Butt tapering - issue cutting ivorine 4 joint collar and metal rings

JohnsonJ

Member
Hello all,

I just attempted to taper my first sneaky conversion butt, and would kindly welcome a pointer in the right direction, as it didn't go too well. It was quite catastrophic 😆.

I'm using a 4 wing carbide cutter in my router at 30k RPM, 800W, and while it cuts wood amazingly well, I could not cut ivorine for the life of me.

With a depth of cut of 0.05mm/0.002in per side, I tried running the lathe both at 300 and 1200 RPM, with the router feed rate going from extremely slow, to extremely fast, and everything in between at both RPM ranges of the lathe, conventional and unconventional milling. The metal rings were cut nicely at a slow router feed rate, but once it got to the ivorine 4, it started to heat it up excessively. Speeding things up did lower the heat buildup by quite a bit, but the cut quality went down exponentially, while still being too hot. So basically, at a low feed rate, the copper rings were cut perfectly, the ivorine badly and overheated, whilst at a high feed rate, both were cut badly, and the ivorine still overheated...

I started off with a relatively fresh cutter (it turned maybe 15 dowels in total before), and the router is very rigidly mounted to my lathe cross slide. I wasn't getting any harmonics/deflection due to the RPMs, the quality of the cut was just simply bad, and the cutter ruined at the end of this experiment.

I'm now thinking on what might have caused it, and having doubts if the 4-wing cutter even is an appropriate tool for cutting ivorine 4 collars. It didn't make an acceptable cut on the ivorine even on the first pass.

One (partial) solution is to either find or make a set of better quality collets for my router, since the ones I have right now aren't as concentric as they should be, but regarding the specific issue at hand, I doubt this would fix my issue, it might just prevent a little less heat build up... which would still be about 500% too high.

Or can ivorine 4 not be cut with a 4-winged router bit at all, and I must turn it down on the lathe and then just match the wooden part to it? Or maybe use some different type of cutter?

Looking forward to your replies, thanks 😊
 
You should have no problem cutting Ivorine, I suspect it's either the way you are cutting or your cutter is toast. Slow RPM and slow feed rate, try taking lighter passes. Any pictures of your cutter and setup?
 

That's my setup, with the cutter I tried to taper with.

I'll try hooking up a potentiometer to the router and see how that goes, I didn't even think about the router rpm being a factor, since it's a simple on/off 30k rpm type deal. But it does make perfect sense now that you mention it...

I was thinking that the higher the rpm the better, and that 70-80% of the heat would get thrown out of the workpiece by the chip. But I guess not with plastic. Wood didn't heat up much though, and it cut it very, very nicely. I will check the temperatures on wood at 9k and 30k, and post back here, it's gotten me curious now.

I'll try to shoot for 9k with the pot and verify it with a digital tachometer. I will also simultaneously upgrade the collets to tighter toleranced ones. Will update when I get everything sorted.

Thank you very much!
 
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