length in steel are just wishful thinking and they are very dangerous. You move up to a corner to take a full 3" cut with an endmill like that and it can grab and walk around the corner, snap and fly across the shop like a bullet. I've dodged a few of them machining out the inner surfaces for rod end clevises for large hydraulic cylinders. Thats shaper work and the shop I was working in, someone higher up got the idea the shaper was obsolete and got rid of it. The shaper is still a very useful piece of equiptment for many machining operations. I have my own shop now and I have one. Long endmills are intended for final cleanup and plastics only. A good rule of thumb on a rougher in steel: never plow any deeper than its width and make multiple passes. A "finish" mill is just that, it was never intended for stock removal in steel although you can
but, again not for very long. You can take a respectable amount of stock out of aluminum with a finish mill using oil or tapmagic to prevent the chips from galding to it, Kool mist is useless in aluminum. The worst sin commited to an endmill is allowing it to dwell against the part or feed it too slowly, spinning and remaining stationary. It will dull it instantly. That squeal you hear is the stock wiping the cutting edges right off. If its turning and not cutting get it it away from your workpiece. The only way deflection can be countered is beat it at its own game. Play the deflection to your advantage. If you are machining taking a full cut not side milling to the right of your line and the endmill is rotating clockwise you know its going to pull towards the line. So stay off the line 30 thou or however much you think it will deflect and you will still be ok for your finish pass. When machining a slot with a rougher, I always hug the right side going across then come back and
machine the inside perimiter and it is there.

Ron




I posted the same scenario to the Mill/Drill group regarding cutter
size and material, and received a similar response. I guess I will
have to re-think the type of work that this machine is doing now. You
mentioned that you have used a 1/2" endmill that produced a shift on
a Bridgeport mill. Trevor

> 1/2" endmill? Getting a 1/2" endmill to do the kind of work it is

capable

> of on a light weight machine is doubtful. You might plan on using

smaller

> cutters. When a larger tool like the 1/2" takes a significant bite

into the

> work, it may deflect the machine enough that it won't return to the

same

> position. I do this pretty routinely on my Bridgeport, but I

really don't

> think you want to use a 1/2" cutter on any machine much lighter

than that.

> (Of course, there are special cases where you use the big cutter for
> stiffness when working at the bottom of a pocket, and take very

light

> cuts with it.)
>
> Jon

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