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Verifying Gage Block Buildups

JoshJay

Plastic
Joined
Apr 20, 2018
Hey guys, I need a bit of input here. This is my first time posting BTW! So I have taken over as the main tech in charge of setting up gages, calibration, purchasing ect.. The past techs were using an old NUMEREX CMM to double check they had the correct blocks.. I have elected to use a caliper as it is nearly 3 times as accurate (.001") (yeah the NUMEREX is that bad)Now the heat is on because of the resolution of the caliper is so low (.0005"). We do have 3 other B&S performer CMM's but those are typically checking parts, it would take too much time to wait and manually check the blocks... I double and triple check everything before assembling my stacks. so onto my question--> what do you guys do to verify gage block buildups???
 
Hey guys, I need a bit of input here. This is my first time posting BTW! So I have taken over as the main tech in charge of setting up gages, calibration, purchasing ect.. The past techs were using an old NUMEREX CMM to double check they had the correct blocks.. I have elected to use a caliper as it is nearly 3 times as accurate (yeah the NUMEREX is that bad)Now the heat is on because of the resolution of the caliper is so high. We do have 3 other B&S performer CMM's but those are typically checking parts, it would take too much time to wait and manually check the blocks... I double and triple check everything before assembling my stacks. so onto my question--> what do you guys do to verify gage block buildups???
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i double check math by using gage block ends and use a .0001 indicating bore gage set to a ring gage so then check gage block stack and should agree within .0001. in theory you can measure .00005" but it is difficult to get repeatability to .00005"
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not sure what you mean by caliper ? dial caliper measuring .0001" ?? you got to be joking. if nothing else my indicating bore gage is wrapped with rags to insulate it from the heat of my hand. no gage directly held with bare hands will give stable readings as its warming up growing the longer you hold it of course
 

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The reason i use a digital caliper with .0005 increments is to verify my stack is not off by a large number for example if i put the wrong block in there.
 
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i double check math by using gage block ends and use a .0001 indicating bore gage set to a ring gage so then check gage block stack and should agree within .0001. in theory you can measure .00005" but it is difficult to get repeatability to .00005"
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not sure what you mean by caliper ? dial caliper measuring .0001" ?? you got to be joking. if nothing else my indicating bore gage is wrapped with rags to insulate it from the heat of my hand. no gage directly held with bare hands will give stable readings as its warming up growing the longer you hold it of course

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I am dealing with a lot of these setups every day so unfortunately I don't have the time or enough bore gages to go around for this method. Although its looking like about the best option so far.
 
The reason i use a digital caliper with .0005 increments is to verify my stack is not off by a large number for example if i put the wrong block in there.

it will tell you if way off but digital caliper resolution of .0005" is only rated accurate .001 per 6" so it can say give a 6.000 +/-.0005 reading but still be off .001"
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i check calipers with gage blocks some are off .001 or more easily depends on how old and worn
 
it will tell you if way off but digital caliper resolution of .0005" is only rated accurate .001 per 6" so it can say give a 6.000 +/-.0005 reading but still be off .001"
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i check calipers with gage blocks some are off .001 or more easily depends on how old and worn

Right I'm aware of their accuracy vs. resolution. :)
 
Right I'm aware of their accuracy vs. resolution. :)

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had a old Prototrak mill with trav a dial wheels and the digital readout read .0005 and i would check with a 6.0000 gage block and indicator basically zero digital readout, zero indicator against gage block remove gage block move til indicator zero and look at readout if it said 6.0015 i put in in special calibration mode and told it it moved 6.0000 and reset digital readout so it reads 6.0000. when i moved 6.0000 then i would repeat to confirm it worked.
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did this once a year. most calipers do not have this ability to reset scale or maybe they do but i am not aware how to access it.
 
A pretty accurate way of checking would be to use a "Cadillac" style height gage (like this: Cadillac Pla-Chek Model 252 Height Gage W Germany | eBay ) with a regular height gage and tenths indicator. You'd want a vertical "nest" you could set the blocks into to ensure they can't fall over.

With a little practice, you could get reliable readings to a couple tenths in under 30 seconds or so. Some initial testing to confirm the Cadillac (or Mitutoyo or similar) gage is reading correctly would be a good idea, but once checked they're very stable.
 
i put ring gage or gage block stacks right in the cnc exposed to coolant temperature. quite often i have seen .0003" changes compared to shop temperature. you can easily get bigger changes if coolant if not temperature controlled
 
A pretty accurate way of checking would be to use a "Cadillac" style height gage (like this: Cadillac Pla-Chek Model 252 Height Gage W Germany | eBay ) with a regular height gage and tenths indicator. You'd want a vertical "nest" you could set the blocks into to ensure they can't fall over.

