2 Suppose the 0.625 hole feature shown below is expected to be produced and loca

Question

2 Suppose the 0.625 hole feature shown below is expected to be produced and located according to the drawing below: 002 2.00 75- 5. 5 2.60 1. 50 25 1.60 03000 D 003 625 lø .00e@ |C |BNO ?A CAL POLY. SAN LUIS OBISPO INDUSTRIAL AND MANUFACTURIN ENGINEERING DEPARTMENT TOLERANCES N/A What size (width) block should be used to check the size of the slot (datum B)? a) b) What size block (fixed to a flat plate) should be used to check the perpen- dicularity of the slot (datum B) with respect to the front surface (datum C)? c) Describe/sketch the gage that should be used to check the position of the slot?

Explanation / Answer

a) Width of block will be = 2.6x(5.5-2) i.e 2.6 x 3.5

b) 1.5 x 2

c_)The part that I'm checking is a casting, so the slot walls are on a 1 degree draft. The drawing calls out to check the position of the slot width at a "gage line" 6.7 from the datum (the gage line is just below the surface of the part). With this being true, would I take a line on each side of the slot at the "gage line" level, construct a midline between the two sides, dimension the position of that midline in one axis only. I did offset the slot so that the axis runs exactly through the center of the slot. Would this give me a correct result?

The alignment is created. It's a simple 3-2-1. The datums are X, Y, and Z. The FCF is "|TP|1|X|Y|Z|".

The slot width is no problem for me. I'm having difficulty understanding on how to report the position of the slot in PC-DMIS or any other software for that matter.

d) Pin will be 0.624 dia

e) 2.6 x 3.5

f) A tri - square, File and Scale is required to ensure the proper location of machining.

g)

Maximum Material Condition or for short, MMC, is a feature of size symbol that describes the condition of a feature or part where the maximum amount of material (volume/size) exists within its dimensional tolerance. The callout also removes GD&T Rule#2 which states that all geometry tolerances are controlled independently of the feature size.

When you have a feature that GD&T is called on:

If it is a hole or internal feature: MMC = smallest hole size

If it is a pin or external feature: MMC = largest size of the pin

The only GD&T Symbols where Max Material Condition can be applied are:

If you want to ensure that two parts never interfere, or limit the amount of interference between the parts when they are at their worst tolerances, MMC can be called out. Take a shaft that must go through a hole with clearance between the two.

The MMC of the shaft would be the Maximum diameter

The MMC of the hole would be its Minimum diameter

If you made sure that the MMC of the shaft was always smaller than the MMC of the hole, you guarantee there will always be clearance between the parts. This is important for any tolerance stack to ensure that when the tolerances are at their least desirable condition, the part still functions properly.

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