Measuring Tool

[Parm]

I've got a job comming up where ive got to meausure the external size of thin wall ducting used in control systems to remove contaminants in the work place. Its about two weeks work for me and involves literaly hunders and hunders of ducts in the factory. I need to be able to measure the external diameter of these ducts as well as recording lots of other measurements.

Have you clever people any ideas for a simple measuring tool that i can make?

The idea floating around in my head is to have two strips of somethign light wweights such as alumimium. These will be drilled an bollted at one one like a pair of compassess and will have some sort of points and 90 degrees to the shaft. Close these around the duct and then measure across the points to get external diameter.

Any advancement on this ?

 

[rtbcomp]

External calipers.

What sort of diameters are you talking about?

If they are a set of standard diameters you could calibrate the calipers so you don't need to measure every time.

 

[eSCHEn]

What rtbcomp said - external calipers.

Would be very easy to knock up. How accurate do you need to be?

 

[Parm]

External calipers.

What sort of diameters are you talking about?

If they are a set of standard diameters you could calibrate the calipers so you don't need to measure every time.

Thats exactly what i was thinking, but i need something that will go from around 100mm diamtere all the way up to about 600mm. Ive had a look on the web and cant find anything that will cover the range hence my investigations to make soemthing my self. It doesnt need to be super accurate

 

[rtbcomp]

..................

If they are a set of standard diameters you could calibrate the calipers so you don't need to measure every time.

You could also make a set of fixed gauges.

 

[Parm]

 

[Parm]

The above is what i had in mind. Ive got some 5mm by 30mm wide ally flat stock. Drill and pivot the bottom end and have a wing nut and spring to control the amouint of tension and fix two points that will contact the measurement location. the just measure across with a tape measure

Should have said that i will be carrying other kit also so need to keep this leight weight and simple

 

[julianf]

Make some U shaped slots in some MDF of standard pipe widths (assuming, as above, theyre standard width pipes!)

Make a selection of them, and just verify the pipes by slotting the U shaped sections over them.

If you have lots to do, you'll know the width by eye quickly enough, and then the gauge will just be for confirmation.

If you have an odd width pipe, just use the next size up, and some standard verniers to measure the difference (the slack between the pipe and your template)

 

[Pete.]

Use a pi tape.

 

[Cobbler]

Use a pi tape.

Beaten to it, never heard one called by name. I used to use one for measuring outside diameters of cables at one time.

 

[Pete.]

You could make a rough one quite easily. Take a small fabric tape and melt/sand off the numbers. Now mark every 314mm as 100mm increments so your 1m mark is 3142mm from the end. Now take a piece of card and mark out every 31.42mm ten times and use this to fill in between the 100mm marks. You now have a pi tape for up to 1m diameter accurate to 10mm.

 

[I'm getting on a bit]

Dress making tape and a calculator.

Measurement divide by 3.142

 

[Maker]

Just wrap a regular tape around it and divide by pi.

 

[Rocketman]

Why make it hard when you CAN BUY DIAMETER TAPE MEASURES

 

[Parm]

Ok guys, I've seen these tape measures and they are quite good and one has been ordered. But for this specific application I need something like a pair of outside calipers as I literaly have hundreds of ducts, quite a few which are at high level and cannot always get all the way round. Since my earler post iv come up with a better design which I'm going to make and incorporates a measuring device

 

[Welderpaul]

I'd buy a set of these, or something similar, weld two angles on the ends of the arms (or small pieces of pipe which are similar rad the ducting i am measuring), then replace the thread with a sliding scale so you simply close it round the pipe and read straight off it. Scale might take a bit of fiddling with to get it right.

 

[Rig Pig]

Buy a line of chords rule

 

[Hitch]

Pair of these bad boys and a tape...
http://www.rdgtools.co.uk/cgi-bin/sh000001.pl?WD=calipers&PN=FIRM-JOINT-CALIPERS--BIG--24--3290.html#SID=346

 

[Kent]

Ok outside the box a bit but if its not in operation all the time could you block it then do the lot in one hit with a volume fill of air? sounds mad but it can be more accurate and quicker than lots of measuring and punching numbers into calculators. Pump it up and look at the CFM against a timed fill to low pressure? The volume fill cant miss a bit can it now?

 

[Parm]

Pair of these bad boys and a tape...
http://www.rdgtools.co.uk/cgi-bin/sh000001.pl?WD=calipers&PN=FIRM-JOINT-CALIPERS--BIG--24--3290.html#SID=346

In the interest of keeping me in the man cave im gonna make something like that