Machining 4042 Profile

[Big John T]

Machining 4142 Profile

I'm machining a small part from 1/8 thick 4142 with a 1/4" diameter 2 flute carbide(cheap) end mill and it eats the corners off the mill. My last attempt was 1800 rpm, 1.0 IPM, .025" DOC and it's a full width cut as I'm cutting the part from a piece of stock. Any ideas on different feeds and speeds?

I just ran ME Consultant again it says 2000 rpm, 4 IPM and I know it won't do that.

I'm running dry as I have no flood coolant.

Thanks
John

 

[g-coder05]

Running 4000 series matirial dry you will have to be carefull not to work harden the matirial "wich it sounds like you have allready accomplished. theres a fine line with cutting matirial off and rubbing it off. you need to ask your vendor what SFM and chip load to use. i would say about 350 SFM with a .0012-.003 chip for starters since your using a cheap mill. you should try a vari-mill series 2. 600 SFM with a .0018 chip 5 flute. it will eat pre hard 4150 as if it where 12L14.

 

[Big John T]

The best I could do with a 1/4" end mill is 3000 rpm or about 200 SFM with my mill. Did I mention it is an old BP series 1... The material never got even warm to the touch so I'm thinking that I did not work harden it but what do I know... on my last attempt with 1800 rpm and a 2 flute cutter at 1 IPM my chip load was about 0.0001", perhaps that is where I went wrong with too low of a chip load. The vendor is McMaster Carr so not much help there for cutting.

Thanks
John

 

[Bobw]

First problem, cheap tool. Did it feel good saving the couple of dollars? Guess what now you get to buy another one, and by the time the job is finished, it will have cost you 10 times what one good tool that would have done the job and still been usable would have cost.

I'm not being a jerk, I'm not picking on you, but you just learned a very valuable lesson, buy the right tool and buy quality, quality DOES NOT have to be expensive.

Some cheap crap chinese carbide is really bad. I've tried that route, hit it with a hammer and throw it in the scrap carbide bin.

I'm guessing since it was "cheap" that it has square corners. Those square corners are fragile, even on good endmills. What you have there is a finishing endmill, finishers are for finishing, and roughers are for roughing.

Roughers for roughing has changed a lot, its not just corncob roughers anymore, its a whole wide world or variable helixes and variable flutes, geometries and coatings. Most of these come with a radius on the tips, really beefs them up. Some like the Hanitas have a chamfer, but I've found you still get failure on the 135 degree corner at the edge of the chamfer. At the very least grind some chamfers on your cheapies, maybe .015-.03" that will keep the chipping away. Or if you are a wiz, grind some radiuses.

If I were you, I would go get a few decent endmills.

http://www.lakeshorecarbide.com

Their prices are good, their quality is good(they don't have the best for all situations, but mild and alloys steels, they do pretty good), made on Kennametal blanks, and they pop in here every so often to answer a question or two.

1/4" variable flute are $18 and change, stubbys, $17. No affiliation.

First get a good endmill.

Then on the incredibly conservative side, going full width, 200sfm, and .0005 per tooth, .030 deep. (3000 rpms, 6ipm). If you are running a thin plate and its jumping around, then you will probably have to slow down, but on something that is rigid, you can go much farther than that.

 

[Big John T]

Bobw,

Thanks for the very informative answer. I only used the cheap ones cause they were handy and if I needed one they are a couple of blocks away. Did not realize the difference between a finish mill and a rougher by the bottom chamfer. I always thought the rougher had big teeth on the side... I have seen lakeshore carbide mentioned before on this forum. I did by accident order a varimill with a chamfer to try out yesterday from MSC.

On speeds and feeds, real high SFM's are not possible with my mill on small diameters. It has a 3000 rpm limit so on a 1/4" diameter cutter the highest I can get is about 200 SFM. So if I keep the chip load within the recommended range will I be ok? Also, at this time I cut dry but I am working on adding flood once I build a proper containment system.

I ordered a sampling of LakeShore Carbide vari flute end mills this morning to try out. I don't mind buying quality tooling when I can find out what to buy and from where...

Thanks
John

 

[Bobw]

Big John, check out the dry vs wet thread going on right now, flood coolant is nice for aluminum, but not always necessary, and sometimes a hinderance.

As for the Lakeshore carbide, I noticed they did just go up about 20% on their price. I can't really blame them with tungsten going through the roof and the dollar where its at.

Their varimills are beefy little bastards though and have worked the best(lasted the longest) on our CNC knee mill, with the lack of rigidity and all.

This may help, this morning I ran some thin stuff, .062 4140, full width profile .057 deep, one shot. 2000rpms and 4 ipm, no problem with a Hanita(they have been hanging around for a while, I'm not a Hanita fan) TiAlN coated varimill. No problem, I didn't mess with it, it was a onesy, so just get it done and get it out of here, no point in trying to speed it up, but it worked fine.