Need help determining cutting speed for parting.

[cyber0826]

Hey everyone! Apologies for the long post:

This is new stuff to me as im a couple of months in as a machine operator/programmer (star swiss) and unfortunately I dont have anyone to ask for help. I have a new parting insert from sandvick to use for stainless steel with a .125" bar diameter. I need help determining if I calculated the correct cutting speed.

I was given the following start values for said insert:

MACL 3 070-N 1105

fnx 0.002 in/r (0.002 - 0.003)
hexx 0.002 in/r (0.002 - 0.003)
vcx 730 sfm (800 - 690)

I used the formula from sandvicks website:

n= (Vc × 12)/(3.14 × Dm)

and ended up with 22,318 r/min.

The number seems a little high to me, probable because my main spindle tops at 15,000 RPM.

Am I doing this right or will I need another insert ? Any help is appreciated.

 

[DouglasJRizzo]

Hey everyone! Apologies for the long post:

This is new stuff to me as im a couple of months in as a machine operator/programmer (star swiss) and unfortunately I dont have anyone to ask for help. I have a new parting insert from sandvick to use for stainless steel with a .125" bar diameter. I need help determining if I calculated the correct cutting speed.

I was given the following start values for said insert:

MACL 3 070-N 1105

fnx 0.002 in/r (0.002 - 0.003)
hexx 0.002 in/r (0.002 - 0.003)
vcx 730 sfm (800 - 690)

I used the formula from sandvicks website:

n= (Vc × 12)/(3.14 × Dm)

and ended up with 22,318 r/min.

The number seems a little high to me, probable because my main spindle tops at 15,000 RPM.

Am I doing this right or will I need another insert ? Any help is appreciated.

Your math is correct. However, that seems a mite high for part off.
You may want to experiment a little and start at the low end, say 6k.

 

[cyber0826]

Looks good so far. 6k is far from the 22k sandvick was suggesting lol. Thank you!

 

[TeachMePlease]

You CAN run that particular insert at the manufacturer recommended rates in a swiss. But you can ALSO run it at about 3000RPM and .001 IPR for cutoff, and get a predictable tool life of thousands of parts without sudden random cutoff explosions. Up to you.

 

[guythatbrews]

What kind of stainless steel? 303 is way different from 316 is way different from 416.

The feedrate seems high for a .028 wide insert in ss. I'd probably run about .0008"/rev. And even on 1/8 material, well directed HP coolant will make a difference.

Those little inserts are $$$, and if you break one end the other end is useless. Unless you have many, many parts to make and need to save a second or two it pays to be more conservative. It takes a lot of seconds to pay for another insert plus insert change time plus maybe something else wrecked.

 

[cyber0826]

What kind of stainless steel? 303 is way different from 316 is way different from 416.

The feedrate seems high for a .028 wide insert in ss. I'd probably run about .0008"/rev. And even on 1/8 material, well directed HP coolant will make a difference.

Those little inserts are $$$, and if you break one end the other end is useless. Unless you have many, many parts to make and need to save a second or two it pays to be more conservative. It takes a lot of seconds to pay for another insert plus insert change time plus maybe something else wrecked.

It's 303 stainless. Sadly, no HP coolant. I ended up breaking one end of the insert, is the other one really useless now? I'll keep that in mind and be as conservative as can be, I will have to run many part using this insert. Thank you

 

[cyber0826]

You CAN run that particular insert at the manufacturer recommended rates in a swiss. But you can ALSO run it at about 3000RPM and .001 IPR for cutoff, and get a predictable tool life of thousands of parts without sudden random cutoff explosions. Up to you.

Thank you

 

[guythatbrews]

I ended up breaking one end of the insert, is the other one really useless now?

Look at how the insert registers in the holder. If only the tip is gone you are fine. If more of the blade is gone the insert may not register properly.