87 inch inside micrometer!

I just won an auction lot of measurement stuff out of the QA dept of a company downsizing. One of the items is an inside micrometer consisting of a number of parts, from 1 to 20 inches long plus a micrometer stage, that screw together to enable inside measurements up to 87 inches with a resolution (but presumably not accuracy!) of 0.001.
I cannot for the life of me imagine what this could be used for, and how would it be used - presumably at full length a 2-3 person job.
I would be fascinated to hear some examples ....

Roman

Romano said:

I just won an auction lot of measurement stuff out of the QA dept of a company downsizing. One of the items is an inside micrometer consisting of a number of parts, from 1 to 20 inches long plus a micrometer stage, that screw together to enable inside measurements up to 87 inches with a resolution (but presumably not accuracy!) of 0.001.
I cannot for the life of me imagine what this could be used for, and how would it be used - presumably at full length a 2-3 person job.
I would be fascinated to hear some examples ....

Roman

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on a printing press the cylindrical rollers are checked for parallel alignment you can use a inside mic that one end fits into a vee base.
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i prefer using a indicator. just saying a inside mic can be used for many things.

Romano said:

I just won an auction lot of measurement stuff out of the QA dept of a company downsizing. One of the items is an inside micrometer consisting of a number of parts, from 1 to 20 inches long plus a micrometer stage, that screw together to enable inside measurements up to 87 inches with a resolution (but presumably not accuracy!) of 0.001.
I cannot for the life of me imagine what this could be used for, and how would it be used - presumably at full length a 2-3 person job.
I would be fascinated to hear some examples ....

Roman

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There's a company 45 minutes from me that machines wind turbine housings.

wind turbine housings - Google Search

The housing have holes (flange) around that diameter. In fact the newest turbines are even bigger.

Enercon E126 - The Most Powerful Wind Turbine in The World - YouTube

Your inside micrometer could be used for anything like that - a large "cylinder". As you say the accuracy won't be "spot on" but better than other inexpensive alternatives and transportable.

The price for a new set would be somewhere between $300 to $450 so maybe you got a bargain, maybe not.

My set goes to 32".Mostly I only use up to 11".

One machine I have to check parallelism of the gibs is at 35" so I have to use gage blocks with the mic.

The only way I have to check the accuracy at this point is a 48" vernier caliper. Which is also fun to handle.

Dave

Pratt & Whitney jib boring machines used inside mics like that, maybe other mfr's too.

Crawl inside and measure a bore to receive a $25k timken bearing....make it squeak.

Make sure you take the measurements in several places.

And yes, I prefer the erector set ones with a dial indicator better, but have
used inside mikes on large bores.

Likely they were end measuring rods not inside mics. We have a set at work (Pratt and Whitney) from a Lucas horizontal bore.

Dave

Romano said:

I just won an auction lot of measurement stuff out of the QA dept of a company downsizing. One of the items is an inside micrometer consisting of a number of parts, from 1 to 20 inches long plus a micrometer stage, that screw together to enable inside measurements up to 87 inches with a resolution (but presumably not accuracy!) of 0.001.
I cannot for the life of me imagine what this could be used for, and how would it be used - presumably at full length a 2-3 person job.
I would be fascinated to hear some examples ....

Roman

Click to expand...

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a shallow bore indicating gage set to gage blocks kept in cnc at temperature is used to measure to .0001" it sits on a surface with tips 0.2" into bore. measuring into a deep bore looking for taper in much harder but still usually a indicating gage set to gage blocks kept at temperature is used. bore taper is common if coolant is cold and the boring bar is getting smaller as it is boring a hole. and if no coolant is used the boring bar can get longer as it warms up making the back of a bore bigger. this is normal on bigger bores
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inside mic only used if +/-.001" or +/-.002" is acceptable. some bigger dimensions tolerances can be +/-.004" (or more) so inside mic is ok to use. i always check inside mic to gage blocks kept at temperature as they can easily be more than .001" off with temperature differences. i have more problems with big outside micrometers. they are not easy to hold when over 16", outside mic get a square smallest reading without excess turning pressure and holding the mic is difficult

DMF_TomB said:

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a shallow bore indicating gage set to gage blocks kept in cnc at temperature is used to measure to .0001"

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Isn't anyone else going to ask what size of dimensions keeps getting measured to 0.0001"?

I know I'd like to see a picture of both the component and the instrument.

No, I'm more curious about the parts being measured....

Why not use a Starrett 128 combination head?

[128 Combination Head with Inside Micrometer ]Accuracy (in): Mic head +.0002" / -.00"; Indicator is +/- one grad per revolution

Gordon B. Clarke said:

Isn't anyone else going to ask what size of dimensions keeps getting measured to 0.0001"?

I know I'd like to see a picture of both the component and the instrument.

