I have a Sheldon 13x40 lathe and just got it leveled with the Starrett
199 level. I now want to use the 2 collar method to check the alignment. I read in an old post that some folks like to use aluminum so I picked some up some 1 1/8" 6061 and put it in a 5C collet.
I cut off a 10" piece and trued it up and the hogged out the middle to form the collars. I had about 8" hanging out of the collet. I sharpened the cutter again and honed it with a small radius and took a cut across the collars at 1000rpm and .00085 feed. The bar chattered terribly on the end but cleaned up beautifully at the headstock end.
I know that is alot of overhang but was not sure how long the bar had to be to be accurate. All SB specifies is 3-4 inches between collars and the picture in the book looks like the bar is only 5-6 inches long.
So how long should the rod be to be accurate and how wide should the collars be?
Also, when the Starrett is "level" the bubble overhangs each side of the "level" mark by about 1 graduation. Is this normal? Also, what if you leveled each end of the lathe and only brought the bubble to the end of the inner line on each end making sure you had the front of the level facing the front of the machine at each end. I assume the lathe would be level in one plane but equally twisted a small amount along its length by 1/2 a graduation?
Thanks, Steve