Small carbide end mill speeds

[radkins]

I came to ask a question and found a similar one already being discussed but my question is not how long can a carbide end mill last but what would be the safest practical speed for a small cutter? Would running slower than optimum recommended speeds shown by the calculators be better or worse?

The particulars are, 1/8" good quality carbide 2 flute end mill being used on 4140 of approximately RC32. Time to do the job is of no concern, I don't care how long it takes within reason, but avoiding the dreaded chatter and resulting chips is a concern! Should I cut dry with air to blow away chips or use coolant? I have searched feed/speed calculators and find best rates for production, etc but I simply need to cut this one slot without chipping/breaking my end mill regardless of how long it takes to do it.

[elf]

It will depend on how rigid your machine is.

[mc_n_g]

You don't give some of the factors needed.
CNC or manual? If CNC it is programmable, if manual you are on your own.
CNC low end recommendation was 0.0001" per tooth, approx 200-300 SFM, which works out to be 6100 RPM and up
You don't say how deep the slot is as this will affect the possible recutting chips. I would say start less than 50% depth to start.
If you have flood coolant why not use it? If not use constant air to blow the chips out of the slot.
No matter what feeds are recommended you can break the end mill for many reasons.
Don't know how rigid your machine is. Don't know how much play you have on your lead screws. Carbide is less tolerant of slop.
The more you hit the carbide with light cuts you are causing it to rub and wear rather can cut, same with HSS

[radkins]

The machine is a manual BP clone and is in good sold condition with max speed of 2700 RPM.

[rkepler]

You're going to need a speeder (I use a TapMatic 62X 6:1) to get the speed up and power feed on the axis you're running to keep the chip load constant. Even then you're likely to blow up an endmill, so have a few spares on hand.

[radkins]

You're going to need a speeder (I use a TapMatic 62X 6:1) to get the speed up and power feed on the axis you're running to keep the chip load constant. Even then you're likely to blow up an endmill, so have a few spares on hand.

So 2750 is not going to work?

[Toolguy]

The 2750 speed will work fine. I've done it lots of times. Run a depth of .05 to .06 per pass, watch the chips you're getting and adjust feedrate accordingly. A 4 flute would work better, but 2 flute will still get the job done. Carbide tools will cut at any speed just like HSS, you just have to match the feedrate to the rpms. I would drill a 1/8" hole at each end of the slot to start and end in.

[Magicniner]

Daishowa do some nice speed increasers, I managed to pick up one of their older 7x models quite cheaply,

- Nick

[Black_Moons]

The 2750 speed will work fine. I've done it lots of times. Run a depth of .05 to .06 per pass, watch the chips you're getting and adjust feedrate accordingly. A 4 flute would work better, but 2 flute will still get the job done. Carbide tools will cut at any speed just like HSS, you just have to match the feedrate to the rpms. I would drill a 1/8" hole at each end of the slot to start and end in.

This. it may just take very slow, presistant feeding to get the job done due to lower RPM's and hence low feed per tooth (feed per tooth goes down as endmill size (and rigidity) goes down)

Do oil your lathe up nicely with way oil. while a tiny cutter won't force the work around, it will be more prone to stick-slip issues.

[lakeside53]

Via a vfd... I run my bp at 5000 often, 6000 now and then, and on rare occassions more... lol. No issues; pay attention to lube - lower the spindle oil weight.