View Full Version : Speeds and feeds

24-03-2016, 07:27 PM
Hello people,

I have tried using FS Wizard for an HSS no coating 6mm cutter, 4 x 13mm flutes, overall length of 57mm but let's say length from holder of 25mm, 35 helix angle, 90 lead angle. Set for cutting "Plastics, soft non-metals". I get:
RPM = 10000
FR = 3500mm/min
DOC = 0.8mm

RPM and FR seem alright to me, but the DOC is strangely low.

Here is the link to the calculation:

This is the type of cutter I have :

According to a rather popular Youtube video (https://www.youtube.com/watch?v=ip2jm_6aUyk):

RPM = surface feet per minute (SFM) * tool diamater * 3.82
Feed rate = RPM * chip load * # flutes

Rule of thumb:
chip load = tool diamater (inches) / 150 => gives weird numbers
DOC = .5 * tool diameter

How do you estimate the Surface Feet per Minute (SFM) when it wasn't provided by the manufacturer ?
The rule of thumb for the chip load gives me weird results: 0.0015" for the example cutter I've used. So instead I used 0.004".

For the same cutter as above, I get:
RPM = 3000
FR = 1200 mm/min
DOC = 3mm

And if I use an SFM of 500:
RPM = 10000
FR = 3200 mm/min
DOC = 3mm

I'm just trying to figure out general rules for slotting, surfacing, etc.

All the best,

24-03-2016, 10:43 PM
Have you noticed the bits highlighted in red?

Slotting/100% WOC is tough on machines. Having 25mm tool stick out (length should be the distance the cutter protrudes from the collet/holder) is the main killer in those figures. If you reduce tool length to 15mm, DOC increases significantly.
However, whether you can achieve that will depend on the overall rigidity of your machine, and the figures produced by any F&S calculator should be treated as starting point. Some machines will be able to run harder, some will need to run slower, so you'll still need to experiment for your particular machine, material, and cutters.

24-03-2016, 10:45 PM
Pretty new to this but I have been machining Acrylic on converted Sieg X1 mill between 1500 -2000 rpm DOC 1mm FR 1200mm/min 6mm 2 flute and getting good results for welding with Dichloromethane faster RPM than this I was starting to have problems with heat softening the Acrylic as cutting without any cooling. I set it running in Mach 3 and adjusted on the fly for first couple of cuts testing the limits, then went with it. 2 flute performed better than 4 flute for me.

26-03-2016, 05:00 PM
Thank you guys for your replies !

Today I took my first cuts and the machine is currently slotting the sploiboard :) Running at 10000 RPM and a FR of 950mm/min. Chips are perfect, and there is a little bit of smoke when the bit does its first pass because of the MDF surface. Otherwise, it's looking great ! I will have to sand it a little bit when i'm done. So far, the slots are being cut. Second operation is the T slotting. I'll post pictures when I'm done. I had to cheat a little bit for the GCode in Masterdom because I had to draw the part bigger than what it really is so I could make pockets for the slots.

I also went to the store and bought a dry/wet vacuum cleaner, because things are getting messy haha. Gotta make that dust shoe when I get my 3d printer !