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Instructor approves cutting steel at 2000sfm

sendithard

Plastic
Joined
May 18, 2021
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.
 

sendithard

Plastic
Joined
May 18, 2021
No. he is a tech school instructor... but I'm old enough to argue with any instructor if I see something I feel is poor education. I'm also old enough to tell a boss to go f himself if he was putting the machine or myself in danger.

I run a business, but my parts are made elsewhere, I'm taking the class to learn to make my own parts before I unload 100K on machinery I don't have any clue about.
 

Milland

Diamond
Joined
Jul 6, 2006
Location
Hillsboro, New Hampshire
You and the caliper measuring guy need to start a union... :D

I suspect you're correct, but give it a go. Machine is likely too low horsepower, too wimpy stiffness-wise, so this may just jam the spindle or toss the part from the vise (stand back).

Enclosed and coolant, or open and dry? Fireworks in the latter case...
 

sendithard

Plastic
Joined
May 18, 2021
It's enclosed running vegetable oil, and I don't know caliper guy sorry. We had to change the vegetable oil in the lathe bc of smoke last year. The mill handles the oil much better, little smoke so far just running aluminum at 1000sfm. My programs are conservative and I don't try and run HSS at these levels. Maybe I'm a panzi.
 

Milland

Diamond
Joined
Jul 6, 2006
Location
Hillsboro, New Hampshire
As long as you're sure nobody will get hurt from flying parts or cutters, have at it. Just be sure to film for Youtube posterity...

[Going by your name, I'm surprised you didn't already "send it hard"]
 

sendithard

Plastic
Joined
May 18, 2021
Maybe I'll repost this question under a different username. Seems you all think this is a joke, it's not. I don't think it is appropriate to teach tech students to run steel parts at 2000sfm. If I am wrong, by all means let me know why. From what I have read I am rightfully concerned.
 

mmurray70

Hot Rolled
Joined
Jan 11, 2003
No. he is a tech school instructor... but I'm old enough to argue with any instructor if I see something I feel is poor education. I'm also old enough to tell a boss to go f himself if he was putting the machine or myself in danger.

I run a business, but my parts are made elsewhere, I'm taking the class to learn to make my own parts before I unload 100K on machinery I don't have any clue about.

Id probably look into other tech schools. Not going to learn much from this guy. 2000 SFM with HSS in steel? Are you sure hes not a welding instructor? Sounds like he knows more about melting steel then machining it.

Seriously, look for another school or just teach yourself online. If you want to learn, everything you need to know is right at your fingertips.
 

sendithard

Plastic
Joined
May 18, 2021
Appreciate the reply...I'm not taking it bad, I'm just surprised people focused more on my username than what I am saying. Maybe I'll get a new account with bacon or pancakes in it to help everyone out from focusing on what isn't important.
 

CITIZEN F16

Titanium
Joined
May 2, 2021
That sounds like an insane speed for a larger more rigid machine using carbide. Unless one has done the same thing with success previously starting out with the pedal to the medal is plain dumb. Wonder what gets destroyed the cutter, tool holder or the vise jaws?

I don't care if the machine has an enclosure I would take cover.
 

barbter

Diamond
Joined
Oct 27, 2007
Location
On Tour...
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.

Seriously - you might snap the pull stud and have a holder drop out and fly. F dangerous!
The biggest diameter I'd run in a Robodrill (BBT30) was 16mm and that was radial - not full slotting (10k RPM and F5000.
For steel - 12mm and again, you have to be selective with # of flutes and geometry because it can squeal like a pig.
You do not have rigidity and strength on your side.
Teacher SHOULD be teaching safety first, accuracy second and then comes speed.
10bucks says he's been watching Titans of CNC vids...
 

michiganbuck

Diamond
Joined
Jun 28, 2012
Location
Mt Clemens, Michigan 48035
We ran CNC grinders on vegetable oil, and a hot spark could turn up the heat and we would have fire in the works.

Likely it is not right for the student not to have a shred of diplomacy.

Possibly the instructor has run this or read about it someplace.
 

BugRobotics

Hot Rolled
Joined
Jun 22, 2015
Location
Denver, CO
That is gonna be fun to watch! I don't think anyone here is thinking you are joking. Like Milland suggested...please record and share.

And for kicks just look up any of the recommended feeds/speeds for a HSS endmill in steel.
 

sendithard

Plastic
Joined
May 18, 2021
I appreciate some of the previous replies that validates my concern.....I'm not looking to record a disaster, I just wanted to know if I am in my right to tell a tech instructor they are wrong.
 

thesidetalker

Hot Rolled
Joined
Jan 11, 2015
Location
Bay Area, CA
Not clear from your post - This .780" slot with a 3/4" cutter, is this a full slotting toolpath?

Or using an HSM path? <.015" rad arcs? 160 ipm?


lol


I guess either way it should put on a nice show.

Please take video! (from a safe distance)
 

Larry Dickman

Titanium
Joined
Jan 30, 2014
Location
Temecula, Ca
here's what you do. Come up with a catch phrase for yourself. Something like "Get er done" and then scream it at the top of your lungs constantly.
Be sure to also scream words like, Awesome, bitchen, radical
Buy yourself a truck with $80K of gaudy accessories and get lots of stupid tatoos.
Now you're ready to host your own show
 








 
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