got mine yesterday as well and do not seem to have these issues either. i will say that once I close the caliper I can put additional pressure on it to change the reading somewhat but it seems accurate if I just allow it to close by itself without any pressure. of course, at my level of woodworking close is good enough :gar-Bi
I can't speak of the particulars of this model, only calipers in general. The most error a moderate amount of force applied to the caliper should create, assuming you are not crushing the object you are measuring, is no more than +/- 0.0005" (1/2000" or 1/2 mil). If you are getting more error then this then either the calipers need adjustment or they suffer from poor design.
A quick test, before adjusting, is to tighten down the locking knob -- not so far that you can not move the caliper but just enough that it moves with some friction. This temporary adjustment should eliminate the play in an improperly adjusted caliper. Now try taking a measurement and applying a bit of force. If this eliminates the error (or gets you to no more than 0.0005" (1/2 mil) error then your calipers need adjustment. If you are still getting unacceptable error then the calipers themselves suffer from poor design and no adjustment can fix this. Afterwards, don't forget to loosen the locking knob.
The Adjustment:
Most calipers ship with two small adjustment set screws located, typically, to either side of the locking knob up top. These are very small screws and will require an equally small straight-blade screwdriver to adjust. Each of the two screws applies pressure to a pressure plate that rides along the top side of the caliper's body to remove play. There are two screws for this adjustment so that the calipers themselves can be adjusted for parallelism if the inner jaws of the caliper don't meet up precisely over their full length. If they don't meet up, then you will tighten one setscrew while equally loosening the other until the jaws close perfectly. Once the jaws are adjusted to close properly you will need to take as much play out of the calipers as possible, which is done by equally tightening both setscrews (e.g. if 1/8 turn on one, then turn the other 1/8 turn as well). When properly set you should be able to fully open the jaws of the caliper over their full 6" adjustment range with no more than a minimal amount of friction over the entire range
When the adjustments are completed you should not be able to see any light between the closed jaws of the caliper and the application of moderate pressure while measuring should not introduce more than +/- 0.0005 (1/2 mil) error. If you hold the caliper jaws in line with a lamp, your eyes should be able to discern as little as a 1/2 mil (0.0005"), or less, of opening between the two jaws.
Comments
Mike, I'm sorry your new purchase did not work out. FWIW, I have a digital caliper (measures in mils and milimeters), two fractional dial calipers (1/64") and a pair of dial gauges (both measure in mils). I very seldom use my digital calipers in the shop, but I use my fractional dial calipers all the time -- one pair is stainless steel (from Woodcraft) and the other is a nylon-fiberglass composite (General brand). The nylon-fiberglass one is great when working around cutters, especially carbide, as it will not chip the cutters if it makes contact. The two dial gauges (one is kept in a magnetic base, the other part of a complete older Align-It kit) are used a good bit for tool setup.
My point being that, aside from my Wixey thickness planer DRO, I really don't use my digital caliper set in the shop much. I almost exclusively use fractional dial calipers -- their analog nature and 1/64" increments (from which one can easily interpolate 1/128" or even 1/256" inch) are more intuitive for most woodworking tasks. For tool setup, I almost exclusively use the two dial gauge setups.
I still can not get over how inexpensive digital calipers are these days. I purchased my digital calipers from Rockler about 10-11 years ago for about $60 at the time and I thought that was an excellent deal. Now there are places that practically give them away, though I sometimes wonder how well made some of the newer models are.
Out of curiosity, do these cheaper calipers still ship with an accuracy certificate that shows their error at different measurements (typically every 5-10mm)? For example, my calipers experience their maximum error of -0.02mm between 130-140mm and 0mm to -0.01mm over the rest of their range -- this corresponds to a maximum error of 1/1250" over their full range.
HTH
