Quiz / Quote this job

There is nothing intended to be tricky or hidden, simply doing the math properly to ensure the tooling is cutting properly.

Start of Quiz: You have a job come across your desk to quote. It is 1018 steel, not difficult to machine. The part is 3? wide, 1? thick and 12? long. There are 2 features to machine in it.

Feature # 1 is a .750? wide, Flat Bottom Channel that is .0215? deep and it runs the complete length (12?) of the part. A Standard Flat Ended Endmill is to be used.

Feature # 2 is a Full Radius Channel, designated as a 3/8? radius, it also is .0215? deep and runs the complete length (12?) of the part. A Standard Ballnose Endmill is to be used.

Both of the Endmills you have available for this job are 4 Flute, Carbide, Stub Flute Length, Coated tools.

The Tool Manufacturer for both of the Endmills you are using suggests you use 500 SFM for this material and a chipload of .002 Feed Per Tooth.

What would be the total Time In The Cut (not including rapid positioning moves) for both of these tools combined to machine both of these features in the part?

Multiple Choice Answers: A. Less than 35 Seconds B. Between 35 and 44 Seconds C. Between 45 and 50 Seconds D. More than 51 seconds but Less Than 1 Minute E. More than 1 Minute

If you want to explain your math behind the answer feel free to do so.

Again, have fun with this.

JR

you said in the subject line to quote this job.

I just sent my answer to Jim.

JRWheels wrote in news:75f5f8eb-2223-4c62-8f98- snipped-for-privacy@f63g2000hsf.googlegroups.com:

Revolutions to complete cut == 12/0.008 (4 flute, 0.002 per flute) == 1500 Revolutions required per cut

Assuming a 0.625 EM to cut the 0.75 slot

Ball EM = 0.17437 actual cut dia

So, for the 0.625 EM, 1500/50.916 = 29.46 seconds x 2 == 58.92 sec for flat slot For the 0.75 EM, 1500/42.43 == 35.35 sec for flat slot For the radius EM, 1500/182.55 = 8.21 sec

So, depending on whether you use a 0.625 em or a 0.75 EM for the flat spot:

Anthony:

To use a 5/8 end mill you'd have to make more than one pass.

.17437 is the chord length for a diameter of 3/8" not a radius of 3/8".

BottleBob wrote in news:X9OdnaiQVMGVKefVnZ2dnUVZ snipped-for-privacy@earthlink.com:

Yes, I knew that and thought I took that into consideration with the cycle time calculation, did I not? (Can't see my post.)

You are correct. I flubbed that one.

Anthony:

Yes. You absolutely did. I missed it first time around.

============================================================ Anth So, for the 0.625 EM, 1500/50.916 = 29.46 seconds x 2 == 58.92 sec for flat slot ============================================================

Why can't you see your post?

I have all my outgoing E-mails and posts copied to a "SENT" folder, so I can review them at a future date if necessary.

BottleBob wrote in news:QradnWWDftsPyubVnZ2dnUVZ snipped-for-privacy@earthlink.com:

It got marked read, so disappeared. I could have reconstructed the thread to get it back, but I was pretty sure I included the double pass. Other than this upper respiratory infection affecting my brain similar to what it has my sense of balance, I cannot explain the 3/8 R vs 3/8 Dia error though. This infection has had some bad side effects......I'm having to hold onto walls just to get to the crapper and back...fluid behind the eardrums is making me dizzy as hell when I move around.

That's terrible. I hope you get over this in a hurry.

Anthony:

Cripes! I sure hope you get over it fast. I HATE being sick, the worst part is using up your sick days actually being SICK!

I hear DAT!!!

Which IS a little scary.... :)

But then, with the likes of jb running around, you gotta do whatchoo gotta do....

So, what, you never let people copy off you in grade school???? Sheesh........

PV:

Why would that be scary? Isn't that what the "SENT" folder is for? You're not scared by Google's archiving process, are you? LOL

PV:

Ahhh, but when you copy from someone else you're never really sure if who you're copying from is correct or not.

Since Jim has posted the answer and explanation, here was what I sent him:

================================================================== Jim:

Well, tool #1 RPM = 3.82 X 500 SF / .750 or 2546 RPM

IPM = .002 X 4 teeth X 2546 RPM or 20.4 IPM

So adding .5 on each end of the bar to clear the 3/8" radius of the end mill should give a 13" length. 13" / 20.4 IPM = .64 min. or

Tool #2 Would be .750 ball end mill. But being that the dept. is only .0215 the width of cut would be c = 2 X square root of h(2r-h) or .2503. So RPM = 7640 IPM = 61.12 Starting off and finishing off the bar by .250 on either side, the length would be 12.5 / 61.12 IPM or .205 min. or 12.3 sec.

So adding 38.4 sec. and 12.3 sec I get 50.7 sec. So my answer would be "D".

Now IF the tool centerlines were started ON the 12" bar length the times would be: 12"/20.4 = .588 min. or 35.28 sec. And 12"/61.12 = .196 min. or 11.76 sec. 35.28 + 11.75 = 47.03 sec. or "C". ==================================================================

After sending that to Jim, I looking at his list of multiple choice answers more closely and a saw I had made an error. So I sent the following addendum:

================================================================== BottleBob wrote: >

Opps, 50.7 seconds is less than 51 seconds, so BOTH of my answers would be "C". ==================================================================

After sending that addendum, I looked at his multiple choice answers AGAIN and saw that there was STILL an error. So I sent the following (I've just now added a copy of his original multiple choice list).

================================================================== Jim:

There's an anomaly in your answer list. My first answer of 50.7 is MORE than "C" and LESS than "D". LOL

Multiple Choice Answers: A. Less than 35 Seconds B. Between 35 and 44 Seconds C. Between 45 and 50 Seconds D. More than 51 seconds but Less Than 1 Minute E. More than 1 Minute ==================================================================

You see how convoluted things can get? And YOU want to copy from ME? LOL

Also, you can see how handy saving E-mails and posts to an accessible "SENT" folder can be now, right?

You ARE scary!! And we're not even getting meteephysical or exeestential!!!

Well, mebbe Jim will give you a make-up quiz.

One thing is for sure: Vinny either has the most profitable shop in the USA, or has no bidniss at all!! :)

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copy from ME?

Bob & PV,

I couldn't have planned that if I tried to, leaving a gap between the (50 second) max of one answer and the (51 second) beginning of the next. I surely didn't plan on that but makes you aware of how things can get twisted around. Of Course Bob fits an answer right in there for me to stumble and bumble on. hahahaha

The whole premise behind the quiz was to simply get everyone that is interested to realize these tools run differently even though they show up on the same page in some tooling catalogs calling them 3/4" endmills and refer to a certain page for Tech Help.

Then to show the theory of calculating the True Diameter that is cutting is how it leads into the High Feed Cutter Designs that look scary as hell to see them run. These tools are money makers when running properly. However, let me repeat this, HOWEVER since they are traveling so fast and shooting chips all over the place, if and when something may turn ugly, its REAL ugly. You don't want to walk away from the control when these things are ripping material off of blocks.

The other thing a shop recently justified while running these cutters on several machines was a Clean-up Kid. The Operators had to keep stopping the machines and clean out chips and dump chip hoppers so often, at which time the machine sat idle, they actually justified the additional cost of a Clean-Up Kid to speed things up. If you measure Milling Effectiveness by the amount of chips coming from a machine, these tools will win you over.

JR

Plain and simple

Get well soon.

Chers: