Instructor approves cutting steel at 2000sfm

[Job Shopper TN]

It’s sad. These are some of the jokers they get to teach the next generation of machinists and tradesmen. What a joke.

 

[sendithard]

From your pic, is this the machine?

R-5030 Model in Ares-Seiki Tapping Machinery

That's only a 30 taper; they have notoriously weak pull studs; it's easy to snap one, which can result in ruining the spindle taper. I would NOT advise running a 3" facemill in steel on a 30 taper unless you REALLY know what you're doing, and then you'll be limited to shallow passes.

Nice grab my fiend...that is the exact machine in question.....I have a question aside from this deal..Wouldn't a simple .04 in face mill pass on this machine work if done at 100sfm and and a proper chip load.?

 

[mhajicek]

Nice grab my fiend...that is the exact machine in question.....I have a question aside from this deal..Wouldn't a simple .04 in face mill pass on this machine work if done at 100sfm and and a proper chip load.?

I'll have to leave that to the 30 taper experts here (there are quite a few). I've run 40 tapers most of my career, and now have a 20 taper with 50,000 RPM.

 

[plastikdreams]

I'm still surprised that this actually happened. I thought maybe it was going to be used as a teaching moment maybe. Like, ok so we talked about running it like this, but actually it should be run this way instead.

I wonder what the actual reasoning was with the instructor...why would he do this and think it would be ok?

 

[Milland]

I wonder what the actual reasoning was with the instructor...why would he do this and think it would be ok?

That's what seems so odd about this whole thing - anyone who's done machining even for a short time has had the concept of speeds and feeds presented to them, and this instructor is being portraided as someone almost willfully ignorant on the matter.

Odd indeed...

I do like the idea of bringing in a tooling representative to give a overview of such things. It could be framed as a general introduction to tooling use (and give the rep an "in" for sales), but with an emphasis on practical S/F and how to balance life vs. metal removal, safety, and factoring in machine HP and stiffness. All of this seems needed for proper education of the students.

 

[DMF_TomB]

I've learned a ton from my machining tech instructor, but we are working on cnc stuff now and it seems he just wants to break world records. I have some CAM experience and watching these young 20 yr olds be instructed to run at max rpm is worrying to me. Maybe I am wrong, that is why I post this issue.

We have a basic small vertical mill with a bt-30 holder and 4-5 horsepower spindle that can run 10,000rpm and weights roughly 2500 lbs. A student always asks me questions on CAM b/c the instructor is an old school hand programmer at heart. I always tell him to try steel at 200-300sfm for our HSS cutters and limit the cut to 15% radially. Today, the instructor tells him I am wrong and to run the 3/4" HSS endmill at max rpm(10,000), b/c we are only cutting at .4 doc. This is still 2000sfm and it is 1018 steel. Then they laugh when I say the .780 slot is going to be quite the experience at 160ipm and 10K rpm with a .75 HSS cutter. Part of the issue is the part is only 4 inches long so many features the machine can't get up to speed, unless I'm wrong on the acceleration...

Anyway, I put my foot down this morning and told them I thought this was wrong. I suggested students should be running parts at 200-400 sfm in steel. I was told I was wrong and parts shouldn't be run with 6 spark plugs pulled out of the engine. I don't have real world experience, but I care about what is right and the students. Am I wrong to fight against 2000sfm in steel?

Thanks.

.
after collecting massive amounts cutting data (trying the impossible) and can find
.
1) yes cutting with carbide or hss tooling at 2000 sfpm at .0030" to .0100" ipt feeds not a good ideal
and horsepower limits and being able to hold tons of cutting forces is a concern
.
2) BUT some use router speeds and feeds that is 2000 sfpm (or much faster rpm) at .0001" to .0002" ipt feeds,
cutters act different when using way different settings from "normal".
.
obviously sudden tool failure that is dull tool not cutting and building up heat and melting and breaking
cutter, tool holder, part, machine etc needs to be a concern. my point is for example
.
metal cutting circular saw blade
7" dia saw with 12 teeth at 7000 sfpm (3800 rpm)and .0003 ipt feed thats cutting at about 14 inch per min feed
.
in theory thats sound impossible but I seen that cut for decades hand held circular saw cutting 1/4" thick
steel plate like cutting plywood..... obviously if you force it especially if blade dull saw gets red hot
and brazing holding carbide teeth lets go and teeth start flying off.
.
obviously horsepower limits, cutting force limits (deflection / breaking), part holding limits etc...
instructor should at least mention normal feeds and speeds based on cutting tool makers recommended setting
..... sounds like instructor used to running a router at very high rpm. he might have used the router
setting many thousands of times over many decades with little if any problems..... but maybe should at least
mention more normal recommendations from the cutting tool manufacturers
...i call it "router" feeds and speeds thats not a universal name for it, not sure what its technically
supposed to be called. typically "router" settings are also very loud

 

[neilho]

Your instructor is an idiot.

And your point would be what, exactly?

 

[plastikdreams]

This is basically the same as if I put 1 firefighter on a 3" line with a combo nozzle and told hime to aim it through a window while standing up so he could advance...dialed it up to 200 psi and told him to open the bail.

If hes light and dumb enough to do it and hold on...he juuuust might fly lol.

Dangerous, pointless, major risk of injury, and just plain foolish.

(Proper would be, min 3 guys, 5 is preferred to advance, 2.5 line not 3", yes it makes a difference lol, pressure starting around 120 and see how it goes from there.)

One person can easily handle the above situations though...its called a Chicago loop. You loop the hose and nozzle under itself and sit on the junction. You are stuck in the spot but you can move the nozzle as needed without having to worry about getting destroyed. Sometimes we will put an extra guy on just to help or have a ready replacement.

 

[sendithard]

Update#2

Thought you all may enjoy how the debacle progresses....I'm in QC this AM drinking coffee and programming the simple part in CMM they are trying to make at God knows whatever sfm they are deciding upon even after the fireworks explosion that happened last week. I saw a renewed gcode with the 3" facemill at 5K rpm and 240ipm....yes I gave up helping at this point... Anyway...the student stepped in mid morning to 'give me some advice' on not over tightening the vise bc he overtightend the vise and it fractured. I told him once again it was from the damage he did running the beast at ungodly numbers, but I'm dumb as usual. Here is our mill at the moment. I've had this part programed at a reasonable 150 sfm for over 3 months, maybe one day I'll get a crack at it, until then, I'm enjoying programming on the CMM and learning some cool skills....

 

[EndlessWaltz]

Curious if we will get a new update in the fall lol...

 

[gkoenig]

Glad to know the bar to be in our industry is so fucking low.

 

[Mtndew]

Tell your instructor to read this thread.
Better yet have him log in and give us his reasoning. We'd LOVE to hear it.

 

[wesg]

Milling course? Or stir friction welding?

 

[TeachMePlease]

Tell your instructor to read this thread.
Better yet have him log in and give us his reasoning. We'd LOVE to hear it.

Send his boss a link to this thread...

 

[zero_divide]

Someone might get hurt or worse. It is a VERY bad idea to spin HSS endmills that fast in any material because they don't instantly disintegrate, but get bent before breaking and transfer all of the rotation speed into horizontal speed and fly out making nice round holes. I have heard people got killed this way.

 

[scarymonkeyman]

seriously though, if the instructor is confident that those numbers are correct then get a video of him confirming it, place the camera on a stand in front of the mill, hit start and run. i do want to see how it goes