A guide to understanding basic Feeds and Speeds

I do a lot of rustic primitive stuff. We do these characters that sit on a porch about 30-40" tall cut in basic 1"x12"48" pine. Using a 1/8" bit. How fast can we cut these and at what depth per pass?. I attached a typical layout so you can see it’s not very complex. We currently us a hand saw but would like a faster cleaner cut.

With a standard size machine, you wouldn’t be able to cut all the pieces out of a 48" long piece of 1x12. My machine has about 30" in X and Y, so you’d have to plan your cuts around that size.

As for the speed and cut depths, that depends on the bit you choose, the spindle you have, and which modifications you make to your machine. With stiffness modifications on the X and Y axes, you can cut a lot deeper and faster because your machine will have a lot less flex.

I recently made a sudoku board out of .75" thick pine (MWP Sudoku Board | Inventables), here’s the details behind my cut with the 1/8" bit:

  • 3/16" steel bar to stiffen the X axis, and Y axis is braced in 3 places on each side
  • Dewalt 611, set to speed ‘2’
  • Used 1/4" shank 1/8" 2 flute downcut bit
  • Final feed/speed was .050" cut depth and 75 IPM

Your speed/feed will vary.

I just ordered my X-Carve yesterday and can’t wait for it to get here! This was a VERY informative post. Thanks very much from someone who has a LOT to learn.

I just “graduated” to a single flute 1/8" shank cutter for carving wood shapes of Lakes. Almost no sanding other than the tabs. Tech support at Precise Bits spent about 30 minutes on phone with me, twice teaching me about chip loads and more. Almost everything you write and more is available from the here. And their bits are excellent and good price.

Great post! We all look forward to your projects.

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Neve, as in Rupert or AMS Neve? Mic/line pre?

Yep!

www.oreillegauche.com to view more

Nice! I had Libra Live in my studio in NYC. May have been the last Neve.

Awesome article

Ok so I am looking for some serious help on something that makes zero sense to me because it seems to defy logic.

I am cutting a 0.062" material with single flute 0.063" carbide cutter. I am cutting a slot that is 0.063" x 0.250" .

I plunge in without a predrilled hole , rout in x axis then exit. The plunge point looks great and I can put a 0.063" guage pin in very snug and am happy … Now the issue … the rout path is measuring 0.055" and is rough and choppy. The exit is the exact same as the plunge …

How is the world is their such a huge difference between the rout path and the plunge ? How can the rout path measure less than the cutter diameter ?

RPM is 40k and table feed is 30 inches per min ( used this for years without any issues)

I ran this on a different machine and it can our perfect , rout path was 0.063"

I am losing my mind because I cant figure this out … Am I crazy ?

What material? Is it possible it’s swelling back into the channel after the cut?

I’m not sure I would call less than a hundredth of an inch a “huge difference”, especially if you’re carving wood.

Your RPM doesn’t need to be anywhere near that high. If you’re using the DW611, keep it set at 1 (around 16k).

The material is a glass and resin composite called FR4. I switched to another machine and the cuts were fine with the same exact tool. I have no clue how in the world a cured rock hard material wont cut the same … I have been a Process Engineer for over 20years and realize how ridiculous this must sound but its defying everything I was ever taught

Making PCBs? In that case, my apologies - yes, even one hundredth of an inch (10 mil, if you prefer) is kind’ve a big deal.

That being said, that’s still a pretty tight tolerance for the X-Carve.

Also, it’s probably not swelling, but could be a form of “tear-out”. Were you using the same bit on both machines? FR4 is essentially fiberglass, so if your bit is starting to dull, you might be pulling fibers into the channel.

Sounds like chatter and potentially bit deflection. What feed rate are you using? Have you tried slowing it down?

So it is definitely machine related, i tried different machines with the same bit and it was perfect. I just for the life of me cannot figure out how a rout path can be smaller than the diameter unless the tool isnt spinning … an 062 tool would break in a an instant if that were the case … Chatter , yes there is absolutely evidence of this on the board and not the plunge hole , could it be the tach board is reading wrong rpm ?

Wait… You’re saying you used the same bit, in both machines, and the path/channel came out perfect both times? Doesn’t that mean the other bit is the problem?

I think he’s saying it was perfect in machines other than the X-carve using the same but he used in the X-carve.

The only reason for a bit of a certain diameter to carve a narrower path would be if the bit is “bobbing” about inside the path and not cutting properly.
Take a 1F tool and measure the cutter width, then turn the bit 90deg and measure again. It will be less.

This is my only suggestion how a bit can in theory cut narrower than its nominal width (unless tool is broken that is…!)

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Excellent post, thanks for sharing

Oh my! I had never seen this. I manage a maker space. I know that sound all too well. I can be in the clean rooms and hear that and know I need to go check out the CNC to see what they are doing wrong. This is so funny! I will have to share. Love the comparison

This is great! This has been the best explanation I’ve found. I think I still need some work but I feel way better equipped to figure this thing out now. Thank you for sharing. AND… the Duck Bom… OMG!!! That is too funny. I had never seen it. Someone linked it in the comments. I manage a maker space and hear that noise way too often. Thanks again for the info!