HELP!! Can't find this tool to measure the I.D. of tubes anywhere..

squale · Feb 12, 2010

Okay I am looking for a tool like what I have drawn up in my attached photo. Does anybody make a tool like this already or know where I could have one made, etc.?

I need to measure the I.D. of plastic tubes used in say hand creams, toothpaste, etc. before the tubes are sealed closed. As we all know these tubes are very flexible plastic so holding them in round perfectly is not very easy. And for any tube sizes bigger than 1" in I.D. I do NOT have PIN gages that big.. my pin gages only go up to 1" in O.D.

Thanks all!

Billtodd · Feb 12, 2010

Do you need to measure them in the round?

If not a couple of round or half round fingers fitted to a pair of verniers and a little simple maths would give you the ID when round.

Mud · Feb 12, 2010

What is your size range, and your precision requirement? You could make your own plug gages, you could make a plug gage with several diameters on it, you could make a tapered gage with sizes scribed on it. Jewelers use a tapered gage with lines scribed on it to measure ring sizes, maybe one of them would work.

johnoder · Feb 12, 2010

One to two inches in the same tool isn't happening. Maybe a half dozen such tools for that 1" of travel.

John Oder

HelEx · Feb 12, 2010

Is the tube even parallel?

For a given tube capacity the size range would be very limited - this is supposing you want this measurement for quality control.

It wouldn't be difficult to make an expanding collet - in effect an adjustable plug gauge with a limited range. Expand it out with a screw until it fits neatly, then measure across the lands with a caliper. In any case, if you want the real diameter with such an expanding gauge the range would be need to be restricted, otherwise you'd be measuring a rounded hexagon, octagon etc.

Then there is the option of a digital caliper fitted with special anvils, as already suggested. You'd need a ring gauge to set the zero. Unless the tube is tapered, that would be the easiest option.

- Mike -

squale · Feb 12, 2010

a few gages could be used, they don't need that much travel in a single gage. Maybe each gage having .500" travel would be good. I need to cover from 1" to 3" in O.D. of the gage.

These tubes need to stay in perfect round when being measured. And the accuracy needs to be at least .002" so we are talking pretty accurate stuff here.

I already tried a taper gage, slide the open end of the tube on the taper, then measure the OD of the tube, minus the wall thickness of the plastic wall on the tube gives you the ID. But if you push the tube down too hard or too soft on the taper gage this will throw your measurement out. So basically I want something like a plug gage that is expandable to go inside the tube and I can expand or contract it to get just the right 'feel' of the I.D. Then I take the gage out of the tube and measure the O.D. of the gage with micrometers, this should give me the .002" accuracy I need.

I just need to find a gage like this. One machine shop I talked to measures tubes this way with a cylindrical grinder expandable mandrel. But I wanted something where I wouldn't need to cut the tube open on the other end for the long mandrel to get through it.

Billtodd · Feb 12, 2010

These tubes need to stay in perfect round when being measured. And the accuracy needs to be at least .002" so we are talking pretty accurate stuff here.

Given that they are flexible then you're probably looking at an optical comparator for that kind of accuracy. That's the way O-rings are measured.

Limy Sami · Feb 12, 2010

Hang on,............unless I've got the wrong end of the stick here,. you're talking 0.002?, surely a simple plug guage would do, GO & NOGO - You know what dia they're supposed to be, and the wall thickness which can be measured with an ordinary mic.

9100 · Feb 12, 2010

Try an air gauge as in this patent US3438244. It will work for blind holes and in your case, it would be like fig. 9 with a point added to insert it.

Bill

oldmech · Feb 12, 2010

We used ss ball bearings tacked to a rod when I worked on aircrafe instrument panels, maighe be able to make a go-no go gauge that way.
re

hickstick_10 · Feb 12, 2010

The animal you seek is already made, well something along those lines.

I dont think it be cheap.

