Thread: this made my math homework somewhat tolerable

so i was sitting down going through my questions when this popped up "Here are two dot plots about two machines a and b. This factory produces pins that must be a diameter of +-8cm. the dot plots are as follows."

so one machine produced parts from 7.89 to 8.03 diametre, whilst the other was from 7.99 to 8.01. So my first reaction was " 80mm, thats a bloody shaft not a pin"

then i carried on with the questions and they foolishly asked me " Whick machine is better and why?

so i took it as a chance to have some fun with it. i wrote

"Machine B has far superior machining capapbilites than Machine A because of several reasons. One being machine backlash. Machine backlash has to do with the cross feed and compound feed. When the lathe is used often ( or the machine has been damaged ) there is a gap between the gibs and or thread faces. Due to the two axis nature of metal turning machining centres, one axis will have slight defects that will produce a cut that differs from the calibrated diametre. Another problem can be due to the machinists using measuring equipments such as micrometres and verniers that have not been properly zeroed and or have not been treated with the attention and care that they required to prevent damaged to the sensors and anvil faces resulting in inaccuracies. The third reason can be due to lathe ridigity which is a problem on newer machines that have not had the advantage of over engineering as have previous models such as the Bridgeports and Southbends. Because the bed and carriage are not as heavy as older models, when cutting metal the carriage can be pushed slighty away from the axis of the lathe. This results in a differentiation from the calibrated depth of cut. Also a note to the manufacturer: Please use all your measurments in millimetres. It is a standard unit for engineering workshops and will svae the time and stress of your machinists.

Now dont get me wrong, i take my maths VERY seriously, but seeing as i had just been forced to drop to general maths after years of being in advanced classes, i needed some cheering up ey?

You forgot to add about the temperature differential and how metal's expand when hot..

For example, measuring a piece of aluminium that has been freshly machined and is still 80C will give you a bigger measurement then if it was measured at 20C. The difference in size can be quite a lot...

Were both machines making the same amount of parts.
Were the machines the same make and model.
Were the cutting tools exactly the same.
Were the machines being used by the same operator.
Were the same amount of parts machined before tolerance checks done.
Was the same measuring instrument used for all items.
Was tooling changed or resharpened on a regular basis and at the same time.
just a few more things to consider in trying to determine why variations in tolerance.
With the question which machine is better and why I would suggest the question isnt warranted both machines are making parts in tolerance.

If they were making straight cylinders, wouldn't they just be better off buying ground rod and cutting it to length?

I remember being at school, I thoroughly enjoyed giving screwball answers like yours. Great minds must think alike

Originally Posted by the fabricator

The third reason can be due to lathe ridigity which is a problem on newer machines that have not had the advantage of over engineering as have previous models such as the Bridgeports and Southbends. Because the bed and carriage are not as heavy as older models

southbends and Bridgeports are not as good as everyone hypes them up dude but your teacher wouldn't know that or he wouldn't have written such a stupid question lol if he does asks say Cincinnati mills and Dean Smith and Grace lathes

u may find 80mm pins on huge mine equipment

Originally Posted by the fabricator

so i was sitting down going through my questions when this popped up

In the semester break and you are working on maths homework? I can understand that you are a good student with diligence,to a point, but hey take a bit of a break.

You know the old saying " all work and no play etc ,etc."

A teacher who sets and open ended question like that, can only expect and open ended answer.

Cheers
Grahame

Originally Posted by Grahame Collins

In the semester break and you are working on maths homework? I can understand that you are a good student with diligence,to a point, but hey take a bit of a break.

i just realized that to YOUR UPING THE STANDARDS OF EVERYONE IN YOUR GENERATION!!!!!!!!!

Hi Patrick,
As a Man Arts teacher taking the same subject that Fabricator is studying, its hard to get my head around.

My students would not even contemplate such action.

Maybe I can talk him into moving north?

Grahame

well theres a story as to why im doing math work. for years i have been an advanced maths student, mostly relating everything to the number line, functions, series and sequences, cubic and exponential curves, but i slipped up on my first assesment task for hsc so they forced, yes forced me to drop to general maths, and its all new so i have to relearn it, which points me away from engineering and has made me look towards fitting and machining but anyway, at least i can work in a big, industrial shop with all the between centres i can handle lol, which brings me to my next thread, so as to not side track this one

YOU GO BOY !!!!!!
Wish I had a math's brain like that when I was at skool all those years ago.
Well done mate.