I have a problem with the calibration of a curved check block for flattness requirement per SAE J442 Nov. 2008. My understanding is that the requirement shall apply to the flat side of the curved check block, and the flat side was requested our calibration organization to check the flatness for the compliance with the requirement +/-0.005mm per SAE J442. However, the calibration said that the requirement shall apply only to the standard zero block to be used for calibration of Almen Gage. In other word, the flatness of the curved check block does not require any check.
So, does the flatness of Zero Block refer to the standard zero block as the organization said or the flat side of the curved check block?
In the latter case, is it possible to ask the calibration organization to calibrate (check) the flatness?
The curved check block, approximately 0.024 inch arc height, is not calibrated and is for reference only. The opposite side, the flat side, is certified flat and this is the side that you should have re-certified.
Thank you for your meaningul suggestion. I'd like to ask you another favor. We are a Japanese Shot Peening Processor. Please let me know where we can ask a re-certification of the flat side of the curved check block.
Please check with:
Yoshihiro Watanabe
Toyo Seiko Co Ltd
3-195-1 Umaganji
Yatomi-City, Aichi 490-1412
JAPAN
81-822-5675-23451
81-822-5675-23457
[email protected] http://www.toyoseiko.co.jp
Please clarify one thing about the re-certification of the flat side of a curved check block. When the re-certification is referred, does it mean that the flat side is checked for the flatness to ensure that the actual value is within the requirement by SAE J442?
Yes, the flat side will be measured and its value must be equal or less than the required flatness of 0.005mm.
The curved side is not measured. It is for reference only. Do not try to measure the curvature of the curved side.
It's been long since I posted my inquiry regarding this issue, which could be a very minor issue.
I want to know how the calibration organization checks the flatness. I mean, do they use CMM or other specific equipment?
There are various methods to check flatness, all acceptable for the flat side of the block. CMM can easily be used as well as dial indicator and granite table in metrology laboratory. Optical flats can be used when the flat side is manufactured since it is very flat and smooth. Optical flats use mono-chromatic light and observation of fringe patterns.