IS this question too hard?

[Jack Mitchell]

Larry,

 

The puzzle was enjoyed by all so please don't fret over this.

 

Many many years ago when I apprenticed, there was a test question. What is the taper per foot of a pipe thread?

 

Being the real world kind of guy that I was, I just did not recall the answer, I did recall that a highly respected English Journeyman told me that the half angle was one degree forty seven minutes when I was trying to program a pipe thread. So I went at it with a calculator, multiplied by 12" and solved the question with .7482"/ft.

 

I got the question wrong - no I didn't go to the instructor and cry foul like most other students constantly did and whine for the credit.

 

Bottom line here is the correct answer was 3/4" per foot. The extra bottom line is I kicked the instructors A$$ and he didn't even know it. Obviously that nasty streak of mine has been around for a few years too many.

 

PS - the decimal answer is from memory only and may not be accurate to the tenth.

 

 

Regards, Jack

 

[ 10-23-2003, 06:56 PM: Message edited by: Jack Mitchell ]

[chip]

What the heck......Here goes nothing:

 

Spindle:150 R.P.M.

 

Feed/rev: .008

 

matl removal: 7(cubed)/min

 

Diameter: 8.750 @ start

 

diameter: 8.350 @ finish

 

 

[jballs]

Chip,

 

How do you figure

[CAM-mando]

L Hanft,

 

My post above regarding SFM should have included

 

I too think the thread interesting, and will put some more thought into it.

 

Murlin,

 

quote:

---

But Slow speed is the key.

---

You call 360SFMHSS on steel Slow ?

 

<---- CAM puts on his tinted saftey glases .

[crazy^millman]

L Hanft you have not offend anyone here with this question. I just wanted to put the ball back into your court as to the real answer to your question. It is a question that does invoke thought and that is good if that is your main goal of this excerise with your students. I just wanted in my own way to point out some reality is all to your question. I am a person who was almost in your same position just could not get the people to give anything in writing and I dont take BS very well. I would love to see the rest of the question to your test and you can email me them at my email address if you feel so inclinded to do so. I will give you another good test that will do all of the things you wanted but teach hand on skills as well as repect for the profession.

 

You get some CRS 1" sqaure stock and have them take a hack saw blade and cut it off trying to keep the part square. then have them take a file and then square up the block using only a machinist square. Once they have got it square then have them polish all of the side also keeping the block square to a finish the block to a mirror finish using lapping producers using wet/dry cloth till you get to 1500 grit paper. They will learn about squareness of parts and how ot look for it and its importance. They will learn how files shape parts and if done wrong will do harm or if doen right will help. They will leran what it take to make that part look good and what it takes to make it look that way. I promise you everytime they go calling out some freaking .0001 tolerance and true postion tolerance of .002 that block and any other real world hands on activites when that is clerance for a bolt on cover for no real purpose and no need of the dumbass tolerances.

 

Crazy Millman

 

 

Nope Rekd wasn't bored just like it when we comapre apples to apples and oranges to oranges is all. I have personally trained 13 guys and help many over the years. I have taking Caclacus and other classes needed for my BS in mechinal enginnering and hate it when I have to be reminded that if I was better in english and typing and spelling which have about as much to do with enginnering that that word problem that I dont have my degree and problay never will.

 

[ 10-24-2003, 01:10 AM: Message edited by: Millman^Crazy ]

[Müřlıń®]

Chris....I was referring the world of HSS....

 

Cam, My point was that you can remove alot of sfm at low rpm with HSS. Course it wont come close to ceramic or carbide.

 

 

Murlin

 

[ 10-24-2003, 05:36 AM: Message edited by: Murlin ]

[MACHINEMASTERG]

quote:

---

You get some CRS 1" sqaure stock and have them take a hack saw blade and cut it off trying to keep the part square. then have them take a file and then square up the block using only a machinist square.

---

hey crazy were you my shop instructor in 1980 ???thats exactly what he had us do in intro to manufacturing

[chris m]

quote:

---

Chris....I was referring the world of HSS....

---

I didn't know anybody made HSS tools anymore

 

quote:

---

You get some CRS 1" sqaure stock and have them take a hack saw blade and cut it off trying to keep the part square. then have them take a file and then square up the block using only a machinist square. Once they have got it square then have them polish all of the side also keeping the block square to a finish the block to a mirror finish using lapping producers using wet/dry cloth till you get to 1500 grit paper.

