Given the inability of most young people to deal with fourths, eights, sixteenths, and thirty-seconds of inches on paper, much less in their text message filled heads, i think measurements in feet, inches, and tenths of inches would make sense in framing construction. Stanley actually makes tape measures marked that way, but they are hard to find in stores.

http://lumberjocks.com/reviews/1156

 

"Given the inability of most young people to deal with fourths, eights, sixteenths, and thirty-seconds of inches on paper"



That's another reason I taught trainees to figure everything in thousandths.
How to transpose fractions into .0000.

 

I'm not really wanting to add fuel to a "metric vs imperial" debate but 0.1" DIP chips are about as obsolete as inches are.
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While that sounds good the fact is it is a hard standard, like it or not. Home hobbiests (especially beginners) can not do SMT well, so I suspect it is going to be here for a long while.

It is like how the width of a train tunnel was selected, it is meant to allow the broad backside of two mules to fit side by side. This in turn affected some of the US space shuttles dimensions.

Standards have a funny way of lingering long after the reasons they were selected are gone.

 

I still have my Architectural scale like the one below. Six scales up to 1/72nd of an inch.

 

I made a glass fronted case for my old slide rule and Underneath,
In Case of Calculator Failure BREAK GLASS.
Max.

 

No need to break the glass ... a virtual slide rule can be found

http://www.antiquark.com/sliderule/sim/virtual-slide-rule.html

 

Yes. But this one attracts curious questions!
And allows me to wax poetic.
Max.

 

I like the metal rulers machinist us, incremented in 10thousands of an inch. I've always heard them called scales, though that could have been local dialect. A caliper is better for general use, but hard to measure hole positions from.

 

I like the metal rulers machinist us, incremented in 10thousands of an inch. I've always heard them called scales, though that could have been local dialect. A caliper is better for general use, but hard to measure hole positions from.

The way to measure hole positions, if your meaning center to center, is the following:

Using either side of the calipers(inside or outside measuring tips) measure the edge to edge distance of the holes. Then add or subtract, depending on the tips used, half of the hole diameter for each hole.

There are many different types of machinist scale graduations, and scale or rule is the correct term, not ruler.But I think the name, rule or scale, is a regional thing. I'm a big fan of the 3R graduations myself, 1/64", 1/32", .100",and .020" are the graduations on the 3R.

http://www.starrett.com/metrology/m...urrentPage=1&displayMode=grid&sortBy=none/asc

 

If the hole is .2" that is how it is done, but what if the hole is 0.007" or smaller? It isn't practical. I've had a lot of experience in machining myself, though nowadays it is out of a garage. I know how to use a lathe and milling machine manually.

Generally though, I'm the one making the holes. I can't do it naked eye any more, which is aggravating.

 

There are a number of ways to do it depending on how critical the measurement is and what you have available. Options include a traveling microscope (generally used for smaller scale features than this, though), an edge/center finder chucked up in a mill (very common and simple technique and the edge/center finders aren't that terribly expensive -- or at least didn't used to be), a machinist's rule under magnification (and still generally better done edge to edge). When doing an edge-to-edge determination I generally took two measurements, one between inside edges and one between outside edges, and averaged them. This also allowed me to get in a sanity check by verifying that the difference between the measurements was equal to the sum of the expected hole diameters. On a couple of occasions this has revealed holes that were not the diameter they were supposed to be by enough of an amount to matter.

 

If the hole is .2" that is how it is done, but what if the hole is 0.007" or smaller? It isn't practical. I've had a lot of experience in machining myself, though nowadays it is out of a garage. I know how to use a lathe and milling machine manually.

Generally though, I'm the one making the holes. I can't do it naked eye any more, which is aggravating.

You can always use the dial handle graduations. As long as you eliminate all backlash.

Even on a manual, those tolerances are pretty easy.

 

Bill, how are you making a .007" hole???? At that size it would have been hard to make even in the high tech shop I worked in. A very rigid, low runout spindle would be needed, most Bridgeport's wouldn't be up to it.

If the hole is a through hole, the easiest way is an optical comparator to measure the distances.

 

Making PCBs require some very small sizes. I may have exaggerated, but the point was made.

 

You can also use two drills that fit your holes to measure center distance with calipers. Put the drill shanks into the holes and measure over them, then apply the same add or subtract half of each drill shank diameter. On thin material like a PCB I would do both a outside and inside measurement and take the average. This allows for the slight angling of the drills when applying the calipers. Measure as close to the surface of the PCB as you can get.

If your using a mill to put in the holes the mill table movement is probably going to be as close or closer than you can measure, like Metalman said.