Feeds and Speeds

I know there’s much reading to be had on this and other forums on Feeds and Speeds, because I’ve read a lot of it. I think, I’ve got myself confused. I’m using the CNC Speed Calculator for Dewalt.xls and unless I’m doing something wrong, will not be the first time. I’m running the following. Downcut 1/8" bit with Baltic Ply using the suggested 180 inches/min on my modified Shakeolo 1000mm x 1000mm with a Dewalt 611 setting 1, aluminum Y axis mod, need to do the X axis mod soon.

From my usage and reading, I’m beginning to think this is too fast, even though I got the 180 from the xls - unless I did something wrong. So my question is - does one use feedrates from the xls when they are this fast? If not what do you adjust down to?

The xls comes from AllenMassey, chipload calculator, posted on this forum.

Robert thanks for the feedback, I’ll try the slower rate.

I am interested if anyone has feedback on the chipload calculator. I was hoping to have a way to calculate feed rates with a tool like the xls, but with it being so fast I’m wondering how to calculate.

Hello Greg,

Yes, that is a spreadsheet I created. The primary purpose is to show that the best speed setting for the Dewalt is 1.

As you can see from the results in the sheet, at the normal RPM’s the Dewalt is spinning you should “theoretically” be using very high feedrates to achieve the optimal chip loads recommended by the tool manufacturers. For a much larger, stiffer, stronger machine those types of feedrates may be possible.

But for the X-Carve feedrates of 180 ipm are not reasonable. So what the spreadsheet is telling you is to keep the RPM as low as you can make it, maybe switch to a smaller diameter tool, use a tool with fewer flutes and set the feedrate to a reasonable value for the material. You are not going to get perfect chips, but they do not need to be perfect to achieve a very good cut.

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Thank you Robert and Allen for your feedback, got it now. Guess I don’t need to ask about the chatter, off sized circles, losing XY steps, indents where tabs are etc. LOL Answer: Slow down cowboy. Like I said, I read too much, I wondered what G-Wizard would do for us hobby cnc’ers when it really gave the same max out feedrates unless you did an override.

I will note, it did work and moved like a bat out of H*** it was fun to watch at that speed.

Thanks again for the clarity.