Milling feed

[dennisa49]

Hello,
I have a small mill (Sieg SX2).
I am unsure of the cutting speeds & feeds with this machine. The machine is much lighter than the two I have previously used.
Steel work:
Rocol cutting fluid.
Small diameter end mills, 6 - 12 mm,
Carbide tipped 20 mm, maximum size indicated for this machine.
I would like to remove chatter from the cutting.
Using medium rpm, lightish cut, slow feed has not worked.
is there a variation that may help?

Many thanks,
Dennis

 

[bazmak]

I have the same mill.Try adjusting the speed as you go you can pinpoint the best.I use a brazed LH carbide tipped lathe tool in a flycutter for best
and speediest way of cutting mild steel.Fast speed just over halfway on the dial
I also found the solid carbide endmills work well at higher speeds.HSS tools need a slower speed to avoid burning the cutter.I posted a video under bazmak
diary of a mill showing my first atttemps mat milling

 

[dennisa49]

Bazz thanks for your advice, a couple of changes and all is well.
I was cutting rebates to make some T nuts.
Next size up end mill, feed against d.o.r., a slight increase in rpm.
The thing that really annoys me, I ignore the fact I am retired and have the luxury of time to complete any job, without pressure.
Kind regards,
Dennis

 

[Swifty]

Cutting speeds should be, relatively speaking, the same for whatever milling machine you have. It's the depth of cut and feed rate that you can use that is determined by your machine. I'm sure you will be able to google a milling cutter speed (and feed) chart, so just select the diameter of cutter you have, the material being cut, and it should give you the speed to run the cutter at, of course you will have to make allowances for the speeds you have available. A bit of experimentation with depth of cut and feed rates will pay off in the end.

But of course, if you are getting vibration and shaking from your machine, it may be just not stable enough. So make sure you do everything you can to make the mill stable first. I have rarely used table feed over the years, preferring to "feel" the cut by using hand feed.

Paul.

 

[Charles Lamont]

Typically recommended cutting speeds for mild steel are something like 100 ft/min for HSS & 300 for Carbide. This is the surface speed between the tool tip and the work, so you have to do a little arithmetic using the tool (or, in the lathe, work) diameter to find the rpm. Halve these figures for cast iron and even slower for tough steels, and multiply by three for brass and aluminium alloys.

These recommendations are based on commercial considerations of tool life v. work rate, so I tend to regard them as a normal maximum, but often find slower is better. (Sometimes, for example to avoid chatter when turning with a broad radius form tool, much, much slower.)

Then, broadly speaking, you can adjust feed rate for a compromise between finish and your impatience, and depth of cut to suit the rigidity of your machine.

 

[bazmak]

When making T nuts I don't try to do it all one pass,use a no cuts AR.I make one length of 4 nuts and cut to length after.When I have the depth right and just a few thou of the width I take the final light pass climb milling at a faster speed
Gives a good finish

 

[Tin Falcon]

Speeds and feed should be the same for any machine depth of cut needs to be reduced for smaller machines,

 

[bazmak]

Have to disagree Tin.Increased depth of cut means reduced feed
its the volume of matl that matters.and although speed can calculated
to known formulas for different materials its rigity of machine or setup
that becomes a variable

 

[tornitore45]

Tin is correct, RPM must set the optimal SFM for the tool in the mill or piece diameter in the late, feed speed must assure a few thousands of chip load give and take; it increases with the number of flutes. The depth of cut is limited by the HP available which indirectly is related to the machine size/rigidity. Volume per minute is proportional to power but only as an upper limit. I does not help having an beefy motor if the machine or the set up can not handle it. My X3 mill for example, reach the rigidity limit long before the power runs out.

 

[Tin Falcon]

Speed = rpm of spindle
Feed Inches per minute or inches per revolution of the tool in thousands f an inch

This determines the thickness of the chip. The chip thickness needs to be such that the heat from the cut goes with the chip. you want minimum heat retained by the tool or the material.
Depth of cut the distance to tool is engaged into the material.

DOC is limited by the power and rigidity of the machine. As you say this is what determines the volume of material removed with each pass.

 

[bazmak]

You are correct,however I was relating to hand feed and using good judgement/sense of touch and sound.If I take too big a cut then then my rate of hand feed slows down.I mentioned volume as regards to matl removal
For example if I use a flycutter at a fixed depth over 10w material the handfeed
would be faster than I would be able to use if the cutter was cutting over the full width say 50mm.I accept the theory and the fact my machining experience is limited.Hope I haven't offended anyone it was not my intension Regards barry

 

[tornitore45]

Hope I haven't offended anyone it was not my intension Regards barry

Absolutely not. We are all sharing ideas in good spirit.

I machine by feel, sound, vibration, chip look and color, do not ask me what is my RPM, (the knob has only 3 marks) FPM, Inch per minute or chip load, unless I am cutting to dimension the dept of cut is advanced as a visual on the dial.

 

[Tin Falcon]

Most of us are Seat of the pants machinist in that few have a rpm gage on the machine . I do have a speed pot and hand tach if I want or need to. When hand feeding feed chip load is by feel . DOC I measure with a dial indicator.
So unless you have a cnc the numbers are just a target.

My original point to the OP was if he is used to other machines he has a good feel for speeds and feed go with it and just take a ligher DOC on the smaller machine.