[Magnum164]

Finding speed and feed information is still a little hard for me. While I am learning the SFM/IPM I am not sure how to determine what the best cut depth vs cut width would be as well as the best starting RPM.

For instance I am about to make a hole pocketing with a 1/6 4FL (or 2FL) carbide end mill.

What's a good way to determine the best starting point for a size tool you are not familiar with?

[judleroy]

A good starting point as standard should be 1/2 the diameter for depth and 50% stepover. That is what is recommended by most tool manufacturers. That is for standard length tools of course.
Judleroy

[benji2505]

Tormach works and cooperates with a website that has a pretty sophisticated feeds and speeds calculator. Check their website and their blog.

In order to give you a quick fix I have attached a spreadsheet that I am using and Ihad a pretty good experience with the results. The calculations are based on experience from other people on this forum and my own speeds and feeds.

The calculation itselfs is on the left, the values to be filled in are on the right. Values to be filled in are colored. Infos about cutting depth and overlap are on the lower right hand corner.

Hope you like it

Benji

[Magnum164]

A good starting point as standard should be 1/2 the diameter for depth and 50% stepover. That is what is recommended by most tool manufacturers. That is for standard length tools of course.
Judleroy

Thanks, I had read about 50% stepover but not the depth. That 1/2 the dia would make since to me for a start.

But the RPM is also going to affect that as well. I tend to run everything at around 3500-4000 RPM, but I know I am probably very low on RPM on the smaller carbide end mills.

[jharvey407]

Magnum164,

I have been having the same problem of not knowing what feed rate or depth of cut to use for my tools so I have been running test cuts to determine the best feeds and depths for tooling.

A couple of days ago I was testing a 1/4" o-flute endmill for cutting aluminum. I programmed a zig-zag pattern with each leg 2" long. I programmed the cut to increase the speed for each leg. I ran the cut starting at 10 ipm and increased 10 ipm for each leg. I ran my first cut at a depth of .1250".

I ran the test with one hand on the e-stop, and I knew that there was a chance that I could break a tool, but I let it rip.

The cuts actually improved markedly upto 50 ipm, and then the quality dropped off rapidly and I stopped the test.

Looking at the test cuts it was easy to pick the proper speed for that particular tool and material. It also showed me that at too slow of a feed speed the tool was not able to eject the chips from the cut properly.

This is going to be my SOP for determining feeds and speeds until I hear of a better method.

I hope this helps.
Good luck,
James

[Magnum164]

Tormach works and cooperates with a website that has a pretty sophisticated feeds and speeds calculator. Check their website and their blog.

In order to give you a quick fix I have attached a spreadsheet that I am using and Ihad a pretty good experience with the results. The calculations are based on experience from other people on this forum and my own speeds and feeds.

The calculation itselfs is on the left, the values to be filled in are on the right. Values to be filled in are colored. Infos about cutting depth and overlap are on the lower right hand corner.

Hope you like it

Benji

Thanks will take a look. Yes, I own G-Wizard if that is the software you are referring to, but I am not fond of that software.

[Magnum164]

Magnum164,

I have been having the same problem of not knowing what feed rate or depth of cut to use for my tools so I have been running test cuts to determine the best feeds and depths for tooling.

A couple of days ago I was testing a 1/4" o-flute endmill for cutting aluminum. I programmed a zig-zag pattern with each leg 2" long. I programmed the cut to increase the speed for each leg. I ran the cut starting at 10 ipm and increased 10 ipm for each leg. I ran my first cut at a depth of .1250".

I ran the test with one hand on the e-stop, and I knew that there was a chance that I could break a tool, but I let it rip.

The cuts actually improved markedly upto 50 ipm, and then the quality dropped off rapidly and I stopped the test.

Looking at the test cuts it was easy to pick the proper speed for that particular tool and material. It also showed me that at too slow of a feed speed the tool was not able to eject the chips from the cut properly.

This is going to be my SOP for determining feeds and speeds until I hear of a better method.

I hope this helps.
Good luck,
James

I tried that with a 1/4" running at 12IPM and broke the bit. I think that was about 3500 RPM.

