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I Forge Iron

What are Go - No Go Gauges?


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Hot dog - finally a question I can answer...:-)

All items that are manufactured are built to a set of tolerances. For any given dimension, there will be an Upper Specification Limit (USL) and a Lower Spec Limit (LSL). The smart manufacturer will try to run to mean or the middle of the range. If a machined hole diameter is .250 plus or minus .001, then it can be .249 or .251 and still meet spec. In practice on the shop floor, a set of four pin gages might be used to check a hole. It takes about .0002 for clearance so a .251 pin should bind in a true .251 hole so that is the USL "No-Go" gage. The next pin will be .2508, which is the "Go" gage. These two check the USL only - the LSL pins would be .2488 for the Go and .249 for the No-Go. Shop practice varies but the middle two pins in the block are usually Go and the outer ones are No-Go.

"Go-no go" can be used in many applications - as scrapman said - threads, flatness, concentricity, TIR, etc.

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Go - No - Go gauges are just that, if you think about it. Simple and a quick answer for the user. Mostly they are used in repetitive production work to maintain consistency of the product. Also used to quickly determine a measurement when needed. An easy example is the open end box wrench you have in your toolbox, you know what size it is because it says so right on it and you can trust that. Slip it on the edge of a sheet of steel and you can see if it fits or if it does'nt. There you go, you have just used a Go - No - Go gauge. Drill bits (backwards) work nice for holes. If you work in a machine shop you probably have a drawerfull of designer gadgets made by such names as starrett etc. You don't have to get fancy, just know for sure what you are using is accurate. Hope this helps. Dan:)

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woodtick-- your truck has fallen prey to an entropic surge. Happens all the time around my place. Entropy, the opposite of energy, has done you in. See the Second Law of Thermodynamics-- things are just going plumb to Hell in a handbasket. In plain English, you probably have a build-up of oxidation on the terminals of your battery or between the ground and the chassis. Get a wire brush and see if that is not it. It usually is with my truck.

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