Climb Milling Vs. Conventional Milling

[astjp2]

taken from: http://www.harveytool.com/secure/Content/Documents/Tech_ConventionalMillingVsClimbMilling.pdf

Found it interesting and the logic sound. Tim

 

[RJSakowski]

taken from: http://www.harveytool.com/secure/Content/Documents/Tech_ConventionalMillingVsClimbMilling.pdf

Found it interesting and the logic sound. Tim

There is one caveat. The above white paper was written for those with industrial machines. Backlash is not the only consideration. Machine flexibility or lost motion is also an issue. It is due to the relatively light frames and drives found on hobby type machines causing the machine to deflect while under load. As far as climb vs. conventional milling, it acts the same as backlash. It can cause chatter when climb cutting because the cutter grabs the material and tries to climb out of the cut.
I use climb cutting on my Tormach because I have relatively little lash but I usually use it for finishing cuts. If you are hogging material, there is a greater tendency to grab and chatter as each tooth makes contact. For light finishing cuts, that "grab" is greatly reduced. I do like the finish that I get with climb cutting. If cutting dry, there is a reduced tendency for chips to bond to the just cut surface.
When I climb cut with my old mill/drill, I can visibly see the cutter pull the work into the cut as I make contact.
The bottom line: Try it out and find out what the limits are for your machine. The machine will tell you if you are pushing too hard. Machine some test pieces and see what you get under various conditions. Check the dimensions to see if you are holding true.

 

[astjp2]

I would think that the more flutes you have the better the finish. Tim

 

[randyc]

I would think that the more flutes you have the better the finish. Tim

Partly correct but cutting geometry is the major problem with that premise. Standard 4-flute end mills are ground assuming that most will be used on ferrous materials. The cutting edges are much "blunter" than one would like for non-ferrous materials, to withstand higher cutting pressures.

When used on aluminum, for example, the cutting edges will tend to heat up much more than free-cutting two and three-flute end mills and in extreme cases, chip welding occurs.

Now on horizontal mills, that's a more accurate statement. The large diameter cutters used on these machines with many spiral teeth can easily be ground with lots of rake and clearance, producing a fine surface finish on almost any material. But if the cutters teeth are sharper than 4-flute end mills, one might ask, then why do they not heat up like 4-flute end mills ?

First, because they have so many teeth, these large cutters remove only a tiny amount of material per tooth compared to an end mill when making an equivalent DOC. Next, and also because of the many teeth, the individual teeth are in actual contact with the workpiece only a small fraction of the time that a 4-flute cutter is, so much less heat is generated.

In the photo below, the sharpness of the teeth in the slab cutter is apparent. Because the teeth are so keen and also due to the high helix angle, the surface finish produced by this tool looks like that produced by a surface grinder on almost any material.