MRR 4140HT (PH)

[soofle616]

I have been looking into some air blast options but right now unless I want to roll my own the only option is the smart cool to the tune of 500 bucks. Granted I've spent probably more than that on failed cutter experiments in the last month but it's still a little bit of a pill to swallow. I know it would be relatively trivial to just fix a nozzle somewhere and attach it to my compressor so I might do that as an interim step

[Bob La Londe]

I have been looking into some air blast options but right now unless I want to roll my own the only option is the smart cool to the tune of 500 bucks. Granted I've spent probably more than that on failed cutter experiments in the last month but it's still a little bit of a pill to swallow. I know it would be relatively trivial to just fix a nozzle somewhere and attach it to my compressor so I might do that as an interim step

Roll your own is pretty easy. A regulator, a manual valve for adjustment, and if you want to machine control it a solenoid valve. Then you could just flip a switch to switch between air blast and coolant if you want to control it by code.

[Bob La Londe]

Roll your own is pretty easy. A regulator, a manual valve for adjustment, and if you want to machine control it a solenoid valve. Then you could just flip a switch to switch between air blast and coolant if you want to control it by code.

I didn't bother to get fancy with mine because I don't cut all that much steel. just every once in awhile. I turn it on and turn it off by hand. I use a little ball valve to control the flow rate and I leave it at shop line pressure
It does use a lot of air. I've got a middle-sized air compressor at 3.7 horsepower with an 80 gallon tank and when I'm running the air blast and a few other machines the compressor is running about 40% of the time.

[Bob La Londe]

I didn't bother to get fancy with mine because I don't cut all that much steel. just every once in awhile. I turn it on and turn it off by hand. I use a little ball valve to control the flow rate and I leave it at shop line pressure
It does use a lot of air. I've got a middle-sized air compressor at 3.7 horsepower with an 80 gallon tank and when I'm running the air blast and a few other machines the compressor is running about 40% of the time.

For shallow slotting I don't need as much air but for deep pocketing or deep slotting I turn the air up more or rather open the valve up more.

[BIRDTOOL]

(currently has a major problem in one lead screw)

Bob is your hurco direct drive from the servo? When ours experienced your issue it was just the belt between the servo and ball screw.

[Bob La Londe]

X axis is direct drive. Almost has to be a catastrophic ball nut failure. Could be a bearing or the coupler, but not likely as bad as it is. It went from about the normal .001 backlash to over .030 in a couple hours while a job was running. Fortunately it just made the roughing OP for a big very simple mold cavity to small. I was able to finish it on the Tormach without scrapping the part.

I've actually been using it "as is" for rough face milling blanks to size using a 3" 5 insert face mill the last few days. Just make sure I am making every pass in conventional with enough bite to keep it pushed back against the backlash.

Y & Z are belt drive, but both have new timing belts. (Relatively new.)

[Bob La Londe]

Been busy. Sorry I have not gotten back to you guys on this. I was just modifying a screwless vise (grinder vise) for use on one of my smaller machines.

Using a totally unscientific hardness test by popping it with a spring punch, and popping a piece of 4140HT with the same spring punch the punch mark was slightly smaller on the vise. I conclude that its likely its harder than the 4140 HT.

I decided to start with a recipe from HSM adviser for 4140HT (with my own parameters to meet the needs.

Tool: Inexpensive Accupro 3/8 4 flute AlTiN coated carbide rougher.
DOC .375 (1xD)
WOC .075 (20%)
RPM 3465
Feed 44.44
MRR 1.36 in^3
HP 1.09
Direction Mixed

I ran the whole cut which was about 16 passes. The first part of the cut was only removing a depth of about 0.250 It was loud, but left a pretty nice finish so I let it run. When it got into the meat of the cut it bogged down on a conventional pass It might have bene the first pass at full depth. I hit the feedhold, adjust the feed down to 17ipm, and then ramped it back up to about 27IPM. At 27IPM it sounded like the .25 depth of cut, and left just as nice of a finish.

I know. I know. Totally not a definitive useful test of anything since the vise is harder than 4140HT.

The 3/8 rougher worked, and left a nice cut. In the mystery metal I was cutting it achieved about 0.77MRR in^3 at full depth, but under the original parameters it was capable of 0.91 MRR in^3 at a DOC of .25.

The first cut was done to quickly to do much more than that. Conclusion... In some mystery medium hard metal I can remove atleast 0.91 MRR. LOL.

[Bob La Londe]

Good thing for autosaved content, or that last post would have been lost.

Forgot two tool parameters in the previous post. 0.875" stick out and 0.500" flute length.

I went back to make the second cut for this, programmed it at 35.5 IPM, and left it as mixed machining. It still sounded about the same and still left a decent finish. Phenomenal for a rougher. I'm not going to take a separate finish pass.

That puts it at 1.00 MRR in^3 in a metal slightly harder than 4140HT.

RECAP:

Tool Accupro 4Flute Carbide Altin Coated 3/8 Rougher.

RPM 3465
DOC 0.375
WOC 0.075
HP 0.800 (if it was 4140HT which its not)
Direction mixed.
Totally dry. No air. No coolant


I picked 35.5 because it worked out to exactly 1 cubic inch per minute. I think it would take a little more, but I'm not going to push it until I am working with a know metal again.

P.S. Of course its not really 1 in^3. A lot of time is wasted to stop and reverse. Its 1 in^3 during the time its engaged in the cut.

[Bob La Londe]

I posted a short video clip of the cut here. That slight surging sound in the video was not audible in person.
https://www.facebook.com/10000044182...65564816801544

That tells me it might be just beyond the limit for that material, or maybe I need to tweak the RPM to change the harmonics.

It was run dry without air, and at 3X (magnifier lamp) that cut and the previous one produced not chipping or noticeable wear on the tool. I expect the tool would not last long run like that, but I'll have to wait and see. This was an ideal cut with plenty of chip clearance. Obviously I'd need something to blast chips out when slotting or pocketing.

To anybody who wants to poo poo for modifying a vise, this modification will allow me to use nearly 100% of the work envelope on the Speedmaster mill. That's worth more than a vise. It had already been modded for the job. This quick chore just modified it further for clearance to drill through and thread mill parts. I have an already similarly modified vise on the other Speedmaster.

[Kenny Duval]

Your vise Bob. If someone wants to have some say about whether a vise gets modded they can buy their own.

[Bob La Londe]

I'm starting to really like that Accupro 4 Flute AlTiN coated rougher. Its not an expensive tool (its not super cheap) but it does a decent job and provides a pretty good finish for a corn cob.

Yesterday I needed to rough off a bit more of one of those vise jaws. I had a fixture plate mounted on the Tormach so I fired up the Hurco with its horrible ball screw failure and used it in just conventional to do the job. Since I was removing part of the face of the jaw which includes the v-grooves it was an interrupted cut. It was a lot lighter DOC (0.100) cut than my tests on the Tormach but it just sounded sweet. Sine I have air blast setup on that machine I used it, but I never saw a spark. Just small blue chips. Otherwise I used all the same cut parameters. This just might become a stock end mill for me. Its stub length with only a 1/2 inch flute length, but it does a good job within its range.