Originally Posted by
cnczoner
On my G0602 (10x22) lathe, I notice that when I drill a hole using the tailstock, the hole is larger than the bit (I take the bit out of the chuck and insert it into the drilled hole, and I notice there's a noticeably lot of slop). So I started tweaking the left-right adjustment screws on the tailstock, but that's a bit too trial and error....
Thanks,
-Neil.
Not only too triall and error too premature.
(take the bit out of the chuck....)
Your tailstock may be perfectly aligned (as perfect as is practical) but your chuck may be off.
Check that the tailstock is true by the proceudres already mentioned. Or do a quick check by using a center in the tailstock and a DTI in the spindle running around the body of the center.
Then check the drill chuck by gripping a short piece of good round bar and running the DTI around this. It will be surprising if the drill chuck is 'perfect.
Even if everything is 'perfect' a drilled hole may be oversize simply due to the drill running out slightly or because it has been sharpened slightly unevenly. The uneven sharpening can sometimes be noticed because one cutting edge will produce a bigger chip than the other.
An open mind is a virtue...so long as all the common sense has not leaked out.