Accuracy of Digital calipers

[Gary Armitstead]

Having spent more than forty years in the machinist trades (I was a Die Sinker and made Drop Forging/press forging dies and cavities), I can tell you that 99.9% of the professional machinists consider calipers of any type.....manual readout or digital.....to be nothing more than "square nut wrenches".

[Harold_V]

Having spent more than forty years in the machinist trades (I was a Die Sinker and made Drop Forging/press forging dies and cavities), I can tell you that 99.9% of the professional machinists consider calipers of any type.....manual readout or digital.....to be nothing more than "square nut wrenches".

You and I will get along just fine!
It borders on the impossible to have some people understand that calipers of any stripe are not very precise instruments. By design, they leave a great deal to be desired, in particular if they are used for both internal and external measurements, where any minor deviation in the jaws alters the true reading of both.

To be clear, I own calipers. Both vernier and dial. I use them when I have no other options, or when appropriate to the task at hand. I never trust the readings.

Harold

[earlgo]

Richard_W wrote:

I bought several Harbor Freight digital calipers back in 2008 and 2009. When comparing them to my Mitutoyo 8" calipers they measure the same! They do not loose position when turned off and when you move the jaw they turn on just like the Mitutoyo.

HF must have changed suppliers because the three 2014 versions that I bought shut off their display and lose their position memory. They do not turn back on when the jaw is moved. I just checked figuring that I might be operating them incorrectly.

Practical calipers are real, just some are more convenient to use than others and therefore, more 'real'. ( I lost my virtual calipers several years ago when I laid them down.)

--earlgo

[spro]

I may have to checkout the 2014 HF calipers. Part of the problem with the older ones, is that they never really "shut down". It may be that memory which drained the battery. It is a fact that people use these as convenient, inexpensive digital slides. They are modified so the condition or integral inaccuracy of the jaws are not an issue.
I see parts advertised more frequently these days where at least a digital caliper is used measuring one dimension of it. It isn't a total mystery for that one dimension allows others to be determined. The display transfers to the picture well and it isn't like someone has to learn to read a micrometer.

[Richard_W]

Having spent more than forty years in the machinist trades (I was a Die Sinker and made Drop Forging/press forging dies and cavities), I can tell you that 99.9% of the professional machinists consider calipers of any type.....manual readout or digital.....to be nothing more than "square nut wrenches".

I disagree on this and I have 43 years in the trade. Digital/dial calipers have there place and if you were looking on my work bench on Friday you would have seen 3 OD micrometers, 1 ID micrometer, depth micrometer, Gem indi-cal groove gauge, 4" digital caliper, 8" digital caliper and a double hook digital depth gauge. The close stuff is measured with the micrometers and everything else is measured with the digital calipers. Why should I measure a fractional dimension with a micrometer? There isn't one and often I am checking location to a cast surface. Some dimensions are fractional because they do absolutely nothing in use and often are painted. Some features are machined just to perform the next operation!

Even when I made injection molds only what needed to be close was made close. If you want to hold everything close then that is a persons option. Some new people do it just to see if they can and that is fine to. Some jobs require everything to be dead on, while most do not. If a measuring tool is worn out and out of spec, then toss it and get a new. I have even sawed Starrett micrometers in half because they were worn out. Better they go in the scrap pile than to Ebay in my opinion.


Richard W.

[Richard_W]

Richard_W wrote:

I bought several Harbor Freight digital calipers back in 2008 and 2009. When comparing them to my Mitutoyo 8" calipers they measure the same! They do not loose position when turned off and when you move the jaw they turn on just like the Mitutoyo.

HF must have changed suppliers because the three 2014 versions that I bought shut off their display and lose their position memory. They do not turn back on when the jaw is moved. I just checked figuring that I might be operating them incorrectly.

Practical calipers are real, just some are more convenient to use than others and therefore, more 'real'. ( I lost my virtual calipers several years ago when I laid them down.)

--earlgo

I think they did change suppliers, because when I was in their store I was looking to get another 8" digital caliper. The fit and finish was bad and the jaws didn't come together right. The Shars were much better.

Richard W.

[Mr Ron]

Having spent more than forty years in the machinist trades (I was a Die Sinker and made Drop Forging/press forging dies and cavities), I can tell you that 99.9% of the professional machinists consider calipers of any type.....manual readout or digital.....to be nothing more than "square nut wrenches".

You and I will get along just fine!
It borders on the impossible to have some people understand that calipers of any stripe are not very precise instruments. By design, they leave a great deal to be desired, in particular if they are used for both internal and external measurements, where any minor deviation in the jaws alters the true reading of both.

To be clear, I own calipers. Both vernier and dial. I use them when I have no other options, or when appropriate to the task at hand. I never trust the readings.

Harold

If they are so imprecise, why then do the precision tool makers (Starrett, Mitutoyo, B&S, Mahr, etc) make them? They are not cheap. According to their catalogs, some can be used in inspection and record the readings in a computer. That just seems to be a big investment for an inherent "imprecise tool". Note: I have also posted a new query on Dec 12, covering this same topic. To be very candid, I love my dial and vernier calipers and would like for anyone to dispel negative feelings that have been raised about them.

[Downwindtracker2]

Think about it, in order to slide they need slop, better brands less slop.

I worked in a machine shop as a millwright, tearing down, rebuilding stuff. I was shocked at the machinists using their dial calipers as dividers to scribe circles. These weren't your cheap Chinese, they didn't exist then, but Mits. That was the level they thought of them. My vernier calipers cost over $50, then, 1/2 day's wages.

[tornitore45]

Why they make tape rulers, wooden Yard sticks, plastic protractors and those poor excuse for compass you see around?

There are application where 3 or 4 thousands do not make any difference at all, each class of tool is adequate for its class of work.

Any one that can consistently fit a bearing, make a shaft in Pittsburgh that will press fit a hole bored in Miami with a dial caliper should continue to do so, the rest should use a mike and some should add a magnifier too.

[ken572]

Why they make tape rulers, wooden Yard sticks, plastic protractors and those poor excuse for compass you see around?

There are application where 3 or 4 thousands do not make any difference at all, each class of tool is adequate for its class of work.

Any one that can consistently fit a bearing, make a shaft in Pittsburgh that will press fit a hole bored in Miami with a dial caliper should continue to do so, the rest should use a mike and some should add a magnifier too.

I have to agree 100% with Mauro.
In the service it was called, Field Expedience.
If you were well trained, and highly skilled you could
always make it happen with what was on hand.
Very Rewarding as well.
Ken.

[ken572]

Please Disregard my question below.
Ken.

Mr Ron.
Is this post kind of related to your other post below?
http://www.chaski.org/homemachinist/vie ... 4&t=100381

Ken.

[Mr Ron]

Please Disregard my question below.
Ken.

Mr Ron.
Is this post kind of related to your other post below?
http://www.chaski.org/homemachinist/vie ... 4&t=100381

Ken.

Yes.