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I've always used climb milling but have been reading testimonials that Climb is for metal and Conventional is for wood.
I've also seen advise to only use climb milling for roughing.
I haven't had a chance to experiment yet.
What's your experience?

Hm. I've not heard about climb cutting for metal unless you have ball screws that basically have zero backlash and are driven with motors. That said, I'm not a machinist or anything. There will be others who will impart more expert knowledge I'm sure.

Ooops. I need to delete my post. Neglected to realize this was the CNC forum so presumably everything is motor driven already. Sorry about that.

Charlton

with CNC mills cutting metal most of the operations are done with climb cutting. I don't know what the conventions are for CNC routing, but when routing a body by hand using a template I generally run climb and conventional, and the use of each depends on the grain direction and geometry of the part I'm routing. The reason is it helps to avoid tearout which can be fairly catastrophic when doing deeper cuts and having heavy cutter engagement. I generally move a router from wide to narrow so at the lower bout on the right hand side I'd move clockwise from the fattest part of the bout towards the tail of the body, and move counterclockwise from the fattest part to the waist between the upper and lower bouts. On the left side lower bout, it would be the opposite, moving counterclockwise from the widest part of the bout towards the tail, and starting a clockwise movement from the wide part towards the waist between the upper and lower bouts.

Where are you reading these testimonials about climb vs. conventional?

As a mater of practice, I always climb cut unless a specific situation calls for something else. As John mentioned, you can avoid a lot of tearout by climb cutting.

When would I use conventional cutting? Well, it seems to sometimes leave a better finish and, you can use it to cheat sizing a little bit - climb cutting can leave the part slightly larger than intended and conv. slightly smaller depending on tool diameter, engagement etc. Climb cutting at a high feed rate can leave a significantly larger than intended (like .001 or .002 larger) so I might climb cut leaving behind .01 and then come back with a conventional cut to finish it off.

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http://www.birkonium.com CNC Products for Luthiers
http://banduramaker.blogspot.com

There are a number of threads in various forums such as practicalmachinist and mycncuk among others that touch on this subject.
I haven't done any testing yet but I will in the next week or so to see what kind of results can be achieved.
My thought was that we'd run into all kinds of tear out, but a quick search turned up a lot of guys using climb milling in wood to achieve better finishes.
We started considering this in our shop as we wondered whether cutting left hand guitars could be as easy as using the mirroring function on our machine (which results in a conventional tool path.)

Depends on so many factors. I cant speak to metal cutting but for wood - here are some things I've learned in the last 20 years or so:

- conventional will always leave a better finish than climb.
- on a heavy, precise machine with proper feeds and speeds, climb vs conv wont change the tolerances/sizes
- climb cross-grain with anything other than spirals in solid wood is no good
- climb machining with-grain allows much higher feed speeds without blow-out

In metal (this may not be of interest to anyone) if you are cutting a profile with the side of a cutter, and you climb cut, the cutter will deflect away from the part even if the machine is rigid. This effect is drive by the cutter diameter, material, length of cut and number of flutes. Conventional cutting will suck the cutter into the work piece. So if you're after accuracy climb cut leaving a schoosh for a clean up pass like Andy indicated.

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Jim Watts
http://jameswattsguitars.com

I can confirm what Jim says - my buddy runs a 5x12 Morbidelli at his day job - it's got probably > 1000lb gantry and the tools still deflect. It's not the machine, it's the tools that are deflecting.

Other than that, Kevin's experiences are the same as mine.

_________________
http://www.birkonium.com CNC Products for Luthiers
http://banduramaker.blogspot.com

In 30+ years as a machinist. I did tool making, cnc mill setup, 12 years of writing programs and designing fixtures and parts I climb milled as long as the machine was tight and could take the stress. Climbing has the tool pulling on the part in the same direction as the feed, I've had old bridgeports with worn out screws pull the table full length of the part. The reason most wood working tools are conventionally fed is the part or tool are being controlled by hand and climbing would pull it out of your hands. In metal working the tool will deflect weather your conventional cutting or climbing, it's standard practice on parts with +/- .001 or less to make a spring pass, a cut with the same program. Climb milling always leaves a better finish in steal,stainless steal, aluminum, plastics, ceramics. unlike the previous materials wood has grain, that needs to be taken into consideration. If the grain will allow climbing my advice is to climb. Never climb when part or tool is hand held. When surfacing, running a ball mill back and forth over the stock to make a shaped part, I'd rough with a 1/4 ball mill leaving .030 taking .05 steps at 50 to 80 feet a minute and finish with an eighth ball mill taking .004 steps and 60 to 100 feet per minute and usually max out the spindle we had 6000, 8000 and 10000 rpm spindles.In wood you'd want to run as fast as you can with out burning or scorching the wood. The speeds and feeds are for aluminum or plastics. Hope this helped, probably more information than needed, but it was my life until I came down with MS.

-sorry, but these testimonials are not true.
-not true as well.
-please do.
-30 yrs tool/die/mold/fixture designer & maker, cnc programmer, mechanical designer, manufacturing engineer, qa manager, blah, blah, blah, in aerospace, hydraulic, medical, & high energy particle physics, blah, blah, blah. and still at it i'm afraid. basically i've been around.

fwiw, i do like to mill to the grain meaning that you need to control chip out during roughing of wood, as well as composites, graphite, etc... sometimes i'll plunge a few quick cuts at a depth of the cutter radius at the entrance and exit of a feature (a step feature for example,) leaving about .005 or so for finishing, then hog the material out and come back in with some finish passes with cutter comp. and climb cutting. this keeps chip-out to near zero in wood, graphite, composites, and some periodic table metals.

Arie, I'd like to know what you think is not true. You also didn't address the subject, climbing or conventional mill in wood.