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Cutting Techniques
Fred Smith said---
"The power required to Climb mill, compared to Conventional milling is approximately 1/3. You can significantly increase your material removal by climb milling, provided your machine is backlash free and has the structural strength to stabilize the higher cutting forces and speeds"
Is the Old ShopBot PR strong enough and backlash free enough to do Climb mill cutting? Does Climb cutting cause more chattering? How does every one aproach their cuts? Cuting poll 101.
Senior Member
David, you may also want to look at this thread.
I get the impression that very few ShopBotters actually care about the difference - because they wouldn't know how to switch the direction. Making provocative statements 101.
Senior Member
There are many "what ifs" invovled in the choice between climb cutting and conventional cutting. The shopbot will handle climb cutting up to a point. If you wanted to climb cut white oak with a 1/2" bit at 3/4" per pass with a 2" per second feed then probably, no. But then it wouldn't convetional cut at that either. I don't think it takes 1/3 the power, you're still removing the same amount of material with the same cutter which takes the same work. I cut both styles based on experience with different materials, cutters etc. An example is 3/4" Elliotis plwood of which we often cut several units a week of. If edge finish isn't critical an up spiral bit doing a climb cut is an ok choice. If edge finish is important then I get the best results with a compression spiral with a conventional cut. I can cut both at the same rate it's just the spiral bit is cheaper than the compression spiral. Plastics often, but not always, cut better with a climb cut as is also true of solid lumber. Experiment and as you gain experience you'll find what works best for you. Just remember that you need a stiff bit to climb cut, I rarely use 1/4" cutters but never for climb cutting as there is just to much deflection.
Fred Smith's comments are probably based on the power it takes to move the bit in the wood. If a tool has 100% feed, 1/2 the cut is "climb" and the rest is "conventional".
Wood is not near as mean or demanding as metal. If one is working on an old "loose" mill with backlash and/or "flex", partial bit cuts combined with "climb" milling sometimes results in the bit pulling itself into the work. The bit starts taking more aggressive bites as the slack is taken out of the drive screws and ways. Depending on the material, bit, clamping, condition of tool and operator "savvy" interesting things start to happen. Material and pieces can become airborne projectiles and this tends to cause things to go "Out of Spec". Blood is not easy to clean from machine tools and causes rust.
My comments are concerning the spindle power requirements. Climb cutting requires less spindle horsepower due to the cutting forces involved with material removal by shearing (climb cutting focus) vs rubbing (conventional cutting focus).
Less heat with climb cutting for the same reason.
Fred Smith - IMService
Senior Member
The actual power consumption (amps drawn by the router) is definitely not 3 times higher for one style of cutting over the other. Those with ampmeters among us can easily confirm this. During a practical test today, I could not measure any significant difference, but Ron will probably laugh at my African ampmeter. (hold two wires on tongue and see how far your toes curl up. . . . . . )
Thanks for the clarification Fred.
It is obvious you don't have a 480 Volt router Gerald.
The only time I even think of climb or conventional is if I am routing the edge of a board, and then also if the grain pattern is of a type that will tear Like hickory etc. if you are routing in the middle of the board as Ron B. was puting it you are in essence routing 1/2 climb 1/2 conventional. David in Wyoming
Member
PapaDave, Most of the edges of my toys need nice edges. I did a little experiment in the shop today.
CAUTION CAUTION CAUTION: DO NOT DO THIS EXPERIMENT THIS COULD CAUSE DANGEROUS KICK BACK AND FLYING PROJECTILES!!!! That is for all the saftey cautious types and worry warts.
I took my 1/2 baltic birch board and I rounded over the edges with a double roundover with a bearing in the middle. I pushed the board from right to left against cutter and then I tried it going with the cutter. Going with the cutter made it much easier to cut, but it didn't leave as nice a cut.
Bye the way the round over was only 1/8 diameter of an inch so it dosn't have much "Kickback ability".
I'm guessing (Since I'm not educated in these matters) that the "decreased power thing" is because the cutter literally drags you along when doing a climb cut. When you are doing the conventional cut your machine has to push against the direction of spindle circular cutting motion.
David I just went to your web site, I'm glad to see the Bot being used in this way. David in Wyoming God Bless
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