Strange indicator reading

[nateman_doo]

I am tramming my new build, and the dial indicator doesn't move going down along the Z, but going up it moves. Any input? Its a swiss style indicator from shars.

"http://www.youtube.com/watch?v=vZbap8T2yPk&feature=plcp&context=C39b6757UDOEgsToPDskLNIf7YvG70gBOWnkciSu0n"]Strange indicator reading - YouTube

[rpovey]

Got to be something moving in the head when it's changing direction.

[SCzEngrgGroup]

There's a reason why expensive indicators are expensive....

[fragger6662000]

the whole thinging is racking.

the screw is not parallel with the axis and causing it to twist.

what happens when it goes down again as it look like it is completely un repeatable?

[nateman_doo]

the only thing I can think of, is the magnetic indicator base that isn't strong enough. Do I accept that its straight (the downward movement) or still needs tramming (upward movement)

[fragger6662000]

1. does the up and down paths cause the same deflections AKA the go UP DOWN UP DOWN do they finish in the same place or different one?

If it is different then you are running the DTI against the hard stop of the inductor or something is moving / twisting.

if the base is not moving as the ammount of displacement appears linear.

[dertsap]

the only thing I can think of, is the magnetic indicator base that isn't strong enough. Do I accept that its straight (the downward movement) or still needs tramming (upward movement)

if the mag base isn't strong or if it isn't seating properly then it can easily cause poor readings , so if you think that may be the problem then try to clamp the base or do something to secure it , then try dialing again

[underthetire]

2 things I would check first

Is the stylus tight in the indicator.

Re position the indicator so the stylus is vertical with the block. Some indicators have too much side play in the gimbal, which can be adjusted.

Go from there.

[nateman_doo]

2 things I would check first

Is the stylus tight in the indicator.

Re position the indicator so the stylus is vertical with the block. Some indicators have too much side play in the gimbal, which can be adjusted.

Go from there.

It seems tight to me, but I will try it parallel with the block.

[fragger6662000]

its not the dti it is the setup something is moving a dti does not gradually move when in error

[nateman_doo]

I ran in parallel with the block and tightened the gibs. Then I just took a reading in one direction (in a "pulling" along the block, not pushing). Works ok.

I got X to +/- 0.0005 & Y is 0.001. I am not a fan of the Y, but its sooo much work to tram the head with shims. I have been at it all day. I will take a break and get back to it tomorrow.