Vent: I ran the same job with two different coolant mixes and the results were night and day

Last week I was cutting a batch of 4140 steel parts. The first half I used our shop's standard 5% mix. The finish was okay, but I got some built-up edge and the inserts wore out after about 30 parts. For the second half, I bumped the concentration to 8% like an old timer suggested. The finish was way cleaner, the chips broke better, and I ran 50 parts before even thinking about the tool. Has anyone else found a sweet spot for coolant concentration on tougher materials?

3 comments

3 Comments

amy_reed792mo ago

Try a refractometer to check your mix. That 7-10% range works great for heavy cuts.

the_gray2mo ago

Wait, you ran 50 parts on one set of inserts? That's crazy, I'd be lucky to get half that.

the_lee2d ago

The 8% mix is the real deal for 4140. I've found anything under 6% on that steel just lets the chips weld up and kills your edge quick. @the_gray, if you're only getting half that part life, check your concentration first before blaming the insert grade. Some guys run 10% on heavy roughing passes and it can actually cut down on tool chatter too. You tried bumping it up yet on your next run?