The frankford arsenal digital calipers I have, have no reference point. No numbers on the scale anywhere.I think he was referring to a guage block, to check the accuracy of the caliper he has...
I know, how do you calibrate a piece of metal? haha. believe it or not there are people who get paid to check that gauges like these are calibrated. the date code in the box it came in states it needs calibrated in another year. I guess I will check with my calipers to make sure the block is still 2 inches.I made my own on my mini-lathe out of round brass stock. I have a 1" that was "calibrated" with a micrometer accurate to .0001". After checking several of my dial and digital calipers, I found they were all within .001" so it sits in one of my caliper boxes collecting dust.
I cut off a liberal section of 1/2" brass rod stock ... a tad over 1" long. I then squared one end and smoothed it. From there I pulled the stock out of the lathe and measured it. I don't remember exactly what the length but it was several thousandths too long. The dial on my cutter is calibrated in .001" increments so I cut the rough end down where the rod was about .001" too long then dressed the end with a jeweler's file until the rod measured exactly 1", using a micrometer with a .0001" resolution. This took several tries to get it exactly 1". Worst case ... it may be off .0001" .... about 10x more accurate than a typical dial or digital caliper can resolve.how do you calibrate a piece of metal?
I haven't replaced a battery on the new Grizzly yet. It has a feature where the display will flash when the battery needs to be replaced, As for the others, the digital display will get dim long before there is any change in accuracy. Matter of fact, I was using one of my digitals when the battery died and it maintained accuracy up to the dying gasp. Batteries are cheap if you know where to get them ... $7.95 each at Wal-Mart or you can get a card with 10 batteries for $5.95 on the Internet or in some stores. One of the venders at our local gun shows sells the 10 battery card for 10 bucks ... which is still a good deal ... a buck a year.I just dont wanna be measuring and my battery goes low and starts giving me inaccurate readings, or set the 0 wrong.