Lathe dro readings wrong.

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Lathe dro readings wrong.

This topic has 7 replies, 4 voices, and was last updated 18 September 2021 at 15:55 by Dave S.

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18 September 2021 at 13:14 #563320
wendy jackson
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@wendyjackson
Hi out there. I fitted a dro to my lathe sometime back, and today I tried to finish the set up and see how good or bit it works. Well it’s not good. I have checked the scale runs with a dro and they run true on both axis. I then measured the movement on the cross slide of the lathe moving it into the center 35mm on the dro. Then I measured the movement of the cross slide with a digital vernier gauge and the measurement was only 17mm. Something is way off. I lost the manual and can’t find one on the internet. It’s a cheap Chinese dro. Anyone have any views. Thanks.
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18 September 2021 at 13:14 #14360
wendy jackson
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@wendyjackson
18 September 2021 at 13:20 #563322
Dave S
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@daves59043
35mm would be the diameter reduction for 17.5mm of movement.

Sounds like your DRO is telling you how much smaller the bar will be vs how far the cross slide has moved

Dave
18 September 2021 at 13:24 #563324
not done it yet
Participant
@notdoneityet
I might suggest there is slop in the cross slide, it ‘slewing’ slightly, dependent on which way it is driven?

The finished cut diameter will depend on the cutter geometry. A change of cutter position should be undertaken after a physical measurement of the diameter in order to finish at the desired dimension. That would be (or should be) precise, provided cutting feed rate and depth of cut is not altered.

There is no guarantee of finished dimensions if the lathe operating parameters are changed between physical measurements.

Edited By not done it yet on 18/09/2021 13:32:27
18 September 2021 at 13:38 #563325
John Baguley
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@johnbaguley78655
Sounds like you have the DRO set to read diameter rather than radius. There should be a D/R button to change between the two.

John
18 September 2021 at 14:01 #563330
not done it yet
Participant
@notdoneityet
Posted by John Baguley on 18/09/2021 13:38:05:

Sounds like you have the DRO set to read diameter rather than radius. There should be a D/R button to change between the two.

John

That will depend on the dro. Mine are simple, stand-alone items – although they can also indicate on a separate reader head. That does not explain the 0.25/0.5/1mm difference in expected movement in practice.

Edited By not done it yet on 18/09/2021 14:04:10
18 September 2021 at 14:21 #563333
wendy jackson
Participant
@wendyjackson
Thanks chaps, that sorted it. Sometimes you just can’t see the answer to an easy answer to the problem.
18 September 2021 at 15:55 #563343
Dave S
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@daves59043
I assumed the 0.5mm difference was down to slightly dodgy measuring technique with the digital very-near

Dave
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