My metal ruler was wrong.

[mtaylor]

Sounds like this all is the moral equivalent of "Measure with a laser interferometer, mark with a piece of chalk, and cut with an axe".  Except that the laser is out of calibration.   Seriously, what level of accuracy do we need?  This isn't rocket science.  To me the question is "how accurate do you need to be when measuring?".  Sometimes, especially with wood models, the best we can do is "close" when measuring since most of us cut, then sand/file to fit.

[robert952]

49 minutes ago, mtaylor said:

Sounds like this all is the moral equivalent of "Measure with a laser interferometer, mark with a piece of chalk, and cut with an axe".  Except that the laser is out of calibration.   Seriously, what level of accuracy do we need?  This isn't rocket science.  To me the question is "how accurate do you need to be when measuring?".  Sometimes, especially with wood models, the best we can do is "close" when measuring since most of us cut, then sand/file to fit.

Don't forget 'paint to hide.'

[modeller_masa]

2 hours ago, BANYAN said:

which is the more accurate?

I would say that 0.01mm or 0.0005 inch (=0.0125mm) digital calipers are enough for wooden models. There must be more accurate tools, but I would say that the digital calipers are cheap and convenient tools for wooden model. If it is a plastic or metal model, where the materials can be more detailed, the huddle increases astronomically. Please consider my opinion as a newcomer's short idea. I don't know the world of the expert modellers.

 

If you were asking about the measuring accuracy of rulers, I use gage blocks. In my experience, I really don't need it frequently. When the zero digit is jumping, I press the zero button. When I tested my 0.01mm accuracy digital calipers with a gage block, I saw less than 0.02mm of errors and I was satisfied at that level. It was a reason I returned 0.1mm accuracy digital calipers. It revealed 0.1~0.2mm errors!

 

In addition, I don't trust 0.001mm accuracy digital micrometers. It was the cheapest ruler, and it revealed 0.010~0.020mm errors... There is no reason to buy the cheapest one. This is the best (and the worst) ruler I used. I'm sorry I couldn't answer you.

[Gaetan Bordeleau]

8 hours ago, modeller_masa said:

which is the more accurate?

Accuracy and ruler can be very much different.

A ruler with 1/64":  0,015"

To measure with accuracy, you need to first make sure that the tool you use is calibrated by measuring a standard measurement; a gage block.

Different precision grades of gage block are available; ,001, ,0001, ,000004, etc.

Calipers are good for ,001", micrometers can easily measure ,0001".

Even if calipers are made to read ,001", it is very easy to apply the wrong pressure and to get a wrong measure. The easiest way to know how much pressure to apply is by measuring a gage block.

 

For model ship building, construction with wood does not need a micrometer.

Calipers are very useful to measure the thickness of board.

For the daily use, a ruler is perfect and 1/32" is easy to use

1/64 is much harder to use, you need a sharp pencil and it is very easy to trace the line  next to the division.

In fact it is easier to use 1/32 and to be relatively sure of the measure than using 1/64 and to have doubts about it's accuracy.

 

photo of my favorite ruler for daily use

[BANYAN]

Sorry all, my point appears to have not been well/clearly made.  If you want consistently accurate measurement, ANY measuring device needs to be accurate to within a 'certified' acceptable tolerance.  In many circumstances in our hobby it does not need super accuracy.  The point I was trying to make was that it is pointless measuring the accuracy of one device with another device unless the accuracy of the measuring device is known/proven.

 

cheers

 

Pat