Sending out isn't an option..
IMHO, Sending out should
always be an option.
Please, I'm not trying to be argumentative or frustrate you, but I truly do not understand.
Ron has some really good alternatives above. but, even as he states, purchasing the equipment to calibrate them in-house is expensive.
How many sets of equipment do you have? If you don't have that much equipment, it will not cost that much to send out. You can even buy a spare set while those are out.
If you have a ton of these, then you might can justify buying higher order standards, comparative equipment, etc. That's expensive; that's a lot of gauge blocks!
Now.... as Ron suggested, and is always necessary to mention: it all depends on your needs and requirements. If you have loose tolerances in your process, then "yes" you might develop a comparison method in-house.
What are you accuracy requirements of your instruments?
How many instruments are we talking about, and how often do you have them calibrated?
As far as calibrating instruments in-house, you have received some pretty good help here. Two names come to mind-Hershal Brewer and Wesley Richardson (among others). I would recommend you follow their threads on setting up a calibration lab, determining uncertainties, controlling environment, support adequate training, etc.
Please be patient with me, and I'll try to help however I can.
