Calibration. Is .002 close as it gets?

[ltlvt]

I checked my Touch DRO for accuracy today with the 1-2-3 blocks and indicator and it was within.002 of exact. I measured the 1-2-3 block and it was exactly 3.000. I should have left it but wanted to try to hit the 3.000. Long story short it is now over .500 short of the 3.000, Is .002 as good as it gets, or should I expect to get it on the money? Frustration got to me, and I was tired, so I quit for the night.

 

[benmychree]

How do you know that the indicator is accurate and repeatable?

 

[ycroosh]

I checked my Touch DRO for accuracy today with the 1-2-3 blocks and indicator and it was within.002 of exact. I measured the 1-2-3 block and it was exactly 3.000. I should have left it but wanted to try to hit the 3.000. Long story short it is now over .500 short of the 3.000, Is .002 as good as it gets, or should I expect to get it on the money? Frustration got to me, and I was tired, so I quit for the night.

TouchDRO uses fractional microns internally, or it doesn't really have a practical resolution limit. It will be as accurate as your scales.
0.002" worth of error can come from a few possible sources:
1. Hysteresis/backlash in your encoders (this is rare with modern glass or magnetic scales)
2. Problems with your indicator (or the setup)
3. Non-linear error in the scales (this is VERY common with Chinese magnetic scales, but not glass scales)

Which guide/video are you following?

Regards
Yuriy

 

[ltlvt]

How do you know that the indicator is accurate and repeatable?

I verified it by moving the X back to Zero and sliding the block between the indicator and the stationary block. Did this several times and it was dead nuts. I am using a Shars .0005 indicator. I have a new Mitutoyo but no need for me to use it with the repeatability I am getting with the Shars.

 

[ltlvt]

TouchDRO uses fractional microns internally, or it doesn't really have a practical resolution limit. It will be as accurate as your scales.
0.002" worth of error can come from a few possible sources:
1. Hysteresis/backlash in your encoders (this is rare with modern glass or magnetic scales)
2. Problems with your indicator (or the setup)
3. Non-linear error in the scales (this is VERY common with Chinese magnetic scales, but not glass scales)

Which guide/video are you following?

Regards
Yuriy

The latest one. I am going to try again tomorrow when I am fresh. I am using the I-Gage scales. Thanks for the speedy reply.

 

[ltlvt]

Problem solved, nothing was wrong with the scale, and nothing was wrong with the Touch DRO. For lack of using dirty words, I shall say it was Operator error. That is what can happen when one is fatigued. Today I used a different setup to hold the indicator and was very careful not to influence the reading on the indicator by accidentally touching it. Seems me touching it the last time is what caused the .002 error. Both the X and Y are dead nuts. I checked several times to insure repeatability. Now to make some chips and verify the entire process makes a product to size.

 

[ycroosh]

Problem solved, nothing was wrong with the scale, and nothing was wrong with the Touch DRO. For lack of using dirty words, I shall say it was Operator error. That is what can happen when one is fatigued. Today I used a different setup to hold the indicator and was very careful not to influence the reading on the indicator by accidentally touching it. Seems me touching it the last time is what caused the .002 error. Both the X and Y are dead nuts. I checked several times to insure repeatability. Now to make some chips and verify the entire process makes a product to size.

Good to see that you have it figured out.
Please let me know how the further testing goes.

Thank you
Yuriy

 

[ltlvt]

Good to see that you have it figured out.
Please let me know how the further testing goes.

Thank you
Yuriy

Will do .

 

[Dabbler]

I'm glad you found out what was wrong. Since 1980s, DROs have been far more accurate than our indicators. Nowadays some of the *really cheap* offshore scales and readers (in both magnetic AND glass) can be quite... poorly made. Every quality scale and reader that I have tried has outperformed my half-tenths Interrapid indicator.

 

[ltlvt]

In regard to further testing asked by Yuriy I did a semi precision test of repeatability yesterday by drilling a series of holes at known different spacing and recorded those dimensions. After drilling all 7 holes I went from left to right hole by hole and again right to left and all numbers were spot on. I am thinking of ways to verify both X and Y by machining 2 different known dimensions with the edge of an end mill and them measuring with my 10th's micrometers. I have calibrated my micrometers to Jo-blocks to dead nuts. Anyone have other ideas of how to check calibration? It might be an interesting challenge for anyone with Touch DRO or any other DRO's. The better we understand our machine tools the better machinist we can be. For me Self-confidence and confidence in my tools is on the top shelf when making or repairing something.