Plug gauge size

[newone]

Trying to confirm if the plug gauge for checking the position is made correctly. Here is the scenario. There is an attribute fixture for checking part we make. Part has some rectangular slots, let say 10mm X 5mm. Tolerances are +/- 0.1mm. Slots are not datums. Length and width of those slots have separate positional callouts of 3.0 associated with them. Everything - feature and datums in those callouts are RFS. Right now rectangular plug gage for checking the position of those slots is made as 6.9mm X 1.9mm. Is this correct or should it be 7.1mm X 2.1mm?

[Kelly_Bramble]

In general, a plug gage for an internal feature of size only verifies size not location - location would normally require a separate check gage.

Since these features are tolerance located at RFS you'll need a go and no-go gage for the feature of sizes and position check fixture that accommodates for the 3.0 (+/- 1.5) position shift. The position check gage will have a size adjustable plug that locks on the the as-built size (RFS) and then verifies the position size.

You should check each size of the slot separately + position check - so technically you need three gages.

if using ASME B89.1.5 the size go gage for the 10 mm+/- 0.1 should be 9.9 + ZZ = 9.9 + 0.00508

The no-go gage would be 10.1 - ZZ = 10.1 - .00508.

Notice in both cases that it's possible to reject an acceptable feature op size in which case when a reject happens further investigation is required.

The proper check gages for

Gage tolerance calculator

https://www.engineersedge.com/mechan...ator_13388.htm

Judging the simplicity of your question and the complexity of my answer you may need to read / study you on the design of functional check gages.

[newone]

Thank you Kelly for your answer. There are separate go/nogo gauges for checking the size of those features. I understand your answer about size adjustable plug for checking the position. But that means that we would need to do separate measurement (outside checking the size with go/no go) of the feature to determine actual size so we can lock adjustable plug gauge at that size, correct?

[Kelly_Bramble]

Yes.... RFS is more challenging then MMC (MMB).

Thank you Kelly for your answer. There are separate go/nogo gauges for checking the size of those features. I understand your answer about size adjustable plug for checking the position. But that means that we would need to do separate measurement (outside checking the size with go/no go) of the feature to determine actual size so we can lock adjustable plug gauge at that size, correct?

[newone]

I am assuming the same would apply to holes if diametrical position was to be checked at RFS? We would need adjustable plug gauge which allows locking actual size of the hole? Btw - we have tons of fixtures, I just checked few drawings and looks like every gauge maker applies MMC to plug gauges, regardless of the callout. Customers review designs before we give ok to build, nobody ever complained...

[Kelly_Bramble]

Yes....

I am assuming the same would apply to holes if diametrical position was to be checked at RFS? We would need adjustable plug gauge which allows locking actual size of the hole? Btw - we have tons of fixtures, I just checked few drawings and looks like every gauge maker applies MMC to plug gauges, regardless of the callout. Customers review designs before we give ok to build, nobody ever complained...