Unable to calibrate axises

ycroosh said:
Checking the calibration from zero is very important here. This is the most common mistake with calibration.
What happens is that TouchDRO has two offsets that it keeps internally: one from the scale zero to the absolute origin and another from absolute origin to incremental origin. Those are stored in microns. When you calibrate the scales, you change the ratio between scale encoder increments and microns, so the offsets change. This is why is VERY important to check the calibration from 0, as redvan22 did above.
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So then I did it right and can now proceed and rely on the DRO?
 
So then I'm good to go and can rely on the DRO readings?


apologies for posting this twice. didn't see the previous on a refresh.
 
5080 is spot on for 5-micron glass scales, so that number makes sense. I think you should be good to go.
 
One last question ycroosch,
How do I calibrate the x and y on a lathe?
 
redvan22 said:
One last question ycroosch,
How do I calibrate the x and y on a lathe?
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Essentially the same as for the mill. For the z axis, I placed a stop on the lathe ways and brought the carriage to touching and zeroed the axis. Then I placed a 1/2/3 block between the stop and the carriage and brought the carriage to touching the block . Alternatively, you can use a dial indicator and zero it against the stop and the 1/2/3 block.

For the x axis, I used my tool post for the stop. My lathe has flat tops so the 1/2/3 block sits nicely. For some older lathes with curved surfaces, it becomes more complicated. It could be done on my Atlas/Craftsman 6x18 by replacing the tool post with a 1/2/3 block to act as the stop for the zero and positioning a second block against the stop for the 3" distance. Basically, you just need a means of fastening a flat surface perpendicular to the direction of travel and supporting a block of known length against it for the change in distance. It needen't be a block or even a fixed length as long as you can accurately measure the length. A pin could be turned on the lathe and measured with a micrometer.
 
If I dismantle the lathe or mill for cleaning and oiling, do I need to recalibrate?
 
redvan22 said:
If I dismantle the lathe or mill for cleaning and oiling, do I need to recalibrate?
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I would think it wouldn't be necessary . The only error that could arise would be a cosine error which would be minuscule. However, it wouldn't hurt to check the calibration from time to time. It's a fairly simple and quick process.
 
redvan22 said:
If I dismantle the lathe or mill for cleaning and oiling, do I need to recalibrate?
Click to expand...
You don't need to calibrate. Most low-end DROs don't even have this option and people use them every day. That said, why wouldn't you want to calibrate? You get more accuracy for free. As RJ said, cosine error is pretty minuscule, but the process takes a few minutes once you get the hang of it.
Regards
Yuriy
 
Thank you everyone. Been very helpful
 
Ycrooch,
After calibration of both the lathe and mill something didnt seem right so on the lathe, I setup for a cut by zeroing out the x axis (x and y same as a mill) and turned a diameter to a random length. Used two vernier calipers to check the length which showed the same value but what the calipers reported was not what the DRO showed so I tweaked the calibration setting number for the x axis until the display matched the calipers. Then I took another cut, measured and again the numbers were off again so I tweaked the setting number again and this became an on going process. Why is this happening?

When I did the calibration, I did it several times to ensure I got the same results each time but the numbers weren't what you stated earlier, 5080. The x axis was 5074 and the y 5087.
 
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