Engineering Question - Tolerances

does the drawing have something like H7 or similar after the dimesion?

there is a tolerance standards chart which defines what the tolerance should be on a scale of hole & shaft sizes,it also charts the various types of fits (clearence, transition and interference) this can be found in most engineering handbooks

p.s. does it state anywhere on the drawing the general tolerances?

ie 0-100 +-0.1mm 100-100 +-0.5mm ?
 
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touch said:
I think we are both talking about mass production here, whereas you are talking about a 1-off school project(?). So there wont be any cost implications for you.

I think that as long as you can justify your tollerances to your teacher (and they are not ridiculous) then you cant be wrong.
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When I justify them, say if I say the thing that goes in the hole can be this much smaller or the hole can be this much bigger, its gonna cause wear or whatever, I wouldnt be able to justify why it'll cause only minimal wear or acceptable as opposed to somethng thats gonna damage the structure.

I'm in my 2nd year of my degree as well :D (not to blow my own horn, but I think from this you can see how mint I'm doin)
 
anksta said:
When I justify them, say if I say the thing that goes in the hole can be this much smaller or the hole can be this much bigger, its gonna cause wear or whatever, I wouldnt be able to justify why it'll cause only minimal wear or acceptable as opposed to somethng thats gonna damage the structure.

I'm in my 2nd year of my degree as well :D (not to blow my own horn, but I think from this you can see how mint I'm doin)
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well if your in 2nd year you should know that everything is drawn and manufactured to a standard, mainly ISO

have a look at some ISO tolerance charts , decide the type of fit needed, and use that to justify your tolerances
 
anksta said:
I'm in my 2nd year of my degree as well
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:s you should know all this stuff then, all of what i'v told you is my knowledge from higher graph comm :/

As for justifying it, you would say that obviously it cant be bigger than the hole it fits into and a maximum of 0.02mm smaller as anything more would cause unacceptable wear/stress on the part.
 
I might point out that I hate my degree.

Anyway, the only thing I had, and which I was told to consult, which I have is LUMED (dont know if any you of have heard of it) and all that was in there was 2 paragraphs explain how to lay out the tolerances on a diagram which, luckily enough :rolleyes: , was the one thing I already knew how to do.
 
Ok I looked up some tables and found some Shaft - Hole Tolerance Data. The data gives you a diameter of your shaft and then gives you your clearance for both.

Now I think thats what I'm looking for, however, the tables are separated into classes, with a description in each. Now, considering I'm talkin about a little 70mm stub thing, used to pivot the ladder sections or something, I think this description is the nearest:
Medium Fit - Running fits under 600 R.P.M and journal pressures under 600 lbs/sqin and for sliding fits. Wobble or shake between mating parts noticed only on parts with short bearing length.
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Does this sound near to you or am I way off?
 
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