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bearing bores usually under 12" often get measured to +/-.0001" using gage blocks and a bore indicator. we measure actual bearing going in to .00001". i believe they do on a CMM. rarely if bore over .0001" big they will try to find a bearing .0001" bigger to go in bore. usually make parts in sets of 3 and make part with smallest bearing bore first. the 3 bearings often have a spread in sizes of .0001, each part has a serial number for that particular size bearing
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over 12" often they give often +/-.0002" tolerance. many types of indicating gages set to gage block stacks kept at cnc and part temperature.
..... i have easily done over 950 bores holes and about 1/3 are +/-.0001" tolerances for bearing bores. usually larger tolerances like +/-.0002" are for ball screw nut assembles that bolts on a face of bore.
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i only use a inside or outside micrometers with its error checked to gage block stacks if i have a +/-.0004" tolerance. even a 20" outside micrometer is big enough to give problems getting squarest reading without excess turning pressure. indicating gages you can rock them and check for bore taper all without anything more than indicating pressure. usually you can pick up bore taper and waviness in the .00005" to .0001" range. bore taper over .0001" is usually a procedure problem not doing something correct although sometimes it is a metal hardness variation problem
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some parts the bearing bores can go out of round when unchucked. there are ways to minimize this of course. obviously if i have to assembly one part into a bore .0005" or less clearance the actual measurements need to be correct. usually part needs to be tapped to go in as the slightest angle and it locks up but once part is seated it will spin to align bolt holes. if out of round enough you can feel as it spins it tightening up. assembly guys obviously prefer being able to align bolt holes without problems. usually need .0003" clearance for that

DMF_TomB said:

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bearing bores usually under 12" often get measured to +/-.0001" using gage blocks and a bore indicator.

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What are these bearings used for?

I used to work at a works that made Turbine Generators ,micrometers of this sort of size were used routinely as well as external ones up to prolly 60" yes it would be a 2 man job ,I remember length bars that would be 10s of feet long ,big parts need big measuring kit.

sable said:

I used to work at a works that made Turbine Generators ,micrometers of this sort of size were used routinely as well as external ones up to prolly 60" yes it would be a 2 man job ,I remember length bars that would be 10s of feet long ,big parts need big measuring kit.

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What kind of accuracy and tolerance was normal?

I've been to Brown Boveri in Switzerland a couple of times when I was working for Danish power plants.

ABB is born - YouTube

Where I had my apprenticeship this type of measurement was pretty much a daily occurrence. But we also had the appropriate outside micrometer along with a standard to verify the inside micrometer reading. Just takes a few more measuring tools to make sure your inside mike reads accurately. Of course your workpiece temperature and the temperature of your measuring instruments are important. If you are going to do work of this type make sure that you have the appropriate measuring tools before you start.

yes i agree temperature control is important i daily see micrometer calibration checked to ring gage or gage blocks kept in a cnc change .0003" or more cause of temperature change (cold coolant). even holding a gage in your hand long enough the heat of your hands can change calibration .0002" or more especially the longer gages
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part tolerances i do not decide. i make parts to a drawing. not many machinist ask about part design and tolerances. obviously some parts with tight tolerances are considered more critical especially on bearing bores. i have seen parts rejected cause bore was .0002" out of tolerance. usually cause somebody made a math error or read gage wrong. rare to happen but thats what inspection is for to catch errors like that.
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larger inside and outside micrometers are not as good as indicating gages which can pick up waviness, out of round and taper a lot faster and easier.
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gravity effects bigger micrometers. how held and how they bend under there own weight requires checking to gage blocks in the measuring orientation. basically calibration changes depending on if held vertical or horizontal. obviously gage block stack needs a flat support so its straight. the same as precision tape measures change depending on continuous support, support on ends and support at center, or multiple supports between the ends. had a $30,000 precision invar tape measure with error compensation table from NIST you had to look up how it was supported and it would list error along the tape at different measurements spots. that invar tape measure was guaranteed to not change much with temperature changes unfortunately most things you measure do change length with temperature. that required 4 people. one held tape end, 2nd held other end of tape measure pulling 10 lbs with a scale. 3rd used magnifying glass to watch zero end of tape measure at target. 4th person watched other end of tape measure to read in using a 30x optical transit. tape always moving back and forth. required guy on each end saying good, good, good. taking many measurements. reading 50 foot distance to .005" only showed parts changing length with temperature often hourly. if temperature not stable than lengths not stable

Gordon B. Clarke said:

What kind of accuracy and tolerance was normal?

I've been to Brown Boveri in Switzerland a couple of times when I was working for Danish power plants.

ABB is born - YouTube

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In theory a thou or two ,whether it is/ was real I have no idea. This kind of thing has been disputed many times on here.

I picked up a Starrett set at a yard sale. I don't know anything about it but for the price I couldn't pass it up. Box looks real old but is in good shape. 21 pieces total box measures approx. 42 1/2" x 20 3/4" x 3 3/8". Can't seem to find much info on the internet about any set this big. Any info anyone could supply such as year(s) of production or model number or any info really would be much appreciated. Thanks I am including a picture