Machining 4140 with LakeShore Carbide & Tormach PCNC - Part 2

I was cutting a piece of 4140 last week and really loved the way it was cutting: it sounded great (very quiet!), it made a beautiful chip stream and left a superb finish. It got me thinking: let's test out various cut recipes to machine 4140 and dive into some of the speeds and feeds details for RPM, feedrate / IPM, chipload per tooth, SFM, etc!

I was using LakeShore Carbide endmills and mentioned this test project idea to Carl at Lakeshore; before I knew it, I had an email from LakeShore Carbide's shipping department - Carl (against my wishes!) supplied the end mills for this test. Please trust his generosity did not influence my review.

The proof is in the pudding, so you'll just have to watch to see how it all ended!

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[Squat]

I dont believe it. I cant believe that finish! I honestly did not see any difference between the conservative cuts and the super hog. Awesome. Absolutely amazing. I am with you on the recipes. I am no cutting expert, and that is where I get hung up. I simply never feel like I hit the right recipe, even with gwizard and patience. Great work, and thanks again for these recipes. 

Next type of failure to try... a high DOC with high MRR. That may lock it up. Basically, this feels like something for a hogging operation.

Last note, 7:45-7:55, don't sell yourself short. You just showed you are a real EFFICIENT machinist, but the rest of your videos show the practical sides of you being a machinist. Real machinist... Real you are. Tormach would not sponsor you if you were not pretty good.

[MrKillavolt]

Man, I am not a machinist, I have a small mill and I am always careful about speeds and feeds. I enjoy your videos immensely.

[zilogfan]

most fun of any video you have done, and I think they are all great! Best part was the stepping up and the discovery. Do this again and start with a length of cut that will after increasing woc it will break the tool. A 3/8 dia tool will get you to your target sfpm with the 5000rpm limit. Really fun video!!!

[daque]

Nice! You asked for some suggestions so here goes nothing. How about showing long depth of cut with small width of cut and fast feed rates like in high speed machining? Something like using an inch of the cutter with 15% step over and see how fast you can push the feed rate. Torque did not seem to be a problem unless I missed it so I'm for more 5, 000 rpm cuts. Keep in mind it's not my machine and body parts that may be injured by such speeds. If your looking to push the cutter until it snaps add some inside corners.

This next set could be as much fun as nascar with crashes and parts flying.

Whatever you come up with I will watch!


Good luck with the open house, I wish I could make it.

[BigMjolnir]

John, that's very interesting data. Knowing how hard you can push your machine and still get good results equates to faster production which means more dollars per day if you have the work available.

If you are going to do more it would be interesting to see how the results differ if the cut is a slot rather than an edge. Chip clearance may be a limiting factor there. Coolant or air blast will probably need to be factored in too.

The Tormach is impressive and Lake Shore Carbide is looking good too!

-- Mike

[Hirudin]

Another great set of videos! Did you forget the still photography or did I just miss it? There really was a STARK difference between 6 and 11 (or, whatever two cuts you showed in your hand at the end).

"What would [I] like to see?"
Hmmm... I like your going up in end mill size idea. Perhaps check 5/16" and 3/8" speeds and feeds and find which size fits with Tormach's power band the best and then see what you can do to get the best MRR. Then that can be your go-to "recipe" (good word) for the times you need to get rid of a lot of stock.

If you're sorta doing the "I'll break some bits for science" thing, maybe increase the stickout to purposely introduce some tool (and holder... and everything else) deflection. You know, see what would be some appropriate speeds and feeds for those times when you need to do a thick part. And speaking of which, it might be interesting to mic the remaining stock every time to see if the amount of deflection is measurable. To take it even further, you could compare your measurements to the estimates in G-Wizard.

(I feel a little bad recommending things I'm too lazy to do myself. :p )

[pierresgarage]

Hi John,
Now You're Talking....
The tools are more prone to heat or break if you get them too slow or don't feed fast enough.
As for wear rate, 30 under rated baby cuts compared to 2-3 well planed cuts, 30 baby cuts are a tool killer...
As you get comfortable with the machine you just push it, except, you plan a safe space in case of a crash, so make the tool break before the machine hits the workpiece.
Great demo, with getting the most from a smaller CNC,
Pierre

[honel]

Something you may want to talk about (if you continue pushing the machine) is holding down the workpiece. As you push things (in my experience width of cut has more effect on this than other things) you impart much more force to the work piece laterally. Typically if you're in a good set of soft jaws or a fixture it's not a problem, but if you're running a vacuum table you should be cautious. I've seen a piece thrown off of a vacuum table before and it's just plain scary. There are enough things to worry about when you're milling- no need to be worried about your part taking leave of the table!

[vdub]

PLEASE run the 5 flutes! I have a few lying around for an upcoming massive cleaver project in CPM 3V.

Love the vids sir

[goptools]

Hi John,
Very interesting video and results!  To increase the load even more, you could try full WOC and increase the DOC too.  The Tormach didn't seem to be straining at all.  I would think the tool would break before the machine would complain.  I don't know how far you want to push it, though.  In any event, it seems like you are pretty safe pushing it a bit harder than you have been for your daily work.
Thanks,
-mike

[BrianFyhnPetersen]

Please also make some HSM videos where you take shallow cuts and go with a significantly higher feedrate, not being too concerned about the surface finish (finishing cut made at last). You should be able to remove much more material. Great video.

[Skraap]

Just a quick FIY: You can get Pi in Excel with pi(), not that it really matters or anything :D

[charles]

from the excel spread sheet it confirmed that you were climb cutting with a depth nearly the width of the cutter.  I have always been told to do normal cuts for roughing and only climb cut for finishing.
What in your setup allows you to do such great cuts?

[GAcaley]

John,

Awesome video great info. Could you do one in the same stlye for like 304 with lakeshores 5 flute mills and maybe a 6061 with Lakeshore's ZrN  coating too. Great info as always

-G
 

[atomkinder]

FYI HSMAdvisor gives a recommended 5120 RPM @ 37.78 IPM for your .25/.1" cuts for 408 SFM @ .00184 chipload. That's a .7 HP cut with an MRR of .94 cubic inches per minute. Let's see it, I bet you'll be surprised ;-)

Also sad to hear you have no spindle load meter!
Also, every number of yours that I put in gives me lower HP. Don't know how GWizard calculates these but I didn't see a coating section. Probably why at that "1.48" HP cut your machine didn't sound close to its limit. At least I didn't get that from the video. It's your machine though, how close do you think it really was to its mechanical limits?

[erichkopp]

I'd like to find out, at what point will you get TTS pullout from the R8?

[jaydeeish]

Ya u should get thats to lens of mine goes great with your Canon 70d

[markrich]

Ramp the feeds n speeds break it or to that point.

[vdub]

Also, see if he will get some of those fireplugs for you. If not I would be more than willing to donate one for you to T&E

[redwingstash]

Keep the higher 5000 rpm as well as upping your feed per tooth it looks like you can go more aggressive