Did you increase RPM any?

[jharvey407]

I tried that with a 1/4" running at 12IPM and broke the bit. I think that was about 3500 RPM.

Did you increase RPM any?

Sorry, I should have been a little more detailed in my explanation.

I am running a 1 3/4 hp router at 27,500 rpm. The tool from amana was marked with a max rpm 35,000. Amana's recommendation was 120 ipm at 18,000 rpm, but my machine is not robust enough to drive the tool at 120 ipm.

You may want to try staring at 1 or 2 ipm, but the method should still work.

James

[howecnc]

I found that the 20% rule on depth of cut will always get you by in aluminum. Then I use a 1% chipload for the cutter. so for a 1/16 4 flute endmill in aluminum I would use 5000 rpm's at a feed of 12.5 and a depth of .0125.

in steels I got to 1/2% on chipload and 10% on depth of cut.

Using percentages to calculate feeds and speeds works very well for me.

SFM is the real variable and usually the rpm is higher that the tormach will go.

[Magnum164]

I found that the 20% rule on depth of cut will always get you by in aluminum. Then I use a 1% chipload for the cutter. so for a 1/16 4 flute endmill in aluminum I would use 5000 rpm's at a feed of 12.5 and a depth of .0125.

in steels I got to 1/2% on chipload and 10% on depth of cut.

Using percentages to calculate feeds and speeds works very well for me.

SFM is the real variable and usually the rpm is higher that the tormach will go.

Thanks, should mention also that I have a 770, so I can go to 10K RPM.

[BobWarfield]

Careful when you go below 1/8" diameter cutters. Micro-milling follows some different rules because you start to get negative rake no matter what you do. You just can't make the tiny cutters sharp enough relative to the chipload. G-Wizard uses a completely different algorithm for these cutters.

Cheers,

BW

[Joe Em-1]

is there just i good formula that i can use to mill aluminum. given that im using small carbide cutters?
im also running at about 20,000 rpms

[dertsap]

is there just i good formula that i can use to mill aluminum. given that im using small carbide cutters?
im also running at about 20,000 rpms

best thing to do is look at the manufacturer specified speeds and feeds or talk to the tool rep , speeds and feeds are dictated by different carbides , coatings and tool geometries , not to mention the variables of what is being machined and how . there isn't a one stop formula , though an educated guess can go a long way

[Magnum164]

though an educated guess can go a long way

Or cost you an expensive EM.:wave:

[dertsap]

Or cost you an expensive EM.:wave:

it can but thats why i say an educated guess
heres an example , I've got a customer who was blowing thru expensive 1" endmills like they were candy (roughly 40 every 2 weeks) and he tried nearly everything on the market . I brought in my tooling to test and told him that full slotting on hardened 4340 at a depth of over 1 1/2" wasn't a good idea , but he demanded that he wanted to and was going to continue machining this way . So based on the manufacturer specs and all of the factors of the job , I came up with speeds and feeds that not only dropped jaws when it started cutting but knocked their tool count and machine time down dramatically .

I've been machining for a long time and have worked thru a lot of ugly materials and situations , and for the most part I am a large believer of following manufacturer specs but there are occasions that some jobs need to be assessed and things need to be tweaked to get optimal performance, following specs is the overall best place to start when calculating speeds and feeds , experience is what will dictate how a guy can go about over riding that

tools that are run too hard risk breakage , wander and poor finish , tools that are running to slow can face breakage , premature tool wear , poor part finish etc , even on butter like aluminum

.

[abesau]

Tormach works and cooperates with a website that has a pretty sophisticated feeds and speeds calculator. Check their website and their blog.

In order to give you a quick fix I have attached a spreadsheet that I am using and Ihad a pretty good experience with the results. The calculations are based on experience from other people on this forum and my own speeds and feeds.

The calculation itselfs is on the left, the values to be filled in are on the right. Values to be filled in are colored. Infos about cutting depth and overlap are on the lower right hand corner.

Hope you like it

Benji

Awesome spreadsheet. would you happen to have one for wood??

[Steve Seebold]

You've told us what tool you're going, now tell us what material you're cutting and what you're doing to it.