Anyone using a 3/8" end mill?

I was doing a deep cut in hard maple with a 1/4" down cut Amana Spectra bit using their suggested feed/ speed and the bit was chattering some when cutting through the end grain. I was cutting at 18k, and had a step down of .2" per pass. I was making a 3/8" (but I could have made it wider) channel so there was plenty of space for the chips to get ejected from the bit. Amana’s chart said 180 IPM. I tried to slow the speed down to 125 IPM and it helped some and then set the step down to .15" per pass but even then it was still chattering.

So I was thinking (now that there’s plenty of users with spindles) of going up to a 3/8" endmill for extra stiffness. I do have a couple more cuts to make and I’ve set the feed/ speed down to 90 IPM and a step down of .1" but haven’t tried that yet. But that’ll take 4 times longer. This is the first time I’ve tried cutting hard maple (I didn’t have a problem using Amana’s settings on cherry and walnut). Just curious if anyone has moved up to a larger diameter endmill to avoid slowing down the speed to a crawl.

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I’ve not done any Sugar Maple milling yet but I can say, based on experience turning it, that it’s much harder on the Janka Hardness Scale than other species of maple, somewhere around 1450, which puts it at the upper end of the scale. It eats HSS for breakfast.

Shallow doc and carbide is recommended and definitely watch for burning. That’s a solid indication that the wood’s eaten your bit.

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What cad/cam are you using? I use fusion 360 and really like its adaptive path which can keep a constant chip load.

Instead of setting RPM and IPM, I use RPM (based on manufacturers recommendation as a not to exceed guideline) and chip load. F360 will set the IPM based on that. If I get chatter, I’ll drop chip load and it will adjust the feed accordingly.

Another idea is to check work holding…if it’s not rock solid, it can be the cause of chatter.

I’m using the free version of Fusion 360 but pocket, not adaptive. When I tried adaptive it wanted the trench to be wider so more material to be removed. I made it 3/8" wide so a 1/4" endmill should have worked just fine. I didn’t want to go back and redo the work. Adaptive clearing set the step down maximum to .625" which would have been too much. When set to .2" with it not removing all the material the machine time was still several minutes longer.

Howdy!
I have used a 3/8” down cut end mill, Amana 46420-K, in Cherry, Walnut and Hard Maple (Sugar Maple). They were cutting boards and I wanted to see if it cuts them out of the stock better. It did chatter less in my spindle and I simply used the settings that come from Amana, but I took too much out at a time and the piece moved. What I realized is with a larger bit, you certainly get more stiffness but you are also applying more force to your work piece so make sure it is down solid. I fixed this by taking less at a time since I could not use outside hold downs. I also use Amana 1/2" up cut ball nose, 46380, for juice groves along the perimeter of the cutting board. Much less chatter then a 1/4” bit but I do this in 2 paces because the force will move the piece.
Be blessed!

These were two phone shape pieces that get glued together and form an oval. I was able to screw it down and then make the inside cuts. Once done I could then clamp it down and make the outside cut. I did notice Amana’s speed for the 3/8" endmill was something like 230 IPM. I’m not sure if I would cut at that speed but it would be nice to cut faster than 90 IPM since the oval is over 24"x48" and cutting an 1 1/2" deep.