Speed for Indexible End Mill

[GordTopps]

I have just taken delivery of this Indexible End Mill

I would like to know what is the best speed (rpm) for using this on Mild Steel.

I have read so much about carbide cutters, they need fast speeds etc.
I certainly don't want to break a cutter on the first use by using incorrect speed.

Also is it suitable for using side cutting as well as face cutting?

Thanks for any further info

Gordy

 

[Blogwitch]

Gordy,

That is exactly the same one as I use. A very robust metal muncher.

It is very difficult to quote accurate speeds for tooling like that. When I last used it on steel, I think I ran it at around 400rpm with a 0.020" (0.5mm) cut. But I do have a beefy machine.

The machine and tool will usually tell you if it is happy at that or not. I don't think you will do any damage to it, the tips have taken a beating on mine, and they are all still in good condition.

I suppose it could be used as a side cutter, as the tips are fitted with the sides at 90 degs to the table, and if I remember correctly, it stated something in the advert about the angle, but I have never tried it for that.

I usually use it for removing metal from the top of a bit of tough stuff when the fly cutter won't touch it, and it gives very good finishes.

Blogs

 

[kvom]

Plugging Bogs' numbers for mild carbon steel into the G-wizard calculator (400 rpm, .02 DOC) with full engagement (i.e., cutting a slot), a feedrate of 15 IPM requires .53 spindle HP. So these would be reasonable for a 1HP mill. Increasing the DOC to .05 gives 1.31HP. So now a feed rate of 5 IPM would give .44 HP. For a roughing cut (65% radial engagement), a feed rate of 10 IPM would require .57 HP.

So there are several "degrees of freedom": DOC, spindle RPM, radial engagement, feed rate to consider.

 

[rake60]

I use the simple formula that I have posted here before.

(SFM ÷ Diameter of Cutter) X 3.82 = RPM

Carbide cuts steel best between 200 and 300 Surface Feet per Minute.
Surface speeds slower than 200SFM on steel will usually result in a chipped edge.
Speeds faster than 300SFM are asking to burn up the cutting edge.

(200 ÷ 2.5) X 3.82 = 305RPM

(300 ÷ 2.5) X 3.82 = 458RPM

Blogs 400RPM is very close to the middle of that range. It would be a great starting point.

When the material is brass or aluminum those speeds increase dramatically.

Those tools are generally considered to be facing mills.
I'd be a little timid about side cutting with one of them.

Rick

 

[Blogwitch]

It is very difficult to quote accurate speeds for tooling like that

That is my quote, and I love it when the lads come along and give such exact figures, nothing wrong with that at all, if you have all the exact facts laid bare before you.

Even though I do use tables sometimes, I never do it religiously, all because something called 'mild steel' could mean a myriad of materials, materials with names such as phos bronze and stainless conjure up a nightmare of a scenario when trying to calculate out exact cutting rates.

It might seem a little slapdash of me talking about listening to the machine and cutter, then adjusting the feeds and speeds to suit, but that is always the way I do it when in first contact with an unknown material, which I think happens a fair amount in our circles, as we are the vultures of the machining world, cleaning up the dregs of other peoples throwaways and recycled materials.

A spark test can sometimes help in pointing you in the right direction, but that is wide open to debate because of the way people interpret their findings. But at least it should put you on the right sort of track.

I would like to think of it as intuition on my part, being able to guesstimate a rough starting point for the material I have in the vice, others just might call it a lucky guess.

Am I wrong doing it the way I do?

Flying by the seat of my pants, and 99% of the time ending up with perfect finishes and exact sizes, or following exact figures and accepting what the machine gives me.

I would bet a lot of the professional machinists amongst us don't stick rigidly to the figures when manually machining up a lump. I'm sure they all give a little tweak here and there to get it 'sounding' or 'feeling' right.

But what other starting point do we have when challenged with an unknown material?

This would be a great article for a debate.

"With an almost unknown lump of metal, where do we start, charts or intuition?"

I personally don't think there is a right or wrong way when it comes to doing jobs like we do. If you find one way works for you, then stick with it, otherwise try another method.

Blogs