|Review by HungryTermite||posted 01-21-2010 08:49 PM||3369 views||0 times favorited||4 comments|
I picked up the Cen-Tech 6” Digital Fractional Caliper over the holidays for $25 at Harbor Freight. It seemed like a pretty decent price compared to what I had seen for similar models at other stores. Overall I like it a lot. I have used regular calipers before but this is my first set of digital calipers and I have to say I am never going back. I bought this model because it does fractions but I don’t really use the fractions setting because I tend to think in thousandths of an inch at work so it’s easier to measure things that way. The parts seem well made and the display is nice and large and easy to read even in low light levels like I have in my garage. It came with a nice little ABS plastic case to store it in, although as a project to learn some new skills, I will probably make one out of wood and just keep all the foam lining.
As far as accuracy goes I think it does a pretty good job. The accuracy listed on the unit is +/-.001 inches. I don’t have any gauge blocks to check this against but I do have some nice fasteners. I had access to 5 aerospace quality, close tolerance fasteners. The ones I had were 5/16 diameter and about 1.25 inches long. Each one comes in its own thick (1/16”) plastic sleeve so the shanks don’t get damaged before they are installed and they cost about $100 each so I would say they are adequate reference standard to measure the calipers against. The shank diameters are supposed to be between 0.3110 and 0.3120 inches.
I got 4 readings of 0.3115 and 1 reading of 0.3120. Also, when I re-checked the readings after resetting the zero on the calipers, I got the same exact readings, so the repeatability isnt too bad. I know this is not enough samples to be statistically significant and I know that the fasteners could have been out of tolerance to begin with. I also know that the accuracy could theoretically be different over different length scales but I dont have any 5 inch diameter fasteners to check and the length tolerances on bolts is not good enough to use as a reference. However, I still think that this level of apparent accuracy is fine for my needs.
Is it a Starrett? No. Does it cost as much as a Starrett? No. I give it 4 stars instead of 5 because I am not sure about how long it will survive, although the return policy at Harbor Freight is pretty good so I could probably just trade it in if it died.
I recommend it. YMMV.
-- Good Judgement Comes From Experience. Experience Comes From Bad Judgement.