A Few Questions About End Mills And Speeds

[doogledee]

Hi everybody,
I have just finished getting my new mill indtalled in my little shop.

I apologise to most of you for using metric measures, but I live in Oslo, Norway and do everything in metric, although I can get by in inchces and stuffbif I have to

Now before I go messing stuff up I have a few questions.
I have an er 32 collet chuck and a new set of end mills from 4 mm to 20mm diameter (HSS endmills with that hard coating that makes them look yellowish gold, TiNi ?), both 2 and 4 flute types, spiral flutes, not straight) My mill can operate from 80 to just over 2000 rpm.
It has a 1,1 kw motor ( it is also labeled 1.5 hp but that is a fair bit more than 1,1 kw so I am assuming the lower number).

Now I will be milling aluminium and mild steel mostly.
Could someone explain the basics around calculating suitable rpms for the various sizes of end mill?
I have seen a lot of info regarding chip loading and stuff, but I dont understand it all.
I would like to be able to work the numbers for myself, but I need some help with how to do that.

I would guess that the softer the metal the higher the rpm for a given diameter of end mill?
Also higher rpm for smaller endmills in the same material? This would keep the speed of the cutting edge through the material similar, which I am led to belive is a good thing.

Look forward to hearing from you all





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[Cobra]

Hi everybody,
I have just finished getting my new mill indtalled in my little shop.

I apologise to most of you for using metric measures, but I live in Oslo, Norway and do everything in metric, although I can get by in inchces and stuffbif I have to

Now before I go messing stuff up I have a few questions.
I have an er 32 collet chuck and a new set of end mills from 4 mm to 20mm diameter (HSS endmills with that hard coating that makes them look yellowish gold, TiNi ?), both 2 and 4 flute types, spiral flutes, not straight) My mill can operate from 80 to just over 2000 rpm.
It has a 1,1 kw motor ( it is also labeled 1.5 hp but that is a fair bit more than 1,1 kw so I am assuming the lower number).

Now I will be milling aluminium and mild steel mostly.
Could someone explain the basics around calculating suitable rpms for the various sizes of end mill?
I have seen a lot of info regarding chip loading and stuff, but I dont understand it all.
I would like to be able to work the numbers for myself, but I need some help with how to do that.

I would guess that the softer the metal the higher the rpm for a given diameter of end mill?
Also higher rpm for smaller endmills in the same material? This would keep the speed of the cutting edge through the material similar, which I am led to belive is a good thing.

Look forward to hearing from you all





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If you want to PM me with your email, I can send you a chart that will give you the SFM for various rpm.
The bottom of the chart also has the recommended ranges of SFM for various materials.

 

[Techie1961]

Speeds and feeds are standardized very well. You can find the information online if you do a search for "cutting feeds and speed", you'll find a lot of information on it. There are charts that you enter your information into and it will give you the RPM to use.

You can also calculate it once you know the speed for the cutting material and the material to be cut. A little math for circumference of the cutter and you can get to the RPM.

Good luck with the new machine.

 

[Sandro]

This is a simple way to remember cutting speeds using high speed steel and cutting ordinary mild steel.

25 mm diameter = 400 rpm
12 mm diameter = 800 rpm
50 mm diameter = 200 rpm

Softer material like aluminum, go twice as fast. Harder materials like tool steels, go half as fast.

If you use carbide cutting tools then just double everything.

This isn't the most accurate way to calculate cutting speeds but it is easy to remember and close enough to get started. If you feel the machine can go faster or needs to go slower then change the speed and see how it goes.

I hope this helps.

Sandro Di Filippo

 

[T Bredehoft]

The above is a good approximation. With experience will come understanding. You also need to understand chip load.It's not really hard, once you get on to it

Two flutes on a cutter should be removing at least one .001 (inches) or .025 mm per tooth as it turns. less and friction (heat) will damage the cutter, Too much more and load will break down the cutting edge.

I would suggest you use endmills from 2 to 12 mm diameter. A 2mm endmill, two flutes, in steel should run about 1500 rpm, or if my math is right 150 meters per minute of surface (circumference of cutter). (I'm not sure about that 150 figure.)

Each cutter should take about .025 mm per cut, less and friction will burn up the edge, Much more and chip load will break down the cutting edge, leading to breakage.

Study these numbers, find my errors and you will realize what is invovled. It's difficult to maintain any feed rate with a manual mill, so don't worry too much about it, once you're cutting regularly, you'll learn the feel of a propper cut.

 

[joshua43214]

This guy a great job of breaking it down and even gives metric examples too boot

 

[doogledee]

You guys are fantastic, I agree I should have googled some more first, sorry. The information here is plenty to get me started


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[doogledee]

The above is a good approximation. With experience will come understanding. You also need to understand chip load.It's not really hard, once you get on to it

Two flutes on a cutter should be removing at least one .001 (inches) or .025 mm per tooth as it turns. less and friction (heat) will damage the cutter, Too much more and load will break down the cutting edge.

I would suggest you use endmills from 2 to 12 mm diameter. A 2mm endmill, two flutes, in steel should run about 1500 rpm, or if my math is right 150 meters per minute of surface (circumference of cutter). (I'm not sure about that 150 figure.)

Each cutter should take about .025 mm per cut, less and friction will burn up the edge, Much more and chip load will break down the cutting edge, leading to breakage.

Study these numbers, find my errors and you will realize what is invovled. It's difficult to maintain any feed rate with a manual mill, so don't worry too much about it, once you're cutting regularly, you'll learn the feel of a propper cut.

So if I understand correctly, a 4 flute endmill should have twice the feed rate of a 2 flute endmill to maintain the same chip load, but the rpm of the cutter is the same for both?




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[doogledee]

This guy a great job of breaking it down and even gives metric examples too boot

Great video, learned a lot, thanks


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[Eddyde]

Sorry I didn't read read it correctly I thought you were referring to feed rate...