Feeds and Speeds

[cconway]

I just tried out an Amana bowl and tray bit #45982. Had it set at 16,00 rmp with a feed rate of 140 ipm and a plunge rate of 70. I'm working in Walnut and have a 2 hp water cooled spindle. I was getting a lot of chatter and stopped the cut. What would be the best way to adjust the feed and speed?

Thanks!

[ger21]

The chatter is likely due to a lack of rigidity, rather than a feed/speed issue.
But I'd reduce the RPM to maybe 14,000.
Try taking shallower cuts.

[cconway]

Thanks Gerry. I'll give that a try.

[martin54]

Speed & feed settings vary a lot from machine to machine, a lot of it is to do with how rigid the CNC machine is. The best way to sort out speed & feed settings is to experiment yourself until you find settings that work well for you.
Manufacturers speed & feed settings tend to be for industrial machines which generally speaking are more rigid than the hobby type machines many buy so reaching these sorts of settings may well not be possible for you.
Not familiar with your particular machine but it doesn't look to be that rigid, for that reason alone I would start off with a much slower feed rate & DOC & then work up. Something else that will help with tool deflection especially with larger bits like this is to use the largest shank diameter bit you can

[wb9tpg]

Right off the Freud site......

Feed Rate = RPM x Flutes x ChipLoad

RPM is your router speed setting
Flutes is the number of cutters on your bit
ChipLoad varies by material and bit (I'm attaching Freud's table)

Rigidity of the machine will have a big effect too.

An example

18,000 RPM * 2 Flutes * 0.006 Chip Load = 216 Inches / Minute. I can only push 70 rpm on my machine with a Freud 76-102 0.25" downcut bit (upcut / downcut affects it too... You need to be able to clear the chips.)

[spinningwood]

Take a look at the GWizard calculator Bob Warfield offers at CNCCookbook. Avoiding a few broken tools or getting more life out of them might make it worth it to you.

Ed

[cconway]

Ed,

I looked at that briefly once, but I git the impression it was geared more toward metal applications. Am I incorrect in that?

[LittleGreyMan]

Bob Warfield has added woods in the material list of GWizard.

IIRC, he also tries to compute the best values given that most routers spindle can't run at low speeds and that amateur CNCs often can't reach high feed speeds nor allow high pass depth.

But I didn't give a try to the last versions.

Just check these features on his website and download the demo.

[Daniel S]

For my two cents worth I also have a Shark Pro 4 with water cooled spindle but 25 x 25. I have found that I cannot exceed 50 inch/min and get good results. I also keep plunge rate low when using end mills or ball nose bits. Only on 3d carving and ruffing passes I up the speed to 70 inch/min. On all my bits I limit cut depth to .075 per pass to accommodate my machine which is not as ridged as the all metal machines. I guess with the purchase of my third machine I'll get it right.
Dan

[scottp55]

Glad I listened when someone I trust said;
"Buy your second machine First!"
Virtually all mistakes are Mine!
scott