---

Christ, that's even worse that the original question. There's a task that I see being performed on a regular basis...

 

C

 

[ 10-24-2003, 07:16 AM: Message edited by: chris m ]

[jbel]

quote:

---

Christ, that's even worse that the original question. There's a task that I see being performed on a regular basis...

 

---

This whole thread is about something you would never do on any basis never mind a regular basis. It's just thrown out there to make you think.

[Müřlıń®]

Yo Crazy.....I had to make a threading guage and a couple extra parts....That was when I was in High School.

 

Yup a file, hacksaw,emory, and crocus cloth was all you got to use.

 

Teaches you alot

 

+1000

 

 

Murlin

[Noel]

In 2nd year we had to make a set of matching V's with a hacksaw and a file.So I took it to work set up a sine bar ground the V's on the surface grinder till they fit then dummied up the edges with a file and no one Knew any different.I realize that the project was designed to teach us how to use a file but at that point I knew how to use a file properly so I figured I might as well practice skills that I would actualy be using in the real world.

 

 

Noel

[CAM-mando]

quote:

---

Cam, My point was that you can remove alot of sfm at low rpm with HSS. Course it wont come close to ceramic or carbide.

---

SFM = Cutting Speed = Surface Feet per Minute

 

Dirrectly related to RPM.

 

I think we have a failure to communicate.

[I2B4U]

Larry don't answer his e-mail no more? heck I like puzzles.

 

with 10 horspower, and a load of .6 hp per ci/min you could remove 16.6667 cubic inches a minute?

if you use the removal rate and divide it by(8ipm*.2doc) wouldn't you get the length of 10.4166 which divide by pi for dia of 3.3157 to start? -.2doc to finish?

if the dia is that then 360fpm*12/(pi*dia) would be 417.72 rpm?

which 8ipm/414.72 rpm= .0192 chip load?

somebody check me here please?

[CAM-mando]

Assuming 1 pass which was not stated.

[Harryman]

16.7 is the correct removal rate.

 

A tube of wall thickness .2" eight inches long has a volume of 16.7in^3.

 

Keep at it

[crazy^millman]

See this was one of the things I really like about soem of the professor I have had over the years show them your smart then they clam up.

 

 

If they are right tell them if they are wrong tell them but you put it out there now be person enough to finish it.

 

 

Crazy Millman

[L Hanft]

Sorry, too busy to check in. Was starting to wonder who was whining more you guys or the students! I'll post the solution next week.

[Müřlıń®]

quote:

---

SFM = Cutting Speed = Surface Feet per Minute

 

Dirrectly related to RPM.

---

You can change the DOC/RPM/IPM to diffrent settings and still keep the same SFM, right?

 

 

If you are cutting at .2 per side with HSS, you dont have to use fast RPM to get 360 SFM. You just need to feed the heck out of it.

 

This would prol need flood coolant, but I think it might be doable with HSS.

 

Since just "steel" could be CRS........

 

BTW guys The old saying "feed cuts, speed doesn't" Is an old saying for those who use HSS.

 

 

Murlin

[CAM-mando]

Murlin,

 

In the problem given 360 SFM means Three Hundred Sixty Surface Feet per Minute.

 

This is a CONSTANT.

 

Agreed though that there is still a place for HSS. I was merely pointing out (for no other reason than to be a pain in the @$$ or to be helpful which ever comes first) that the parameters were not really in line.

 

 

Harry,

 

quote:

---

A tube of wall thickness .2" eight inches long has a volume of 16.7in^3.

---

Again we must assume the cut time is only 1 minute... no ? This is the second assumption. The whining of the students is justified.

 

I always was annoyed by proffesors / teachers who left out vital information to make a simple problem impossible. Then show the answer using information that wasnt given.

 

Always made me feel like my tuition was being wasted ... ya know we could be doing something productiove like chasing girlz or guzzlin' beer.

 

If the students are reading this, they should take advantage of the fact that teach supplied insufficient data, therefore rather than solve for Pi*r1^2-(Pi*((r1-.2)^2) they can simply pick an arbitrary r1 value and work from there. The solution will come much quicker and be vaklid since teach didnt supply sufficient data ... Oh did I say that already ?

 

This is actually a very good REAL WORLD example from which a valuable lesson can be learned.

