flatness gauge

[mielke]

We have an irregular shaped steel flange that is approximately 20" diameter, and we require a flatness tolerance of a couple thousandths of an inch. Does anyone have any recomendations on gauges to be used to ensure/prove that it is within flatness tolorance?

Thank you

 

[ornerynorsk]

surface plate and feeler gauges.

 

[Ron]

Precision straight edge and feeler gauges.

 

[IRstuff]

Laser profilometer
Optical flat

TTFN

FAQ731-376

 

[mfgenggear]

All the suggestions are good

if its humanly possible to pick up, then surface plate. if its part of a tank, precision straight edge.

or a laser (jig transit).

 

[racookpe1978]

Straight edge, held upright (straight edge perp to the surface) then shine a light from behind.

Your eye will catch the waves and low/high spots.

2. Get a "perfect" flat surface the needed diameter - by one of the better (more expensive) proper solutions above. From the back, drill and tap into it (into the back of your cal surface) three threaded holes for lift points.

Place your flange flat, face up with a appropirate dowel or "pipe" up the middle to center the cal plate and pprevent movement as it is lowered onto the tested flange.

Apply bluing to the cal plate, lower it (but don't rotate or bump it!) then raise it back up with your crane or hoist. What is not "blued" is low with respect to your cal plate.

 

[unclesyd]

I would use the surface plates as mentioned above, In my case I would use our granite plate (5' x 5').

A straight edge only gives you two readings and doesn't readily show any waviness.

If possible I would use something like Green Plastigage all around to get the general layout.

Do you require any out of plane measurements?

 

[photoengineer]

Coordinate measuring machine.


Cedar Bluff Engineering

http://cedarbluffengineering.webs.com

 

[Pud]

Coordinate measuring machine.

Exactly! Easy*!

*Although "A couple of thou" over 20 inches would suggest (imho) that you have your design of your jointing system wrong somewhere...

Cheers

http://www.tynevalleyplastics.co.uk

 

[lumenharold]

This is an interesting option for non-contact:

http://www.coherix.com/surface_flatness_measurement_in_precision_manufacturing

Harold
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