CNC Machinists

Use climb. Better surface and accuracy. On rough where accuracy is not so important milling use both conventional and climb to reduce milling time.

>20:1 aspect ratio (thin wall) machining... conventional can be advantageous.

Also favorable when machining of high-strength super alloys with ceramic inserts.

Thanks.

I've heard conventional cutting can sometimes cause the end of an endmill to gouge in to corners when pocket cutting. Is this true? If so, how much gouging should be anticipated?

That can be true but pocketing is typically a roughing operation, so you'll need to leave stock for cleanup. Whether conventional or climb, tools flex in corners, whether from the increased engagement angle (inside-out pocketing) or normal flex from 100% engagement (outside-in pocketing). That said, if the tool has a lot of movement (e.g. longer, smaller core tool) you may want to pocket from outside-in, if that's feasible.

Otherwise, size a tool for finishing the corners that's 1.5x or less than the required radius and, leave enough stock to get a full cleanup.

A warning, as far as safety.

If you are using a manual machine (not CNC) stay away from climb cutting. The axis screw/nut always have a slack and it can jump while doing a climb cut thus breaking the cutter and flying every where and that includes your body.

Some machines have a zero backlash "climb cutting" mode. As long as the machine is in good condition, climb cutting shouldn't be an issue. An a Bridgeport type mill, you can lightly cinch the locks, and climb cut.. again, as long as the machine is in good condition.

Just a warning so the new comers do not get hurt.

From my experience and people I have worked with, we all learn the lesson on climb milling by breaking a tool.

Is conventional ever used for finish cutting or strictly roughing passes? Is a carbide or HSS endmill better for the job or is that dependent on material and setup same as climb cutting?

From my experience, it is all about the condition of the machine, end mill, and feed rates per cut. A manual machine with dovetail ways and an acme screw for x and y axis is not as precise as a CNC machine with linear bearing ways a ball crew as far a "finishing cut". Concluding, conventional or climb cutting can yield the same results as long as the cutting is very small and air or liquid force is applied on the cutting tool to blow out ships. I hope this information is of some help.

The two place the workpiece under different loads, and I would only use conventional when the workpiece, fixture and machine are not suited to the pulling forces generated in climb. A designer should keep these things in mind when designing fixtures, but of course, a lot of times you're making the best of what you have.

The only other place for conventional is when using negative ceramic inserts. Positive inserts should be used in climb.

For finishing, IMO, you should always climb. If the machine has no way of adequately resisting the pulling forces... then use conventional.

Conventional places a greater load against the cutter on exit when forming the chip, it creates more friction at the start of forming a chip and in some materials; high strength, low thermal transfer, cold work hardening, etc., conventional will impact cutter life significantly.

Whether to use carbide or HSS is a question of rigidity. If your machine and/or fixture isn't rigid and/or poorly damped, you may find yourself struggling with carbide edge retention. HSS is more forgiving but significantly less rigid.