 

STUDENTS TAKE NOTES THIS IS THE MOST IMPORTANT LESSON YOU WILL LEARN

 

Always make sure you have ALL of the correct information you need to do a job (solve a problem) before you sink valuable shop hours into it only to find you were working based upon an incorrect assumption. ANd the Job is scrap.

 

ex. " Oh that sketch was'nt metric ... ummm were gonna need bigger bar stock "

 

CAM teh teachers pet

 

[ 10-24-2003, 11:32 PM: Message edited by: CAMmando ]

[crazy^millman]

Well you know what you can take your answer and post it on the moon for all I care. I dont need the snobish attitude from you buddy. I will smoke your xxxx in any machine shop on any machine any time. I dont give a **** if you been doing this for a 100 years I will teach you some real world old school and new school machining.

 

You want to solve one of my problems huh buddy boy. I have a polycarbonate lens that has to be optically clear. I will need a .0001 steepover to even think about beign to that point. My boss has promised the customer that this 10-1/2 diameter part wil be done in 6 hours for shipment this afternoon on a Saturday. I fiugre with the machine I have it will be a 50 hour run time how do I get it done. That is a good real world question to aks your students.

 

Crazy Hates Profs that need to be brought down about 2 notches.

[chris m]

Hey Millman, sounds like you work for a real brainsurgeon; my condolences. That sounds somewhat like some guys I used to work for who'd come down on a Friday at 1:00 and say "We need to get those such-and-such parts done [meaning program, fixture, tools, setup, run, deburred, inspected] this weekend because we have a customer coming to pick them up Monday."

 

Then, an hour later when you went looking for them to say "we don't have a boring head big enough to make this" the secretary would say "Oh, he's gone to The Cape (our local seashore area) for the weekend."

 

In all of these cases, WE means YOU. Lousy spot to be in man, I feel your pain.

 

Hey Dave

 

quote:

---

Agreed though that there is still a place for HSS

---

3 places; spot drills, punch press dies and the trash can

 

Nobody makes any money going slow brother

 

Have a good weekend guys

 

C

[Müřlıń®]

Yo Mill, cant you just polish it somehow?

Maybe you can wet sand it....

 

And I will agree that the academic problem that started this post will not teach anyone anything except what kind of asprin to use in order to relieve a headache.

 

While everyone else was getting their degree in Injun-Earing, I was out in the shop building molds for the computers they were using.

 

I did not fully understand the lessons that I learned by making a thread guage tool by hand until years later.

 

I was very proud of my little shiny part I had polished to a mirror finish with crocus cloth.

I got the top score in my class.

It lay in my box in the top drawer for years.

 

Every once in a while I would pick it up and examine it. I would think about why the edges looked a little rolled instead of being strait and sharp.

 

I even thought about why a piece of CRS had layed in my box for 12 years and did not have one spec of oxidation on it.

 

Some of the simplest problems will teach us the most.

 

Your square lesson with the 1" square stock is another good one.

 

 

Murlin

[crazy^millman]

Yeah Murlin I can have it vapor polished but it really needed a good finish and it is funky part realyl detailed surface for each one of the holes it has over 300 holes and each hole has 30 fillets with raduis from .005 to .200 and they are begin picky about every detail. No probelm with good equipment just not soemthing done in a few hours.

 

I got another projetc I did Back in highschool worked on it my Junior and Senior year of Highschool. I made a 36" diameter by 12" wide ferris whell out of Alumninum. Me an another guy made the whole thing compelete as well as polished it to a chrome looking finish. It was sweet I had taken old aluminum rails out of a old IBM copier and used them for legs. We put hole for weight reduction all over every where. I made double french curves for the feet. I made the Hex nuts for the shaft. I made the reduction pullyes for the gear down to make it spin at 2.4 rpms. I made the exchanger system for the gear box to the pulleys. It was really cool all my pics for this thing are back in Jacksonville I keep asking my mom to see if she can find them but no luck yet when she does I will post them.

 

Crazy Millman

[Harryman]

There really is enough info to solve this thing.

 

We know that the 10 HP will get us 16.7in^3 of steel turned to chips in one minute. We know that the feed rate is 8 in/min and doc is .2in. So now we need to know the OD and ID of of a tube that is .2in thk and 8in long with a volume of 16.7^3. Once you have OD you can solve for RPM from SFM.

 

Please be kind to the prof.

[crazy^millman]

Ok another little twist to this equation what if the wall thinkness of the pipe is .2 what would you end up for the diameter.

 

 

Crazy Millman