Digital Fraction Calipers are everywhere!

[AndyF]

Wow! I don't recall seeing this many digital fraction calipers 3 months ago:


http://www.rockler.com/product.cfm?page=17287


http://www.highlandwoodworking.com/i...OD&ProdID=7690


http://www.hartvilletool.com/product/12270


http://www.wixey.com/calipers/index.html



Looks like they all do some combination of cycling between mm, decimal inches, and fraction display or combining decimal/fraction inches at the same time.

I wonder if they were all waiting on the same developer/supplier for that "key" part...


Now to persuade the "boss".

Andy

[Thom2]

I wonder if they were all waiting on the same developer/supplier for that "key" part...

I seem to remember a discussion about Wixey bringing these to the states, I believe the owner had a few of these confiscated while trying to bring back demo's. It may have been Holbren that gave a head's up about these 'coming soon', looks like they're finally here

[LCHIEN]

Wow! I don't recall seeing this many digital fraction calipers 3 months ago:


http://www.rockler.com/product.cfm?page=17287
http://www.highlandwoodworking.com/i...OD&ProdID=7690
http://www.hartvilletool.com/product/12270
http://www.wixey.com/calipers/index.html


I wonder if they were all waiting on the same developer/supplier for that "key" part...


Now to persuade the "boss".

Andy

It's not uncommon that an application specific IC (electronic integrated circuit) is developed to do these tasks, then several manufacturers build around that one part that makes it possible to be small and low power and cheap. When demand emerges and someone provides the part, then you'll find several sources of the finished good. Unless, the manufacturer sponsored the part's design in which case it becomes proprietary.

[jarhead]

Here's a related item... a digital height gauge:

http://www.harborfreight.com/cpi/cta...emnumber=93488

[radhak]

and of course, the less pricey version :
http://www.harborfreight.com/cpi/cta...emnumber=47257

[drumpriest]

I'm not a fan of the digital fractional calipers. They don't have enough accuracy being reported as a fractional number for my taste. And converting from .xxx to 1/yyy is easy enough that I guess it doesn't bother me.

[JR]

I'm not a fan of the digital fractional calipers. They don't have enough accuracy being reported as a fractional number for my taste. And converting from .xxx to 1/yyy is easy enough that I guess it doesn't bother me.

I've gotten used to measuring in decimal and making the conversion, but It would speed things up for my pea brain if I didn't have to. 1/64" accuracy would be good enough for my work.

JR

[radhak]

I'm not a fan of the digital fractional calipers. They don't have enough accuracy being reported as a fractional number for my taste. And converting from .xxx to 1/yyy is easy enough that I guess it doesn't bother me.

Did you mean they are in-accurate while displaying the fractions, or did you need more than 1/64" accuracy?

[jAngiel]

So are these new fractional ones more accurate than the digital ones from HF? The 6 inch one from HF is accurate to .001 with a resolution of .0005, so to me looking at the significant digits that are available, it sounds like it is only accurate to around 1/8 inch with a resolution around 1/16.

If the new fractional ones actually go to 1/64 they sound like they are more accurate. I could be all wrong on this, Loring may be able to enlighten us...

[Kristofor]

So are these new fractional ones more accurate than the digital ones from HF? The 6 inch one from HF is accurate to .001 with a resolution of .0005, so to me looking at the significant digits that are available, it sounds like it is only accurate to around 1/8 inch with a resolution around 1/16.

If the new fractional ones actually go to 1/64 they sound like they are more accurate. I could be all wrong on this, Loring may be able to enlighten us...

Perhaps I'm misunderstanding you, but accuracy to 0.001 is 1/1000... Which is much more precise than 1/64th (~0.016)? Or maybe the HF version is different than the one I own which will sill read to thousandths even if the value is greater than one inch?

I guess maybe I'm just not understanding?

Kristofor.

