M04 – Simple Command, Powerful Result

By Joe Thole, Application Engineer

If I could intone my text, this article would be in that old 1950’s PSA films for fallout shelters and gas mask sales pitches. What I have to say is going to sound about as comical as some of the gadgets and propaganda spread about around that time. So in my best 1950’s PSA voice:

  • Are chips and coolant splashing on the door glass of your CNC lathe obscuring your vision?
  • Is your machine not holding tolerances as well as it once had?
  • Are your parts showing chatter you don’t traditionally expect?
  • Is that chatter causing unpredictable tool life?

What if I told you about an amazing option available to use your CNC lathe that will add $0 cost to your machine while alleviating the aforementioned ailments?
This simple option can help all of those areas, and more!

It’s called “M OH Four” That’s right: M04.

M04 is an often forgotten feature with few limitations but many benefits which greatly outweigh the downfalls. However, this is one of the most overlooked, simple techniques that can be used in this ultra-modern world to help your shop become that much better.

If you’re already using M04, you are in a small but growing group of people who have seen these benefits first hand.

Why is this Simple Command So Powerful? … Simple Physics Really.

As you program your lathe to run, typically, one would use “M Oh Three” or M03, “spindle rotation, clockwise”. However, when they say “Clockwise” it is from the spindle’s perspective looking to the tailstock or what I refer to as the top of the chuck towards the operator. Simply put, anything that flies around inside your machine will promptly be thrown at the door, and its glass. This is not only irritating but can be dangerous. As chips fly, so will large parts, chuck jaws or anything else that may come loose. This means a part will have the tendency to fly towards the door and the operator. With the chuck rotating in M04, these chips, coolant, and parts will tend to fly first to the back of the machine, or, if they come loose on the downward portion of the rotation, be thrown first into the chip conveyor or at the way covers.

By the way, operators, wouldn’t it be easier to change your inserts out if they were on the top of the stick tooling instead of the bottom?
Well, with M04, it is! How about that?

What does that have to do with chatter and tolerances? I’m glad you asked! You see, with M03, as your part rotates, a tool needs to be mounted upside down in the turret to be in cutting position. This means the forces transferred to the tool are pushing up, or in the theoretical Y+ direction. That means all those cutting forces being used to shear metal are being transmitted into an area, the smallest area possible really, on your box ways, almost negating all gains boxed ways offer. I say almost because using linear or roller guides in the same fashion, the boxed ways STILL offer more rigidity. In fact, I would argue that using boxed ways incorrectly and linear guides correctly, the boxed ways are still the better choice, but I digress. Transmission of these forces on such a small area will, obviously, wear that small area out much more quickly than if it was 3-4x the area. Not to mention, pulling up on the turret is going against gravity, which means as you engage in a cut, you are pulling the turret off its ways, and as you come out of the cut, the turret is falling. This could also be caused by varying depths of cut or hardness of the material, which could, in turn, cause vibration. Don’t we all know what vibration does to carbide too well as it is? With M04, those cutting forces are playing a game of Follow the Leader and follow gravity, pushing the turret back into the X axis ways, and the carriage into the Z axis ways. As a result, there is no room for vibration; No vibration, less premature tool failure caused by vibration from the turret being lifted from the ways.

In one easy step, we’ve limited vibration to limit chatter, extended machine life by spreading the cutting forces to a larger area of ways, helped prevent premature tool failure, AND made it easier for the operator to change/service tooling.

But wait, there’s more!

This paragraph is usually exciting to the bean counters, I won’t lie. You see, when you use M04, not only do you get the above-mentioned perks, but you also get the added peace of mind that your tolerances will continue to hold tight for years and that you and your company are doing everything in its power to keep it that way. All those forces being pushed into an immovable object like the base casting prevent vibration and wear on the ways. This also assures the best setup for finish and tolerances. Using M04 will help assure the longest possible machine life, with one less issue possible. Then there’s one final perk. At least, for those using a sub-spindle machine, there is. When using a sub spindle, so many times, the main spindle runs in M03 and so does the sub spindle. This means that in relation to each other they are rotating BACKWARDS! Sub spindle tooling is, of course, mounted to be right side up, while main spindle tooling is upside down. This means, when you pick off a part, you must stop the sub spindle, rotate it in relative “reverse” to pick off a part, then stop it again to rotate it the correct direction for cutting. This equals lost time and extra wear just stopping and starting the spindle for no actual manufacturing good. Simply using M04 on the main spindle, and improving main spindle manufacturing means now your two spindles both rotate top away from the operator, meaning with regards to bar fed machines with pick-off, you never even need to stop the spindle unless you choose to when ejecting the part except during bar load.

Free efficiency gains, no investment required (other than tooling if you don’t already have it), better parts, potential longer tool and machine life, happier operators…

How much better can it get?


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