Practice exercise

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This is a practice exercise video solution.

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When we're looking at detailed drawings,

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whenever we're planning to machine apart,

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it's always important to focus on the details of the dimensions and tolerances.

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For this example, we're gonna navigate to page five for the piston.

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Now,

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one of the problems that we have here is we've got a detailed

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drawing with provided dimensions 0.63 for the depth of the piston on the outside

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and 0.55 for the depth of the piston on the inside.

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Now, when this part is modeled, that gives it a consistent wall thickness,

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but the problem comes in when we start to introduce tolerances.

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Now, tolerances unless otherwise specified,

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such as the OD of the piston itself are often found in the title block.

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In this instance,

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anything that has two decimal places is subject to a 0.05 inch tolerance.

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This means that the outside values can be plus 0.05

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and the inside or minimum values can be minus 0.05.

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When we take a look at a detailed part like this,

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that has a consistent wall thickness that's relatively thin

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when we start to factor in those tolerance values, we start to get into problems.

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So whenever you're reviewing a detailed drawing,

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make sure that you take a look at the details.

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And if there are no additional tolerance values,

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get a calculator out and take a look at the values that we have on the screen.

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For example,

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the inside depth of 0.55 if this had the additional tolerance

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value of plus 0.05 putting it at its maximum tolerance value,

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that would give us an inside depth of 0.60.

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Now,

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if we factor in the outside being 0.63 and if

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it was at its nominal or its middle value there,

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that means that it would be a very thin wall on the bottom of the part.

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However, if we were to factor in the negative tolerance value of minus 0.05

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that leaves the outside at 0.58

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now

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we're left with a ring and not an actual piston part.

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So this means that the tolerances included on the T block

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are likely going to be too loose for this specific part.

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If this happens to you,

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it's always important to go back to whoever provided the drawing

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and get clarification on the dimensions and the tolerances required.

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It's important to ensure that these dimensions and

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tolerances get sorted out before parts are manufactured.

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It's possible that you could machine dozens,

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if not hundreds of these parts and still be

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well within tolerance value and not have a problem.

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But there may be a couple instances that reach the min

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and max values that are just parts that cannot be used.

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So make sure that you pay close attention to your detailed drawings and take

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a look at ours to see if you can find any other issues.

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Some of these will be sorted in a final detailed drawing

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package that's provided at the end of all the courses.

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But you can pay close attention and see if you can pick up any more.