[jAngiel]

The way I see it is

1/64 = .015625 so if you only have accuracy to .001 and a resolution of .0005 you will never be able to accurately measure .015625

1/64 = .015625
1/32 = .03125
1/16 = .0625
1/8 = .125
1/4 = .25
1/2 = .5

It seems to me that to measure to 1/8 inch accuracy, you need accuracy to .001 (actually I think .005), to get 1/16 you need accuracy to .0005, to get 1/32 you need accuracy to .00005.

Like I said I could be all wrong on this, this is just my interpretation of the numbers.

[burrellski]

The way I see it is

1/64 = .015625 so if you only have accuracy to .001 and a resolution of .0005 you will never be able to accurately measure .015625

1/64 = .015625
1/32 = .03125
1/16 = .0625
1/8 = .125
1/4 = .25
1/2 = .5

It seems to me that to measure to 1/8 inch accuracy, you need accuracy to .001 (actually I think .005), to get 1/16 you need accuracy to .0005, to get 1/32 you need accuracy to .00005.

Like I said I could be all wrong on this, this is just my interpretation of the numbers.

That is an incorrect interpretation of the numbers. An accuracy of .001 with a resolution of .0005 allows you to determine a value to the nearest 1/1000th of an inch. You would be able to take measurements of .0155, .0156, .0157, etc... in the 1/64th area. If you are limited to fractions with an accuracy of 1/64th your resolution around .0156 is 0, 1/64, or 1/32, much less precision.

In other words, something with a true thickness of 0.0077 (a hair less than 1/128) would read 0.008 on a normal caliper and 0 on a fractional. You're cutting an inch into 64 pieces vs. 1000 pieces.

Am I correct in my understanding of the digital fractional calipers? Maybe someone else can explain it better.

[Tom Miller]

It seems to me that to measure to 1/8 inch accuracy, you need accuracy to .001 ...

This may just be a matter of semantics, but what you're really trying to do is measure an 1/8" object to a decimal accuracy of 0.001 (or 0.005). Otherwise, 1/8" accuracy is 1/8" accuracy, and an object either measures 0, or 1/8", or 2/8", etc.

Putting it another way, if you wanted to measure to an accuracy of "pi", would you need a readout with infinite digits?

I always thought I wanted one of these calipers, but giving it a little more thought like this, I'm not so sure. I think it would be useful in picking out the right drill bit to use, since they come in 1/64's. Otherwise, when I pull out my calipers, I'm probably interested in the 1/1000's place.

Regards,
Tom

[edit] James, I'm afraid you're going to have to get one of these things and report your findings.

[jAngiel]

I agree. I may have to get one to check it out, or I may just stick with my little printed table that I use to look up the conversions. But I still think that there is no way you can precisely measure 2 and 1/32 inches with my HF digital caliper. "Precisely" is the key word though, you can get close enough for all practical purposes but not precisely.

If I can find one cheap enough I will buy it though, a tool is a tool, gotta have it.

[burrellski]

But I still think that there is no way you can precisely measure 2 and 1/32 inches with my HF digital caliper. "Precisely" is the key word though, you can get close enough for all practical purposes but not precisely.

The most accurate measurement you are going to get from a caliper is going to come from one that reads to three decimals, not fractions. If you are measuring something that is 2.0464000000 (just shy of 2 and 3/64 or 2.046875) with a decimal caliper your result is going to be 2.046 +/- .001 or somewhere in the range of 2.045 to 2.047 (assuming .0005 resolution). The same measurement on a caliper that reads to the 64th with a resolution of 1/128 would be 2 and 3/64 +/- 1/64 or in decimal equivalent somewhere in the range of 2.03125 to 2.06250. You're looking at a .002 window of error with the decimal and a .031 window with the fractional.

When you're talking about the fit of a dado or the thickness of veneer, .030 can make a huge difference.

The point is when the fractional caliper tells you something is 2 and 3/64 it is not saying the object is 2.046875, its saying it is somewhere in the 2.03125 to 2.06250 range.

If you've got a good steel rule with 32nd graduations, you can already read to the nearest 64th with a pretty minimal margin of error. Just my opinion though.