PI and PI Plate Gages - The L.S. Starrett Company

squale · Feb 13, 2010

that gage won't go INSIDE of plastic tubes.. I need something to go down about 1" INSIDE of plastic tubes to measure the I.D. of the flexible plastic tube. So the tool must keep the tube in perfect round while at the same time measuring the ID. I will need to cover a range of tube I.D. sizes from 1" I.D. to 3" I.D. graduated in .002" of an inch. So we are talking an 'adjustable' gage here, not specific go-no-go gages.. I would need HUNDREDS of those..

homemade · Feb 13, 2010

Are you to measure every one or every now and again for quality control. Why must it be held round when all you need know is the circumference of the circle you wish for? Assuming the material is very flexible. Even easier if an occasional destructive test is allowed.

squale · Feb 13, 2010

no I need to measure all different sized tubes all the time...

this is what one of the machine shops I use now has: MSC Item Detail

only problem with this is if you have a tube that is only 2" long and around 2" in I.D.. then you have to cut off the cap end of the tube so this mandrel can stick all the way through the tube in order to measure the I.D. I would prefer NOT to have to cut the cap ends off the tubes.

Limy Sami · Feb 13, 2010

I think you're barking up the wrong tree, I'd measure them as Bill Todd mentioned in his first post, I can't honestly think of another method offering both accuracy and versatility.

Either that or hope NASA's having a fire sale

HelEx · Feb 13, 2010

Squale,

Why do you need to cut the end off the tube? If you go the route I suggested, of using an expanding collet - see Expanding collets - Dunham Tool expanding collet
you will have almost exactly what you want but it will be necessary to modify them slightly with a different arrangement to operate the draw bolt. They will insert from one end, and holes could be drilled at the ends of the slits to make them more flexible. They are machinable to suit each size of tube.

- Mike -

PixMan · Feb 13, 2010

A shop near me used to specialize in making gauges for plastic parts. Brookfield Machine made gauges for Gillette, Proctor & Gamble (now the same company) and a lot of other consumer product makers. Most of those gauges were air gauge type.

Unfortunately, they've gone under due to a company buyout by a guy who ended up in court for absconding funds.

Starrett's Special Gauge Division got some of their toolmakers, and should be able to help you.

squale · Feb 13, 2010

you need many points of contact on the ID of the tube to keep it perfectly round. Using only 2 or 3 points of contact will not do any good because that won't keep the tube perfectly round.

I also have an optical comparator, somebody mentioned using that, but I don't see how that would help measure the ID of the tube, also how to keep the tube prefectly round while measuring it.

Limy Sami said:
I think you're barking up the wrong tree, I'd measure them as Bill Todd mentioned in his first post, I can't honestly think of another method offering both accuracy and versatility.

Either that or hope NASA's having a fire sale

squale · Feb 13, 2010

mike,
this might be the closest idea yet to what I'm trying to do. Something to keep in mind... I will need to be able to have the collet hold it's exact size when I take it out of the tube to measure it with micrometers.. will that work or will the collet change size once out of the tube?

also, anywhere you can give a little photo illustration of what you are talking of with modifying the collet, I'm not a machinist and i'm a little uncertain of exactly what you mean by drilling holes, etc.

thanks!

HelEx said:
Squale,

Why do you need to cut the end off the tube? If you go the route I suggested, of using an expanding collet - see Expanding collets - Dunham Tool expanding collet
you will have almost exactly what you want but it will be necessary to modify them slightly with a different arrangement to operate the draw bolt. They will insert from one end, and holes could be drilled at the ends of the slits to make them more flexible. They are machinable to suit each size of tube.

- Mike -

Limy Sami · Feb 13, 2010

squale said:
you need many points of contact on the ID of the tube to keep it perfectly round. Using only 2 or 3 points of contact will not do any good because that won't keep the tube perfectly round.

I also have an optical comparator, somebody mentioned using that, but I don't see how that would help measure the ID of the tube, also how to keep the tube prefectly round while measuring it.

One more try!

You've already told us they're flexible as in hand cream type tubes?......... I hope so or I'm going mad

........ so measure them as a rectangular tube with rounded ends.

With any type of expanding mandrel you will end up with a series of flats, which although they may be small will not give you a true reading.

HELP!! Can't find this tool to measure the I.D. of tubes anywhere..

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