Cloudy finish on 4140

[Camputer]

A larger radius or a wiper on the insert would help would help. So would positive, sharp geometry like someone else mentioned.

You said 1inch at 1000sfm and 3000rpm, but 1000sfm at 1inch dia would be 3800 rpm, so I'm imagining you're capping the speed at 3000 (which sounds like plenty to me). You said you ran it up at 1300sfm (5000rpm) and had the same finish, but were you still capping the speed at 3000?

Regardless, if this was me I would drop the feed to .003 or even less. It might still be shmeary but it should be smoother.

 

[William Lynn]

Total.

You stated your insert has a Tool Nose Radius of .015". That is equal to the depth of cut. Increase it .005" or more. When referring to Depth of Cut, it's actual, not total on the diameter.

 

[Neil101]

A larger radius or a wiper on the insert would help would help. So would positive, sharp geometry like someone else mentioned.

You said 1inch at 1000sfm and 3000rpm, but 1000sfm at 1inch dia would be 3800 rpm, so I'm imagining you're capping the speed at 3000 (which sounds like plenty to me). You said you ran it up at 1300sfm (5000rpm) and had the same finish, but were you still capping the speed at 3000?

Regardless, if this was me I would drop the feed to .003 or even less. It might still be shmeary but it should be smoother.

No, I bumped it up to 4000. I’ll try the slower feed and see if that helps.

 

[Neil101]

You stated your insert has a Tool Nose Radius of .015". That is equal to the depth of cut. Increase it .005" or more. When referring to Depth of Cut, it's actual, not total on the diameter.

Okay, thanks.

 

[yowzman]

4140 not common here in the UK but EN19 is similar I think (is it a bastard to break a chip roughing till you get to about 12 thou feed?) I've used similar speeds and feeds and got a good result, but the two things I find after speed feed and DOC for finish is make sure you insert tip is dead nuts on centreline and use a positive enough geometry. I normally use VNMG R0.4 (.015) high positive chip breaker, 300 SMM (980SFM) 0.4mmDOC Radial (.015) 0.1mmFPR (0.004) and get a DVD finish everytime regardless of steel until I have to cut D2 or something gnarly and I just back the surface speed down. The pic looks like smearing so I would check insert centre height and coolant condition/concentration first.

 

[Orange Vise]

Total.

Your DOC, 0.030 total, is fine. In fact, I'd probably take it down to 0.020, which is plenty on a 0.015 TNR insert.

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.

Keep going up. If you're running out of RPM, perform your tests at a larger diameter to nail down your problem. I would go all the way up to 2,000 SFM. I've gotten mirror finishes on 1018 in the 1500-2000 SFM range.

 

[Neil101]

4140 not common here in the UK but EN19 is similar I think (is it a bastard to break a chip roughing till you get to about 12 thou feed?) I've used similar speeds and feeds and got a good result, but the two things I find after speed feed and DOC for finish is make sure you insert tip is dead nuts on centreline and use a positive enough geometry. I normally use VNMG R0.4 (.015) high positive chip breaker, 300 SMM (980SFM) 0.4mmDOC Radial (.015) 0.1mmFPR (0.004) and get a DVD finish everytime regardless of steel until I have to cut D2 or something gnarly and I just back the surface speed down. The pic looks like smearing so I would check insert centre height and coolant condition/concentration first.

Thanks

 

[Neil101]

Your DOC, 0.030 total, is fine. In fact, I'd probably take it down to 0.020, which is plenty on a 0.015 TNR insert.



Keep going up. If you're running out of RPM, perform your tests at a larger diameter to nail down your problem. I would go all the way up to 2,000 SFM. I've gotten mirror finishes on 1018 in the 1500-2000 SFM range.

Thanks.

 

[gcodeguy]

Total.

Then DOC is .015. No help here as I personally don't see why you aren't getting a good finish. I've always liked a cermet for finishing.