Measuring Holes in Perforated Sheets

Sounds like you need a set of plug gages. These are pins/rods of a calibrated diameter. The accuracy of these range from 0.005mm to 0.0015mm depending on the class. The size increases 0.0254mm from one pin to the next pin. Depending on the size and range you need the set will cost between $200 to $1000 USD.

Depending upon the required level of accuracy, you may be able to use a substitute for the pin gages: I'd suggest considering a set of drill bits. One of the large sets with fractional, letter, and number bits in a case can be obtained for $40 or so routinely (USA - don't know elsewhere). A set of metric bits would also work fine, especially if in the finest increments you can find. You can use your caliper to double-check the largest shank that fits through the hole without forcing it, if you don't trust the calibration of cheap bits. Another US$15 - 20 will get a set of #61 - #80 if you need smaller sizes.

I recall in a local PCB manufacturer the guy had a tapered pin gage that was marked in a way that you just look to see where it stops when you insert it. Also, in tool catalogs you can buy a magnifier with calibrated markings that you place on a surface and measure directly. They come in various configurations. There might even be one with calibrated circles but even a linear scale would probably be pretty accurate.

What if you used a liquid like water. Somehow let it flow through the holes. Weigh it or measure it with a measureing cup of sorts. Then calculate volume to size of holes.

Thats NOT a good idea you must work for NASA .How about a torch tip cleaner $4.95 no brainer or any other good suggestion previously mentioned

Hydraulics are not my area of expertise, but I have an idea that it would be difficult to accurately know and control all the variables to get accurate results. I guess if you're looking for other ways, you could use a light meter and a lamp but again you would have numerous variables to calibrate and control. You could shine a light through the hole, control the distance between the light and a target screen on the other side and measure the size of the image on the screen with your caliper. That might be your best bet. You could more easily control the variables involved and accuracy would be a mater of the distances you chose.

A less expensive option would be to purcase a set of tapered pins. McMaster-Carr in the US offers a set of 120 metric tapered steel pins for $98. Use a permanent marker to darken the surface of the sizes of pins you need. Place the closest size pin into the hole and use a sharp scribe to mark a line around the pin where it tightly fits into the hole. Remove the pin and measure the diameter of the pin at the inscribed line with your caliper.

Taper pin gauge is the best way but most expensive as each one covers a very small range of diameters. Cheapest for very small holes is a tapered gas jet reamer come diameter tester.Check your gas equipment suppliers.

Use a flatbed scanner. you can then try one of three ways to size the holes. 1. import into a CAD program which will have measuring capabilities. 2. use a program for scanning that records the holes in DPI and then convert them to metric or IPS. 3. use a photo mgr software which will give you sizes in pixels and you can convert to metric or IPS. I favor the idea of using Solidworks and the autodimensioning function.

Wow! That's an inspired idea. I'll try to buy sets of pins covering the sizes I work with, but your idea is second and that's a good thing.

not all scanners will scan at 1:1; sometimes as low as 97% actual size. Scan a scale/ruler to find out if scale factor required when importing image.

Well, that's inspired too! Thanks a lot.

A very quick, simple, and accurate tool is manufactured by L.S. Starrett, as well as others. It was mentioned earlier in this thread, but it is a tapered thin steel guage that is graduated in either .001" or 0,02mm divisions. Fast, simple, accurate, and cheap; who would not go for that? It can be used to measure square, rectangular, or round holes at will.

Ing. Robert Forbus

I suggest only two methods of measuring the holes in the perforated sheets and that are pin gauge or Profile projector.

You dont have to buy them, just go to any industry ask to them for the pin gauge measure there and return to them.

For profile projector you have to find the industry having the profile projector. Place your proposal in front of them and if they allow use it and find the various dimensions of the hole.

I hope this will help you...