test question

[cherokeechief79]

i have a test to give students and one of the questions is ......why is grinding allowance left on the workpiece prior to heat treatment process.

a.....material shrinkage

b.....material hardening

c....material distortion

d....material expansion

 

the answer i have here is a     but couldnt it be c as well?

i dont want to give a misleading question.

[htm01]

e... both a and c

[Leon82]

17-4 will shrink and distort.

 

[crazy^millman]

I hate questions like this. One the 10 possible choices 5 are the best choice. Funny the test that was on was only 2 were not related to the question. 8 of the answers in certain situations I have run into at those points in time where the best possible choice. You should do like htm01 mentioned. There are some materials that grow, but you never count on that for leaving grind stock. A and C were always the reasons we left grind stock when I did molds along with tool and die. 

[htm01]

13 minutes ago, crazy^millman said:

 tool and die. 

tool and die shop grad here, my teacher just died a couple years ago, was in his 90's.

still picking out things he taught me that i didn't really grasp at the time

[JoshC]

it can distort and shrink, typically Both happen in my experience, you can send the part out to HT straight but it doesn't always come back that way, so i also agree both A and C both happen in my experience. 

[JoshC]

38 minutes ago, ONLYBLM said:

a, b, c, d

Tink it out. All rite. No rong.

B is incorrect man, we don't leave stock on parts because the material will get hard, we leave stock on parts because we are worried they will grow or distort. If the material was hardened without growing or distorting no one would ever need to leave stock on the part, so i don't know why you would think b is correct.

D isn't correct either because why would we leave extra stock on a part if it expanded... if anything cut it to size and then machine it down if it expanded since you would have more stock on the part, we wouldn't leave extra stock on a part if we expected it to grow otherwise you would be compensating for a growing part by adding more stock, that doesn't make sense. 

I am pretty sure you are a Troll though anyways though by any of your responses i have read and from your profile and intentional illiteracy, everything from what i can see that you have said on your profile and or your responses on other topics leads me to think your nothing more than a forum troll, probably a former member that was banned back to be a troll if i had to guess. Also like your interest in "tyger huntin", what does that mean on your profile, are you saying you are a poacher... just a troll is my guess.

[gcode]

54 minutes ago, JoshC said:

Also like your interest in "tyger huntin",

ain't no tigers in Zambia or New Jersey

[Leon82]

You're eye pee address lol

[crazy^millman]

12 minutes ago, ONLYBLM said:

See illiteracy comon here.

Some of us do suffer from Dyslexia is that is the way you want to play it.

[crazy^millman]

What time in the afternoon is it in Zambia? Seeing how English is the official language why do you have such difficulty with it?

[ostie01]

1 hour ago, crazy^millman said:

What time in the afternoon is it in Zambia? Seeing how English is the official language why do you have such difficulty with it?

Are you a Zambiaphobe

[gcode]

1 minute ago, ostie01 said:

Are you a Zambiaphobe

Nope.. he's from Jersey and acting all uptown and fancy pants

[So not a Guru]

Stop feeding the troll.

[Redfire427]

20 hours ago, JoshC said:

D isn't correct either because why would we leave extra stock on a part if it expanded... if anything cut it to size and then machine it down if it expanded since you would have more stock on the part, we wouldn't leave extra stock on a part if we expected it to grow otherwise you would be compensating for a growing part by adding more stock, that doesn't make sense. 

 

Think about it...………… if you have a block with a bore, and the block expands, then the bore gets larger and thus reduces stock, not increasing stock.

Carmen

[JoshC]

8 minutes ago, Redfire427 said:

Think about it...………… if you have a block with a bore, and the block expands, then the bore gets larger and thus reduces stock, not increasing stock.

Carmen

doesn't the bore get smaller? I thought bores get smaller after heat treat which is why they make and people sometimes use oversized taps even prior to heat treat, like +.005" oversized taps for example. Its like maximum material condition on shafts verses holes, the part grows in all areas which means holes get smaller. 

[Guest]

2 minutes ago, JoshC said:

doesn't the bore get smaller? I thought bores get smaller after heat treat which is why they make and people sometimes use oversized taps even prior to heat treat, like +.005" oversized taps for example. Its like maximum material condition, the part grows in all areas which means holes get smaller. 

Correct ^

[Redfire427]

Every situation is different, but picture a 4" square block with a 3 in bore through it. If the block expands, the bore gets larger too.

You are also correct with your description

[JoshC]

Just now, Redfire427 said:

Every situation is different, but picture a 4" square block with a 3 in bore through it. If the block expands, the bore gets larger too.

You are also correct with your description

I disagree but don't know how to explain it any better so lets agree to disagree

[JoshC]

21 minutes ago, ONLYBLM said:

You are rite. Very basic sum poeple don't know basics. He also dont know when heat part has bad finish. Recut with endmill too hard RC65. Must grind. Very very basic skils Josh not have. He miss basics but think he know.

Who said I was talking about surface finish... this topic has nothing to do with surface finish, if you need a specific flatness or surface finish then grinding may be required but just because you heat treat a part doesn't mean your required to grind the part and i never said he should recut a 65 HRC part with an endmill. there are parts out there that need to be hardened but dont need a grind finish. I have seen many parts go out to heat treat and not require a secondary grind operation. 
Also if you are talking about rockwell C scale its HRC buddy not RC

your just mad because i called you out for being the troll that you are, trying to troll me but not smart enough to make a valid point.

[crazy^millman]

29 minutes ago, ONLYBLM said:

You are rite. Very basic sum poeple don't know basics. He also dont know when heat part has bad finish. Recut with endmill too hard RC65. Must grind. Very very basic skils Josh not have. He miss basics but think he know.

You're trolling and doing a very poor job at it. You have no idea about Josh's ability and to even call his ability into question is part of your trolling method. Troll on Mr Troll. 

[Guest]

2 hours ago, Redfire427 said:

Every situation is different, but picture a 4" square block with a 3 in bore through it. If the block expands, the bore gets larger too.

You are also correct with your description

No, that is not how material properties work,

what gave you that idea?

[JHyder2]

1 hour ago, byte said:

No, that is not how material properties work,

what gave you that idea?

 

Seems like he may be getting hung up on the semantics of "growing" vs. "shrinking" as it relates to this conversation.  I.E., the outside of the block will get bigger so the perimeter of the bore would get bigger. 

In reality with thermal expansion what we have is not "growth" or "shrinkage", but an increased separation of the particles that make up the block.  Thinking of it in terms of all the particles that make up the block, they are all further apart from each other than prior to heat-treatment.  Maybe that would make it clearer to see that internal faces will be closer together, and external faces will be further apart.