Cloudy finish on 4140

[Neil101]

Hey fellas,

Any recommendations on FEED, SFM, DOC for 4140 steel?

The finish diameter is 1 inch.

I’m using a 35 degree insert w/ .015 TNR and running 1000 SFM, 3000 RPM, .030 DOC, and F.005 for the finishing OP.

I’ve tried a lower DOC of .010 but got the same finish.

These are recommended fn, ap and vc on the back of the insert pack

fn: .003 - .012
vc: 1000 - 1300
ap: .01 - .059

 

[Panza]

1000 rpm is too slow, 3000 is probably too fast if it's HT and you want your inserts to last. The max recomended Vc on the package is not for 4140HT. I've seen that haze too, but never after the finish pass. I usually run Ap of 0.012" with a DCMT insert.

 

[david n]

Looks like the chip is rubbing?...................What's the TNR? Your finish DOC should be more than the TNR...........and many times a deeper finish cut will yield better results.

 

[escapethewrmhole]

Use CSS and an SFM of about 800. If you used RPM over SFM and used 3k rpm you are basically there anyway.
Feedrate of .008 IPR
DOC something slightly more than tool nose radius.
This assumes you used coolant so your built up edge isn't depositing on the bar as it goes.

 

[Neil101]

Looks like the chip is rubbing?...................What's the TNR? Your finish DOC should be more than the TNR...........and many times a deeper finish cut will yield better results.

It’s .015

 

[Neil101]

Use CSS and an SFM of about 800. If you used RPM over SFM and used 3k rpm you are basically there anyway.
Feedrate of .008 IPR
DOC something slightly more than tool nose radius.
This assumes you used coolant so your built up edge isn't depositing on the bar as it goes.

I’ll give this a try. Thanks.

 

[Milland]

Dumb suggestion from a guy who's predominantly a milling hand, but plunge in to face, then move to the right for the finish pass? Or is that what you're doing?

 

[Orange Vise]

Finish looks normalish for 4140 annealed.

For unhardened material, 1000 SFM is about the minimum required to get a smear-free finish. Try 1300-1500 if you can.

P.S. Parts made with 4140 annealed generally don't have a strict surface finish requirement. This material is meant to be heat treated. If you're not heat treating, there are better materials available that'll allow you to get better finishes without cranking up the SFM so high, like Stressproof. Of course that's up to the designer.

 

[Neil101]

Finish looks normalish for 4140 annealed.

For unhardened material, 1000 SFM is about the minimum required to get a smear-free finish. Try 1300-1500 if you can.

P.S. Parts made with 4140 annealed generally don't have a strict surface finish requirement. This material is meant to be heat treated. If you're not heat treating, there are better materials available that'll allow you to get better finishes without cranking up the SFM so high, like Stressproof. Of course that's up to the designer.

Okay, I'll try that.

 

[Mtndew]

Are you using coolant? I would feed a little faster if the finish requirements allow it.

 

[DanASM]

Looks like a standard finish for 4140 colld drawn annealed. It likes to tear at lower hardness.

 

[david n]

For finishing anneal 4140 sometimes likes a bigger TNR and even a stainless grade insert................little more shearing action than the regular honed edge of a steel grade..............

 

[CarbideBob]

Cute.
This type finish a big problem for so many.
And yet so many ways out.

 

[Neil101]

Are you using coolant? I would feed a little faster if the finish requirements allow it.

Yes, I’m using coolant.

 

[Neil101]

For finishing anneal 4140 sometimes likes a bigger TNR and even a stainless grade insert................little more shearing action than the regular honed edge of a steel grade..............

Okay, I’ll try that. Thanks

 

[csteen]

Okay, I’ll try that. Thanks

Get yourself any manufactures coated cermet. Run it finishing at least 1,000 SFM and your tool nose radius deep. Adjust feed per finish requirement.

 

[Neil101]

Get yourself any manufactures coated cermet. Run it finishing at least 1,000 SFM and your tool nose radius deep. Adjust feed per finish requirement.

I’m using a coated cermet insert, taking a .030 DOC and running the finish at 1,000 SFM. Today, I bumped it up to 1,200 SFM but I’m still getting the same finish.

 

[Nerdlinger]

Is the material prehard or annealed?

 

[Mtndew]

taking a .030 DOC

Is that per side or total?

 

[Neil101]

Total.