MadModder
The Breakroom => The Water Cooler => Topic started by: DavidA on September 25, 2013, 02:45:44 PM
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DON'T CLIMB MILL !!
How often do we hear that. But when does it cease to become climb milling and become sawing ?
A circular saw is really just a high speed very thin bladed milling cutter; or a milling cutter is a slow thick saw blade.
Either way, saws cut by the blade rotating down into the job. But it is recommended that we use our thin milling cutters in the opposite direction. This runs the risk of the cutter pulling the job up out of the vice.
So, where is the demarcation line ?
Dave.
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Most circular saws are set up for conventional milling -- radial arm saws and chop saws are often used in climb milling mode, but table saws and hand circular saws feed against rotation.
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Climb milling usually requires low backlash and high machine stiffness, as well as sufficient clamping.
ps. I should have said sliding chop saws above. Conventional chop saws are more analogous to a plunge cut.
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Just re-reading your post, David, is it possible you have the terms reversed?
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I was a carpenter for50 years and iff you tried to cut backwards the saw or the wood would be thrown out violently .
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Consider the forces involved and the machine limitations. With conventional milling the force of the cutter is in opposition to the backlash so it keeps everything nice and tight. With climb milling, you feed a bit then take up the backlash, feed a bit more, then take up the backlash. When there's a lot of slop it means that the cutter can feed UP TO the amount of backlash with ONE FLUTE... potentially.... and usually this results in either launching the workpiece or breaking the tool.
If you're having a bad day, both.
If your machine has almost no backlash (read: ballscrews) then ignore everything I just wrote and carry on without caring which way you run the tool. Fact is most hobby machines have levels of backlash that are pretty much unacceptable but we all live with them due to the price point of the machines. You effectively compensate for it by conventional milling.
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Oh my, he's got a whiteboard now.... look out! :poke:
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VT,
...Just re-reading your post, David, is it possible you have the terms reversed? ..
No. but I did use a rather bad example with the circular saw blade. The main difference being that, when looking at the end of the horizontal mill arbour, it turns anti clockwise and the job is fed in from the right hand side. The job, of course, passes under the centre line of the arbour.
With a circular saw it passes above the centre line. So it is effectively conventional milling.
I use the terms in the same way DoubleBoost refers to them in his video.
Chipenter,
Not sure what you mean by feeding the wood in backwards.
Dave.
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Ah, much clearer now that you mention a horizontal mill. Yes the conventional circular saws rotate opposite the direction of feed, so they are similar to conventional milling.
And as I said before, when cross cutting a radial arm saw rotates in the same direction as the feed, so it is similar in action to climb milling. The reason the radial arm saw does this is because the material is held between the table and the fence, and so represents a situation where the material is trapped in that direction and there is no "backlash" possible. If the blade rotation were the opposite direction it would tend to kick the material out toward the operator.
"Backwards" is a term which could be applied to either conventional or climb rotations and feeds if the meaning is simply "opposed to normal" for a particular woodworking machine.
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If you go off line with a wood saw and pull the saw back to get back to the line , the blade can grab and throw the saw right out and gouge the wood , it happens very quickly .
Jeff