Tailstock Alignment

chips&more said:
Sorry, but no I don’t think so, at least not my test indicators. Yes, gravity can effect an indicator if you drop it on the floor! But to have the reading change because gravity pulls on the stylus/probe??? If there was any change in the reading, then IMHO it’s probably due to lack in rigidity somewhere in the total indicator set-up and not gravity pulling on the stylus. However, when using a test indicator you can get readings that are not quantitative. 1) Using the stylus at an angle other than from its true origin (straight out) will cause cosine error in the readings. 2) Using a stylus with a different length other than the calibrated length. If you are using the test indicator just for comparison readings, as in this authors example, then the above 2 concerns do not apply. And the top and bottom readings do not apply as well…Good Luck, Dave.
Click to expand...

I stand by my original statement however poorly described. Gravity indeed is pulling pressure away from the stylus or probe. I should have said gravity can affect the reading on the indicator because gravity has a effect on the indicator holder and indicator, which however small, can cause a sag which effects the indicated reading. This is a separate issue from cosine error. http://www.practicalmachinist.com/vb/general/headstock-bed-tailstock-alignment-257375/index2.html Thanks for pointing out my poorly worded description.

Darrell
 
I presumed Darrell's initial statement to be set-up related (Dave pointed out the same thing). Nice to get a clarification, however.

Regarding the link that Darrell posted: I'm a Richard King and Forrest Addy fan. When those two guys make the same/similar statements, I'm inclined to treat it as carved in stone, LOL.
 
18w said:
Two things, Dial indicators and the coax indicator are affected by gravity. When a dti is held in a horizontal position and you sweep your tailstock the top and side readings will be correct. The reading on the bottom can be several tenths off do to gravity pulling on the probe. Richard King always suggested chucking up a piece and turning to the exact dia. of your tail stock spindle.Do not support it with a center, just turn about a 6" long area. You then put your dti on the top of the turned piece and then move the saddle towards the tailstock and traverse the top of the tailstock and do the same on the side. This give you your readings for height, side to side and parallelism of the tailstock. This is of course, after assuring that your lathe bed and headstock are aligned first. The above posters are correct though in that your coax may get you close enough. Depends on your requirements.

Darrell
Click to expand...
I disagree with every thing you said... except for your last statement "Depends on your requirements" However if your working for NASA or lives depend on it and your getting payed large sums of dollars to do it ... I totally agree with everything you said plus ten. ( its a hobby ) Just saying Dawner
 
You must log in or register to reply here.
Back
Top