Need a super-sized micrometer

pbiYoung

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What would be a few acceptable methods to measure (nearest .005) the thickness of the bottom of the box (in the middle) on the attached drawing ? The dimensions are in inches, but not precise. No access to a surface plate large enough.

case3d-Layout2.jpg case3d-Layout1.jpg
 
What’s the material and what measurement tolerance? There are ultrasonic thickness measuring instruments for sheet and film applications like this.

Example: Mxmoonfree Ultrasonic Thickness Gauge Meter 0.8-350mm/0.03-13.77" | 0.01mm/0.001" Thickness Measuring Tools with QC Mode, Data Recording, Auto Calibration, NDT for Metals, Glass, Ceramics, Plastics https://a.co/d/2h1DoUp
 
Yep, I have an ultrasonic thickness measuring tool.
I use it to measure the thickness of piston crowns when I need to fly cut valve reliefs into them and also when reworking the squish areas.

you could also use something like this with a 1-2-3 block:


someone out there might also make a 1” mic with a deep throat, but I’ve never seen one. But that doesn’t mean there isn’t one out there…
 
Is the thickness uniform? On a mill with a Quill DRO, I would mount a dial test indicator in the spindle and lower it to zero out on the table and zero the DRO, Then I would place the box on the table and lower the quill to zero the dial test indicator and read my thickness on the DRO. You should be able to get within a thou of the actual thickness.

The gotcha is that the bottom of the box has to be flat or at least the point of contact of the test indicator probe has to be in contact with the table so yo may have to press down in that area to establish contact.
 
Mill table?
If you have a vertical mill this would work. Use a .0005" test indicator set up in the mill's tool holder. Zero the indicator on the table, raise the tool holder, mount the box and zero the indicator on the box's bottom. Depending on the condition of your equipment you should be accurate to +/-.0025".

Same as RJ posted.
 
What’s the material and what measurement tolerance? There are ultrasonic thickness measuring instruments for sheet and film applications like this.

Example: Mxmoonfree Ultrasonic Thickness Gauge Meter 0.8-350mm/0.03-13.77" | 0.01mm/0.001" Thickness Measuring Tools with QC Mode, Data Recording, Auto Calibration, NDT for Metals, Glass, Ceramics, Plastics https://a.co/d/2h1DoUp
What’s the material and what measurement tolerance? There are ultrasonic thickness measuring instruments for sheet and film applications like this.

Example: Mxmoonfree Ultrasonic Thickness Gauge Meter 0.8-350mm/0.03-13.77" | 0.01mm/0.001" Thickness Measuring Tools with QC Mode, Data Recording, Auto Calibration, NDT for Metals, Glass, Ceramics, Plastics https://a.co/d/2h1DoUp
That is a good solution if an ultrasonic thickness measuring instrument is available. What might be another method ?
 
Yep, I have an ultrasonic thickness measuring tool.
I use it to measure the thickness of piston crowns when I need to fly cut valve reliefs into them and also when reworking the squish areas.

you could also use something like this with a 1-2-3 block:


someone out there might also make a 1” mic with a deep throat, but I’ve never seen one. But that doesn’t mean there isn’t one out there…
Its over 10" to the center of the box.
 
You did not say if you have a vertical mill or a lathy with a 10" swing. Either of those should make short work of measuring to a 0.005" accuracy.
 
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