With a little practice, you could get reliable readings to a couple tenths in under 30 seconds or so. Some initial testing to confirm the Cadillac (or Mitutoyo or similar) gage is reading correctly would be a good idea, but once checked they're very stable.

There we go.. Thank you for your input! :D
 

You're reading that wrong. Up to and including 200mm/8" then the accuracy is ±0.001" and up to and including 300mm/12" (and in fact up to 600mm/24") accuracy is ± 0.015".

Those numbers/values are derived from the standard used by as good as all standard digital caliper manufacturers (DIN 862 and the identical ISO 2012):

Caliper Calibration

http://www.f-m-s.dk/DIN862.pdf

The specified accuracy will vary for special calipers. i.e. long legs or special purpose.

Just in case you or anyone else wants the standard for micrometers too then it's:

http://www.f-m-s.dk/DIN862+863.pdf
 
I would have thought that an electronic height gage would be a good investment for such a place. Accuracy for surfaces is 2 microns or so - about 7 hundredths of a thou. Also quick. IT sounds to me though that you aren't looking to validate that the gage blocks are accurate, just that you have stacked them properly. Depending on your smallest block, a good caliper should get you there but a micrometer is better.

For calibrating the gage blocks, I have a Mahr 828 PC universal length measuring machine but you still need a very accurate setting master and temperature control. And patience.
 
Where have you found that "fact"?

tool manufacturer lists tool spec and .001 per 6" is the most common spec for calipers
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my guess is cause any tool held in the bare hand is being exposed to the heat of the hand is changing length. obviously i use a excel spreadsheet to auto calculate changes in length to temperature changes.
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if nothing else a 20F temperature change per 6" is 0.0007" change in length for the steel caliper
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i have worked with many DRO digital readouts where you use a gage block and indicator to reset the digital readout so 6.0000 of actual movement reads 6.0000 of digital readout. many a time i have seen 6.0000 of actual movement read 6.0010 or 6.0020 and had to put it in calibration mode to reset the scale.
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had one DRO when in calibrated mode a little light blinked and it was easily turned off and then light was not blinking and it would be inaccurate. that was frustrating cause some machinist trying to zero the DRO would accidentally turn calibrated mode off not realizing what it was. all electronic scales have a mode to reset the scale so a distance moved reads a certain distance. with a caliper i am not sure how but there has to be a way possibly they connect it too a special device to calibrate to fix it so 6.0000 of movement reads 6.0000, i believe its called setting the scale of the readout compensation value could be like 1.000005 per inch
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obviously in a shop a aluminum part and a steel caliper are changing size at different rates so at different temperatures calibration changes. for example hot part on a lathe might measure 6.0010 and cooled off to shop room temperature read 6.0000. sometimes you make a part at a certain size at 75F temperature so when part is at 70F it is the desired size. it gets complicated cause gage blocks and ring gages change size too when at different temperatures
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thus why gage blocks and ring gages are often kept in a CNC so at coolant temperature and a indicating gage set to gage compares. quite often i have seen a micrometer read a gage block ok at room temperature but be off 0.0005 reading gage blocks at coolant temperature. temperature compensation can get complicated. when dealing with larger parts it can be the difference in parts going together or not going together. nothing worse that putting one part into another and you cannot rotate the one part to align to put in the bolts. you get clearances under 0.0005" and usually have to watch the temperatures
 
You also know that gage blocks are not perfect right? Where's the deviation chart for each set of blocks? If you are concerned about tenths a stack of 4 or 5 blocks could be off by 2 tenths or more if deviation not taken into account.
 
I would have thought that an electronic height gage would be a good investment for such a place. Accuracy for surfaces is 2 microns or so - about 7 hundredths of a thou. Also quick. IT sounds to me though that you aren't looking to validate that the gage blocks are accurate, just that you have stacked them properly. Depending on your smallest block, a good caliper should get you there but a micrometer is better.

For calibrating the gage blocks, I have a Mahr 828 PC universal length measuring machine but you still need a very accurate setting master and temperature control. And patience.

That is correct.. My blocks are calibrated yearly to Grade 0 so I know they're fine. Personally I have never made an incorrect stack but I assume they have ran into issues with bad ones in the past.. I am simply trying to get away from that POS NUMEREX to verify I've got the correct blocks.. thats why i thought a caliper is sufficient to begin with.
 








 
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