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hwingo
08-18-2010, 09:16 AM
I've had a set of radius gauges for years but until recently, the set was never been put to use. After comparing and contrasting several gauges to a remaining arc left from a broken-away hole, I chose the one marked "5/32". Having my head up my butt I ordered a 5/32" cutter and the 5/32" R8 collet. On arrival, and excited to complete a project, I compared the cutter with the broken piece and immediately realized I had succumb to ANOTHER stupid, senior moment. I should have doubled the radius marked on the gauge.

All this being said, I am curious as to why the gauges are expressed in radii rather than diameter. I'm certain there is a *real* answer. Wouldn't it be more practical to label and mark these gauges as "diameter gauges"?

Harold

Peter S
08-18-2010, 09:44 AM
Harold,

There are many occasions when a radius is specified on an engineering drawing, and it has nothing to do with diameter. It could be something as simple as the radius on the edge of a block of steel, or the radius on the shoulder of a crankshaft journal etc. I can't say I have ever used radius gauges to check a hole diameter. You can use radius gauges when you are grinding a radius on a piece of toolsteel which is then used to machine a radius on a work piece (external rad. or internal rad.). In tool and die work there are radii specified on all sorts of parts, of many shapes. I like the Starrett separate gauges (No. 167), each gauge has several different forms of one radius size.

hwingo
08-18-2010, 09:51 AM
Harold,

There are many occasions when a radius is specified on an engineering drawing, and it has nothing to do with diameter. It could be something as simple as the radius on the edge of a block of steel, or the radius on the shoulder of a crankshaft journal etc. I can't say I have ever used radius gauges to check a hole diameter. You can use radius gauges when you are grinding a radius on a piece of toolsteel which is then used to machine a radius on a work piece (external rad. or internal rad.). In tool and die work there are radii specified on all sorts of parts, of many shapes. I like the Starrett separate gauges (No. 167), each gauge has several different forms of one radius size.

Peter,

A good point well taken.
Harold