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milling on the lathe and milling attachment:

Is it possible? What are the limitations?

 Yes milling on the lathe is possible but with a lot of shortcomings and limitations. The most critical is the rigidity. Only by looking the Optimum D180, or any other similar mini lathe you can tell that the capabilities are limited. To reduce the vibrations that produced from the cutting forces we have to reduce the already limited size of the work piece, the distance that the work piece is extended from the vice and the depth of cut.  The gibs must be properly adjusted and the axis that we don’t use must be locked.

 The second limitation is the small travel of the axis and for that reason the position of the milling attachment must be planned carefully otherwise you are risking to reduce furthermore that travel.

 Another problem is the vertical position of the vice that in some cases makes difficult the positioning of the work piece.

 Another issue is the time that it takes to set up and to align the milling attachment and the fact that we use the same machine for milling and lathe operations. Let’s assume that we are working on some lathe project and somewhere in the middle we need just a single milling future on our work piece. A five minutes job it can take more than an hour.

 Those are some of the factors that making the milling on the lathe difficult but they are not the only ones.  We will discuss in more depth some of those later on and we will also talk about the red thin lines that we should never cross.

 If we try to make a parallelism between the milling machine and a motorcycle probable the “milling attachment” would be just a bicycle that we have attached a motor on it. So, if you plan to use the milling attachment only for some futures on some pieces it is fine. You can use that bicycle to travel for a few blocks. But if you plan to use it for a long distance trip you must be prepared for a big adventure.

What makes things worse.

If we ask from an experienced machinist to “ride” our bicycle he will laugh but finally by applying  good milling techniques and by exploring the machine’s capabilities he will accomplish the task. At the other hand a newbie will look like a boy who trying to ride a bicycle for a first time.  I believe that this is the biggest problem, the lack of experience.

Let’s jump into

 Hold your horses mister!! There is something extremely important that I must mention before we continue. Do not, I repeat do not attempt any milling operation without eye protection. Chips are flying all over the place and they are very hot.

 Keep your hands away from the cutters especially when the machine is turned off. We tend to feel safe when the machine it’s not running but be aware you can cut yourself badly.

Climb milling vs Conventional milling

From Wikipedia

” Conventional milling (left): The chip thickness starts at zero thickness, and increases up to the maximum. The cut is so light at the beginning that the tool does not cut, but slides across the surface of the material, until sufficient pressure is built up and the tooth suddenly bites and begins to cut. This deforms the material (at point A on the diagram, left), work hardening it, and dulling the tool. The sliding and biting behaviour leaves a poor finish on the material.

 Climb milling (right): Each tooth engages the material at a definite point, and the width of the cut starts at the maximum and decreases to zero. The chips are disposed behind the cutter, leading to easier swarf removal. The tooth does not rub on the material, and so tool life may be longer. However, climb milling can apply larger loads to the machine, and so is not recommended for older milling machines, or machines which are not in good condition. This type of milling is used predominantly on mills with a backlash eliminator. “

 From the above looks like that Climb milling has some benefits in comparison to Conventional milling but if we focus on the two last underlined phrases looks that we have some serious disadvantages in our case.  About the “larger loads” I believe that we don’t need more explanations, this is something that we definitely need to avoid but it seems that it something is wrong with the backlash also.

	Let’s take a look at some live picture from Climb milling and notice the direction of feed and the direction of the cutting forces.
	Now let’s see in conventional milling. The cutter from the point that touches the work piece and on, rotates against the direction of feed when in climb milling the cutter rotates in the same direction with feed.
	And how that affects our work? If we advance the cross slide in order to eliminate the backlash…
	and replicate the cutting forces from conventional milling by hand, in other words push against the feed, the cross slide it will remain stationary.
	However, if we apply some force on the opposite direction, like climb milling does, the cross slide it will jump forward  because of the backlash.
	That means that the cutter at the most critical point, the point of impact, it will move the work piece in the same direction with it and it will cancel the basic principle of the metal-cutting which is, a knife-shaped tool, harder than the material that needs be to cut, moves to the opposite direction of the material. The end mill it will fail to take the cut, instead it will climb or ride onto the work piece and it will force it out of the vice until the work piece build enough pressure to stop the end mill.
	Those are the results of climb milling on a piece of aluminum. Whatever you do, do not attempt climb milling with the milling attachment.End of page 1
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