Hard milling

[Tim Pruett]

I'm getting excessive tool wear when cutting hardened H13. It's about 53 on the C scale. I'm using Garr ball endmills and  the tips of the tools are wearing away no matter what I do. I was running a 3/8 ball 350MX at 3500 rpm and 55 ipm with a scallop, and parallel toolpaths. I put a lead in arc of .02 in the toolpaths but that didn't help either. Stepover amount is approximately .0045. Then I tried 6500 rpm with 70 ipm. Same thing, the tip of the tool is wore really bad. Probably about .0025 to .003 gone off of the end. I'm using flush coolant. I tried it once with an air blast with the coolant barely turned on so it acts like a spray mist, but got the same results. That was still at 3500 rpm though. I'm on a YCM NSV 102A machine , using NIKKEN NCAT40-MMC8C-90U holders. Thanks,

Tim

[BenK]

I would run only air on hardened H13. Can you post a picture or file so we have a better idea of what you are trying to do? 

[Tim Pruett]

I'm not doing anything complicated at all just using a raster toolpath with a 3/8 ball garr .0045 stepover. The face I'm maching is aprox 5 deg from flat. I will try straight air blast and see if that helps. I'm just not sure where to start with my rpm and ipm. Please advise.

[BenK]

Using a Fraisa D5886.436 .375 BALL I would cut at 12000rpm @ 88ipm. I always try avoiding the tool tip. Maybe try using a bull endmill instead.

[Tim Pruett]

Yeah, I switched to a bull nose about an hour ago cause they seem to be holding up pretty good. Thanks for the help. I appreciate it.

[Redfire427]

Your speed and feed seem a little slow, but having said that, it would all depend on the slope angle you are cutting. Ball tools cut like crap at the centre, so in shallow slope angles, poor surface finish, and tool-life will result. Calculate your true SFM based on the contact point of the ball. You will probably find that your actual SFM is very low. One thing I will suggest is adding an Acculube system to your machine. It only costs a few hundred dollars, and your tool-life will increase dramatically. Our company specializes in high precision, high speed machining in hardened steel, and all of our machines are equipped with Acculube systems. Although the oil consumption is only about one litre per year ( yes, that little ), it is completely safe as it is basically vegetable oil and food colouring. Trust me, it works like a charm.

 

The system on the right is the type we use.

http://metalworking-lubricants.acculuberustlick.com/viewitems/accu-lube-products/minimum-quantity-lubrication-mql-systems

 

Carmen

[Tim Pruett]

Carmen,

 

That must be part of why they're getting better tool life on the roders machines we have. They have a system like that built in. Thanks for the response.

[JoshC]

Well with a similar to 5deg slope and a ball nose tool im sure you can imagine how close to center cutting you are doing. The RPM needed there for optimum tool life may not be achievable with your machine when using ball nose tools with surfaces that close to flat so bull nose pushes the rad to a larger dia and which makes sense why your increasing tool life. I was also going to ask what type of coating you are using on the tool, the coating is another important factor that you may want to consider when buying tooling.

 

but 3500 rpm was too slow in my opinion for a ball nose on a slope that shallow. Unfortunately with surfacing we cant just look at the sfm and rpm but also have to consider tool cutting position.

 

thats just my $0.02

[K2csq7]

How much stock was on before the finish pass?